Complex division, imag part

Percentage Accurate: 61.9% → 80.6%
Time: 9.4s
Alternatives: 8
Speedup: 1.5×

Specification

?
\[\begin{array}{l} \\ \frac{b \cdot c - a \cdot d}{c \cdot c + d \cdot d} \end{array} \]
(FPCore (a b c d)
 :precision binary64
 (/ (- (* b c) (* a d)) (+ (* c c) (* d d))))
double code(double a, double b, double c, double d) {
	return ((b * c) - (a * d)) / ((c * c) + (d * d));
}
real(8) function code(a, b, c, d)
    real(8), intent (in) :: a
    real(8), intent (in) :: b
    real(8), intent (in) :: c
    real(8), intent (in) :: d
    code = ((b * c) - (a * d)) / ((c * c) + (d * d))
end function
public static double code(double a, double b, double c, double d) {
	return ((b * c) - (a * d)) / ((c * c) + (d * d));
}
def code(a, b, c, d):
	return ((b * c) - (a * d)) / ((c * c) + (d * d))
function code(a, b, c, d)
	return Float64(Float64(Float64(b * c) - Float64(a * d)) / Float64(Float64(c * c) + Float64(d * d)))
end
function tmp = code(a, b, c, d)
	tmp = ((b * c) - (a * d)) / ((c * c) + (d * d));
end
code[a_, b_, c_, d_] := N[(N[(N[(b * c), $MachinePrecision] - N[(a * d), $MachinePrecision]), $MachinePrecision] / N[(N[(c * c), $MachinePrecision] + N[(d * d), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
\frac{b \cdot c - a \cdot d}{c \cdot c + d \cdot d}
\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 8 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: 61.9% accurate, 1.0× speedup?

\[\begin{array}{l} \\ \frac{b \cdot c - a \cdot d}{c \cdot c + d \cdot d} \end{array} \]
(FPCore (a b c d)
 :precision binary64
 (/ (- (* b c) (* a d)) (+ (* c c) (* d d))))
double code(double a, double b, double c, double d) {
	return ((b * c) - (a * d)) / ((c * c) + (d * d));
}
real(8) function code(a, b, c, d)
    real(8), intent (in) :: a
    real(8), intent (in) :: b
    real(8), intent (in) :: c
    real(8), intent (in) :: d
    code = ((b * c) - (a * d)) / ((c * c) + (d * d))
end function
public static double code(double a, double b, double c, double d) {
	return ((b * c) - (a * d)) / ((c * c) + (d * d));
}
def code(a, b, c, d):
	return ((b * c) - (a * d)) / ((c * c) + (d * d))
function code(a, b, c, d)
	return Float64(Float64(Float64(b * c) - Float64(a * d)) / Float64(Float64(c * c) + Float64(d * d)))
end
function tmp = code(a, b, c, d)
	tmp = ((b * c) - (a * d)) / ((c * c) + (d * d));
end
code[a_, b_, c_, d_] := N[(N[(N[(b * c), $MachinePrecision] - N[(a * d), $MachinePrecision]), $MachinePrecision] / N[(N[(c * c), $MachinePrecision] + N[(d * d), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
\frac{b \cdot c - a \cdot d}{c \cdot c + d \cdot d}
\end{array}

Alternative 1: 80.6% accurate, 0.8× speedup?

