subtraction fraction

Percentage Accurate: 100.0% → 100.0%
Time: 5.7s
Alternatives: 7
Speedup: 1.1×

Specification

?
\[\begin{array}{l} \\ \frac{-\left(f + n\right)}{f - n} \end{array} \]
(FPCore (f n) :precision binary64 (/ (- (+ f n)) (- f n)))
double code(double f, double n) {
	return -(f + n) / (f - n);
}
real(8) function code(f, n)
    real(8), intent (in) :: f
    real(8), intent (in) :: n
    code = -(f + n) / (f - n)
end function
public static double code(double f, double n) {
	return -(f + n) / (f - n);
}
def code(f, n):
	return -(f + n) / (f - n)
function code(f, n)
	return Float64(Float64(-Float64(f + n)) / Float64(f - n))
end
function tmp = code(f, n)
	tmp = -(f + n) / (f - n);
end
code[f_, n_] := N[((-N[(f + n), $MachinePrecision]) / N[(f - n), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
\frac{-\left(f + n\right)}{f - n}
\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 7 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: 100.0% accurate, 1.0× speedup?

\[\begin{array}{l} \\ \frac{-\left(f + n\right)}{f - n} \end{array} \]
(FPCore (f n) :precision binary64 (/ (- (+ f n)) (- f n)))
double code(double f, double n) {
	return -(f + n) / (f - n);
}
real(8) function code(f, n)
    real(8), intent (in) :: f
    real(8), intent (in) :: n
    code = -(f + n) / (f - n)
end function
public static double code(double f, double n) {
	return -(f + n) / (f - n);
}
def code(f, n):
	return -(f + n) / (f - n)
function code(f, n)
	return Float64(Float64(-Float64(f + n)) / Float64(f - n))
end
function tmp = code(f, n)
	tmp = -(f + n) / (f - n);
end
code[f_, n_] := N[((-N[(f + n), $MachinePrecision]) / N[(f - n), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
\frac{-\left(f + n\right)}{f - n}
\end{array}

Alternative 1: 100.0% accurate, 0.7× speedup?

\[\begin{array}{l} \\ \frac{f}{n - f} + \frac{n}{n - f} \end{array} \]
(FPCore (f n) :precision binary64 (+ (/ f (- n f)) (/ n (- n f))))
double code(double f, double n) {
	return (f / (n - f)) + (n / (n - f));
}
real(8) function code(f, n)
    real(8), intent (in) :: f
    real(8), intent (in) :: n
    code = (f / (n - f)) + (n / (n - f))
end function
public static double code(double f, double n) {
	return (f / (n - f)) + (n / (n - f));
}
def code(f, n):
	return (f / (n - f)) + (n / (n - f))
function code(f, n)
	return Float64(Float64(f / Float64(n - f)) + Float64(n / Float64(n - f)))
end
function tmp = code(f, n)
	tmp = (f / (n - f)) + (n / (n - f));
end
code[f_, n_] := N[(N[(f / N[(n - f), $MachinePrecision]), $MachinePrecision] + N[(n / N[(n - f), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
\frac{f}{n - f} + \frac{n}{n - f}
\end{array}
Derivation
  1. Initial program 99.9%

    \[\frac{-\left(f + n\right)}{f - n} \]
  2. Step-by-step derivation
    1. neg-mul-199.9%

      \[\leadsto \frac{\color{blue}{-1 \cdot \left(f + n\right)}}{f - n} \]
    2. *-commutative99.9%

      \[\leadsto \frac{\color{blue}{\left(f + n\right) \cdot -1}}{f - n} \]
    3. associate-/l*99.9%

      \[\leadsto \color{blue}{\frac{f + n}{\frac{f - n}{-1}}} \]
    4. div-sub99.9%

      \[\leadsto \frac{f + n}{\color{blue}{\frac{f}{-1} - \frac{n}{-1}}} \]
    5. metadata-eval99.9%

      \[\leadsto \frac{f + n}{\frac{f}{\color{blue}{\frac{1}{-1}}} - \frac{n}{-1}} \]
    6. metadata-eval99.9%

      \[\leadsto \frac{f + n}{\frac{f}{\frac{\color{blue}{--1}}{-1}} - \frac{n}{-1}} \]
    7. associate-/l*99.9%

      \[\leadsto \frac{f + n}{\color{blue}{\frac{f \cdot -1}{--1}} - \frac{n}{-1}} \]
    8. *-commutative99.9%

      \[\leadsto \frac{f + n}{\frac{\color{blue}{-1 \cdot f}}{--1} - \frac{n}{-1}} \]
    9. neg-mul-199.9%

      \[\leadsto \frac{f + n}{\frac{\color{blue}{-f}}{--1} - \frac{n}{-1}} \]
    10. metadata-eval99.9%

      \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{n}{\color{blue}{\frac{1}{-1}}}} \]
    11. metadata-eval99.9%

      \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{n}{\frac{\color{blue}{--1}}{-1}}} \]
    12. associate-/l*99.9%

      \[\leadsto \frac{f + n}{\frac{-f}{--1} - \color{blue}{\frac{n \cdot -1}{--1}}} \]
    13. *-commutative99.9%

      \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{\color{blue}{-1 \cdot n}}{--1}} \]
    14. neg-mul-199.9%

      \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{\color{blue}{-n}}{--1}} \]
    15. div-sub99.9%

      \[\leadsto \frac{f + n}{\color{blue}{\frac{\left(-f\right) - \left(-n\right)}{--1}}} \]
    16. unsub-neg99.9%

      \[\leadsto \frac{f + n}{\frac{\color{blue}{\left(-f\right) + \left(-\left(-n\right)\right)}}{--1}} \]
    17. remove-double-neg99.9%

      \[\leadsto \frac{f + n}{\frac{\left(-f\right) + \color{blue}{n}}{--1}} \]
    18. +-commutative99.9%

      \[\leadsto \frac{f + n}{\frac{\color{blue}{n + \left(-f\right)}}{--1}} \]
    19. sub-neg99.9%

      \[\leadsto \frac{f + n}{\frac{\color{blue}{n - f}}{--1}} \]
    20. metadata-eval99.9%

      \[\leadsto \frac{f + n}{\frac{n - f}{\color{blue}{1}}} \]
    21. /-rgt-identity99.9%

      \[\leadsto \frac{f + n}{\color{blue}{n - f}} \]
  3. Simplified99.9%

    \[\leadsto \color{blue}{\frac{f + n}{n - f}} \]
  4. Step-by-step derivation
    1. log1p-expm1-u100.0%

      \[\leadsto \color{blue}{\mathsf{log1p}\left(\mathsf{expm1}\left(\frac{f + n}{n - f}\right)\right)} \]
  5. Applied egg-rr100.0%

    \[\leadsto \color{blue}{\mathsf{log1p}\left(\mathsf{expm1}\left(\frac{f + n}{n - f}\right)\right)} \]
  6. Step-by-step derivation
    1. log1p-expm1-u99.9%

