Numeric.SpecFunctions:invIncompleteGamma from math-functions-0.1.5.2, B

Percentage Accurate: 72.5% → 99.5%
Time: 12.1s
Alternatives: 14
Speedup: 1.0×

Specification

?
\[\begin{array}{l} \\ 1 - \log \left(1 - \frac{x - y}{1 - y}\right) \end{array} \]
(FPCore (x y) :precision binary64 (- 1.0 (log (- 1.0 (/ (- x y) (- 1.0 y))))))
double code(double x, double y) {
	return 1.0 - log((1.0 - ((x - y) / (1.0 - y))));
}
real(8) function code(x, y)
    real(8), intent (in) :: x
    real(8), intent (in) :: y
    code = 1.0d0 - log((1.0d0 - ((x - y) / (1.0d0 - y))))
end function
public static double code(double x, double y) {
	return 1.0 - Math.log((1.0 - ((x - y) / (1.0 - y))));
}
def code(x, y):
	return 1.0 - math.log((1.0 - ((x - y) / (1.0 - y))))
function code(x, y)
	return Float64(1.0 - log(Float64(1.0 - Float64(Float64(x - y) / Float64(1.0 - y)))))
end
function tmp = code(x, y)
	tmp = 1.0 - log((1.0 - ((x - y) / (1.0 - y))));
end
code[x_, y_] := N[(1.0 - N[Log[N[(1.0 - N[(N[(x - y), $MachinePrecision] / N[(1.0 - y), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
1 - \log \left(1 - \frac{x - y}{1 - y}\right)
\end{array}

Sampling outcomes in binary64 precision:

Local Percentage Accuracy vs ?

The average percentage accuracy by input value. Horizontal axis shows value of an input variable; the variable is choosen in the title. Vertical axis is accuracy; higher is better. Red represent the original program, while blue represents Herbie's suggestion. These can be toggled with buttons below the plot. The line is an average while dots represent individual samples.

Accuracy vs Speed?

Herbie found 14 alternatives:

AlternativeAccuracySpeedup
The accuracy (vertical axis) and speed (horizontal axis) of each alternatives. Up and to the right is better. The red square shows the initial program, and each blue circle shows an alternative.The line shows the best available speed-accuracy tradeoffs.

Initial Program: 72.5% accurate, 1.0× speedup?

\[\begin{array}{l} \\ 1 - \log \left(1 - \frac{x - y}{1 - y}\right) \end{array} \]
(FPCore (x y) :precision binary64 (- 1.0 (log (- 1.0 (/ (- x y) (- 1.0 y))))))
double code(double x, double y) {
	return 1.0 - log((1.0 - ((x - y) / (1.0 - y))));
}
real(8) function code(x, y)
    real(8), intent (in) :: x
    real(8), intent (in) :: y
    code = 1.0d0 - log((1.0d0 - ((x - y) / (1.0d0 - y))))
end function
public static double code(double x, double y) {
	return 1.0 - Math.log((1.0 - ((x - y) / (1.0 - y))));
}
def code(x, y):
	return 1.0 - math.log((1.0 - ((x - y) / (1.0 - y))))
function code(x, y)
	return Float64(1.0 - log(Float64(1.0 - Float64(Float64(x - y) / Float64(1.0 - y)))))
end
function tmp = code(x, y)
	tmp = 1.0 - log((1.0 - ((x - y) / (1.0 - y))));
end
code[x_, y_] := N[(1.0 - N[Log[N[(1.0 - N[(N[(x - y), $MachinePrecision] / N[(1.0 - y), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
1 - \log \left(1 - \frac{x - y}{1 - y}\right)
\end{array}

Alternative 1: 99.5% accurate, 0.2× speedup?

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;y \leq -2000:\\ \;\;\;\;1 + \left(\left(\left(\frac{-1}{y} - \frac{0.5}{y \cdot y}\right) - \left(\log \left(\frac{-1}{y}\right) + \frac{0.3333333333333333}{{y}^{3}}\right)\right) - \mathsf{log1p}\left(-x\right)\right)\\ \mathbf{elif}\;y \leq 6 \cdot 10^{+38}:\\ \;\;\;\;1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)\\ \mathbf{else}:\\ \;\;\;\;1 - \log \left(\frac{1}{y} \cdot e^{\mathsf{log1p}\left(x\right) + \mathsf{fma}\left(0.5, {y}^{-2}, \frac{1}{y}\right)}\right)\\ \end{array} \end{array} \]
(FPCore (x y)
 :precision binary64
 (if (<= y -2000.0)
   (+
    1.0
    (-
     (-
      (- (/ -1.0 y) (/ 0.5 (* y y)))
      (+ (log (/ -1.0 y)) (/ 0.3333333333333333 (pow y 3.0))))
     (log1p (- x))))
   (if (<= y 6e+38)
     (- 1.0 (log1p (/ (- y x) (- 1.0 y))))
     (-
      1.0
      (log
       (* (/ 1.0 y) (exp (+ (log1p x) (fma 0.5 (pow y -2.0) (/ 1.0 y))))))))))
double code(double x, double y) {
	double tmp;
	if (y <= -2000.0) {
		tmp = 1.0 + ((((-1.0 / y) - (0.5 / (y * y))) - (log((-1.0 / y)) + (0.3333333333333333 / pow(y, 3.0)))) - log1p(-x));
	} else if (y <= 6e+38) {
		tmp = 1.0 - log1p(((y - x) / (1.0 - y)));
	} else {
		tmp = 1.0 - log(((1.0 / y) * exp((log1p(x) + fma(0.5, pow(y, -2.0), (1.0 / y))))));
	}
	return tmp;
}
function code(x, y)
	tmp = 0.0
	if (y <= -2000.0)
		tmp = Float64(1.0 + Float64(Float64(Float64(Float64(-1.0 / y) - Float64(0.5 / Float64(y * y))) - Float64(log(Float64(-1.0 / y)) + Float64(0.3333333333333333 / (y ^ 3.0)))) - log1p(Float64(-x))));
	elseif (y <= 6e+38)
		tmp = Float64(1.0 - log1p(Float64(Float64(y - x) / Float64(1.0 - y))));
	else
		tmp = Float64(1.0 - log(Float64(Float64(1.0 / y) * exp(Float64(log1p(x) + fma(0.5, (y ^ -2.0), Float64(1.0 / y)))))));
	end
	return tmp
end
code[x_, y_] := If[LessEqual[y, -2000.0], N[(1.0 + N[(N[(N[(N[(-1.0 / y), $MachinePrecision] - N[(0.5 / N[(y * y), $MachinePrecision]), $MachinePrecision]), $MachinePrecision] - N[(N[Log[N[(-1.0 / y), $MachinePrecision]], $MachinePrecision] + N[(0.3333333333333333 / N[Power[y, 3.0], $MachinePrecision]), $MachinePrecision]), $MachinePrecision]), $MachinePrecision] - N[Log[1 + (-x)], $MachinePrecision]), $MachinePrecision]), $MachinePrecision], If[LessEqual[y, 6e+38], N[(1.0 - N[Log[1 + N[(N[(y - x), $MachinePrecision] / N[(1.0 - y), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision], N[(1.0 - N[Log[N[(N[(1.0 / y), $MachinePrecision] * N[Exp[N[(N[Log[1 + x], $MachinePrecision] + N[(0.5 * N[Power[y, -2.0], $MachinePrecision] + N[(1.0 / y), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]]]
\begin{array}{l}

\\
\begin{array}{l}
\mathbf{if}\;y \leq -2000:\\
\;\;\;\;1 + \left(\left(\left(\frac{-1}{y} - \frac{0.5}{y \cdot y}\right) - \left(\log \left(\frac{-1}{y}\right) + \frac{0.3333333333333333}{{y}^{3}}\right)\right) - \mathsf{log1p}\left(-x\right)\right)\\

\mathbf{elif}\;y \leq 6 \cdot 10^{+38}:\\
\;\;\;\;1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)\\

\mathbf{else}:\\
\;\;\;\;1 - \log \left(\frac{1}{y} \cdot e^{\mathsf{log1p}\left(x\right) + \mathsf{fma}\left(0.5, {y}^{-2}, \frac{1}{y}\right)}\right)\\


\end{array}
\end{array}
Derivation
  1. Split input into 3 regimes
  2. if y < -2e3

    1. Initial program 23.5%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg23.5%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def23.5%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified23.5%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]
    4. Step-by-step derivation
      1. flip--23.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{y - x}{\color{blue}{\frac{1 \cdot 1 - y \cdot y}{1 + y}}}\right) \]
      2. associate-/r/24.2%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{y - x}{1 \cdot 1 - y \cdot y} \cdot \left(1 + y\right)}\right) \]
      3. metadata-eval24.2%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{y - x}{\color{blue}{1} - y \cdot y} \cdot \left(1 + y\right)\right) \]
      4. +-commutative24.2%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{y - x}{1 - y \cdot y} \cdot \color{blue}{\left(y + 1\right)}\right) \]
    5. Applied egg-rr24.2%

      \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{y - x}{1 - y \cdot y} \cdot \left(y + 1\right)}\right) \]
    6. Taylor expanded in y around -inf 99.4%

      \[\leadsto 1 - \color{blue}{\left(\log \left(1 + -1 \cdot x\right) + \left(\log \left(\frac{-1}{y}\right) + \left(0.3333333333333333 \cdot \frac{1}{{y}^{3}} + \left(0.5 \cdot \frac{1}{{y}^{2}} + \frac{1}{y}\right)\right)\right)\right)} \]
    7. Step-by-step derivation
      1. log1p-def99.4%

        \[\leadsto 1 - \left(\color{blue}{\mathsf{log1p}\left(-1 \cdot x\right)} + \left(\log \left(\frac{-1}{y}\right) + \left(0.3333333333333333 \cdot \frac{1}{{y}^{3}} + \left(0.5 \cdot \frac{1}{{y}^{2}} + \frac{1}{y}\right)\right)\right)\right) \]
      2. mul-1-neg99.4%

        \[\leadsto 1 - \left(\mathsf{log1p}\left(\color{blue}{-x}\right) + \left(\log \left(\frac{-1}{y}\right) + \left(0.3333333333333333 \cdot \frac{1}{{y}^{3}} + \left(0.5 \cdot \frac{1}{{y}^{2}} + \frac{1}{y}\right)\right)\right)\right) \]
      3. associate-+r+99.4%

        \[\leadsto 1 - \left(\mathsf{log1p}\left(-x\right) + \color{blue}{\left(\left(\log \left(\frac{-1}{y}\right) + 0.3333333333333333 \cdot \frac{1}{{y}^{3}}\right) + \left(0.5 \cdot \frac{1}{{y}^{2}} + \frac{1}{y}\right)\right)}\right) \]
      4. associate-*r/99.4%

        \[\leadsto 1 - \left(\mathsf{log1p}\left(-x\right) + \left(\left(\log \left(\frac{-1}{y}\right) + \color{blue}{\frac{0.3333333333333333 \cdot 1}{{y}^{3}}}\right) + \left(0.5 \cdot \frac{1}{{y}^{2}} + \frac{1}{y}\right)\right)\right) \]
      5. metadata-eval99.4%

        \[\leadsto 1 - \left(\mathsf{log1p}\left(-x\right) + \left(\left(\log \left(\frac{-1}{y}\right) + \frac{\color{blue}{0.3333333333333333}}{{y}^{3}}\right) + \left(0.5 \cdot \frac{1}{{y}^{2}} + \frac{1}{y}\right)\right)\right) \]
      6. +-commutative99.4%

        \[\leadsto 1 - \left(\mathsf{log1p}\left(-x\right) + \left(\left(\log \left(\frac{-1}{y}\right) + \frac{0.3333333333333333}{{y}^{3}}\right) + \color{blue}{\left(\frac{1}{y} + 0.5 \cdot \frac{1}{{y}^{2}}\right)}\right)\right) \]
      7. associate-*r/99.4%

        \[\leadsto 1 - \left(\mathsf{log1p}\left(-x\right) + \left(\left(\log \left(\frac{-1}{y}\right) + \frac{0.3333333333333333}{{y}^{3}}\right) + \left(\frac{1}{y} + \color{blue}{\frac{0.5 \cdot 1}{{y}^{2}}}\right)\right)\right) \]
      8. metadata-eval99.4%

        \[\leadsto 1 - \left(\mathsf{log1p}\left(-x\right) + \left(\left(\log \left(\frac{-1}{y}\right) + \frac{0.3333333333333333}{{y}^{3}}\right) + \left(\frac{1}{y} + \frac{\color{blue}{0.5}}{{y}^{2}}\right)\right)\right) \]
      9. unpow299.4%

        \[\leadsto 1 - \left(\mathsf{log1p}\left(-x\right) + \left(\left(\log \left(\frac{-1}{y}\right) + \frac{0.3333333333333333}{{y}^{3}}\right) + \left(\frac{1}{y} + \frac{0.5}{\color{blue}{y \cdot y}}\right)\right)\right) \]
    8. Simplified99.4%

      \[\leadsto 1 - \color{blue}{\left(\mathsf{log1p}\left(-x\right) + \left(\left(\log \left(\frac{-1}{y}\right) + \frac{0.3333333333333333}{{y}^{3}}\right) + \left(\frac{1}{y} + \frac{0.5}{y \cdot y}\right)\right)\right)} \]

    if -2e3 < y < 6.0000000000000002e38

    1. Initial program 100.0%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg100.0%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def100.0%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified100.0%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]

    if 6.0000000000000002e38 < y

    1. Initial program 43.1%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg43.1%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def43.1%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac43.1%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg43.1%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in43.1%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg43.1%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative43.1%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg43.1%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified43.1%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]
    4. Step-by-step derivation
      1. flip--19.7%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{y - x}{\color{blue}{\frac{1 \cdot 1 - y \cdot y}{1 + y}}}\right) \]
      2. associate-/r/19.7%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{y - x}{1 \cdot 1 - y \cdot y} \cdot \left(1 + y\right)}\right) \]
      3. metadata-eval19.7%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{y - x}{\color{blue}{1} - y \cdot y} \cdot \left(1 + y\right)\right) \]
      4. +-commutative19.7%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{y - x}{1 - y \cdot y} \cdot \color{blue}{\left(y + 1\right)}\right) \]
    5. Applied egg-rr19.7%