\[\begin{array}{l} \\ \begin{array}{l} t_0 := \frac{\mathsf{fma}\left(c, \frac{b}{d}, -a\right)}{d}\\ \mathbf{if}\;d \leq -3 \cdot 10^{+118}:\\ \;\;\;\;t\_0\\ \mathbf{elif}\;d \leq -1.12 \cdot 10^{-138}:\\ \;\;\;\;\frac{b \cdot c - d \cdot a}{c \cdot c + d \cdot d}\\ \mathbf{elif}\;d \leq 0.28:\\ \;\;\;\;\frac{\mathsf{fma}\left(a, -\frac{d}{c}, b\right)}{c}\\ \mathbf{else}:\\ \;\;\;\;t\_0\\ \end{array} \end{array} \]
(FPCore (a b c d)
 :precision binary64
 (let* ((t_0 (/ (fma c (/ b d) (- a)) d)))
   (if (<= d -3e+118)
     t_0
     (if (<= d -1.12e-138)
       (/ (- (* b c) (* d a)) (+ (* c c) (* d d)))
       (if (<= d 0.28) (/ (fma a (- (/ d c)) b) c) t_0)))))
double code(double a, double b, double c, double d) {
	double t_0 = fma(c, (b / d), -a) / d;
	double tmp;
	if (d <= -3e+118) {
		tmp = t_0;
	} else if (d <= -1.12e-138) {
		tmp = ((b * c) - (d * a)) / ((c * c) + (d * d));
	} else if (d <= 0.28) {
		tmp = fma(a, -(d / c), b) / c;
	} else {
		tmp = t_0;
	}
	return tmp;
}
function code(a, b, c, d)
	t_0 = Float64(fma(c, Float64(b / d), Float64(-a)) / d)
	tmp = 0.0
	if (d <= -3e+118)
		tmp = t_0;
	elseif (d <= -1.12e-138)
		tmp = Float64(Float64(Float64(b * c) - Float64(d * a)) / Float64(Float64(c * c) + Float64(d * d)));
	elseif (d <= 0.28)
		tmp = Float64(fma(a, Float64(-Float64(d / c)), b) / c);
	else
		tmp = t_0;
	end
	return tmp
end
code[a_, b_, c_, d_] := Block[{t$95$0 = N[(N[(c * N[(b / d), $MachinePrecision] + (-a)), $MachinePrecision] / d), $MachinePrecision]}, If[LessEqual[d, -3e+118], t$95$0, If[LessEqual[d, -1.12e-138], N[(N[(N[(b * c), $MachinePrecision] - N[(d * a), $MachinePrecision]), $MachinePrecision] / N[(N[(c * c), $MachinePrecision] + N[(d * d), $MachinePrecision]), $MachinePrecision]), $MachinePrecision], If[LessEqual[d, 0.28], N[(N[(a * (-N[(d / c), $MachinePrecision]) + b), $MachinePrecision] / c), $MachinePrecision], t$95$0]]]]
\begin{array}{l}

\\
\begin{array}{l}
t_0 := \frac{\mathsf{fma}\left(c, \frac{b}{d}, -a\right)}{d}\\
\mathbf{if}\;d \leq -3 \cdot 10^{+118}:\\
\;\;\;\;t\_0\\

\mathbf{elif}\;d \leq -1.12 \cdot 10^{-138}:\\
\;\;\;\;\frac{b \cdot c - d \cdot a}{c \cdot c + d \cdot d}\\

\mathbf{elif}\;d \leq 0.28:\\
\;\;\;\;\frac{\mathsf{fma}\left(a, -\frac{d}{c}, b\right)}{c}\\

\mathbf{else}:\\
\;\;\;\;t\_0\\


\end{array}
\end{array}
Derivation
  1. Split input into 3 regimes
  2. if d < -3e118 or 0.28000000000000003 < d

    1. Initial program 39.8%

      \[\frac{b \cdot c - a \cdot d}{c \cdot c + d \cdot d} \]
    2. Add Preprocessing
    3. Taylor expanded in c around 0

      \[\leadsto \color{blue}{-1 \cdot \frac{a}{d} + \frac{b \cdot c}{{d}^{2}}} \]
    4. Step-by-step derivation
      1. +-commutativeN/A

        \[\leadsto \color{blue}{\frac{b \cdot c}{{d}^{2}} + -1 \cdot \frac{a}{d}} \]
      2. mul-1-negN/A

        \[\leadsto \frac{b \cdot c}{{d}^{2}} + \color{blue}{\left(\mathsf{neg}\left(\frac{a}{d}\right)\right)} \]
      3. unsub-negN/A

        \[\leadsto \color{blue}{\frac{b \cdot c}{{d}^{2}} - \frac{a}{d}} \]
      4. unpow2N/A

        \[\leadsto \frac{b \cdot c}{\color{blue}{d \cdot d}} - \frac{a}{d} \]
      5. associate-/r*N/A