      \[\leadsto \color{blue}{\frac{f + n}{n - f}} \]
    2. *-un-lft-identity99.9%

      \[\leadsto \frac{\color{blue}{1 \cdot \left(f + n\right)}}{n - f} \]
    3. associate-*l/99.7%

      \[\leadsto \color{blue}{\frac{1}{n - f} \cdot \left(f + n\right)} \]
    4. distribute-rgt-in99.7%

      \[\leadsto \color{blue}{f \cdot \frac{1}{n - f} + n \cdot \frac{1}{n - f}} \]
    5. un-div-inv99.9%

      \[\leadsto \color{blue}{\frac{f}{n - f}} + n \cdot \frac{1}{n - f} \]
    6. un-div-inv100.0%

      \[\leadsto \frac{f}{n - f} + \color{blue}{\frac{n}{n - f}} \]
  7. Applied egg-rr100.0%

    \[\leadsto \color{blue}{\frac{f}{n - f} + \frac{n}{n - f}} \]
  8. Final simplification100.0%

    \[\leadsto \frac{f}{n - f} + \frac{n}{n - f} \]

Alternative 2: 73.7% accurate, 0.5× speedup?

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;f \leq -1.6 \cdot 10^{+53} \lor \neg \left(f \leq -1.3 \cdot 10^{-22}\right) \land \left(f \leq -1.3 \cdot 10^{-107} \lor \neg \left(f \leq 2 \cdot 10^{-47}\right)\right):\\ \;\;\;\;-2 \cdot \frac{n}{f} + -1\\ \mathbf{else}:\\ \;\;\;\;1 + 2 \cdot \frac{f}{n}\\ \end{array} \end{array} \]
(FPCore (f n)
 :precision binary64
 (if (or (<= f -1.6e+53)
         (and (not (<= f -1.3e-22)) (or (<= f -1.3e-107) (not (<= f 2e-47)))))
   (+ (* -2.0 (/ n f)) -1.0)
   (+ 1.0 (* 2.0 (/ f n)))))
double code(double f, double n) {
	double tmp;
	if ((f <= -1.6e+53) || (!(f <= -1.3e-22) && ((f <= -1.3e-107) || !(f <= 2e-47)))) {
		tmp = (-2.0 * (n / f)) + -1.0;
	} else {
		tmp = 1.0 + (2.0 * (f / n));
	}
	return tmp;
}
real(8) function code(f, n)
    real(8), intent (in) :: f
    real(8), intent (in) :: n
    real(8) :: tmp
    if ((f <= (-1.6d+53)) .or. (.not. (f <= (-1.3d-22))) .and. (f <= (-1.3d-107)) .or. (.not. (f <= 2d-47))) then
        tmp = ((-2.0d0) * (n / f)) + (-1.0d0)
    else
        tmp = 1.0d0 + (2.0d0 * (f / n))
    end if
    code = tmp
end function
public static double code(double f, double n) {
	double tmp;
	if ((f <= -1.6e+53) || (!(f <= -1.3e-22) && ((f <= -1.3e-107) || !(f <= 2e-47)))) {
		tmp = (-2.0 * (n / f)) + -1.0;
	} else {
		tmp = 1.0 + (2.0 * (f / n));
	}
	return tmp;
}
def code(f, n):
	tmp = 0
	if (f <= -1.6e+53) or (not (f <= -1.3e-22) and ((f <= -1.3e-107) or not (f <= 2e-47))):
		tmp = (-2.0 * (n / f)) + -1.0
	else:
		tmp = 1.0 + (2.0 * (f / n))
	return tmp
function code(f, n)
	tmp = 0.0
	if ((f <= -1.6e+53) || (!(f <= -1.3e-22) && ((f <= -1.3e-107) || !(f <= 2e-47))))
		tmp = Float64(Float64(-2.0 * Float64(n / f)) + -1.0);
	else
		tmp = Float64(1.0 + Float64(2.0 * Float64(f / n)));
	end
	return tmp
end
function tmp_2 = code(f, n)
	tmp = 0.0;
	if ((f <= -1.6e+53) || (~((f <= -1.3e-22)) && ((f <= -1.3e-107) || ~((f <= 2e-47)))))
		tmp = (-2.0 * (n / f)) + -1.0;
	else
		tmp = 1.0 + (2.0 * (f / n));
	end
	tmp_2 = tmp;
end
code[f_, n_] := If[Or[LessEqual[f, -1.6e+53], And[N[Not[LessEqual[f, -1.3e-22]], $MachinePrecision], Or[LessEqual[f, -1.3e-107], N[Not[LessEqual[f, 2e-47]], $MachinePrecision]]]], N[(N[(-2.0 * N[(n / f), $MachinePrecision]), $MachinePrecision] + -1.0), $MachinePrecision], N[(1.0 + N[(2.0 * N[(f / n), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]]
\begin{array}{l}

\\
\begin{array}{l}
\mathbf{if}\;f \leq -1.6 \cdot 10^{+53} \lor \neg \left(f \leq -1.3 \cdot 10^{-22}\right) \land \left(f \leq -1.3 \cdot 10^{-107} \lor \neg \left(f \leq 2 \cdot 10^{-47}\right)\right):\\
\;\;\;\;-2 \cdot \frac{n}{f} + -1\\

\mathbf{else}:\\
\;\;\;\;1 + 2 \cdot \frac{f}{n}\\


\end{array}
\end{array}
Derivation
  1. Split input into 2 regimes
  2. if f < -1.6e53 or -1.3e-22 < f < -1.3e-107 or 1.9999999999999999e-47 < f

    1. Initial program 99.9%

      \[\frac{-\left(f + n\right)}{f - n} \]
    2. Step-by-step derivation
      1. neg-mul-199.9%

        \[\leadsto \frac{\color{blue}{-1 \cdot \left(f + n\right)}}{f - n} \]
      2. *-commutative99.9%

        \[\leadsto \frac{\color{blue}{\left(f + n\right) \cdot -1}}{f - n} \]
      3. associate-/l*99.9%

        \[\leadsto \color{blue}{\frac{f + n}{\frac{f - n}{-1}}} \]
      4. div-sub99.9%

        \[\leadsto \frac{f + n}{\color{blue}{\frac{f}{-1} - \frac{n}{-1}}} \]
      5. metadata-eval99.9%

        \[\leadsto \frac{f + n}{\frac{f}{\color{blue}{\frac{1}{-1}}} - \frac{n}{-1}} \]
      6. metadata-eval99.9%

        \[\leadsto \frac{f + n}{\frac{f}{\frac{\color{blue}{--1}}{-1}} - \frac{n}{-1}} \]
      7. associate-/l*99.9%