      \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{y - x}{1 - y \cdot y} \cdot \left(y + 1\right)}\right) \]
    6. Taylor expanded in y around -inf 0.0%

      \[\leadsto 1 - \color{blue}{\left(\log \left(1 + -1 \cdot x\right) + \left(\log \left(\frac{-1}{y}\right) + \left(0.5 \cdot \frac{1}{{y}^{2}} + \frac{1}{y}\right)\right)\right)} \]
    7. Step-by-step derivation
      1. +-commutative0.0%

        \[\leadsto 1 - \left(\log \left(1 + -1 \cdot x\right) + \color{blue}{\left(\left(0.5 \cdot \frac{1}{{y}^{2}} + \frac{1}{y}\right) + \log \left(\frac{-1}{y}\right)\right)}\right) \]
      2. associate-+r+0.0%

        \[\leadsto 1 - \color{blue}{\left(\left(\log \left(1 + -1 \cdot x\right) + \left(0.5 \cdot \frac{1}{{y}^{2}} + \frac{1}{y}\right)\right) + \log \left(\frac{-1}{y}\right)\right)} \]
      3. log1p-def0.0%

        \[\leadsto 1 - \left(\left(\color{blue}{\mathsf{log1p}\left(-1 \cdot x\right)} + \left(0.5 \cdot \frac{1}{{y}^{2}} + \frac{1}{y}\right)\right) + \log \left(\frac{-1}{y}\right)\right) \]
      4. mul-1-neg0.0%

        \[\leadsto 1 - \left(\left(\mathsf{log1p}\left(\color{blue}{-x}\right) + \left(0.5 \cdot \frac{1}{{y}^{2}} + \frac{1}{y}\right)\right) + \log \left(\frac{-1}{y}\right)\right) \]
      5. +-commutative0.0%

        \[\leadsto 1 - \left(\left(\mathsf{log1p}\left(-x\right) + \color{blue}{\left(\frac{1}{y} + 0.5 \cdot \frac{1}{{y}^{2}}\right)}\right) + \log \left(\frac{-1}{y}\right)\right) \]
      6. associate-*r/0.0%

        \[\leadsto 1 - \left(\left(\mathsf{log1p}\left(-x\right) + \left(\frac{1}{y} + \color{blue}{\frac{0.5 \cdot 1}{{y}^{2}}}\right)\right) + \log \left(\frac{-1}{y}\right)\right) \]
      7. metadata-eval0.0%

        \[\leadsto 1 - \left(\left(\mathsf{log1p}\left(-x\right) + \left(\frac{1}{y} + \frac{\color{blue}{0.5}}{{y}^{2}}\right)\right) + \log \left(\frac{-1}{y}\right)\right) \]
      8. unpow20.0%

        \[\leadsto 1 - \left(\left(\mathsf{log1p}\left(-x\right) + \left(\frac{1}{y} + \frac{0.5}{\color{blue}{y \cdot y}}\right)\right) + \log \left(\frac{-1}{y}\right)\right) \]
    8. Simplified0.0%

      \[\leadsto 1 - \color{blue}{\left(\left(\mathsf{log1p}\left(-x\right) + \left(\frac{1}{y} + \frac{0.5}{y \cdot y}\right)\right) + \log \left(\frac{-1}{y}\right)\right)} \]
    9. Step-by-step derivation
      1. +-commutative0.0%

        \[\leadsto 1 - \color{blue}{\left(\log \left(\frac{-1}{y}\right) + \left(\mathsf{log1p}\left(-x\right) + \left(\frac{1}{y} + \frac{0.5}{y \cdot y}\right)\right)\right)} \]
      2. add-log-exp0.0%

        \[\leadsto 1 - \left(\log \left(\frac{-1}{y}\right) + \color{blue}{\log \left(e^{\mathsf{log1p}\left(-x\right) + \left(\frac{1}{y} + \frac{0.5}{y \cdot y}\right)}\right)}\right) \]
      3. sum-log0.0%

        \[\leadsto 1 - \color{blue}{\log \left(\frac{-1}{y} \cdot e^{\mathsf{log1p}\left(-x\right) + \left(\frac{1}{y} + \frac{0.5}{y \cdot y}\right)}\right)} \]
      4. add-sqr-sqrt0.0%

        \[\leadsto 1 - \log \left(\color{blue}{\left(\sqrt{\frac{-1}{y}} \cdot \sqrt{\frac{-1}{y}}\right)} \cdot e^{\mathsf{log1p}\left(-x\right) + \left(\frac{1}{y} + \frac{0.5}{y \cdot y}\right)}\right) \]
      5. sqrt-unprod0.0%

        \[\leadsto 1 - \log \left(\color{blue}{\sqrt{\frac{-1}{y} \cdot \frac{-1}{y}}} \cdot e^{\mathsf{log1p}\left(-x\right) + \left(\frac{1}{y} + \frac{0.5}{y \cdot y}\right)}\right) \]
      6. frac-times0.0%

        \[\leadsto 1 - \log \left(\sqrt{\color{blue}{\frac{-1 \cdot -1}{y \cdot y}}} \cdot e^{\mathsf{log1p}\left(-x\right) + \left(\frac{1}{y} + \frac{0.5}{y \cdot y}\right)}\right) \]
      7. metadata-eval0.0%

        \[\leadsto 1 - \log \left(\sqrt{\frac{\color{blue}{1}}{y \cdot y}} \cdot e^{\mathsf{log1p}\left(-x\right) + \left(\frac{1}{y} + \frac{0.5}{y \cdot y}\right)}\right) \]
      8. metadata-eval0.0%

        \[\leadsto 1 - \log \left(\sqrt{\frac{\color{blue}{1 \cdot 1}}{y \cdot y}} \cdot e^{\mathsf{log1p}\left(-x\right) + \left(\frac{1}{y} + \frac{0.5}{y \cdot y}\right)}\right) \]
      9. frac-times0.0%

        \[\leadsto 1 - \log \left(\sqrt{\color{blue}{\frac{1}{y} \cdot \frac{1}{y}}} \cdot e^{\mathsf{log1p}\left(-x\right) + \left(\frac{1}{y} + \frac{0.5}{y \cdot y}\right)}\right) \]
      10. sqrt-unprod0.0%

        \[\leadsto 1 - \log \left(\color{blue}{\left(\sqrt{\frac{1}{y}} \cdot \sqrt{\frac{1}{y}}\right)} \cdot e^{\mathsf{log1p}\left(-x\right) + \left(\frac{1}{y} + \frac{0.5}{y \cdot y}\right)}\right) \]
      11. add-sqr-sqrt0.0%

        \[\leadsto 1 - \log \left(\color{blue}{\frac{1}{y}} \cdot e^{\mathsf{log1p}\left(-x\right) + \left(\frac{1}{y} + \frac{0.5}{y \cdot y}\right)}\right) \]
      12. add-sqr-sqrt0.0%

        \[\leadsto 1 - \log \left(\frac{1}{y} \cdot e^{\mathsf{log1p}\left(\color{blue}{\sqrt{-x} \cdot \sqrt{-x}}\right) + \left(\frac{1}{y} + \frac{0.5}{y \cdot y}\right)}\right) \]
      13. sqrt-unprod50.7%

        \[\leadsto 1 - \log \left(\frac{1}{y} \cdot e^{\mathsf{log1p}\left(\color{blue}{\sqrt{\left(-x\right) \cdot \left(-x\right)}}\right) + \left(\frac{1}{y} + \frac{0.5}{y \cdot y}\right)}\right) \]
      14. sqr-neg50.7%

        \[\leadsto 1 - \log \left(\frac{1}{y} \cdot e^{\mathsf{log1p}\left(\sqrt{\color{blue}{x \cdot x}}\right) + \left(\frac{1}{y} + \frac{0.5}{y \cdot y}\right)}\right) \]
      15. sqrt-unprod98.4%

        \[\leadsto 1 - \log \left(\frac{1}{y} \cdot e^{\mathsf{log1p}\left(\color{blue}{\sqrt{x} \cdot \sqrt{x}}\right) + \left(\frac{1}{y} + \frac{0.5}{y \cdot y}\right)}\right) \]
      16. add-sqr-sqrt98.4%

        \[\leadsto 1 - \log \left(\frac{1}{y} \cdot e^{\mathsf{log1p}\left(\color{blue}{x}\right) + \left(\frac{1}{y} + \frac{0.5}{y \cdot y}\right)}\right) \]
      17. +-commutative98.4%

        \[\leadsto 1 - \log \left(\frac{1}{y} \cdot e^{\mathsf{log1p}\left(x\right) + \color{blue}{\left(\frac{0.5}{y \cdot y} + \frac{1}{y}\right)}}\right) \]
    10. Applied egg-rr98.4%

      \[\leadsto 1 - \color{blue}{\log \left(\frac{1}{y} \cdot e^{\mathsf{log1p}\left(x\right) + \mathsf{fma}\left(0.5, {y}^{-2}, \frac{1}{y}\right)}\right)} \]
  3. Recombined 3 regimes into one program.
  4. Final simplification99.6%

    \[\leadsto \begin{array}{l} \mathbf{if}\;y \leq -2000:\\ \;\;\;\;1 + \left(\left(\left(\frac{-1}{y} - \frac{0.5}{y \cdot y}\right) - \left(\log \left(\frac{-1}{y}\right) + \frac{0.3333333333333333}{{y}^{3}}\right)\right) - \mathsf{log1p}\left(-x\right)\right)\\ \mathbf{elif}\;y \leq 6 \cdot 10^{+38}:\\ \;\;\;\;1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)\\ \mathbf{else}:\\ \;\;\;\;1 - \log \left(\frac{1}{y} \cdot e^{\mathsf{log1p}\left(x\right) + \mathsf{fma}\left(0.5, {y}^{-2}, \frac{1}{y}\right)}\right)\\ \end{array} \]

Alternative 2: 99.7% accurate, 0.3× speedup?

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;y \leq -2000:\\ \;\;\;\;1 + \left(\left(\left(\frac{-1}{y} - \frac{0.5}{y \cdot y}\right) - \left(\log \left(\frac{-1}{y}\right) + \frac{0.3333333333333333}{{y}^{3}}\right)\right) - \mathsf{log1p}\left(-x\right)\right)\\ \mathbf{elif}\;y \leq 5.8 \cdot 10^{+41}:\\ \;\;\;\;1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)\\ \mathbf{else}:\\ \;\;\;\;1 + \left(\log y - \log \left(x + -1\right)\right)\\ \end{array} \end{array} \]
(FPCore (x y)
 :precision binary64
 (if (<= y -2000.0)
   (+
    1.0
    (-
     (-
      (- (/ -1.0 y) (/ 0.5 (* y y)))
      (+ (log (/ -1.0 y)) (/ 0.3333333333333333 (pow y 3.0))))
     (log1p (- x))))
   (if (<= y 5.8e+41)
     (- 1.0 (log1p (/ (- y x) (- 1.0 y))))
     (+ 1.0 (- (log y) (log (+ x -1.0)))))))
double code(double x, double y) {
	double tmp;
	if (y <= -2000.0) {
		tmp = 1.0 + ((((-1.0 / y) - (0.5 / (y * y))) - (log((-1.0 / y)) + (0.3333333333333333 / pow(y, 3.0)))) - log1p(-x));
	} else if (y <= 5.8e+41) {
		tmp = 1.0 - log1p(((y - x) / (1.0 - y)));
	} else {
		tmp = 1.0 + (log(y) - log((x + -1.0)));
	}
	return tmp;
}
public static double code(double x, double y) {
	double tmp;
	if (y <= -2000.0) {
		tmp = 1.0 + ((((-1.0 / y) - (0.5 / (y * y))) - (Math.log((-1.0 / y)) + (0.3333333333333333 / Math.pow(y, 3.0)))) - Math.log1p(-x));
	} else if (y <= 5.8e+41) {
		tmp = 1.0 - Math.log1p(((y - x) / (1.0 - y)));
	} else {
		tmp = 1.0 + (Math.log(y) - Math.log((x + -1.0)));
	}
	return tmp;
}
def code(x, y):
	tmp = 0
	if y <= -2000.0:
		tmp = 1.0 + ((((-1.0 / y) - (0.5 / (y * y))) - (math.log((-1.0 / y)) + (0.3333333333333333 / math.pow(y, 3.0)))) - math.log1p(-x))
	elif y <= 5.8e+41:
		tmp = 1.0 - math.log1p(((y - x) / (1.0 - y)))
	else:
		tmp = 1.0 + (math.log(y) - math.log((x + -1.0)))
	return tmp
function code(x, y)
	tmp = 0.0
	if (y <= -2000.0)
		tmp = Float64(1.0 + Float64(Float64(Float64(Float64(-1.0 / y) - Float64(0.5 / Float64(y * y))) - Float64(log(Float64(-1.0 / y)) + Float64(0.3333333333333333 / (y ^ 3.0)))) - log1p(Float64(-x))));
	elseif (y <= 5.8e+41)
		tmp = Float64(1.0 - log1p(Float64(Float64(y - x) / Float64(1.0 - y))));
	else
		tmp = Float64(1.0 + Float64(log(y) - log(Float64(x + -1.0))));
	end
	return tmp
end
code[x_, y_] := If[LessEqual[y, -2000.0], N[(1.0 + N[(N[(N[(N[(-1.0 / y), $MachinePrecision] - N[(0.5 / N[(y * y), $MachinePrecision]), $MachinePrecision]), $MachinePrecision] - N[(N[Log[N[(-1.0 / y), $MachinePrecision]], $MachinePrecision] + N[(0.3333333333333333 / N[Power[y, 3.0], $MachinePrecision]), $MachinePrecision]), $MachinePrecision]), $MachinePrecision] - N[Log[1 + (-x)], $MachinePrecision]), $MachinePrecision]), $MachinePrecision], If[LessEqual[y, 5.8e+41], N[(1.0 - N[Log[1 + N[(N[(y - x), $MachinePrecision] / N[(1.0 - y), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision], N[(1.0 + N[(N[Log[y], $MachinePrecision] - N[Log[N[(x + -1.0), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]), $MachinePrecision]]]
\begin{array}{l}

\\
\begin{array}{l}
\mathbf{if}\;y \leq -2000:\\
\;\;\;\;1 + \left(\left(\left(\frac{-1}{y} - \frac{0.5}{y \cdot y}\right) - \left(\log \left(\frac{-1}{y}\right) + \frac{0.3333333333333333}{{y}^{3}}\right)\right) - \mathsf{log1p}\left(-x\right)\right)\\

\mathbf{elif}\;y \leq 5.8 \cdot 10^{+41}:\\
\;\;\;\;1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)\\

\mathbf{else}:\\
\;\;\;\;1 + \left(\log y - \log \left(x + -1\right)\right)\\


\end{array}
\end{array}
Derivation
  1. Split input into 3 regimes
  2. if y < -2e3

    1. Initial program 23.5%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg23.5%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def23.5%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified23.5%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]
    4. Step-by-step derivation
      1. flip--23.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{y - x}{\color{blue}{\frac{1 \cdot 1 - y \cdot y}{1 + y}}}\right) \]
      2. associate-/r/24.2%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{y - x}{1 \cdot 1 - y \cdot y} \cdot \left(1 + y\right)}\right) \]
      3. metadata-eval24.2%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{y - x}{\color{blue}{1} - y \cdot y} \cdot \left(1 + y\right)\right) \]
      4. +-commutative24.2%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{y - x}{1 - y \cdot y} \cdot \color{blue}{\left(y + 1\right)}\right) \]
    5. Applied egg-rr24.2%