        \[\leadsto \color{blue}{\frac{\frac{b \cdot c}{d}}{d}} - \frac{a}{d} \]
      6. div-subN/A

        \[\leadsto \color{blue}{\frac{\frac{b \cdot c}{d} - a}{d}} \]
      7. lower-/.f64N/A

        \[\leadsto \color{blue}{\frac{\frac{b \cdot c}{d} - a}{d}} \]
      8. sub-negN/A

        \[\leadsto \frac{\color{blue}{\frac{b \cdot c}{d} + \left(\mathsf{neg}\left(a\right)\right)}}{d} \]
      9. *-commutativeN/A

        \[\leadsto \frac{\frac{\color{blue}{c \cdot b}}{d} + \left(\mathsf{neg}\left(a\right)\right)}{d} \]
      10. associate-/l*N/A

        \[\leadsto \frac{\color{blue}{c \cdot \frac{b}{d}} + \left(\mathsf{neg}\left(a\right)\right)}{d} \]
      11. mul-1-negN/A

        \[\leadsto \frac{c \cdot \frac{b}{d} + \color{blue}{-1 \cdot a}}{d} \]
      12. lower-fma.f64N/A

        \[\leadsto \frac{\color{blue}{\mathsf{fma}\left(c, \frac{b}{d}, -1 \cdot a\right)}}{d} \]
      13. lower-/.f64N/A

        \[\leadsto \frac{\mathsf{fma}\left(c, \color{blue}{\frac{b}{d}}, -1 \cdot a\right)}{d} \]
      14. mul-1-negN/A

        \[\leadsto \frac{\mathsf{fma}\left(c, \frac{b}{d}, \color{blue}{\mathsf{neg}\left(a\right)}\right)}{d} \]
      15. lower-neg.f6481.8

        \[\leadsto \frac{\mathsf{fma}\left(c, \frac{b}{d}, \color{blue}{-a}\right)}{d} \]
    5. Applied rewrites81.8%

      \[\leadsto \color{blue}{\frac{\mathsf{fma}\left(c, \frac{b}{d}, -a\right)}{d}} \]

    if -3e118 < d < -1.1199999999999999e-138

    1. Initial program 84.9%

      \[\frac{b \cdot c - a \cdot d}{c \cdot c + d \cdot d} \]
    2. Add Preprocessing

    if -1.1199999999999999e-138 < d < 0.28000000000000003

    1. Initial program 65.2%

      \[\frac{b \cdot c - a \cdot d}{c \cdot c + d \cdot d} \]
    2. Add Preprocessing
    3. Taylor expanded in c around 0

      \[\leadsto \color{blue}{-1 \cdot \frac{a}{d}} \]
    4. Step-by-step derivation
      1. mul-1-negN/A

        \[\leadsto \color{blue}{\mathsf{neg}\left(\frac{a}{d}\right)} \]
      2. distribute-neg-frac2N/A

        \[\leadsto \color{blue}{\frac{a}{\mathsf{neg}\left(d\right)}} \]
      3. mul-1-negN/A

        \[\leadsto \frac{a}{\color{blue}{-1 \cdot d}} \]
      4. lower-/.f64N/A

        \[\leadsto \color{blue}{\frac{a}{-1 \cdot d}} \]
      5. mul-1-negN/A

        \[\leadsto \frac{a}{\color{blue}{\mathsf{neg}\left(d\right)}} \]
      6. lower-neg.f6414.9

        \[\leadsto \frac{a}{\color{blue}{-d}} \]
    5. Applied rewrites14.9%

      \[\leadsto \color{blue}{\frac{a}{-d}} \]
    6. Taylor expanded in c around inf

      \[\leadsto \color{blue}{\frac{b + -1 \cdot \frac{a \cdot d}{c}}{c}} \]
    7. Step-by-step derivation
      1. lower-/.f64N/A

        \[\leadsto \color{blue}{\frac{b + -1 \cdot \frac{a \cdot d}{c}}{c}} \]
      2. +-commutativeN/A

        \[\leadsto \frac{\color{blue}{-1 \cdot \frac{a \cdot d}{c} + b}}{c} \]
      3. mul-1-negN/A