        \[\leadsto \frac{f + n}{\color{blue}{\frac{f \cdot -1}{--1}} - \frac{n}{-1}} \]
      8. *-commutative99.9%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{-1 \cdot f}}{--1} - \frac{n}{-1}} \]
      9. neg-mul-199.9%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{-f}}{--1} - \frac{n}{-1}} \]
      10. metadata-eval99.9%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{n}{\color{blue}{\frac{1}{-1}}}} \]
      11. metadata-eval99.9%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{n}{\frac{\color{blue}{--1}}{-1}}} \]
      12. associate-/l*99.9%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \color{blue}{\frac{n \cdot -1}{--1}}} \]
      13. *-commutative99.9%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{\color{blue}{-1 \cdot n}}{--1}} \]
      14. neg-mul-199.9%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{\color{blue}{-n}}{--1}} \]
      15. div-sub99.9%

        \[\leadsto \frac{f + n}{\color{blue}{\frac{\left(-f\right) - \left(-n\right)}{--1}}} \]
      16. unsub-neg99.9%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{\left(-f\right) + \left(-\left(-n\right)\right)}}{--1}} \]
      17. remove-double-neg99.9%

        \[\leadsto \frac{f + n}{\frac{\left(-f\right) + \color{blue}{n}}{--1}} \]
      18. +-commutative99.9%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{n + \left(-f\right)}}{--1}} \]
      19. sub-neg99.9%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{n - f}}{--1}} \]
      20. metadata-eval99.9%

        \[\leadsto \frac{f + n}{\frac{n - f}{\color{blue}{1}}} \]
      21. /-rgt-identity99.9%

        \[\leadsto \frac{f + n}{\color{blue}{n - f}} \]
    3. Simplified99.9%

      \[\leadsto \color{blue}{\frac{f + n}{n - f}} \]
    4. Taylor expanded in n around 0 76.4%

      \[\leadsto \color{blue}{-2 \cdot \frac{n}{f} - 1} \]

    if -1.6e53 < f < -1.3e-22 or -1.3e-107 < f < 1.9999999999999999e-47

    1. Initial program 100.0%

      \[\frac{-\left(f + n\right)}{f - n} \]
    2. Step-by-step derivation
      1. neg-mul-1100.0%

        \[\leadsto \frac{\color{blue}{-1 \cdot \left(f + n\right)}}{f - n} \]
      2. *-commutative100.0%

        \[\leadsto \frac{\color{blue}{\left(f + n\right) \cdot -1}}{f - n} \]
      3. associate-/l*100.0%

        \[\leadsto \color{blue}{\frac{f + n}{\frac{f - n}{-1}}} \]
      4. div-sub100.0%

        \[\leadsto \frac{f + n}{\color{blue}{\frac{f}{-1} - \frac{n}{-1}}} \]
      5. metadata-eval100.0%

        \[\leadsto \frac{f + n}{\frac{f}{\color{blue}{\frac{1}{-1}}} - \frac{n}{-1}} \]
      6. metadata-eval100.0%

        \[\leadsto \frac{f + n}{\frac{f}{\frac{\color{blue}{--1}}{-1}} - \frac{n}{-1}} \]
      7. associate-/l*100.0%

        \[\leadsto \frac{f + n}{\color{blue}{\frac{f \cdot -1}{--1}} - \frac{n}{-1}} \]
      8. *-commutative100.0%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{-1 \cdot f}}{--1} - \frac{n}{-1}} \]
      9. neg-mul-1100.0%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{-f}}{--1} - \frac{n}{-1}} \]
      10. metadata-eval100.0%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{n}{\color{blue}{\frac{1}{-1}}}} \]
      11. metadata-eval100.0%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{n}{\frac{\color{blue}{--1}}{-1}}} \]
      12. associate-/l*100.0%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \color{blue}{\frac{n \cdot -1}{--1}}} \]
      13. *-commutative100.0%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{\color{blue}{-1 \cdot n}}{--1}} \]
      14. neg-mul-1100.0%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{\color{blue}{-n}}{--1}} \]
      15. div-sub100.0%

        \[\leadsto \frac{f + n}{\color{blue}{\frac{\left(-f\right) - \left(-n\right)}{--1}}} \]
      16. unsub-neg100.0%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{\left(-f\right) + \left(-\left(-n\right)\right)}}{--1}} \]
      17. remove-double-neg100.0%

        \[\leadsto \frac{f + n}{\frac{\left(-f\right) + \color{blue}{n}}{--1}} \]
      18. +-commutative100.0%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{n + \left(-f\right)}}{--1}} \]
      19. sub-neg100.0%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{n - f}}{--1}} \]
      20. metadata-eval100.0%

        \[\leadsto \frac{f + n}{\frac{n - f}{\color{blue}{1}}} \]
      21. /-rgt-identity100.0%

        \[\leadsto \frac{f + n}{\color{blue}{n - f}} \]
    3. Simplified100.0%

      \[\leadsto \color{blue}{\frac{f + n}{n - f}} \]
    4. Taylor expanded in f around 0 86.3%

      \[\leadsto \color{blue}{2 \cdot \frac{f}{n} + 1} \]
  3. Recombined 2 regimes into one program.
  4. Final simplification80.6%

    \[\leadsto \begin{array}{l} \mathbf{if}\;f \leq -1.6 \cdot 10^{+53} \lor \neg \left(f \leq -1.3 \cdot 10^{-22}\right) \land \left(f \leq -1.3 \cdot 10^{-107} \lor \neg \left(f \leq 2 \cdot 10^{-47}\right)\right):\\ \;\;\;\;-2 \cdot \frac{n}{f} + -1\\ \mathbf{else}:\\ \;\;\;\;1 + 2 \cdot \frac{f}{n}\\ \end{array} \]

Alternative 3: 73.1% accurate, 0.5× speedup?