      \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{y - x}{1 - y \cdot y} \cdot \left(y + 1\right)}\right) \]
    6. Taylor expanded in y around -inf 99.4%

      \[\leadsto 1 - \color{blue}{\left(\log \left(1 + -1 \cdot x\right) + \left(\log \left(\frac{-1}{y}\right) + \left(0.3333333333333333 \cdot \frac{1}{{y}^{3}} + \left(0.5 \cdot \frac{1}{{y}^{2}} + \frac{1}{y}\right)\right)\right)\right)} \]
    7. Step-by-step derivation
      1. log1p-def99.4%

        \[\leadsto 1 - \left(\color{blue}{\mathsf{log1p}\left(-1 \cdot x\right)} + \left(\log \left(\frac{-1}{y}\right) + \left(0.3333333333333333 \cdot \frac{1}{{y}^{3}} + \left(0.5 \cdot \frac{1}{{y}^{2}} + \frac{1}{y}\right)\right)\right)\right) \]
      2. mul-1-neg99.4%

        \[\leadsto 1 - \left(\mathsf{log1p}\left(\color{blue}{-x}\right) + \left(\log \left(\frac{-1}{y}\right) + \left(0.3333333333333333 \cdot \frac{1}{{y}^{3}} + \left(0.5 \cdot \frac{1}{{y}^{2}} + \frac{1}{y}\right)\right)\right)\right) \]
      3. associate-+r+99.4%

        \[\leadsto 1 - \left(\mathsf{log1p}\left(-x\right) + \color{blue}{\left(\left(\log \left(\frac{-1}{y}\right) + 0.3333333333333333 \cdot \frac{1}{{y}^{3}}\right) + \left(0.5 \cdot \frac{1}{{y}^{2}} + \frac{1}{y}\right)\right)}\right) \]
      4. associate-*r/99.4%

        \[\leadsto 1 - \left(\mathsf{log1p}\left(-x\right) + \left(\left(\log \left(\frac{-1}{y}\right) + \color{blue}{\frac{0.3333333333333333 \cdot 1}{{y}^{3}}}\right) + \left(0.5 \cdot \frac{1}{{y}^{2}} + \frac{1}{y}\right)\right)\right) \]
      5. metadata-eval99.4%

        \[\leadsto 1 - \left(\mathsf{log1p}\left(-x\right) + \left(\left(\log \left(\frac{-1}{y}\right) + \frac{\color{blue}{0.3333333333333333}}{{y}^{3}}\right) + \left(0.5 \cdot \frac{1}{{y}^{2}} + \frac{1}{y}\right)\right)\right) \]
      6. +-commutative99.4%

        \[\leadsto 1 - \left(\mathsf{log1p}\left(-x\right) + \left(\left(\log \left(\frac{-1}{y}\right) + \frac{0.3333333333333333}{{y}^{3}}\right) + \color{blue}{\left(\frac{1}{y} + 0.5 \cdot \frac{1}{{y}^{2}}\right)}\right)\right) \]
      7. associate-*r/99.4%

        \[\leadsto 1 - \left(\mathsf{log1p}\left(-x\right) + \left(\left(\log \left(\frac{-1}{y}\right) + \frac{0.3333333333333333}{{y}^{3}}\right) + \left(\frac{1}{y} + \color{blue}{\frac{0.5 \cdot 1}{{y}^{2}}}\right)\right)\right) \]
      8. metadata-eval99.4%

        \[\leadsto 1 - \left(\mathsf{log1p}\left(-x\right) + \left(\left(\log \left(\frac{-1}{y}\right) + \frac{0.3333333333333333}{{y}^{3}}\right) + \left(\frac{1}{y} + \frac{\color{blue}{0.5}}{{y}^{2}}\right)\right)\right) \]
      9. unpow299.4%

        \[\leadsto 1 - \left(\mathsf{log1p}\left(-x\right) + \left(\left(\log \left(\frac{-1}{y}\right) + \frac{0.3333333333333333}{{y}^{3}}\right) + \left(\frac{1}{y} + \frac{0.5}{\color{blue}{y \cdot y}}\right)\right)\right) \]
    8. Simplified99.4%

      \[\leadsto 1 - \color{blue}{\left(\mathsf{log1p}\left(-x\right) + \left(\left(\log \left(\frac{-1}{y}\right) + \frac{0.3333333333333333}{{y}^{3}}\right) + \left(\frac{1}{y} + \frac{0.5}{y \cdot y}\right)\right)\right)} \]

    if -2e3 < y < 5.79999999999999977e41

    1. Initial program 100.0%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg100.0%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def100.0%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified100.0%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]

    if 5.79999999999999977e41 < y

    1. Initial program 40.8%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg40.8%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def40.8%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac40.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg40.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in40.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg40.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative40.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg40.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified40.8%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]
    4. Taylor expanded in y around inf 98.3%

      \[\leadsto 1 - \color{blue}{\left(\log \left(x - 1\right) + \log \left(\frac{1}{y}\right)\right)} \]
    5. Step-by-step derivation
      1. log-rec98.3%

        \[\leadsto 1 - \left(\log \left(x - 1\right) + \color{blue}{\left(-\log y\right)}\right) \]
      2. unsub-neg98.3%

        \[\leadsto 1 - \color{blue}{\left(\log \left(x - 1\right) - \log y\right)} \]
      3. sub-neg98.3%

        \[\leadsto 1 - \left(\log \color{blue}{\left(x + \left(-1\right)\right)} - \log y\right) \]
      4. metadata-eval98.3%

        \[\leadsto 1 - \left(\log \left(x + \color{blue}{-1}\right) - \log y\right) \]
      5. +-commutative98.3%

        \[\leadsto 1 - \left(\log \color{blue}{\left(-1 + x\right)} - \log y\right) \]
    6. Simplified98.3%

      \[\leadsto 1 - \color{blue}{\left(\log \left(-1 + x\right) - \log y\right)} \]
  3. Recombined 3 regimes into one program.
  4. Final simplification99.6%

    \[\leadsto \begin{array}{l} \mathbf{if}\;y \leq -2000:\\ \;\;\;\;1 + \left(\left(\left(\frac{-1}{y} - \frac{0.5}{y \cdot y}\right) - \left(\log \left(\frac{-1}{y}\right) + \frac{0.3333333333333333}{{y}^{3}}\right)\right) - \mathsf{log1p}\left(-x\right)\right)\\ \mathbf{elif}\;y \leq 5.8 \cdot 10^{+41}:\\ \;\;\;\;1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)\\ \mathbf{else}:\\ \;\;\;\;1 + \left(\log y - \log \left(x + -1\right)\right)\\ \end{array} \]

Alternative 3: 99.7% accurate, 0.5× speedup?

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;y \leq -16000:\\ \;\;\;\;1 + \left(\left(\left(\frac{-1}{y} - \frac{0.5}{y \cdot y}\right) - \mathsf{log1p}\left(-x\right)\right) - \log \left(\frac{-1}{y}\right)\right)\\ \mathbf{elif}\;y \leq 9 \cdot 10^{+40}:\\ \;\;\;\;1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)\\ \mathbf{else}:\\ \;\;\;\;1 + \left(\log y - \log \left(x + -1\right)\right)\\ \end{array} \end{array} \]
(FPCore (x y)
 :precision binary64
 (if (<= y -16000.0)
   (+
    1.0
    (- (- (- (/ -1.0 y) (/ 0.5 (* y y))) (log1p (- x))) (log (/ -1.0 y))))
   (if (<= y 9e+40)
     (- 1.0 (log1p (/ (- y x) (- 1.0 y))))
     (+ 1.0 (- (log y) (log (+ x -1.0)))))))
double code(double x, double y) {
	double tmp;
	if (y <= -16000.0) {
		tmp = 1.0 + ((((-1.0 / y) - (0.5 / (y * y))) - log1p(-x)) - log((-1.0 / y)));
	} else if (y <= 9e+40) {
		tmp = 1.0 - log1p(((y - x) / (1.0 - y)));
	} else {
		tmp = 1.0 + (log(y) - log((x + -1.0)));
	}
	return tmp;
}
public static double code(double x, double y) {
	double tmp;
	if (y <= -16000.0) {
		tmp = 1.0 + ((((-1.0 / y) - (0.5 / (y * y))) - Math.log1p(-x)) - Math.log((-1.0 / y)));
	} else if (y <= 9e+40) {
		tmp = 1.0 - Math.log1p(((y - x) / (1.0 - y)));
	} else {
		tmp = 1.0 + (Math.log(y) - Math.log((x + -1.0)));
	}
	return tmp;
}
def code(x, y):
	tmp = 0
	if y <= -16000.0:
		tmp = 1.0 + ((((-1.0 / y) - (0.5 / (y * y))) - math.log1p(-x)) - math.log((-1.0 / y)))
	elif y <= 9e+40:
		tmp = 1.0 - math.log1p(((y - x) / (1.0 - y)))
	else:
		tmp = 1.0 + (math.log(y) - math.log((x + -1.0)))
	return tmp
function code(x, y)
	tmp = 0.0
	if (y <= -16000.0)
		tmp = Float64(1.0 + Float64(Float64(Float64(Float64(-1.0 / y) - Float64(0.5 / Float64(y * y))) - log1p(Float64(-x))) - log(Float64(-1.0 / y))));
	elseif (y <= 9e+40)
		tmp = Float64(1.0 - log1p(Float64(Float64(y - x) / Float64(1.0 - y))));
	else
		tmp = Float64(1.0 + Float64(log(y) - log(Float64(x + -1.0))));
	end
	return tmp
end
code[x_, y_] := If[LessEqual[y, -16000.0], N[(1.0 + N[(N[(N[(N[(-1.0 / y), $MachinePrecision] - N[(0.5 / N[(y * y), $MachinePrecision]), $MachinePrecision]), $MachinePrecision] - N[Log[1 + (-x)], $MachinePrecision]), $MachinePrecision] - N[Log[N[(-1.0 / y), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]), $MachinePrecision], If[LessEqual[y, 9e+40], N[(1.0 - N[Log[1 + N[(N[(y - x), $MachinePrecision] / N[(1.0 - y), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision], N[(1.0 + N[(N[Log[y], $MachinePrecision] - N[Log[N[(x + -1.0), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]), $MachinePrecision]]]
\begin{array}{l}

\\
\begin{array}{l}
\mathbf{if}\;y \leq -16000:\\
\;\;\;\;1 + \left(\left(\left(\frac{-1}{y} - \frac{0.5}{y \cdot y}\right) - \mathsf{log1p}\left(-x\right)\right) - \log \left(\frac{-1}{y}\right)\right)\\

\mathbf{elif}\;y \leq 9 \cdot 10^{+40}:\\
\;\;\;\;1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)\\

\mathbf{else}:\\
\;\;\;\;1 + \left(\log y - \log \left(x + -1\right)\right)\\


\end{array}
\end{array}
Derivation
  1. Split input into 3 regimes
  2. if y < -16000

    1. Initial program 23.5%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg23.5%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def23.5%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified23.5%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]
    4. Step-by-step derivation
      1. flip--23.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{y - x}{\color{blue}{\frac{1 \cdot 1 - y \cdot y}{1 + y}}}\right) \]
      2. associate-/r/24.2%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{y - x}{1 \cdot 1 - y \cdot y} \cdot \left(1 + y\right)}\right) \]
      3. metadata-eval24.2%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{y - x}{\color{blue}{1} - y \cdot y} \cdot \left(1 + y\right)\right) \]
      4. +-commutative24.2%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{y - x}{1 - y \cdot y} \cdot \color{blue}{\left(y + 1\right)}\right) \]
    5. Applied egg-rr24.2%

      \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{y - x}{1 - y \cdot y} \cdot \left(y + 1\right)}\right) \]
    6. Taylor expanded in y around -inf 99.4%

      \[\leadsto 1 - \color{blue}{\left(\log \left(1 + -1 \cdot x\right) + \left(\log \left(\frac{-1}{y}\right) + \left(0.5 \cdot \frac{1}{{y}^{2}} + \frac{1}{y}\right)\right)\right)} \]
    7. Step-by-step derivation
      1. +-commutative99.4%

        \[\leadsto 1 - \left(\log \left(1 + -1 \cdot x\right) + \color{blue}{\left(\left(0.5 \cdot \frac{1}{{y}^{2}} + \frac{1}{y}\right) + \log \left(\frac{-1}{y}\right)\right)}\right) \]
      2. associate-+r+99.4%

        \[\leadsto 1 - \color{blue}{\left(\left(\log \left(1 + -1 \cdot x\right) + \left(0.5 \cdot \frac{1}{{y}^{2}} + \frac{1}{y}\right)\right) + \log \left(\frac{-1}{y}\right)\right)} \]
      3. log1p-def99.4%

        \[\leadsto 1 - \left(\left(\color{blue}{\mathsf{log1p}\left(-1 \cdot x\right)} + \left(0.5 \cdot \frac{1}{{y}^{2}} + \frac{1}{y}\right)\right) + \log \left(\frac{-1}{y}\right)\right) \]
      4. mul-1-neg99.4%

        \[\leadsto 1 - \left(\left(\mathsf{log1p}\left(\color{blue}{-x}\right) + \left(0.5 \cdot \frac{1}{{y}^{2}} + \frac{1}{y}\right)\right) + \log \left(\frac{-1}{y}\right)\right) \]
      5. +-commutative99.4%

        \[\leadsto 1 - \left(\left(\mathsf{log1p}\left(-x\right) + \color{blue}{\left(\frac{1}{y} + 0.5 \cdot \frac{1}{{y}^{2}}\right)}\right) + \log \left(\frac{-1}{y}\right)\right) \]
      6. associate-*r/99.4%

        \[\leadsto 1 - \left(\left(\mathsf{log1p}\left(-x\right) + \left(\frac{1}{y} + \color{blue}{\frac{0.5 \cdot 1}{{y}^{2}}}\right)\right) + \log \left(\frac{-1}{y}\right)\right) \]
      7. metadata-eval99.4%

        \[\leadsto 1 - \left(\left(\mathsf{log1p}\left(-x\right) + \left(\frac{1}{y} + \frac{\color{blue}{0.5}}{{y}^{2}}\right)\right) + \log \left(\frac{-1}{y}\right)\right) \]
      8. unpow299.4%

        \[\leadsto 1 - \left(\left(\mathsf{log1p}\left(-x\right) + \left(\frac{1}{y} + \frac{0.5}{\color{blue}{y \cdot y}}\right)\right) + \log \left(\frac{-1}{y}\right)\right) \]
    8. Simplified99.4%