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;f \leq -5.8 \cdot 10^{+49}:\\ \;\;\;\;-1\\ \mathbf{elif}\;f \leq -1.6 \cdot 10^{-19} \lor \neg \left(f \leq -1.3 \cdot 10^{-107}\right) \land f \leq 7.2 \cdot 10^{-53}:\\ \;\;\;\;1 + 2 \cdot \frac{f}{n}\\ \mathbf{else}:\\ \;\;\;\;-1\\ \end{array} \end{array} \]
(FPCore (f n)
 :precision binary64
 (if (<= f -5.8e+49)
   -1.0
   (if (or (<= f -1.6e-19) (and (not (<= f -1.3e-107)) (<= f 7.2e-53)))
     (+ 1.0 (* 2.0 (/ f n)))
     -1.0)))
double code(double f, double n) {
	double tmp;
	if (f <= -5.8e+49) {
		tmp = -1.0;
	} else if ((f <= -1.6e-19) || (!(f <= -1.3e-107) && (f <= 7.2e-53))) {
		tmp = 1.0 + (2.0 * (f / n));
	} else {
		tmp = -1.0;
	}
	return tmp;
}
real(8) function code(f, n)
    real(8), intent (in) :: f
    real(8), intent (in) :: n
    real(8) :: tmp
    if (f <= (-5.8d+49)) then
        tmp = -1.0d0
    else if ((f <= (-1.6d-19)) .or. (.not. (f <= (-1.3d-107))) .and. (f <= 7.2d-53)) then
        tmp = 1.0d0 + (2.0d0 * (f / n))
    else
        tmp = -1.0d0
    end if
    code = tmp
end function
public static double code(double f, double n) {
	double tmp;
	if (f <= -5.8e+49) {
		tmp = -1.0;
	} else if ((f <= -1.6e-19) || (!(f <= -1.3e-107) && (f <= 7.2e-53))) {
		tmp = 1.0 + (2.0 * (f / n));
	} else {
		tmp = -1.0;
	}
	return tmp;
}
def code(f, n):
	tmp = 0
	if f <= -5.8e+49:
		tmp = -1.0
	elif (f <= -1.6e-19) or (not (f <= -1.3e-107) and (f <= 7.2e-53)):
		tmp = 1.0 + (2.0 * (f / n))
	else:
		tmp = -1.0
	return tmp
function code(f, n)
	tmp = 0.0
	if (f <= -5.8e+49)
		tmp = -1.0;
	elseif ((f <= -1.6e-19) || (!(f <= -1.3e-107) && (f <= 7.2e-53)))
		tmp = Float64(1.0 + Float64(2.0 * Float64(f / n)));
	else
		tmp = -1.0;
	end
	return tmp
end
function tmp_2 = code(f, n)
	tmp = 0.0;
	if (f <= -5.8e+49)
		tmp = -1.0;
	elseif ((f <= -1.6e-19) || (~((f <= -1.3e-107)) && (f <= 7.2e-53)))
		tmp = 1.0 + (2.0 * (f / n));
	else
		tmp = -1.0;
	end
	tmp_2 = tmp;
end
code[f_, n_] := If[LessEqual[f, -5.8e+49], -1.0, If[Or[LessEqual[f, -1.6e-19], And[N[Not[LessEqual[f, -1.3e-107]], $MachinePrecision], LessEqual[f, 7.2e-53]]], N[(1.0 + N[(2.0 * N[(f / n), $MachinePrecision]), $MachinePrecision]), $MachinePrecision], -1.0]]
\begin{array}{l}

\\
\begin{array}{l}
\mathbf{if}\;f \leq -5.8 \cdot 10^{+49}:\\
\;\;\;\;-1\\

\mathbf{elif}\;f \leq -1.6 \cdot 10^{-19} \lor \neg \left(f \leq -1.3 \cdot 10^{-107}\right) \land f \leq 7.2 \cdot 10^{-53}:\\
\;\;\;\;1 + 2 \cdot \frac{f}{n}\\

\mathbf{else}:\\
\;\;\;\;-1\\


\end{array}
\end{array}
Derivation
  1. Split input into 2 regimes
  2. if f < -5.8e49 or -1.59999999999999991e-19 < f < -1.3e-107 or 7.1999999999999998e-53 < f

    1. Initial program 99.9%

      \[\frac{-\left(f + n\right)}{f - n} \]
    2. Step-by-step derivation
      1. neg-mul-199.9%

        \[\leadsto \frac{\color{blue}{-1 \cdot \left(f + n\right)}}{f - n} \]
      2. *-commutative99.9%

        \[\leadsto \frac{\color{blue}{\left(f + n\right) \cdot -1}}{f - n} \]
      3. associate-/l*99.9%

        \[\leadsto \color{blue}{\frac{f + n}{\frac{f - n}{-1}}} \]
      4. div-sub99.9%

        \[\leadsto \frac{f + n}{\color{blue}{\frac{f}{-1} - \frac{n}{-1}}} \]
      5. metadata-eval99.9%

        \[\leadsto \frac{f + n}{\frac{f}{\color{blue}{\frac{1}{-1}}} - \frac{n}{-1}} \]
      6. metadata-eval99.9%

        \[\leadsto \frac{f + n}{\frac{f}{\frac{\color{blue}{--1}}{-1}} - \frac{n}{-1}} \]
      7. associate-/l*99.9%

        \[\leadsto \frac{f + n}{\color{blue}{\frac{f \cdot -1}{--1}} - \frac{n}{-1}} \]
      8. *-commutative99.9%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{-1 \cdot f}}{--1} - \frac{n}{-1}} \]
      9. neg-mul-199.9%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{-f}}{--1} - \frac{n}{-1}} \]
      10. metadata-eval99.9%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{n}{\color{blue}{\frac{1}{-1}}}} \]
      11. metadata-eval99.9%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{n}{\frac{\color{blue}{--1}}{-1}}} \]
      12. associate-/l*99.9%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \color{blue}{\frac{n \cdot -1}{--1}}} \]
      13. *-commutative99.9%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{\color{blue}{-1 \cdot n}}{--1}} \]
      14. neg-mul-199.9%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{\color{blue}{-n}}{--1}} \]
      15. div-sub99.9%

        \[\leadsto \frac{f + n}{\color{blue}{\frac{\left(-f\right) - \left(-n\right)}{--1}}} \]
      16. unsub-neg99.9%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{\left(-f\right) + \left(-\left(-n\right)\right)}}{--1}} \]
      17. remove-double-neg99.9%

        \[\leadsto \frac{f + n}{\frac{\left(-f\right) + \color{blue}{n}}{--1}} \]
      18. +-commutative99.9%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{n + \left(-f\right)}}{--1}} \]
      19. sub-neg99.9%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{n - f}}{--1}} \]
      20. metadata-eval99.9%

        \[\leadsto \frac{f + n}{\frac{n - f}{\color{blue}{1}}} \]
      21. /-rgt-identity99.9%

        \[\leadsto \frac{f + n}{\color{blue}{n - f}} \]
    3. Simplified99.9%

      \[\leadsto \color{blue}{\frac{f + n}{n - f}} \]
    4. Taylor expanded in f around inf 74.6%

      \[\leadsto \color{blue}{-1} \]

    if -5.8e49 < f < -1.59999999999999991e-19 or -1.3e-107 < f < 7.1999999999999998e-53

    1. Initial program 100.0%

      \[\frac{-\left(f + n\right)}{f - n} \]
    2. Step-by-step derivation
      1. neg-mul-1100.0%

        \[\leadsto \frac{\color{blue}{-1 \cdot \left(f + n\right)}}{f - n} \]
      2. *-commutative100.0%

        \[\leadsto \frac{\color{blue}{\left(f + n\right) \cdot -1}}{f - n} \]
      3. associate-/l*100.0%

        \[\leadsto \color{blue}{\frac{f + n}{\frac{f - n}{-1}}} \]
      4. div-sub100.0%

        \[\leadsto \frac{f + n}{\color{blue}{\frac{f}{-1} - \frac{n}{-1}}} \]
      5. metadata-eval100.0%

        \[\leadsto \frac{f + n}{\frac{f}{\color{blue}{\frac{1}{-1}}} - \frac{n}{-1}} \]
      6. metadata-eval100.0%

        \[\leadsto \frac{f + n}{\frac{f}{\frac{\color{blue}{--1}}{-1}} - \frac{n}{-1}} \]
      7. associate-/l*100.0%

        \[\leadsto \frac{f + n}{\color{blue}{\frac{f \cdot -1}{--1}} - \frac{n}{-1}} \]
      8. *-commutative100.0%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{-1 \cdot f}}{--1} - \frac{n}{-1}} \]
      9. neg-mul-1100.0%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{-f}}{--1} - \frac{n}{-1}} \]
      10. metadata-eval100.0%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{n}{\color{blue}{\frac{1}{-1}}}} \]
      11. metadata-eval100.0%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{n}{\frac{\color{blue}{--1}}{-1}}} \]
      12. associate-/l*100.0%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \color{blue}{\frac{n \cdot -1}{--1}}} \]
      13. *-commutative100.0%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{\color{blue}{-1 \cdot n}}{--1}} \]
      14. neg-mul-1100.0%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{\color{blue}{-n}}{--1}} \]
      15. div-sub100.0%

        \[\leadsto \frac{f + n}{\color{blue}{\frac{\left(-f\right) - \left(-n\right)}{--1}}} \]
      16. unsub-neg100.0%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{\left(-f\right) + \left(-\left(-n\right)\right)}}{--1}} \]
      17. remove-double-neg100.0%

        \[\leadsto \frac{f + n}{\frac{\left(-f\right) + \color{blue}{n}}{--1}} \]
      18. +-commutative100.0%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{n + \left(-f\right)}}{--1}} \]
      19. sub-neg100.0%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{n - f}}{--1}} \]
      20. metadata-eval100.0%

        \[\leadsto \frac{f + n}{\frac{n - f}{\color{blue}{1}}} \]
      21. /-rgt-identity100.0%

        \[\leadsto \frac{f + n}{\color{blue}{n - f}} \]
    3. Simplified100.0%

      \[\leadsto \color{blue}{\frac{f + n}{n - f}} \]
    4. Taylor expanded in f around 0 86.9%

      \[\leadsto \color{blue}{2 \cdot \frac{f}{n} + 1} \]
  3. Recombined 2 regimes into one program.
  4. Final simplification79.8%

    \[\leadsto \begin{array}{l} \mathbf{if}\;f \leq -5.8 \cdot 10^{+49}:\\ \;\;\;\;-1\\ \mathbf{elif}\;f \leq -1.6 \cdot 10^{-19} \lor \neg \left(f \leq -1.3 \cdot 10^{-107}\right) \land f \leq 7.2 \cdot 10^{-53}:\\ \;\;\;\;1 + 2 \cdot \frac{f}{n}\\ \mathbf{else}:\\ \;\;\;\;-1\\ \end{array} \]

Alternative 4: 72.5% accurate, 0.9× speedup?

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;f \leq -1100000000000:\\ \;\;\;\;-1\\ \mathbf{elif}\;f \leq -1 \cdot 10^{-19}:\\ \;\;\;\;1\\ \mathbf{elif}\;f \leq -1.3 \cdot 10^{-107}:\\ \;\;\;\;-1\\ \mathbf{elif}\;f \leq 6.6 \cdot 10^{-68}:\\ \;\;\;\;1\\ \mathbf{else}:\\ \;\;\;\;-1\\ \end{array} \end{array} \]
(FPCore (f n)
 :precision binary64
 (if (<= f -1100000000000.0)
   -1.0
   (if (<= f -1e-19)
     1.0
     (if (<= f -1.3e-107) -1.0 (if (<= f 6.6e-68) 1.0 -1.0)))))
double code(double f, double n) {
	double tmp;
	if (f <= -1100000000000.0) {
		tmp = -1.0;
	} else if (f <= -1e-19) {
		tmp = 1.0;
	} else if (f <= -1.3e-107) {
		tmp = -1.0;
	} else if (f <= 6.6e-68) {
		tmp = 1.0;
	} else {
		tmp = -1.0;
	}
	return tmp;
}
real(8) function code(f, n)
    real(8), intent (in) :: f
    real(8), intent (in) :: n
    real(8) :: tmp
    if (f <= (-1100000000000.0d0)) then
        tmp = -1.0d0
    else if (f <= (-1d-19)) then
        tmp = 1.0d0
    else if (f <= (-1.3d-107)) then
        tmp = -1.0d0
    else if (f <= 6.6d-68) then
        tmp = 1.0d0
    else
        tmp = -1.0d0
    end if
    code = tmp
end function
public static double code(double f, double n) {
	double tmp;
	if (f <= -1100000000000.0) {
		tmp = -1.0;
	} else if (f <= -1e-19) {
		tmp = 1.0;
	} else if (f <= -1.3e-107) {
		tmp = -1.0;
	} else if (f <= 6.6e-68) {
		tmp = 1.0;
	} else {
		tmp = -1.0;
	}
	return tmp;
}
def code(f, n):
	tmp = 0
	if f <= -1100000000000.0:
		tmp = -1.0
	elif f <= -1e-19:
		tmp = 1.0
	elif f <= -1.3e-107:
		tmp = -1.0
	elif f <= 6.6e-68:
		tmp = 1.0
	else:
		tmp = -1.0
	return tmp
function code(f, n)
	tmp = 0.0
	if (f <= -1100000000000.0)
		tmp = -1.0;
	elseif (f <= -1e-19)
		tmp = 1.0;
	elseif (f <= -1.3e-107)
		tmp = -1.0;
	elseif (f <= 6.6e-68)
		tmp = 1.0;
	else
		tmp = -1.0;
	end
	return tmp
end
function tmp_2 = code(f, n)
	tmp = 0.0;
	if (f <= -1100000000000.0)
		tmp = -1.0;
	elseif (f <= -1e-19)
		tmp = 1.0;
	elseif (f <= -1.3e-107)
		tmp = -1.0;
	elseif (f <= 6.6e-68)
		tmp = 1.0;
	else
		tmp = -1.0;
	end
	tmp_2 = tmp;
end
code[f_, n_] := If[LessEqual[f, -1100000000000.0], -1.0, If[LessEqual[f, -1e-19], 1.0, If[LessEqual[f, -1.3e-107], -1.0, If[LessEqual[f, 6.6e-68], 1.0, -1.0]]]]
\begin{array}{l}

\\
\begin{array}{l}
\mathbf{if}\;f \leq -1100000000000:\\
\;\;\;\;-1\\

\mathbf{elif}\;f \leq -1 \cdot 10^{-19}:\\
\;\;\;\;1\\

\mathbf{elif}\;f \leq -1.3 \cdot 10^{-107}:\\
\;\;\;\;-1\\

\mathbf{elif}\;f \leq 6.6 \cdot 10^{-68}:\\
\;\;\;\;1\\

\mathbf{else}:\\
\;\;\;\;-1\\


\end{array}
\end{array}
Derivation
  1. Split input into 2 regimes
  2. if f < -1.1e12 or -9.9999999999999998e-20 < f < -1.3e-107 or 6.5999999999999997e-68 < f