      \[\leadsto 1 - \color{blue}{\left(\left(\mathsf{log1p}\left(-x\right) + \left(\frac{1}{y} + \frac{0.5}{y \cdot y}\right)\right) + \log \left(\frac{-1}{y}\right)\right)} \]

    if -16000 < y < 9.00000000000000064e40

    1. Initial program 100.0%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg100.0%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def100.0%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified100.0%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]

    if 9.00000000000000064e40 < y

    1. Initial program 40.8%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg40.8%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def40.8%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac40.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg40.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in40.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg40.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative40.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg40.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified40.8%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]
    4. Taylor expanded in y around inf 98.3%

      \[\leadsto 1 - \color{blue}{\left(\log \left(x - 1\right) + \log \left(\frac{1}{y}\right)\right)} \]
    5. Step-by-step derivation
      1. log-rec98.3%

        \[\leadsto 1 - \left(\log \left(x - 1\right) + \color{blue}{\left(-\log y\right)}\right) \]
      2. unsub-neg98.3%

        \[\leadsto 1 - \color{blue}{\left(\log \left(x - 1\right) - \log y\right)} \]
      3. sub-neg98.3%

        \[\leadsto 1 - \left(\log \color{blue}{\left(x + \left(-1\right)\right)} - \log y\right) \]
      4. metadata-eval98.3%

        \[\leadsto 1 - \left(\log \left(x + \color{blue}{-1}\right) - \log y\right) \]
      5. +-commutative98.3%

        \[\leadsto 1 - \left(\log \color{blue}{\left(-1 + x\right)} - \log y\right) \]
    6. Simplified98.3%

      \[\leadsto 1 - \color{blue}{\left(\log \left(-1 + x\right) - \log y\right)} \]
  3. Recombined 3 regimes into one program.
  4. Final simplification99.6%

    \[\leadsto \begin{array}{l} \mathbf{if}\;y \leq -16000:\\ \;\;\;\;1 + \left(\left(\left(\frac{-1}{y} - \frac{0.5}{y \cdot y}\right) - \mathsf{log1p}\left(-x\right)\right) - \log \left(\frac{-1}{y}\right)\right)\\ \mathbf{elif}\;y \leq 9 \cdot 10^{+40}:\\ \;\;\;\;1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)\\ \mathbf{else}:\\ \;\;\;\;1 + \left(\log y - \log \left(x + -1\right)\right)\\ \end{array} \]

Alternative 4: 99.6% accurate, 0.5× speedup?

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;y \leq -51000000:\\ \;\;\;\;1 - \left(\mathsf{log1p}\left(-x\right) + \left(\log \left(\frac{-1}{y}\right) + \frac{1}{y}\right)\right)\\ \mathbf{elif}\;y \leq 7.8 \cdot 10^{+51}:\\ \;\;\;\;1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)\\ \mathbf{else}:\\ \;\;\;\;1 + \left(\log y - \log \left(x + -1\right)\right)\\ \end{array} \end{array} \]
(FPCore (x y)
 :precision binary64
 (if (<= y -51000000.0)
   (- 1.0 (+ (log1p (- x)) (+ (log (/ -1.0 y)) (/ 1.0 y))))
   (if (<= y 7.8e+51)
     (- 1.0 (log1p (/ (- y x) (- 1.0 y))))
     (+ 1.0 (- (log y) (log (+ x -1.0)))))))
double code(double x, double y) {
	double tmp;
	if (y <= -51000000.0) {
		tmp = 1.0 - (log1p(-x) + (log((-1.0 / y)) + (1.0 / y)));
	} else if (y <= 7.8e+51) {
		tmp = 1.0 - log1p(((y - x) / (1.0 - y)));
	} else {
		tmp = 1.0 + (log(y) - log((x + -1.0)));
	}
	return tmp;
}
public static double code(double x, double y) {
	double tmp;
	if (y <= -51000000.0) {
		tmp = 1.0 - (Math.log1p(-x) + (Math.log((-1.0 / y)) + (1.0 / y)));
	} else if (y <= 7.8e+51) {
		tmp = 1.0 - Math.log1p(((y - x) / (1.0 - y)));
	} else {
		tmp = 1.0 + (Math.log(y) - Math.log((x + -1.0)));
	}
	return tmp;
}
def code(x, y):
	tmp = 0
	if y <= -51000000.0:
		tmp = 1.0 - (math.log1p(-x) + (math.log((-1.0 / y)) + (1.0 / y)))
	elif y <= 7.8e+51:
		tmp = 1.0 - math.log1p(((y - x) / (1.0 - y)))
	else:
		tmp = 1.0 + (math.log(y) - math.log((x + -1.0)))
	return tmp
function code(x, y)
	tmp = 0.0
	if (y <= -51000000.0)
		tmp = Float64(1.0 - Float64(log1p(Float64(-x)) + Float64(log(Float64(-1.0 / y)) + Float64(1.0 / y))));
	elseif (y <= 7.8e+51)
		tmp = Float64(1.0 - log1p(Float64(Float64(y - x) / Float64(1.0 - y))));
	else
		tmp = Float64(1.0 + Float64(log(y) - log(Float64(x + -1.0))));
	end
	return tmp
end
code[x_, y_] := If[LessEqual[y, -51000000.0], N[(1.0 - N[(N[Log[1 + (-x)], $MachinePrecision] + N[(N[Log[N[(-1.0 / y), $MachinePrecision]], $MachinePrecision] + N[(1.0 / y), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]), $MachinePrecision], If[LessEqual[y, 7.8e+51], N[(1.0 - N[Log[1 + N[(N[(y - x), $MachinePrecision] / N[(1.0 - y), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision], N[(1.0 + N[(N[Log[y], $MachinePrecision] - N[Log[N[(x + -1.0), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]), $MachinePrecision]]]
\begin{array}{l}

\\
\begin{array}{l}
\mathbf{if}\;y \leq -51000000:\\
\;\;\;\;1 - \left(\mathsf{log1p}\left(-x\right) + \left(\log \left(\frac{-1}{y}\right) + \frac{1}{y}\right)\right)\\

\mathbf{elif}\;y \leq 7.8 \cdot 10^{+51}:\\
\;\;\;\;1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)\\

\mathbf{else}:\\
\;\;\;\;1 + \left(\log y - \log \left(x + -1\right)\right)\\


\end{array}
\end{array}
Derivation
  1. Split input into 3 regimes
  2. if y < -5.1e7

    1. Initial program 20.0%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg20.0%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def20.0%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac20.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg20.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in20.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg20.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative20.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg20.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified20.0%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]
    4. Step-by-step derivation
      1. flip--19.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{y - x}{\color{blue}{\frac{1 \cdot 1 - y \cdot y}{1 + y}}}\right) \]
      2. associate-/r/20.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{y - x}{1 \cdot 1 - y \cdot y} \cdot \left(1 + y\right)}\right) \]
      3. metadata-eval20.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{y - x}{\color{blue}{1} - y \cdot y} \cdot \left(1 + y\right)\right) \]
      4. +-commutative20.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{y - x}{1 - y \cdot y} \cdot \color{blue}{\left(y + 1\right)}\right) \]
    5. Applied egg-rr20.8%

      \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{y - x}{1 - y \cdot y} \cdot \left(y + 1\right)}\right) \]
    6. Taylor expanded in y around -inf 99.4%

      \[\leadsto 1 - \color{blue}{\left(\log \left(1 + -1 \cdot x\right) + \left(\log \left(\frac{-1}{y}\right) + \frac{1}{y}\right)\right)} \]
    7. Step-by-step derivation
      1. log1p-def99.4%

        \[\leadsto 1 - \left(\color{blue}{\mathsf{log1p}\left(-1 \cdot x\right)} + \left(\log \left(\frac{-1}{y}\right) + \frac{1}{y}\right)\right) \]
      2. mul-1-neg99.4%

        \[\leadsto 1 - \left(\mathsf{log1p}\left(\color{blue}{-x}\right) + \left(\log \left(\frac{-1}{y}\right) + \frac{1}{y}\right)\right) \]
      3. +-commutative99.4%

        \[\leadsto 1 - \left(\mathsf{log1p}\left(-x\right) + \color{blue}{\left(\frac{1}{y} + \log \left(\frac{-1}{y}\right)\right)}\right) \]
    8. Simplified99.4%

      \[\leadsto 1 - \color{blue}{\left(\mathsf{log1p}\left(-x\right) + \left(\frac{1}{y} + \log \left(\frac{-1}{y}\right)\right)\right)} \]

    if -5.1e7 < y < 7.79999999999999968e51

    1. Initial program 99.7%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg99.7%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def99.8%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac99.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg99.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in99.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg99.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative99.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg99.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified99.8%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]

    if 7.79999999999999968e51 < y

    1. Initial program 40.8%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg40.8%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def40.8%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac40.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg40.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in40.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg40.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative40.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg40.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified40.8%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]
    4. Taylor expanded in y around inf 98.3%

      \[\leadsto 1 - \color{blue}{\left(\log \left(x - 1\right) + \log \left(\frac{1}{y}\right)\right)} \]
    5. Step-by-step derivation
      1. log-rec98.3%

        \[\leadsto 1 - \left(\log \left(x - 1\right) + \color{blue}{\left(-\log y\right)}\right) \]
      2. unsub-neg98.3%

        \[\leadsto 1 - \color{blue}{\left(\log \left(x - 1\right) - \log y\right)} \]
      3. sub-neg98.3%

        \[\leadsto 1 - \left(\log \color{blue}{\left(x + \left(-1\right)\right)} - \log y\right) \]
      4. metadata-eval98.3%

        \[\leadsto 1 - \left(\log \left(x + \color{blue}{-1}\right) - \log y\right) \]
      5. +-commutative98.3%

        \[\leadsto 1 - \left(\log \color{blue}{\left(-1 + x\right)} - \log y\right) \]
    6. Simplified98.3%

      \[\leadsto 1 - \color{blue}{\left(\log \left(-1 + x\right) - \log y\right)} \]
  3. Recombined 3 regimes into one program.
  4. Final simplification99.5%

    \[\leadsto \begin{array}{l} \mathbf{if}\;y \leq -51000000:\\ \;\;\;\;1 - \left(\mathsf{log1p}\left(-x\right) + \left(\log \left(\frac{-1}{y}\right) + \frac{1}{y}\right)\right)\\ \mathbf{elif}\;y \leq 7.8 \cdot 10^{+51}:\\ \;\;\;\;1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)\\ \mathbf{else}:\\ \;\;\;\;1 + \left(\log y - \log \left(x + -1\right)\right)\\ \end{array} \]

Alternative 5: 99.5% accurate, 0.5× speedup?

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;y \leq -900000000:\\ \;\;\;\;1 - \left(\mathsf{log1p}\left(-x\right) + \log \left(\frac{-1}{y}\right)\right)\\ \mathbf{elif}\;y \leq 1.46 \cdot 10^{+40}:\\ \;\;\;\;1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)\\ \mathbf{else}:\\ \;\;\;\;1 + \left(\log y - \log \left(x + -1\right)\right)\\ \end{array} \end{array} \]
(FPCore (x y)
 :precision binary64
 (if (<= y -900000000.0)
   (- 1.0 (+ (log1p (- x)) (log (/ -1.0 y))))
   (if (<= y 1.46e+40)
     (- 1.0 (log1p (/ (- y x) (- 1.0 y))))
     (+ 1.0 (- (log y) (log (+ x -1.0)))))))
double code(double x, double y) {
	double tmp;
	if (y <= -900000000.0) {
		tmp = 1.0 - (log1p(-x) + log((-1.0 / y)));
	} else if (y <= 1.46e+40) {
		tmp = 1.0 - log1p(((y - x) / (1.0 - y)));
	} else {
		tmp = 1.0 + (log(y) - log((x + -1.0)));
	}
	return tmp;
}
public static double code(double x, double y) {
	double tmp;
	if (y <= -900000000.0) {
		tmp = 1.0 - (Math.log1p(-x) + Math.log((-1.0 / y)));
	} else if (y <= 1.46e+40) {
		tmp = 1.0 - Math.log1p(((y - x) / (1.0 - y)));
	} else {
		tmp = 1.0 + (Math.log(y) - Math.log((x + -1.0)));
	}
	return tmp;
}
def code(x, y):
	tmp = 0
	if y <= -900000000.0:
		tmp = 1.0 - (math.log1p(-x) + math.log((-1.0 / y)))
	elif y <= 1.46e+40:
		tmp = 1.0 - math.log1p(((y - x) / (1.0 - y)))
	else:
		tmp = 1.0 + (math.log(y) - math.log((x + -1.0)))
	return tmp
function code(x, y)
	tmp = 0.0
	if (y <= -900000000.0)
		tmp = Float64(1.0 - Float64(log1p(Float64(-x)) + log(Float64(-1.0 / y))));
	elseif (y <= 1.46e+40)
		tmp = Float64(1.0 - log1p(Float64(Float64(y - x) / Float64(1.0 - y))));
	else
		tmp = Float64(1.0 + Float64(log(y) - log(Float64(x + -1.0))));
	end
	return tmp
end
code[x_, y_] := If[LessEqual[y, -900000000.0], N[(1.0 - N[(N[Log[1 + (-x)], $MachinePrecision] + N[Log[N[(-1.0 / y), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]), $MachinePrecision], If[LessEqual[y, 1.46e+40], N[(1.0 - N[Log[1 + N[(N[(y - x), $MachinePrecision] / N[(1.0 - y), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision], N[(1.0 + N[(N[Log[y], $MachinePrecision] - N[Log[N[(x + -1.0), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]), $MachinePrecision]]]
\begin{array}{l}

\\
\begin{array}{l}
\mathbf{if}\;y \leq -900000000:\\
\;\;\;\;1 - \left(\mathsf{log1p}\left(-x\right) + \log \left(\frac{-1}{y}\right)\right)\\

\mathbf{elif}\;y \leq 1.46 \cdot 10^{+40}:\\
\;\;\;\;1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)\\

\mathbf{else}:\\
\;\;\;\;1 + \left(\log y - \log \left(x + -1\right)\right)\\


\end{array}
\end{array}
Derivation
  1. Split input into 3 regimes
  2. if y < -9e8