    1. Initial program 99.9%

      \[\frac{-\left(f + n\right)}{f - n} \]
    2. Step-by-step derivation
      1. neg-mul-199.9%

        \[\leadsto \frac{\color{blue}{-1 \cdot \left(f + n\right)}}{f - n} \]
      2. *-commutative99.9%

        \[\leadsto \frac{\color{blue}{\left(f + n\right) \cdot -1}}{f - n} \]
      3. associate-/l*99.9%

        \[\leadsto \color{blue}{\frac{f + n}{\frac{f - n}{-1}}} \]
      4. div-sub99.9%

        \[\leadsto \frac{f + n}{\color{blue}{\frac{f}{-1} - \frac{n}{-1}}} \]
      5. metadata-eval99.9%

        \[\leadsto \frac{f + n}{\frac{f}{\color{blue}{\frac{1}{-1}}} - \frac{n}{-1}} \]
      6. metadata-eval99.9%

        \[\leadsto \frac{f + n}{\frac{f}{\frac{\color{blue}{--1}}{-1}} - \frac{n}{-1}} \]
      7. associate-/l*99.9%

        \[\leadsto \frac{f + n}{\color{blue}{\frac{f \cdot -1}{--1}} - \frac{n}{-1}} \]
      8. *-commutative99.9%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{-1 \cdot f}}{--1} - \frac{n}{-1}} \]
      9. neg-mul-199.9%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{-f}}{--1} - \frac{n}{-1}} \]
      10. metadata-eval99.9%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{n}{\color{blue}{\frac{1}{-1}}}} \]
      11. metadata-eval99.9%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{n}{\frac{\color{blue}{--1}}{-1}}} \]
      12. associate-/l*99.9%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \color{blue}{\frac{n \cdot -1}{--1}}} \]
      13. *-commutative99.9%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{\color{blue}{-1 \cdot n}}{--1}} \]
      14. neg-mul-199.9%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{\color{blue}{-n}}{--1}} \]
      15. div-sub99.9%

        \[\leadsto \frac{f + n}{\color{blue}{\frac{\left(-f\right) - \left(-n\right)}{--1}}} \]
      16. unsub-neg99.9%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{\left(-f\right) + \left(-\left(-n\right)\right)}}{--1}} \]
      17. remove-double-neg99.9%

        \[\leadsto \frac{f + n}{\frac{\left(-f\right) + \color{blue}{n}}{--1}} \]
      18. +-commutative99.9%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{n + \left(-f\right)}}{--1}} \]
      19. sub-neg99.9%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{n - f}}{--1}} \]
      20. metadata-eval99.9%

        \[\leadsto \frac{f + n}{\frac{n - f}{\color{blue}{1}}} \]
      21. /-rgt-identity99.9%

        \[\leadsto \frac{f + n}{\color{blue}{n - f}} \]
    3. Simplified99.9%

      \[\leadsto \color{blue}{\frac{f + n}{n - f}} \]
    4. Taylor expanded in f around inf 72.8%

      \[\leadsto \color{blue}{-1} \]

    if -1.1e12 < f < -9.9999999999999998e-20 or -1.3e-107 < f < 6.5999999999999997e-68

    1. Initial program 100.0%

      \[\frac{-\left(f + n\right)}{f - n} \]
    2. Step-by-step derivation
      1. neg-mul-1100.0%

        \[\leadsto \frac{\color{blue}{-1 \cdot \left(f + n\right)}}{f - n} \]
      2. *-commutative100.0%

        \[\leadsto \frac{\color{blue}{\left(f + n\right) \cdot -1}}{f - n} \]
      3. associate-/l*100.0%

        \[\leadsto \color{blue}{\frac{f + n}{\frac{f - n}{-1}}} \]
      4. div-sub100.0%

        \[\leadsto \frac{f + n}{\color{blue}{\frac{f}{-1} - \frac{n}{-1}}} \]
      5. metadata-eval100.0%

        \[\leadsto \frac{f + n}{\frac{f}{\color{blue}{\frac{1}{-1}}} - \frac{n}{-1}} \]
      6. metadata-eval100.0%

        \[\leadsto \frac{f + n}{\frac{f}{\frac{\color{blue}{--1}}{-1}} - \frac{n}{-1}} \]
      7. associate-/l*100.0%

        \[\leadsto \frac{f + n}{\color{blue}{\frac{f \cdot -1}{--1}} - \frac{n}{-1}} \]
      8. *-commutative100.0%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{-1 \cdot f}}{--1} - \frac{n}{-1}} \]
      9. neg-mul-1100.0%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{-f}}{--1} - \frac{n}{-1}} \]
      10. metadata-eval100.0%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{n}{\color{blue}{\frac{1}{-1}}}} \]
      11. metadata-eval100.0%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{n}{\frac{\color{blue}{--1}}{-1}}} \]
      12. associate-/l*100.0%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \color{blue}{\frac{n \cdot -1}{--1}}} \]
      13. *-commutative100.0%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{\color{blue}{-1 \cdot n}}{--1}} \]
      14. neg-mul-1100.0%

        \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{\color{blue}{-n}}{--1}} \]
      15. div-sub100.0%

        \[\leadsto \frac{f + n}{\color{blue}{\frac{\left(-f\right) - \left(-n\right)}{--1}}} \]
      16. unsub-neg100.0%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{\left(-f\right) + \left(-\left(-n\right)\right)}}{--1}} \]
      17. remove-double-neg100.0%

        \[\leadsto \frac{f + n}{\frac{\left(-f\right) + \color{blue}{n}}{--1}} \]
      18. +-commutative100.0%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{n + \left(-f\right)}}{--1}} \]
      19. sub-neg100.0%

        \[\leadsto \frac{f + n}{\frac{\color{blue}{n - f}}{--1}} \]
      20. metadata-eval100.0%

        \[\leadsto \frac{f + n}{\frac{n - f}{\color{blue}{1}}} \]
      21. /-rgt-identity100.0%

        \[\leadsto \frac{f + n}{\color{blue}{n - f}} \]
    3. Simplified100.0%

      \[\leadsto \color{blue}{\frac{f + n}{n - f}} \]
    4. Taylor expanded in f around 0 90.4%

      \[\leadsto \color{blue}{1} \]
  3. Recombined 2 regimes into one program.
  4. Final simplification79.4%

    \[\leadsto \begin{array}{l} \mathbf{if}\;f \leq -1100000000000:\\ \;\;\;\;-1\\ \mathbf{elif}\;f \leq -1 \cdot 10^{-19}:\\ \;\;\;\;1\\ \mathbf{elif}\;f \leq -1.3 \cdot 10^{-107}:\\ \;\;\;\;-1\\ \mathbf{elif}\;f \leq 6.6 \cdot 10^{-68}:\\ \;\;\;\;1\\ \mathbf{else}:\\ \;\;\;\;-1\\ \end{array} \]

Alternative 5: 100.0% accurate, 0.9× speedup?

\[\begin{array}{l} \\ \frac{1}{\frac{n - f}{f + n}} \end{array} \]
(FPCore (f n) :precision binary64 (/ 1.0 (/ (- n f) (+ f n))))
double code(double f, double n) {
	return 1.0 / ((n - f) / (f + n));
}
real(8) function code(f, n)
    real(8), intent (in) :: f
    real(8), intent (in) :: n
    code = 1.0d0 / ((n - f) / (f + n))
end function
public static double code(double f, double n) {
	return 1.0 / ((n - f) / (f + n));
}
def code(f, n):
	return 1.0 / ((n - f) / (f + n))
function code(f, n)
	return Float64(1.0 / Float64(Float64(n - f) / Float64(f + n)))
end
function tmp = code(f, n)
	tmp = 1.0 / ((n - f) / (f + n));
end
code[f_, n_] := N[(1.0 / N[(N[(n - f), $MachinePrecision] / N[(f + n), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
\frac{1}{\frac{n - f}{f + n}}
\end{array}
Derivation
  1. Initial program 99.9%

    \[\frac{-\left(f + n\right)}{f - n} \]
  2. Step-by-step derivation
    1. neg-mul-199.9%

      \[\leadsto \frac{\color{blue}{-1 \cdot \left(f + n\right)}}{f - n} \]
    2. *-commutative99.9%

      \[\leadsto \frac{\color{blue}{\left(f + n\right) \cdot -1}}{f - n} \]
    3. associate-/l*99.9%

      \[\leadsto \color{blue}{\frac{f + n}{\frac{f - n}{-1}}} \]
    4. div-sub99.9%

      \[\leadsto \frac{f + n}{\color{blue}{\frac{f}{-1} - \frac{n}{-1}}} \]
    5. metadata-eval99.9%

      \[\leadsto \frac{f + n}{\frac{f}{\color{blue}{\frac{1}{-1}}} - \frac{n}{-1}} \]
    6. metadata-eval99.9%

      \[\leadsto \frac{f + n}{\frac{f}{\frac{\color{blue}{--1}}{-1}} - \frac{n}{-1}} \]
    7. associate-/l*99.9%

      \[\leadsto \frac{f + n}{\color{blue}{\frac{f \cdot -1}{--1}} - \frac{n}{-1}} \]
    8. *-commutative99.9%

      \[\leadsto \frac{f + n}{\frac{\color{blue}{-1 \cdot f}}{--1} - \frac{n}{-1}} \]
    9. neg-mul-199.9%

      \[\leadsto \frac{f + n}{\frac{\color{blue}{-f}}{--1} - \frac{n}{-1}} \]
    10. metadata-eval99.9%

      \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{n}{\color{blue}{\frac{1}{-1}}}} \]
    11. metadata-eval99.9%

      \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{n}{\frac{\color{blue}{--1}}{-1}}} \]
    12. associate-/l*99.9%

      \[\leadsto \frac{f + n}{\frac{-f}{--1} - \color{blue}{\frac{n \cdot -1}{--1}}} \]
    13. *-commutative99.9%

      \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{\color{blue}{-1 \cdot n}}{--1}} \]
    14. neg-mul-199.9%

      \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{\color{blue}{-n}}{--1}} \]
    15. div-sub99.9%

      \[\leadsto \frac{f + n}{\color{blue}{\frac{\left(-f\right) - \left(-n\right)}{--1}}} \]
    16. unsub-neg99.9%

      \[\leadsto \frac{f + n}{\frac{\color{blue}{\left(-f\right) + \left(-\left(-n\right)\right)}}{--1}} \]
    17. remove-double-neg99.9%

      \[\leadsto \frac{f + n}{\frac{\left(-f\right) + \color{blue}{n}}{--1}} \]
    18. +-commutative99.9%

      \[\leadsto \frac{f + n}{\frac{\color{blue}{n + \left(-f\right)}}{--1}} \]
    19. sub-neg99.9%

      \[\leadsto \frac{f + n}{\frac{\color{blue}{n - f}}{--1}} \]
    20. metadata-eval99.9%

      \[\leadsto \frac{f + n}{\frac{n - f}{\color{blue}{1}}} \]
    21. /-rgt-identity99.9%

      \[\leadsto \frac{f + n}{\color{blue}{n - f}} \]
  3. Simplified99.9%

    \[\leadsto \color{blue}{\frac{f + n}{n - f}} \]
  4. Step-by-step derivation
    1. log1p-expm1-u100.0%

      \[\leadsto \color{blue}{\mathsf{log1p}\left(\mathsf{expm1}\left(\frac{f + n}{n - f}\right)\right)} \]
  5. Applied egg-rr100.0%

    \[\leadsto \color{blue}{\mathsf{log1p}\left(\mathsf{expm1}\left(\frac{f + n}{n - f}\right)\right)} \]
  6. Step-by-step derivation
    1. log1p-expm1-u99.9%

      \[\leadsto \color{blue}{\frac{f + n}{n - f}} \]
    2. clear-num99.9%

      \[\leadsto \color{blue}{\frac{1}{\frac{n - f}{f + n}}} \]
  7. Applied egg-rr99.9%

    \[\leadsto \color{blue}{\frac{1}{\frac{n - f}{f + n}}} \]
  8. Final simplification99.9%

    \[\leadsto \frac{1}{\frac{n - f}{f + n}} \]

Alternative 6: 100.0% accurate, 1.1× speedup?

\[\begin{array}{l} \\ \frac{f + n}{n - f} \end{array} \]
(FPCore (f n) :precision binary64 (/ (+ f n) (- n f)))
double code(double f, double n) {
	return (f + n) / (n - f);
}
real(8) function code(f, n)
    real(8), intent (in) :: f
    real(8), intent (in) :: n
    code = (f + n) / (n - f)
end function
public static double code(double f, double n) {
	return (f + n) / (n - f);
}
def code(f, n):
	return (f + n) / (n - f)
function code(f, n)
	return Float64(Float64(f + n) / Float64(n - f))
end
function tmp = code(f, n)
	tmp = (f + n) / (n - f);
end
code[f_, n_] := N[(N[(f + n), $MachinePrecision] / N[(n - f), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
\frac{f + n}{n - f}
\end{array}
Derivation
  1. Initial program 99.9%

    \[\frac{-\left(f + n\right)}{f - n} \]
  2. Step-by-step derivation
    1. neg-mul-199.9%

      \[\leadsto \frac{\color{blue}{-1 \cdot \left(f + n\right)}}{f - n} \]
    2. *-commutative99.9%

      \[\leadsto \frac{\color{blue}{\left(f + n\right) \cdot -1}}{f - n} \]
    3. associate-/l*99.9%

      \[\leadsto \color{blue}{\frac{f + n}{\frac{f - n}{-1}}} \]
    4. div-sub99.9%

      \[\leadsto \frac{f + n}{\color{blue}{\frac{f}{-1} - \frac{n}{-1}}} \]
    5. metadata-eval99.9%

      \[\leadsto \frac{f + n}{\frac{f}{\color{blue}{\frac{1}{-1}}} - \frac{n}{-1}} \]
    6. metadata-eval99.9%

      \[\leadsto \frac{f + n}{\frac{f}{\frac{\color{blue}{--1}}{-1}} - \frac{n}{-1}} \]
    7. associate-/l*99.9%

      \[\leadsto \frac{f + n}{\color{blue}{\frac{f \cdot -1}{--1}} - \frac{n}{-1}} \]
    8. *-commutative99.9%

      \[\leadsto \frac{f + n}{\frac{\color{blue}{-1 \cdot f}}{--1} - \frac{n}{-1}} \]
    9. neg-mul-199.9%

      \[\leadsto \frac{f + n}{\frac{\color{blue}{-f}}{--1} - \frac{n}{-1}} \]
    10. metadata-eval99.9%