    1. Initial program 20.0%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg20.0%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def20.0%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac20.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg20.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in20.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg20.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative20.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg20.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified20.0%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]
    4. Taylor expanded in y around -inf 99.1%

      \[\leadsto 1 - \color{blue}{\left(\log \left(-1 \cdot \left(x - 1\right)\right) + \log \left(\frac{-1}{y}\right)\right)} \]
    5. Step-by-step derivation
      1. sub-neg99.1%

        \[\leadsto 1 - \left(\log \left(-1 \cdot \color{blue}{\left(x + \left(-1\right)\right)}\right) + \log \left(\frac{-1}{y}\right)\right) \]
      2. metadata-eval99.1%

        \[\leadsto 1 - \left(\log \left(-1 \cdot \left(x + \color{blue}{-1}\right)\right) + \log \left(\frac{-1}{y}\right)\right) \]
      3. distribute-lft-in99.1%

        \[\leadsto 1 - \left(\log \color{blue}{\left(-1 \cdot x + -1 \cdot -1\right)} + \log \left(\frac{-1}{y}\right)\right) \]
      4. metadata-eval99.1%

        \[\leadsto 1 - \left(\log \left(-1 \cdot x + \color{blue}{1}\right) + \log \left(\frac{-1}{y}\right)\right) \]
      5. +-commutative99.1%

        \[\leadsto 1 - \left(\log \color{blue}{\left(1 + -1 \cdot x\right)} + \log \left(\frac{-1}{y}\right)\right) \]
      6. log1p-def99.1%

        \[\leadsto 1 - \left(\color{blue}{\mathsf{log1p}\left(-1 \cdot x\right)} + \log \left(\frac{-1}{y}\right)\right) \]
      7. mul-1-neg99.1%

        \[\leadsto 1 - \left(\mathsf{log1p}\left(\color{blue}{-x}\right) + \log \left(\frac{-1}{y}\right)\right) \]
    6. Simplified99.1%

      \[\leadsto 1 - \color{blue}{\left(\mathsf{log1p}\left(-x\right) + \log \left(\frac{-1}{y}\right)\right)} \]

    if -9e8 < y < 1.46e40

    1. Initial program 99.7%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg99.7%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def99.8%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac99.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg99.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in99.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg99.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative99.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg99.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified99.8%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]

    if 1.46e40 < y

    1. Initial program 40.8%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg40.8%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def40.8%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac40.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg40.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in40.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg40.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative40.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg40.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified40.8%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]
    4. Taylor expanded in y around inf 98.3%

      \[\leadsto 1 - \color{blue}{\left(\log \left(x - 1\right) + \log \left(\frac{1}{y}\right)\right)} \]
    5. Step-by-step derivation
      1. log-rec98.3%

        \[\leadsto 1 - \left(\log \left(x - 1\right) + \color{blue}{\left(-\log y\right)}\right) \]
      2. unsub-neg98.3%

        \[\leadsto 1 - \color{blue}{\left(\log \left(x - 1\right) - \log y\right)} \]
      3. sub-neg98.3%

        \[\leadsto 1 - \left(\log \color{blue}{\left(x + \left(-1\right)\right)} - \log y\right) \]
      4. metadata-eval98.3%

        \[\leadsto 1 - \left(\log \left(x + \color{blue}{-1}\right) - \log y\right) \]
      5. +-commutative98.3%

        \[\leadsto 1 - \left(\log \color{blue}{\left(-1 + x\right)} - \log y\right) \]
    6. Simplified98.3%

      \[\leadsto 1 - \color{blue}{\left(\log \left(-1 + x\right) - \log y\right)} \]
  3. Recombined 3 regimes into one program.
  4. Final simplification99.4%

    \[\leadsto \begin{array}{l} \mathbf{if}\;y \leq -900000000:\\ \;\;\;\;1 - \left(\mathsf{log1p}\left(-x\right) + \log \left(\frac{-1}{y}\right)\right)\\ \mathbf{elif}\;y \leq 1.46 \cdot 10^{+40}:\\ \;\;\;\;1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)\\ \mathbf{else}:\\ \;\;\;\;1 + \left(\log y - \log \left(x + -1\right)\right)\\ \end{array} \]

Alternative 6: 90.7% accurate, 0.9× speedup?

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;\frac{x - y}{1 - y} \leq 0.999999999996:\\ \;\;\;\;1 - \mathsf{log1p}\left(\left(y - x\right) \cdot \frac{1}{1 - y}\right)\\ \mathbf{else}:\\ \;\;\;\;1 - \log \left(\frac{-1}{y}\right)\\ \end{array} \end{array} \]
(FPCore (x y)
 :precision binary64
 (if (<= (/ (- x y) (- 1.0 y)) 0.999999999996)
   (- 1.0 (log1p (* (- y x) (/ 1.0 (- 1.0 y)))))
   (- 1.0 (log (/ -1.0 y)))))
double code(double x, double y) {
	double tmp;
	if (((x - y) / (1.0 - y)) <= 0.999999999996) {
		tmp = 1.0 - log1p(((y - x) * (1.0 / (1.0 - y))));
	} else {
		tmp = 1.0 - log((-1.0 / y));
	}
	return tmp;
}
public static double code(double x, double y) {
	double tmp;
	if (((x - y) / (1.0 - y)) <= 0.999999999996) {
		tmp = 1.0 - Math.log1p(((y - x) * (1.0 / (1.0 - y))));
	} else {
		tmp = 1.0 - Math.log((-1.0 / y));
	}
	return tmp;
}
def code(x, y):
	tmp = 0
	if ((x - y) / (1.0 - y)) <= 0.999999999996:
		tmp = 1.0 - math.log1p(((y - x) * (1.0 / (1.0 - y))))
	else:
		tmp = 1.0 - math.log((-1.0 / y))
	return tmp
function code(x, y)
	tmp = 0.0
	if (Float64(Float64(x - y) / Float64(1.0 - y)) <= 0.999999999996)
		tmp = Float64(1.0 - log1p(Float64(Float64(y - x) * Float64(1.0 / Float64(1.0 - y)))));
	else
		tmp = Float64(1.0 - log(Float64(-1.0 / y)));
	end
	return tmp
end
code[x_, y_] := If[LessEqual[N[(N[(x - y), $MachinePrecision] / N[(1.0 - y), $MachinePrecision]), $MachinePrecision], 0.999999999996], N[(1.0 - N[Log[1 + N[(N[(y - x), $MachinePrecision] * N[(1.0 / N[(1.0 - y), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision], N[(1.0 - N[Log[N[(-1.0 / y), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]]
\begin{array}{l}

\\
\begin{array}{l}
\mathbf{if}\;\frac{x - y}{1 - y} \leq 0.999999999996:\\
\;\;\;\;1 - \mathsf{log1p}\left(\left(y - x\right) \cdot \frac{1}{1 - y}\right)\\

\mathbf{else}:\\
\;\;\;\;1 - \log \left(\frac{-1}{y}\right)\\


\end{array}
\end{array}
Derivation
  1. Split input into 2 regimes
  2. if (/.f64 (-.f64 x y) (-.f64 1 y)) < 0.999999999995999977

    1. Initial program 99.1%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg99.1%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def99.1%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac99.1%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg99.1%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in99.1%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg99.1%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative99.1%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg99.1%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified99.1%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]
    4. Step-by-step derivation
      1. clear-num99.1%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{1}{\frac{1 - y}{y - x}}}\right) \]
      2. associate-/r/99.1%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{1}{1 - y} \cdot \left(y - x\right)}\right) \]
    5. Applied egg-rr99.1%

      \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{1}{1 - y} \cdot \left(y - x\right)}\right) \]

    if 0.999999999995999977 < (/.f64 (-.f64 x y) (-.f64 1 y))

    1. Initial program 3.8%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg3.8%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def3.8%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac3.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg3.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in3.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg3.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative3.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg3.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified3.8%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]
    4. Taylor expanded in y around -inf 80.7%

      \[\leadsto 1 - \color{blue}{\left(\log \left(-1 \cdot \left(x - 1\right)\right) + \log \left(\frac{-1}{y}\right)\right)} \]
    5. Step-by-step derivation
      1. sub-neg80.7%

        \[\leadsto 1 - \left(\log \left(-1 \cdot \color{blue}{\left(x + \left(-1\right)\right)}\right) + \log \left(\frac{-1}{y}\right)\right) \]
      2. metadata-eval80.7%

        \[\leadsto 1 - \left(\log \left(-1 \cdot \left(x + \color{blue}{-1}\right)\right) + \log \left(\frac{-1}{y}\right)\right) \]
      3. distribute-lft-in80.7%

        \[\leadsto 1 - \left(\log \color{blue}{\left(-1 \cdot x + -1 \cdot -1\right)} + \log \left(\frac{-1}{y}\right)\right) \]
      4. metadata-eval80.7%

        \[\leadsto 1 - \left(\log \left(-1 \cdot x + \color{blue}{1}\right) + \log \left(\frac{-1}{y}\right)\right) \]
      5. +-commutative80.7%

        \[\leadsto 1 - \left(\log \color{blue}{\left(1 + -1 \cdot x\right)} + \log \left(\frac{-1}{y}\right)\right) \]
      6. log1p-def80.7%

        \[\leadsto 1 - \left(\color{blue}{\mathsf{log1p}\left(-1 \cdot x\right)} + \log \left(\frac{-1}{y}\right)\right) \]
      7. mul-1-neg80.7%

        \[\leadsto 1 - \left(\mathsf{log1p}\left(\color{blue}{-x}\right) + \log \left(\frac{-1}{y}\right)\right) \]
    6. Simplified80.7%

      \[\leadsto 1 - \color{blue}{\left(\mathsf{log1p}\left(-x\right) + \log \left(\frac{-1}{y}\right)\right)} \]
    7. Taylor expanded in x around 0 66.5%

      \[\leadsto 1 - \color{blue}{\log \left(\frac{-1}{y}\right)} \]
  3. Recombined 2 regimes into one program.
  4. Final simplification89.1%

    \[\leadsto \begin{array}{l} \mathbf{if}\;\frac{x - y}{1 - y} \leq 0.999999999996:\\ \;\;\;\;1 - \mathsf{log1p}\left(\left(y - x\right) \cdot \frac{1}{1 - y}\right)\\ \mathbf{else}:\\ \;\;\;\;1 - \log \left(\frac{-1}{y}\right)\\ \end{array} \]

Alternative 7: 90.7% accurate, 0.9× speedup?

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;\frac{x - y}{1 - y} \leq 0.999999999996:\\ \;\;\;\;1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)\\ \mathbf{else}:\\ \;\;\;\;1 - \log \left(\frac{-1}{y}\right)\\ \end{array} \end{array} \]
(FPCore (x y)
 :precision binary64
 (if (<= (/ (- x y) (- 1.0 y)) 0.999999999996)
   (- 1.0 (log1p (/ (- y x) (- 1.0 y))))
   (- 1.0 (log (/ -1.0 y)))))
double code(double x, double y) {
	double tmp;
	if (((x - y) / (1.0 - y)) <= 0.999999999996) {
		tmp = 1.0 - log1p(((y - x) / (1.0 - y)));
	} else {
		tmp = 1.0 - log((-1.0 / y));
	}
	return tmp;
}
public static double code(double x, double y) {
	double tmp;
	if (((x - y) / (1.0 - y)) <= 0.999999999996) {
		tmp = 1.0 - Math.log1p(((y - x) / (1.0 - y)));
	} else {
		tmp = 1.0 - Math.log((-1.0 / y));
	}
	return tmp;
}
def code(x, y):
	tmp = 0
	if ((x - y) / (1.0 - y)) <= 0.999999999996:
		tmp = 1.0 - math.log1p(((y - x) / (1.0 - y)))
	else:
		tmp = 1.0 - math.log((-1.0 / y))
	return tmp
function code(x, y)
	tmp = 0.0
	if (Float64(Float64(x - y) / Float64(1.0 - y)) <= 0.999999999996)
		tmp = Float64(1.0 - log1p(Float64(Float64(y - x) / Float64(1.0 - y))));
	else
		tmp = Float64(1.0 - log(Float64(-1.0 / y)));
	end
	return tmp
end
code[x_, y_] := If[LessEqual[N[(N[(x - y), $MachinePrecision] / N[(1.0 - y), $MachinePrecision]), $MachinePrecision], 0.999999999996], N[(1.0 - N[Log[1 + N[(N[(y - x), $MachinePrecision] / N[(1.0 - y), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision], N[(1.0 - N[Log[N[(-1.0 / y), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]]
\begin{array}{l}

\\
\begin{array}{l}
\mathbf{if}\;\frac{x - y}{1 - y} \leq 0.999999999996:\\
\;\;\;\;1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)\\

\mathbf{else}:\\
\;\;\;\;1 - \log \left(\frac{-1}{y}\right)\\


\end{array}
\end{array}
Derivation
  1. Split input into 2 regimes
  2. if (/.f64 (-.f64 x y) (-.f64 1 y)) < 0.999999999995999977

    1. Initial program 99.1%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg99.1%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def99.1%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac99.1%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg99.1%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in99.1%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg99.1%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative99.1%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg99.1%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified99.1%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]

    if 0.999999999995999977 < (/.f64 (-.f64 x y) (-.f64 1 y))

    1. Initial program 3.8%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg3.8%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def3.8%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac3.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg3.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in3.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg3.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative3.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg3.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified3.8%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]
    4. Taylor expanded in y around -inf 80.7%

      \[\leadsto 1 - \color{blue}{\left(\log \left(-1 \cdot \left(x - 1\right)\right) + \log \left(\frac{-1}{y}\right)\right)} \]
    5. Step-by-step derivation
      1. sub-neg80.7%

        \[\leadsto 1 - \left(\log \left(-1 \cdot \color{blue}{\left(x + \left(-1\right)\right)}\right) + \log \left(\frac{-1}{y}\right)\right) \]
      2. metadata-eval80.7%

        \[\leadsto 1 - \left(\log \left(-1 \cdot \left(x + \color{blue}{-1}\right)\right) + \log \left(\frac{-1}{y}\right)\right) \]
      3. distribute-lft-in80.7%

        \[\leadsto 1 - \left(\log \color{blue}{\left(-1 \cdot x + -1 \cdot -1\right)} + \log \left(\frac{-1}{y}\right)\right) \]
      4. metadata-eval80.7%

        \[\leadsto 1 - \left(\log \left(-1 \cdot x + \color{blue}{1}\right) + \log \left(\frac{-1}{y}\right)\right) \]
      5. +-commutative80.7%

        \[\leadsto 1 - \left(\log \color{blue}{\left(1 + -1 \cdot x\right)} + \log \left(\frac{-1}{y}\right)\right) \]
      6. log1p-def80.7%

        \[\leadsto 1 - \left(\color{blue}{\mathsf{log1p}\left(-1 \cdot x\right)} + \log \left(\frac{-1}{y}\right)\right) \]
      7. mul-1-neg80.7%

        \[\leadsto 1 - \left(\mathsf{log1p}\left(\color{blue}{-x}\right) + \log \left(\frac{-1}{y}\right)\right) \]
    6. Simplified80.7%

      \[\leadsto 1 - \color{blue}{\left(\mathsf{log1p}\left(-x\right) + \log \left(\frac{-1}{y}\right)\right)} \]
    7. Taylor expanded in x around 0 66.5%

      \[\leadsto 1 - \color{blue}{\log \left(\frac{-1}{y}\right)} \]
  3. Recombined 2 regimes into one program.
  4. Final simplification89.0%

    \[\leadsto \begin{array}{l} \mathbf{if}\;\frac{x - y}{1 - y} \leq 0.999999999996:\\ \;\;\;\;1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)\\ \mathbf{else}:\\ \;\;\;\;1 - \log \left(\frac{-1}{y}\right)\\ \end{array} \]

Alternative 8: 84.6% accurate, 1.0× speedup?