      \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{n}{\color{blue}{\frac{1}{-1}}}} \]
    11. metadata-eval99.9%

      \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{n}{\frac{\color{blue}{--1}}{-1}}} \]
    12. associate-/l*99.9%

      \[\leadsto \frac{f + n}{\frac{-f}{--1} - \color{blue}{\frac{n \cdot -1}{--1}}} \]
    13. *-commutative99.9%

      \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{\color{blue}{-1 \cdot n}}{--1}} \]
    14. neg-mul-199.9%

      \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{\color{blue}{-n}}{--1}} \]
    15. div-sub99.9%

      \[\leadsto \frac{f + n}{\color{blue}{\frac{\left(-f\right) - \left(-n\right)}{--1}}} \]
    16. unsub-neg99.9%

      \[\leadsto \frac{f + n}{\frac{\color{blue}{\left(-f\right) + \left(-\left(-n\right)\right)}}{--1}} \]
    17. remove-double-neg99.9%

      \[\leadsto \frac{f + n}{\frac{\left(-f\right) + \color{blue}{n}}{--1}} \]
    18. +-commutative99.9%

      \[\leadsto \frac{f + n}{\frac{\color{blue}{n + \left(-f\right)}}{--1}} \]
    19. sub-neg99.9%

      \[\leadsto \frac{f + n}{\frac{\color{blue}{n - f}}{--1}} \]
    20. metadata-eval99.9%

      \[\leadsto \frac{f + n}{\frac{n - f}{\color{blue}{1}}} \]
    21. /-rgt-identity99.9%

      \[\leadsto \frac{f + n}{\color{blue}{n - f}} \]
  3. Simplified99.9%

    \[\leadsto \color{blue}{\frac{f + n}{n - f}} \]
  4. Final simplification99.9%

    \[\leadsto \frac{f + n}{n - f} \]

Alternative 7: 49.7% accurate, 8.0× speedup?

\[\begin{array}{l} \\ -1 \end{array} \]
(FPCore (f n) :precision binary64 -1.0)
double code(double f, double n) {
	return -1.0;
}
real(8) function code(f, n)
    real(8), intent (in) :: f
    real(8), intent (in) :: n
    code = -1.0d0
end function
public static double code(double f, double n) {
	return -1.0;
}
def code(f, n):
	return -1.0
function code(f, n)
	return -1.0
end
function tmp = code(f, n)
	tmp = -1.0;
end
code[f_, n_] := -1.0
\begin{array}{l}

\\
-1
\end{array}
Derivation
  1. Initial program 99.9%

    \[\frac{-\left(f + n\right)}{f - n} \]
  2. Step-by-step derivation
    1. neg-mul-199.9%

      \[\leadsto \frac{\color{blue}{-1 \cdot \left(f + n\right)}}{f - n} \]
    2. *-commutative99.9%

      \[\leadsto \frac{\color{blue}{\left(f + n\right) \cdot -1}}{f - n} \]
    3. associate-/l*99.9%

      \[\leadsto \color{blue}{\frac{f + n}{\frac{f - n}{-1}}} \]
    4. div-sub99.9%

      \[\leadsto \frac{f + n}{\color{blue}{\frac{f}{-1} - \frac{n}{-1}}} \]
    5. metadata-eval99.9%

      \[\leadsto \frac{f + n}{\frac{f}{\color{blue}{\frac{1}{-1}}} - \frac{n}{-1}} \]
    6. metadata-eval99.9%

      \[\leadsto \frac{f + n}{\frac{f}{\frac{\color{blue}{--1}}{-1}} - \frac{n}{-1}} \]
    7. associate-/l*99.9%

      \[\leadsto \frac{f + n}{\color{blue}{\frac{f \cdot -1}{--1}} - \frac{n}{-1}} \]
    8. *-commutative99.9%

      \[\leadsto \frac{f + n}{\frac{\color{blue}{-1 \cdot f}}{--1} - \frac{n}{-1}} \]
    9. neg-mul-199.9%

      \[\leadsto \frac{f + n}{\frac{\color{blue}{-f}}{--1} - \frac{n}{-1}} \]
    10. metadata-eval99.9%

      \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{n}{\color{blue}{\frac{1}{-1}}}} \]
    11. metadata-eval99.9%

      \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{n}{\frac{\color{blue}{--1}}{-1}}} \]
    12. associate-/l*99.9%

      \[\leadsto \frac{f + n}{\frac{-f}{--1} - \color{blue}{\frac{n \cdot -1}{--1}}} \]
    13. *-commutative99.9%

      \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{\color{blue}{-1 \cdot n}}{--1}} \]
    14. neg-mul-199.9%

      \[\leadsto \frac{f + n}{\frac{-f}{--1} - \frac{\color{blue}{-n}}{--1}} \]
    15. div-sub99.9%

      \[\leadsto \frac{f + n}{\color{blue}{\frac{\left(-f\right) - \left(-n\right)}{--1}}} \]
    16. unsub-neg99.9%

      \[\leadsto \frac{f + n}{\frac{\color{blue}{\left(-f\right) + \left(-\left(-n\right)\right)}}{--1}} \]
    17. remove-double-neg99.9%

      \[\leadsto \frac{f + n}{\frac{\left(-f\right) + \color{blue}{n}}{--1}} \]
    18. +-commutative99.9%

      \[\leadsto \frac{f + n}{\frac{\color{blue}{n + \left(-f\right)}}{--1}} \]
    19. sub-neg99.9%

      \[\leadsto \frac{f + n}{\frac{\color{blue}{n - f}}{--1}} \]
    20. metadata-eval99.9%

      \[\leadsto \frac{f + n}{\frac{n - f}{\color{blue}{1}}} \]
    21. /-rgt-identity99.9%

      \[\leadsto \frac{f + n}{\color{blue}{n - f}} \]
  3. Simplified99.9%

    \[\leadsto \color{blue}{\frac{f + n}{n - f}} \]
  4. Taylor expanded in f around inf 48.9%

    \[\leadsto \color{blue}{-1} \]
  5. Final simplification48.9%

    \[\leadsto -1 \]

Reproduce

?
herbie shell --seed 2023189 
(FPCore (f n)
  :name "subtraction fraction"
  :precision binary64
  (/ (- (+ f n)) (- f n)))