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;y \leq -7.8:\\ \;\;\;\;1 - \log \left(\frac{-1}{y}\right)\\ \mathbf{elif}\;y \leq 1:\\ \;\;\;\;1 - \left(y + \mathsf{log1p}\left(-x\right)\right)\\ \mathbf{else}:\\ \;\;\;\;1 - \mathsf{log1p}\left(-1 + \frac{x}{y}\right)\\ \end{array} \end{array} \]
(FPCore (x y)
 :precision binary64
 (if (<= y -7.8)
   (- 1.0 (log (/ -1.0 y)))
   (if (<= y 1.0)
     (- 1.0 (+ y (log1p (- x))))
     (- 1.0 (log1p (+ -1.0 (/ x y)))))))
double code(double x, double y) {
	double tmp;
	if (y <= -7.8) {
		tmp = 1.0 - log((-1.0 / y));
	} else if (y <= 1.0) {
		tmp = 1.0 - (y + log1p(-x));
	} else {
		tmp = 1.0 - log1p((-1.0 + (x / y)));
	}
	return tmp;
}
public static double code(double x, double y) {
	double tmp;
	if (y <= -7.8) {
		tmp = 1.0 - Math.log((-1.0 / y));
	} else if (y <= 1.0) {
		tmp = 1.0 - (y + Math.log1p(-x));
	} else {
		tmp = 1.0 - Math.log1p((-1.0 + (x / y)));
	}
	return tmp;
}
def code(x, y):
	tmp = 0
	if y <= -7.8:
		tmp = 1.0 - math.log((-1.0 / y))
	elif y <= 1.0:
		tmp = 1.0 - (y + math.log1p(-x))
	else:
		tmp = 1.0 - math.log1p((-1.0 + (x / y)))
	return tmp
function code(x, y)
	tmp = 0.0
	if (y <= -7.8)
		tmp = Float64(1.0 - log(Float64(-1.0 / y)));
	elseif (y <= 1.0)
		tmp = Float64(1.0 - Float64(y + log1p(Float64(-x))));
	else
		tmp = Float64(1.0 - log1p(Float64(-1.0 + Float64(x / y))));
	end
	return tmp
end
code[x_, y_] := If[LessEqual[y, -7.8], N[(1.0 - N[Log[N[(-1.0 / y), $MachinePrecision]], $MachinePrecision]), $MachinePrecision], If[LessEqual[y, 1.0], N[(1.0 - N[(y + N[Log[1 + (-x)], $MachinePrecision]), $MachinePrecision]), $MachinePrecision], N[(1.0 - N[Log[1 + N[(-1.0 + N[(x / y), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]]]
\begin{array}{l}

\\
\begin{array}{l}
\mathbf{if}\;y \leq -7.8:\\
\;\;\;\;1 - \log \left(\frac{-1}{y}\right)\\

\mathbf{elif}\;y \leq 1:\\
\;\;\;\;1 - \left(y + \mathsf{log1p}\left(-x\right)\right)\\

\mathbf{else}:\\
\;\;\;\;1 - \mathsf{log1p}\left(-1 + \frac{x}{y}\right)\\


\end{array}
\end{array}
Derivation
  1. Split input into 3 regimes
  2. if y < -7.79999999999999982

    1. Initial program 23.5%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg23.5%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def23.5%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified23.5%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]
    4. Taylor expanded in y around -inf 97.0%

      \[\leadsto 1 - \color{blue}{\left(\log \left(-1 \cdot \left(x - 1\right)\right) + \log \left(\frac{-1}{y}\right)\right)} \]
    5. Step-by-step derivation
      1. sub-neg97.0%

        \[\leadsto 1 - \left(\log \left(-1 \cdot \color{blue}{\left(x + \left(-1\right)\right)}\right) + \log \left(\frac{-1}{y}\right)\right) \]
      2. metadata-eval97.0%

        \[\leadsto 1 - \left(\log \left(-1 \cdot \left(x + \color{blue}{-1}\right)\right) + \log \left(\frac{-1}{y}\right)\right) \]
      3. distribute-lft-in97.0%

        \[\leadsto 1 - \left(\log \color{blue}{\left(-1 \cdot x + -1 \cdot -1\right)} + \log \left(\frac{-1}{y}\right)\right) \]
      4. metadata-eval97.0%

        \[\leadsto 1 - \left(\log \left(-1 \cdot x + \color{blue}{1}\right) + \log \left(\frac{-1}{y}\right)\right) \]
      5. +-commutative97.0%

        \[\leadsto 1 - \left(\log \color{blue}{\left(1 + -1 \cdot x\right)} + \log \left(\frac{-1}{y}\right)\right) \]
      6. log1p-def97.0%

        \[\leadsto 1 - \left(\color{blue}{\mathsf{log1p}\left(-1 \cdot x\right)} + \log \left(\frac{-1}{y}\right)\right) \]
      7. mul-1-neg97.0%

        \[\leadsto 1 - \left(\mathsf{log1p}\left(\color{blue}{-x}\right) + \log \left(\frac{-1}{y}\right)\right) \]
    6. Simplified97.0%

      \[\leadsto 1 - \color{blue}{\left(\mathsf{log1p}\left(-x\right) + \log \left(\frac{-1}{y}\right)\right)} \]
    7. Taylor expanded in x around 0 66.6%

      \[\leadsto 1 - \color{blue}{\log \left(\frac{-1}{y}\right)} \]

    if -7.79999999999999982 < y < 1

    1. Initial program 100.0%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg100.0%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def100.0%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified100.0%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]
    4. Step-by-step derivation
      1. flip--100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{y - x}{\color{blue}{\frac{1 \cdot 1 - y \cdot y}{1 + y}}}\right) \]
      2. associate-/r/100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{y - x}{1 \cdot 1 - y \cdot y} \cdot \left(1 + y\right)}\right) \]
      3. metadata-eval100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{y - x}{\color{blue}{1} - y \cdot y} \cdot \left(1 + y\right)\right) \]
      4. +-commutative100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{y - x}{1 - y \cdot y} \cdot \color{blue}{\left(y + 1\right)}\right) \]
    5. Applied egg-rr100.0%

      \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{y - x}{1 - y \cdot y} \cdot \left(y + 1\right)}\right) \]
    6. Taylor expanded in y around 0 98.5%

      \[\leadsto 1 - \color{blue}{\left(y + \log \left(1 + -1 \cdot x\right)\right)} \]
    7. Step-by-step derivation
      1. log1p-def98.5%

        \[\leadsto 1 - \left(y + \color{blue}{\mathsf{log1p}\left(-1 \cdot x\right)}\right) \]
      2. mul-1-neg98.5%

        \[\leadsto 1 - \left(y + \mathsf{log1p}\left(\color{blue}{-x}\right)\right) \]
    8. Simplified98.5%

      \[\leadsto 1 - \color{blue}{\left(y + \mathsf{log1p}\left(-x\right)\right)} \]

    if 1 < y

    1. Initial program 50.7%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg50.7%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def50.7%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac50.7%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg50.7%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in50.7%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg50.7%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative50.7%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg50.7%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified50.7%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]
    4. Step-by-step derivation
      1. clear-num50.8%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{1}{\frac{1 - y}{y - x}}}\right) \]
      2. associate-/r/52.2%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{1}{1 - y} \cdot \left(y - x\right)}\right) \]
    5. Applied egg-rr52.2%

      \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{1}{1 - y} \cdot \left(y - x\right)}\right) \]
    6. Taylor expanded in y around inf 50.5%

      \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-1}{y}} \cdot \left(y - x\right)\right) \]
    7. Taylor expanded in y around 0 49.1%

      \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{x}{y} - 1}\right) \]
  3. Recombined 3 regimes into one program.
  4. Final simplification82.5%

    \[\leadsto \begin{array}{l} \mathbf{if}\;y \leq -7.8:\\ \;\;\;\;1 - \log \left(\frac{-1}{y}\right)\\ \mathbf{elif}\;y \leq 1:\\ \;\;\;\;1 - \left(y + \mathsf{log1p}\left(-x\right)\right)\\ \mathbf{else}:\\ \;\;\;\;1 - \mathsf{log1p}\left(-1 + \frac{x}{y}\right)\\ \end{array} \]

Alternative 9: 84.7% accurate, 1.0× speedup?

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;y \leq -19:\\ \;\;\;\;1 - \log \left(\frac{-1}{y}\right)\\ \mathbf{elif}\;y \leq 1:\\ \;\;\;\;1 - \left(y + \mathsf{log1p}\left(-x\right)\right)\\ \mathbf{else}:\\ \;\;\;\;1 - \mathsf{log1p}\left(\frac{x}{y}\right)\\ \end{array} \end{array} \]
(FPCore (x y)
 :precision binary64
 (if (<= y -19.0)
   (- 1.0 (log (/ -1.0 y)))
   (if (<= y 1.0) (- 1.0 (+ y (log1p (- x)))) (- 1.0 (log1p (/ x y))))))
double code(double x, double y) {
	double tmp;
	if (y <= -19.0) {
		tmp = 1.0 - log((-1.0 / y));
	} else if (y <= 1.0) {
		tmp = 1.0 - (y + log1p(-x));
	} else {
		tmp = 1.0 - log1p((x / y));
	}
	return tmp;
}
public static double code(double x, double y) {
	double tmp;
	if (y <= -19.0) {
		tmp = 1.0 - Math.log((-1.0 / y));
	} else if (y <= 1.0) {
		tmp = 1.0 - (y + Math.log1p(-x));
	} else {
		tmp = 1.0 - Math.log1p((x / y));
	}
	return tmp;
}
def code(x, y):
	tmp = 0
	if y <= -19.0:
		tmp = 1.0 - math.log((-1.0 / y))
	elif y <= 1.0:
		tmp = 1.0 - (y + math.log1p(-x))
	else:
		tmp = 1.0 - math.log1p((x / y))
	return tmp
function code(x, y)
	tmp = 0.0
	if (y <= -19.0)
		tmp = Float64(1.0 - log(Float64(-1.0 / y)));
	elseif (y <= 1.0)
		tmp = Float64(1.0 - Float64(y + log1p(Float64(-x))));
	else
		tmp = Float64(1.0 - log1p(Float64(x / y)));
	end
	return tmp
end
code[x_, y_] := If[LessEqual[y, -19.0], N[(1.0 - N[Log[N[(-1.0 / y), $MachinePrecision]], $MachinePrecision]), $MachinePrecision], If[LessEqual[y, 1.0], N[(1.0 - N[(y + N[Log[1 + (-x)], $MachinePrecision]), $MachinePrecision]), $MachinePrecision], N[(1.0 - N[Log[1 + N[(x / y), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]]]
\begin{array}{l}

\\
\begin{array}{l}
\mathbf{if}\;y \leq -19:\\
\;\;\;\;1 - \log \left(\frac{-1}{y}\right)\\

\mathbf{elif}\;y \leq 1:\\
\;\;\;\;1 - \left(y + \mathsf{log1p}\left(-x\right)\right)\\

\mathbf{else}:\\
\;\;\;\;1 - \mathsf{log1p}\left(\frac{x}{y}\right)\\


\end{array}
\end{array}
Derivation
  1. Split input into 3 regimes
  2. if y < -19

    1. Initial program 23.5%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg23.5%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def23.5%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified23.5%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]
    4. Taylor expanded in y around -inf 97.0%

      \[\leadsto 1 - \color{blue}{\left(\log \left(-1 \cdot \left(x - 1\right)\right) + \log \left(\frac{-1}{y}\right)\right)} \]
    5. Step-by-step derivation
      1. sub-neg97.0%

        \[\leadsto 1 - \left(\log \left(-1 \cdot \color{blue}{\left(x + \left(-1\right)\right)}\right) + \log \left(\frac{-1}{y}\right)\right) \]
      2. metadata-eval97.0%

        \[\leadsto 1 - \left(\log \left(-1 \cdot \left(x + \color{blue}{-1}\right)\right) + \log \left(\frac{-1}{y}\right)\right) \]
      3. distribute-lft-in97.0%

        \[\leadsto 1 - \left(\log \color{blue}{\left(-1 \cdot x + -1 \cdot -1\right)} + \log \left(\frac{-1}{y}\right)\right) \]
      4. metadata-eval97.0%

        \[\leadsto 1 - \left(\log \left(-1 \cdot x + \color{blue}{1}\right) + \log \left(\frac{-1}{y}\right)\right) \]
      5. +-commutative97.0%

        \[\leadsto 1 - \left(\log \color{blue}{\left(1 + -1 \cdot x\right)} + \log \left(\frac{-1}{y}\right)\right) \]
      6. log1p-def97.0%

        \[\leadsto 1 - \left(\color{blue}{\mathsf{log1p}\left(-1 \cdot x\right)} + \log \left(\frac{-1}{y}\right)\right) \]
      7. mul-1-neg97.0%

        \[\leadsto 1 - \left(\mathsf{log1p}\left(\color{blue}{-x}\right) + \log \left(\frac{-1}{y}\right)\right) \]
    6. Simplified97.0%

      \[\leadsto 1 - \color{blue}{\left(\mathsf{log1p}\left(-x\right) + \log \left(\frac{-1}{y}\right)\right)} \]
    7. Taylor expanded in x around 0 66.6%

      \[\leadsto 1 - \color{blue}{\log \left(\frac{-1}{y}\right)} \]

    if -19 < y < 1

    1. Initial program 100.0%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg100.0%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def100.0%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified100.0%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]
    4. Step-by-step derivation
      1. flip--100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{y - x}{\color{blue}{\frac{1 \cdot 1 - y \cdot y}{1 + y}}}\right) \]
      2. associate-/r/100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{y - x}{1 \cdot 1 - y \cdot y} \cdot \left(1 + y\right)}\right) \]
      3. metadata-eval100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{y - x}{\color{blue}{1} - y \cdot y} \cdot \left(1 + y\right)\right) \]
      4. +-commutative100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{y - x}{1 - y \cdot y} \cdot \color{blue}{\left(y + 1\right)}\right) \]
    5. Applied egg-rr100.0%

      \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{y - x}{1 - y \cdot y} \cdot \left(y + 1\right)}\right) \]
    6. Taylor expanded in y around 0 98.5%

      \[\leadsto 1 - \color{blue}{\left(y + \log \left(1 + -1 \cdot x\right)\right)} \]
    7. Step-by-step derivation
      1. log1p-def98.5%

        \[\leadsto 1 - \left(y + \color{blue}{\mathsf{log1p}\left(-1 \cdot x\right)}\right) \]
      2. mul-1-neg98.5%

        \[\leadsto 1 - \left(y + \mathsf{log1p}\left(\color{blue}{-x}\right)\right) \]
    8. Simplified98.5%

      \[\leadsto 1 - \color{blue}{\left(y + \mathsf{log1p}\left(-x\right)\right)} \]

    if 1 < y

    1. Initial program 50.7%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg50.7%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def50.7%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac50.7%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg50.7%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in50.7%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg50.7%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative50.7%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg50.7%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified50.7%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]
    4. Taylor expanded in x around inf 50.1%

      \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{-1 \cdot \frac{x}{1 - y}}\right) \]
    5. Step-by-step derivation
      1. neg-mul-150.1%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{-\frac{x}{1 - y}}\right) \]
      2. distribute-neg-frac50.1%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-x}{1 - y}}\right) \]
    6. Simplified50.1%

      \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-x}{1 - y}}\right) \]
    7. Taylor expanded in y around inf 48.5%

      \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{x}{y}}\right) \]
  3. Recombined 3 regimes into one program.
  4. Final simplification82.4%

    \[\leadsto \begin{array}{l} \mathbf{if}\;y \leq -19:\\ \;\;\;\;1 - \log \left(\frac{-1}{y}\right)\\ \mathbf{elif}\;y \leq 1:\\ \;\;\;\;1 - \left(y + \mathsf{log1p}\left(-x\right)\right)\\ \mathbf{else}:\\ \;\;\;\;1 - \mathsf{log1p}\left(\frac{x}{y}\right)\\ \end{array} \]

Alternative 10: 84.7% accurate, 1.0× speedup?

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;y \leq -820000000:\\ \;\;\;\;1 - \log \left(\frac{-1}{y}\right)\\ \mathbf{else}:\\ \;\;\;\;1 - \mathsf{log1p}\left(\frac{-x}{1 - y}\right)\\ \end{array} \end{array} \]
(FPCore (x y)
 :precision binary64
 (if (<= y -820000000.0)
   (- 1.0 (log (/ -1.0 y)))
   (- 1.0 (log1p (/ (- x) (- 1.0 y))))))
double code(double x, double y) {
	double tmp;
	if (y <= -820000000.0) {
		tmp = 1.0 - log((-1.0 / y));
	} else {
		tmp = 1.0 - log1p((-x / (1.0 - y)));
	}
	return tmp;
}
public static double code(double x, double y) {
	double tmp;
	if (y <= -820000000.0) {
		tmp = 1.0 - Math.log((-1.0 / y));
	} else {
		tmp = 1.0 - Math.log1p((-x / (1.0 - y)));
	}
	return tmp;
}
def code(x, y):
	tmp = 0
	if y <= -820000000.0:
		tmp = 1.0 - math.log((-1.0 / y))
	else:
		tmp = 1.0 - math.log1p((-x / (1.0 - y)))
	return tmp
function code(x, y)
	tmp = 0.0
	if (y <= -820000000.0)
		tmp = Float64(1.0 - log(Float64(-1.0 / y)));
	else
		tmp = Float64(1.0 - log1p(Float64(Float64(-x) / Float64(1.0 - y))));
	end
	return tmp
end
code[x_, y_] := If[LessEqual[y, -820000000.0], N[(1.0 - N[Log[N[(-1.0 / y), $MachinePrecision]], $MachinePrecision]), $MachinePrecision], N[(1.0 - N[Log[1 + N[((-x) / N[(1.0 - y), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]]
\begin{array}{l}

\\
\begin{array}{l}
\mathbf{if}\;y \leq -820000000:\\
\;\;\;\;1 - \log \left(\frac{-1}{y}\right)\\

\mathbf{else}:\\
\;\;\;\;1 - \mathsf{log1p}\left(\frac{-x}{1 - y}\right)\\


\end{array}
\end{array}
Derivation
  1. Split input into 2 regimes
  2. if y < -8.2e8

    1. Initial program 20.0%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg20.0%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def20.0%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac20.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg20.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in20.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg20.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative20.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg20.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified20.0%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]
    4. Taylor expanded in y around -inf 99.1%

      \[\leadsto 1 - \color{blue}{\left(\log \left(-1 \cdot \left(x - 1\right)\right) + \log \left(\frac{-1}{y}\right)\right)} \]
    5. Step-by-step derivation
      1. sub-neg99.1%

        \[\leadsto 1 - \left(\log \left(-1 \cdot \color{blue}{\left(x + \left(-1\right)\right)}\right) + \log \left(\frac{-1}{y}\right)\right) \]
      2. metadata-eval99.1%

        \[\leadsto 1 - \left(\log \left(-1 \cdot \left(x + \color{blue}{-1}\right)\right) + \log \left(\frac{-1}{y}\right)\right) \]
      3. distribute-lft-in99.1%

        \[\leadsto 1 - \left(\log \color{blue}{\left(-1 \cdot x + -1 \cdot -1\right)} + \log \left(\frac{-1}{y}\right)\right) \]
      4. metadata-eval99.1%

        \[\leadsto 1 - \left(\log \left(-1 \cdot x + \color{blue}{1}\right) + \log \left(\frac{-1}{y}\right)\right) \]
      5. +-commutative99.1%

        \[\leadsto 1 - \left(\log \color{blue}{\left(1 + -1 \cdot x\right)} + \log \left(\frac{-1}{y}\right)\right) \]
      6. log1p-def99.1%

        \[\leadsto 1 - \left(\color{blue}{\mathsf{log1p}\left(-1 \cdot x\right)} + \log \left(\frac{-1}{y}\right)\right) \]
      7. mul-1-neg99.1%

        \[\leadsto 1 - \left(\mathsf{log1p}\left(\color{blue}{-x}\right) + \log \left(\frac{-1}{y}\right)\right) \]
    6. Simplified99.1%

      \[\leadsto 1 - \color{blue}{\left(\mathsf{log1p}\left(-x\right) + \log \left(\frac{-1}{y}\right)\right)} \]
    7. Taylor expanded in x around 0 68.7%

      \[\leadsto 1 - \color{blue}{\log \left(\frac{-1}{y}\right)} \]

    if -8.2e8 < y

    1. Initial program 91.5%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg91.5%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def91.5%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac91.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg91.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in91.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg91.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative91.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg91.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified91.5%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]
    4. Taylor expanded in x around inf 89.3%

      \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{-1 \cdot \frac{x}{1 - y}}\right) \]
    5. Step-by-step derivation
      1. neg-mul-189.3%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{-\frac{x}{1 - y}}\right) \]
      2. distribute-neg-frac89.3%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-x}{1 - y}}\right) \]
    6. Simplified89.3%

      \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-x}{1 - y}}\right) \]
  3. Recombined 2 regimes into one program.
  4. Final simplification83.0%

    \[\leadsto \begin{array}{l} \mathbf{if}\;y \leq -820000000:\\ \;\;\;\;1 - \log \left(\frac{-1}{y}\right)\\ \mathbf{else}:\\ \;\;\;\;1 - \mathsf{log1p}\left(\frac{-x}{1 - y}\right)\\ \end{array} \]

Alternative 11: 84.1% accurate, 1.0× speedup?

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;y \leq -44:\\ \;\;\;\;1 - \log \left(\frac{-1}{y}\right)\\ \mathbf{elif}\;y \leq 1:\\ \;\;\;\;1 - \mathsf{log1p}\left(-x\right)\\ \mathbf{else}:\\ \;\;\;\;1 - \mathsf{log1p}\left(\frac{x}{y}\right)\\ \end{array} \end{array} \]
(FPCore (x y)
 :precision binary64
 (if (<= y -44.0)
   (- 1.0 (log (/ -1.0 y)))
   (if (<= y 1.0) (- 1.0 (log1p (- x))) (- 1.0 (log1p (/ x y))))))
double code(double x, double y) {
	double tmp;
	if (y <= -44.0) {
		tmp = 1.0 - log((-1.0 / y));
	} else if (y <= 1.0) {
		tmp = 1.0 - log1p(-x);
	} else {
		tmp = 1.0 - log1p((x / y));
	}
	return tmp;
}
public static double code(double x, double y) {
	double tmp;
	if (y <= -44.0) {
		tmp = 1.0 - Math.log((-1.0 / y));
	} else if (y <= 1.0) {
		tmp = 1.0 - Math.log1p(-x);
	} else {
		tmp = 1.0 - Math.log1p((x / y));
	}
	return tmp;
}
def code(x, y):
	tmp = 0
	if y <= -44.0:
		tmp = 1.0 - math.log((-1.0 / y))
	elif y <= 1.0:
		tmp = 1.0 - math.log1p(-x)
	else:
		tmp = 1.0 - math.log1p((x / y))
	return tmp
function code(x, y)
	tmp = 0.0
	if (y <= -44.0)
		tmp = Float64(1.0 - log(Float64(-1.0 / y)));
	elseif (y <= 1.0)
		tmp = Float64(1.0 - log1p(Float64(-x)));
	else
		tmp = Float64(1.0 - log1p(Float64(x / y)));
	end
	return tmp
end
code[x_, y_] := If[LessEqual[y, -44.0], N[(1.0 - N[Log[N[(-1.0 / y), $MachinePrecision]], $MachinePrecision]), $MachinePrecision], If[LessEqual[y, 1.0], N[(1.0 - N[Log[1 + (-x)], $MachinePrecision]), $MachinePrecision], N[(1.0 - N[Log[1 + N[(x / y), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]]]
\begin{array}{l}

\\
\begin{array}{l}
\mathbf{if}\;y \leq -44:\\
\;\;\;\;1 - \log \left(\frac{-1}{y}\right)\\

\mathbf{elif}\;y \leq 1:\\
\;\;\;\;1 - \mathsf{log1p}\left(-x\right)\\

\mathbf{else}:\\
\;\;\;\;1 - \mathsf{log1p}\left(\frac{x}{y}\right)\\


\end{array}
\end{array}
Derivation
  1. Split input into 3 regimes
  2. if y < -44

    1. Initial program 23.5%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg23.5%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def23.5%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified23.5%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]
    4. Taylor expanded in y around -inf 97.0%

      \[\leadsto 1 - \color{blue}{\left(\log \left(-1 \cdot \left(x - 1\right)\right) + \log \left(\frac{-1}{y}\right)\right)} \]
    5. Step-by-step derivation
      1. sub-neg97.0%

        \[\leadsto 1 - \left(\log \left(-1 \cdot \color{blue}{\left(x + \left(-1\right)\right)}\right) + \log \left(\frac{-1}{y}\right)\right) \]
      2. metadata-eval97.0%

        \[\leadsto 1 - \left(\log \left(-1 \cdot \left(x + \color{blue}{-1}\right)\right) + \log \left(\frac{-1}{y}\right)\right) \]
      3. distribute-lft-in97.0%

        \[\leadsto 1 - \left(\log \color{blue}{\left(-1 \cdot x + -1 \cdot -1\right)} + \log \left(\frac{-1}{y}\right)\right) \]
      4. metadata-eval97.0%

        \[\leadsto 1 - \left(\log \left(-1 \cdot x + \color{blue}{1}\right) + \log \left(\frac{-1}{y}\right)\right) \]
      5. +-commutative97.0%

        \[\leadsto 1 - \left(\log \color{blue}{\left(1 + -1 \cdot x\right)} + \log \left(\frac{-1}{y}\right)\right) \]
      6. log1p-def97.0%

        \[\leadsto 1 - \left(\color{blue}{\mathsf{log1p}\left(-1 \cdot x\right)} + \log \left(\frac{-1}{y}\right)\right) \]
      7. mul-1-neg97.0%

        \[\leadsto 1 - \left(\mathsf{log1p}\left(\color{blue}{-x}\right) + \log \left(\frac{-1}{y}\right)\right) \]
    6. Simplified97.0%

      \[\leadsto 1 - \color{blue}{\left(\mathsf{log1p}\left(-x\right) + \log \left(\frac{-1}{y}\right)\right)} \]
    7. Taylor expanded in x around 0 66.6%

      \[\leadsto 1 - \color{blue}{\log \left(\frac{-1}{y}\right)} \]

    if -44 < y < 1

    1. Initial program 100.0%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg100.0%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def100.0%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg100.0%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified100.0%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]
    4. Taylor expanded in y around 0 97.2%

      \[\leadsto 1 - \color{blue}{\log \left(1 + -1 \cdot x\right)} \]
    5. Step-by-step derivation
      1. log1p-def97.2%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-1 \cdot x\right)} \]
      2. mul-1-neg97.2%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{-x}\right) \]
    6. Simplified97.2%

      \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-x\right)} \]

    if 1 < y

    1. Initial program 50.7%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg50.7%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def50.7%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac50.7%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg50.7%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in50.7%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg50.7%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative50.7%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg50.7%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified50.7%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]
    4. Taylor expanded in x around inf 50.1%

      \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{-1 \cdot \frac{x}{1 - y}}\right) \]
    5. Step-by-step derivation
      1. neg-mul-150.1%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{-\frac{x}{1 - y}}\right) \]
      2. distribute-neg-frac50.1%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-x}{1 - y}}\right) \]
    6. Simplified50.1%

      \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-x}{1 - y}}\right) \]
    7. Taylor expanded in y around inf 48.5%

      \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{x}{y}}\right) \]
  3. Recombined 3 regimes into one program.
  4. Final simplification81.7%

    \[\leadsto \begin{array}{l} \mathbf{if}\;y \leq -44:\\ \;\;\;\;1 - \log \left(\frac{-1}{y}\right)\\ \mathbf{elif}\;y \leq 1:\\ \;\;\;\;1 - \mathsf{log1p}\left(-x\right)\\ \mathbf{else}:\\ \;\;\;\;1 - \mathsf{log1p}\left(\frac{x}{y}\right)\\ \end{array} \]

Alternative 12: 78.7% accurate, 1.0× speedup?

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;y \leq -215:\\ \;\;\;\;1 - \log \left(\frac{-1}{y}\right)\\ \mathbf{else}:\\ \;\;\;\;1 - \mathsf{log1p}\left(-x\right)\\ \end{array} \end{array} \]
(FPCore (x y)
 :precision binary64
 (if (<= y -215.0) (- 1.0 (log (/ -1.0 y))) (- 1.0 (log1p (- x)))))
double code(double x, double y) {
	double tmp;
	if (y <= -215.0) {
		tmp = 1.0 - log((-1.0 / y));
	} else {
		tmp = 1.0 - log1p(-x);
	}
	return tmp;
}
public static double code(double x, double y) {
	double tmp;
	if (y <= -215.0) {
		tmp = 1.0 - Math.log((-1.0 / y));
	} else {
		tmp = 1.0 - Math.log1p(-x);
	}
	return tmp;
}
def code(x, y):
	tmp = 0
	if y <= -215.0:
		tmp = 1.0 - math.log((-1.0 / y))
	else:
		tmp = 1.0 - math.log1p(-x)
	return tmp
function code(x, y)
	tmp = 0.0
	if (y <= -215.0)
		tmp = Float64(1.0 - log(Float64(-1.0 / y)));
	else
		tmp = Float64(1.0 - log1p(Float64(-x)));
	end
	return tmp
end
code[x_, y_] := If[LessEqual[y, -215.0], N[(1.0 - N[Log[N[(-1.0 / y), $MachinePrecision]], $MachinePrecision]), $MachinePrecision], N[(1.0 - N[Log[1 + (-x)], $MachinePrecision]), $MachinePrecision]]
\begin{array}{l}

\\
\begin{array}{l}
\mathbf{if}\;y \leq -215:\\
\;\;\;\;1 - \log \left(\frac{-1}{y}\right)\\

\mathbf{else}:\\
\;\;\;\;1 - \mathsf{log1p}\left(-x\right)\\


\end{array}
\end{array}
Derivation
  1. Split input into 2 regimes
  2. if y < -215

    1. Initial program 23.5%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg23.5%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def23.5%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg23.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified23.5%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]
    4. Taylor expanded in y around -inf 97.0%

      \[\leadsto 1 - \color{blue}{\left(\log \left(-1 \cdot \left(x - 1\right)\right) + \log \left(\frac{-1}{y}\right)\right)} \]
    5. Step-by-step derivation
      1. sub-neg97.0%

        \[\leadsto 1 - \left(\log \left(-1 \cdot \color{blue}{\left(x + \left(-1\right)\right)}\right) + \log \left(\frac{-1}{y}\right)\right) \]
      2. metadata-eval97.0%

        \[\leadsto 1 - \left(\log \left(-1 \cdot \left(x + \color{blue}{-1}\right)\right) + \log \left(\frac{-1}{y}\right)\right) \]
      3. distribute-lft-in97.0%

        \[\leadsto 1 - \left(\log \color{blue}{\left(-1 \cdot x + -1 \cdot -1\right)} + \log \left(\frac{-1}{y}\right)\right) \]
      4. metadata-eval97.0%

        \[\leadsto 1 - \left(\log \left(-1 \cdot x + \color{blue}{1}\right) + \log \left(\frac{-1}{y}\right)\right) \]
      5. +-commutative97.0%

        \[\leadsto 1 - \left(\log \color{blue}{\left(1 + -1 \cdot x\right)} + \log \left(\frac{-1}{y}\right)\right) \]
      6. log1p-def97.0%

        \[\leadsto 1 - \left(\color{blue}{\mathsf{log1p}\left(-1 \cdot x\right)} + \log \left(\frac{-1}{y}\right)\right) \]
      7. mul-1-neg97.0%

        \[\leadsto 1 - \left(\mathsf{log1p}\left(\color{blue}{-x}\right) + \log \left(\frac{-1}{y}\right)\right) \]
    6. Simplified97.0%

      \[\leadsto 1 - \color{blue}{\left(\mathsf{log1p}\left(-x\right) + \log \left(\frac{-1}{y}\right)\right)} \]
    7. Taylor expanded in x around 0 66.6%

      \[\leadsto 1 - \color{blue}{\log \left(\frac{-1}{y}\right)} \]

    if -215 < y

    1. Initial program 91.5%

      \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
    2. Step-by-step derivation
      1. sub-neg91.5%

        \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
      2. log1p-def91.5%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
      3. distribute-neg-frac91.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
      4. sub-neg91.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
      5. distribute-neg-in91.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
      6. remove-double-neg91.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
      7. +-commutative91.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
      8. sub-neg91.5%

        \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
    3. Simplified91.5%

      \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]
    4. Taylor expanded in y around 0 80.4%

      \[\leadsto 1 - \color{blue}{\log \left(1 + -1 \cdot x\right)} \]
    5. Step-by-step derivation
      1. log1p-def80.4%

        \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-1 \cdot x\right)} \]
      2. mul-1-neg80.4%

        \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{-x}\right) \]
    6. Simplified80.4%

      \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-x\right)} \]
  3. Recombined 2 regimes into one program.
  4. Final simplification76.0%

    \[\leadsto \begin{array}{l} \mathbf{if}\;y \leq -215:\\ \;\;\;\;1 - \log \left(\frac{-1}{y}\right)\\ \mathbf{else}:\\ \;\;\;\;1 - \mathsf{log1p}\left(-x\right)\\ \end{array} \]

Alternative 13: 62.7% accurate, 1.1× speedup?

\[\begin{array}{l} \\ 1 - \mathsf{log1p}\left(-x\right) \end{array} \]
(FPCore (x y) :precision binary64 (- 1.0 (log1p (- x))))
double code(double x, double y) {
	return 1.0 - log1p(-x);
}
public static double code(double x, double y) {
	return 1.0 - Math.log1p(-x);
}
def code(x, y):
	return 1.0 - math.log1p(-x)
function code(x, y)
	return Float64(1.0 - log1p(Float64(-x)))
end
code[x_, y_] := N[(1.0 - N[Log[1 + (-x)], $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
1 - \mathsf{log1p}\left(-x\right)
\end{array}
Derivation
  1. Initial program 69.7%

    \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
  2. Step-by-step derivation
    1. sub-neg69.7%

      \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
    2. log1p-def69.7%

      \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
    3. distribute-neg-frac69.7%

      \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
    4. sub-neg69.7%

      \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
    5. distribute-neg-in69.7%

      \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
    6. remove-double-neg69.7%

      \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
    7. +-commutative69.7%

      \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
    8. sub-neg69.7%

      \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
  3. Simplified69.7%

    \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]
  4. Taylor expanded in y around 0 58.7%

    \[\leadsto 1 - \color{blue}{\log \left(1 + -1 \cdot x\right)} \]
  5. Step-by-step derivation
    1. log1p-def58.8%

      \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-1 \cdot x\right)} \]
    2. mul-1-neg58.8%

      \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{-x}\right) \]
  6. Simplified58.8%

    \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-x\right)} \]
  7. Final simplification58.8%

    \[\leadsto 1 - \mathsf{log1p}\left(-x\right) \]

Alternative 14: 43.3% accurate, 37.0× speedup?

\[\begin{array}{l} \\ 1 + x \end{array} \]
(FPCore (x y) :precision binary64 (+ 1.0 x))
double code(double x, double y) {
	return 1.0 + x;
}
real(8) function code(x, y)
    real(8), intent (in) :: x
    real(8), intent (in) :: y
    code = 1.0d0 + x
end function
public static double code(double x, double y) {
	return 1.0 + x;
}
def code(x, y):
	return 1.0 + x
function code(x, y)
	return Float64(1.0 + x)
end
function tmp = code(x, y)
	tmp = 1.0 + x;
end
code[x_, y_] := N[(1.0 + x), $MachinePrecision]
\begin{array}{l}

\\
1 + x
\end{array}
Derivation
  1. Initial program 69.7%

    \[1 - \log \left(1 - \frac{x - y}{1 - y}\right) \]
  2. Step-by-step derivation
    1. sub-neg69.7%

      \[\leadsto 1 - \log \color{blue}{\left(1 + \left(-\frac{x - y}{1 - y}\right)\right)} \]
    2. log1p-def69.7%

      \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-\frac{x - y}{1 - y}\right)} \]
    3. distribute-neg-frac69.7%

      \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{\frac{-\left(x - y\right)}{1 - y}}\right) \]
    4. sub-neg69.7%

      \[\leadsto 1 - \mathsf{log1p}\left(\frac{-\color{blue}{\left(x + \left(-y\right)\right)}}{1 - y}\right) \]
    5. distribute-neg-in69.7%

      \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{\left(-x\right) + \left(-\left(-y\right)\right)}}{1 - y}\right) \]
    6. remove-double-neg69.7%

      \[\leadsto 1 - \mathsf{log1p}\left(\frac{\left(-x\right) + \color{blue}{y}}{1 - y}\right) \]
    7. +-commutative69.7%

      \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y + \left(-x\right)}}{1 - y}\right) \]
    8. sub-neg69.7%

      \[\leadsto 1 - \mathsf{log1p}\left(\frac{\color{blue}{y - x}}{1 - y}\right) \]
  3. Simplified69.7%

    \[\leadsto \color{blue}{1 - \mathsf{log1p}\left(\frac{y - x}{1 - y}\right)} \]
  4. Taylor expanded in y around 0 58.7%

    \[\leadsto 1 - \color{blue}{\log \left(1 + -1 \cdot x\right)} \]
  5. Step-by-step derivation
    1. log1p-def58.8%

      \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-1 \cdot x\right)} \]
    2. mul-1-neg58.8%

      \[\leadsto 1 - \mathsf{log1p}\left(\color{blue}{-x}\right) \]
  6. Simplified58.8%

    \[\leadsto 1 - \color{blue}{\mathsf{log1p}\left(-x\right)} \]
  7. Taylor expanded in x around 0 39.7%

    \[\leadsto \color{blue}{1 + x} \]
  8. Final simplification39.7%

    \[\leadsto 1 + x \]

Developer target: 99.8% accurate, 0.5× speedup?

\[\begin{array}{l} \\ \begin{array}{l} t_0 := 1 - \log \left(\frac{x}{y \cdot y} - \left(\frac{1}{y} - \frac{x}{y}\right)\right)\\ \mathbf{if}\;y < -81284752.61947241:\\ \;\;\;\;t_0\\ \mathbf{elif}\;y < 3.0094271212461764 \cdot 10^{+25}:\\ \;\;\;\;\log \left(\frac{e^{1}}{1 - \frac{x - y}{1 - y}}\right)\\ \mathbf{else}:\\ \;\;\;\;t_0\\ \end{array} \end{array} \]
(FPCore (x y)
 :precision binary64
 (let* ((t_0 (- 1.0 (log (- (/ x (* y y)) (- (/ 1.0 y) (/ x y)))))))
   (if (< y -81284752.61947241)
     t_0
     (if (< y 3.0094271212461764e+25)
       (log (/ (exp 1.0) (- 1.0 (/ (- x y) (- 1.0 y)))))
       t_0))))
double code(double x, double y) {
	double t_0 = 1.0 - log(((x / (y * y)) - ((1.0 / y) - (x / y))));
	double tmp;
	if (y < -81284752.61947241) {
		tmp = t_0;
	} else if (y < 3.0094271212461764e+25) {
		tmp = log((exp(1.0) / (1.0 - ((x - y) / (1.0 - y)))));
	} else {
		tmp = t_0;
	}
	return tmp;
}
real(8) function code(x, y)
    real(8), intent (in) :: x
    real(8), intent (in) :: y
    real(8) :: t_0
    real(8) :: tmp
    t_0 = 1.0d0 - log(((x / (y * y)) - ((1.0d0 / y) - (x / y))))
    if (y < (-81284752.61947241d0)) then
        tmp = t_0
    else if (y < 3.0094271212461764d+25) then
        tmp = log((exp(1.0d0) / (1.0d0 - ((x - y) / (1.0d0 - y)))))
    else
        tmp = t_0
    end if
    code = tmp
end function
public static double code(double x, double y) {
	double t_0 = 1.0 - Math.log(((x / (y * y)) - ((1.0 / y) - (x / y))));
	double tmp;
	if (y < -81284752.61947241) {
		tmp = t_0;
	} else if (y < 3.0094271212461764e+25) {
		tmp = Math.log((Math.exp(1.0) / (1.0 - ((x - y) / (1.0 - y)))));
	} else {
		tmp = t_0;
	}
	return tmp;
}
def code(x, y):
	t_0 = 1.0 - math.log(((x / (y * y)) - ((1.0 / y) - (x / y))))
	tmp = 0
	if y < -81284752.61947241:
		tmp = t_0
	elif y < 3.0094271212461764e+25:
		tmp = math.log((math.exp(1.0) / (1.0 - ((x - y) / (1.0 - y)))))
	else:
		tmp = t_0
	return tmp
function code(x, y)
	t_0 = Float64(1.0 - log(Float64(Float64(x / Float64(y * y)) - Float64(Float64(1.0 / y) - Float64(x / y)))))
	tmp = 0.0
	if (y < -81284752.61947241)
		tmp = t_0;
	elseif (y < 3.0094271212461764e+25)
		tmp = log(Float64(exp(1.0) / Float64(1.0 - Float64(Float64(x - y) / Float64(1.0 - y)))));
	else
		tmp = t_0;
	end
	return tmp
end
function tmp_2 = code(x, y)
	t_0 = 1.0 - log(((x / (y * y)) - ((1.0 / y) - (x / y))));
	tmp = 0.0;
	if (y < -81284752.61947241)
		tmp = t_0;
	elseif (y < 3.0094271212461764e+25)
		tmp = log((exp(1.0) / (1.0 - ((x - y) / (1.0 - y)))));
	else
		tmp = t_0;
	end
	tmp_2 = tmp;
end
code[x_, y_] := Block[{t$95$0 = N[(1.0 - N[Log[N[(N[(x / N[(y * y), $MachinePrecision]), $MachinePrecision] - N[(N[(1.0 / y), $MachinePrecision] - N[(x / y), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]}, If[Less[y, -81284752.61947241], t$95$0, If[Less[y, 3.0094271212461764e+25], N[Log[N[(N[Exp[1.0], $MachinePrecision] / N[(1.0 - N[(N[(x - y), $MachinePrecision] / N[(1.0 - y), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]], $MachinePrecision], t$95$0]]]
\begin{array}{l}

\\
\begin{array}{l}
t_0 := 1 - \log \left(\frac{x}{y \cdot y} - \left(\frac{1}{y} - \frac{x}{y}\right)\right)\\
\mathbf{if}\;y < -81284752.61947241:\\
\;\;\;\;t_0\\

\mathbf{elif}\;y < 3.0094271212461764 \cdot 10^{+25}:\\
\;\;\;\;\log \left(\frac{e^{1}}{1 - \frac{x - y}{1 - y}}\right)\\

\mathbf{else}:\\
\;\;\;\;t_0\\


\end{array}
\end{array}

Reproduce

?
herbie shell --seed 2023290 
(FPCore (x y)
  :name "Numeric.SpecFunctions:invIncompleteGamma from math-functions-0.1.5.2, B"
  :precision binary64

  :herbie-target
  (if (< y -81284752.61947241) (- 1.0 (log (- (/ x (* y y)) (- (/ 1.0 y) (/ x y))))) (if (< y 3.0094271212461764e+25) (log (/ (exp 1.0) (- 1.0 (/ (- x y) (- 1.0 y))))) (- 1.0 (log (- (/ x (* y y)) (- (/ 1.0 y) (/ x y)))))))

  (- 1.0 (log (- 1.0 (/ (- x y) (- 1.0 y))))))