        \[\leadsto \frac{\color{blue}{\left(\mathsf{neg}\left(\frac{a \cdot d}{c}\right)\right)} + b}{c} \]
      4. associate-/l*N/A

        \[\leadsto \frac{\left(\mathsf{neg}\left(\color{blue}{a \cdot \frac{d}{c}}\right)\right) + b}{c} \]
      5. distribute-rgt-neg-inN/A

        \[\leadsto \frac{\color{blue}{a \cdot \left(\mathsf{neg}\left(\frac{d}{c}\right)\right)} + b}{c} \]
      6. mul-1-negN/A

        \[\leadsto \frac{a \cdot \color{blue}{\left(-1 \cdot \frac{d}{c}\right)} + b}{c} \]
      7. lower-fma.f64N/A

        \[\leadsto \frac{\color{blue}{\mathsf{fma}\left(a, -1 \cdot \frac{d}{c}, b\right)}}{c} \]
      8. mul-1-negN/A

        \[\leadsto \frac{\mathsf{fma}\left(a, \color{blue}{\mathsf{neg}\left(\frac{d}{c}\right)}, b\right)}{c} \]
      9. distribute-neg-frac2N/A

        \[\leadsto \frac{\mathsf{fma}\left(a, \color{blue}{\frac{d}{\mathsf{neg}\left(c\right)}}, b\right)}{c} \]
      10. mul-1-negN/A

        \[\leadsto \frac{\mathsf{fma}\left(a, \frac{d}{\color{blue}{-1 \cdot c}}, b\right)}{c} \]
      11. lower-/.f64N/A

        \[\leadsto \frac{\mathsf{fma}\left(a, \color{blue}{\frac{d}{-1 \cdot c}}, b\right)}{c} \]
      12. mul-1-negN/A

        \[\leadsto \frac{\mathsf{fma}\left(a, \frac{d}{\color{blue}{\mathsf{neg}\left(c\right)}}, b\right)}{c} \]
      13. lower-neg.f6486.8

        \[\leadsto \frac{\mathsf{fma}\left(a, \frac{d}{\color{blue}{-c}}, b\right)}{c} \]
    8. Applied rewrites86.8%

      \[\leadsto \color{blue}{\frac{\mathsf{fma}\left(a, \frac{d}{-c}, b\right)}{c}} \]
  3. Recombined 3 regimes into one program.
  4. Final simplification84.4%

    \[\leadsto \begin{array}{l} \mathbf{if}\;d \leq -3 \cdot 10^{+118}:\\ \;\;\;\;\frac{\mathsf{fma}\left(c, \frac{b}{d}, -a\right)}{d}\\ \mathbf{elif}\;d \leq -1.12 \cdot 10^{-138}:\\ \;\;\;\;\frac{b \cdot c - d \cdot a}{c \cdot c + d \cdot d}\\ \mathbf{elif}\;d \leq 0.28:\\ \;\;\;\;\frac{\mathsf{fma}\left(a, -\frac{d}{c}, b\right)}{c}\\ \mathbf{else}:\\ \;\;\;\;\frac{\mathsf{fma}\left(c, \frac{b}{d}, -a\right)}{d}\\ \end{array} \]
  5. Add Preprocessing

Alternative 2: 72.5% accurate, 0.7× speedup?

\[\begin{array}{l} \\ \begin{array}{l} t_0 := -\frac{a}{d}\\ t_1 := \frac{b \cdot c - d \cdot a}{d \cdot d}\\ \mathbf{if}\;d \leq -9.5 \cdot 10^{+139}:\\ \;\;\;\;t\_0\\ \mathbf{elif}\;d \leq -3.3 \cdot 10^{-76}:\\ \;\;\;\;t\_1\\ \mathbf{elif}\;d \leq 0.28:\\ \;\;\;\;\frac{b - \frac{d \cdot a}{c}}{c}\\ \mathbf{elif}\;d \leq 10^{+102}:\\ \;\;\;\;t\_1\\ \mathbf{else}:\\ \;\;\;\;t\_0\\ \end{array} \end{array} \]
(FPCore (a b c d)
 :precision binary64
 (let* ((t_0 (- (/ a d))) (t_1 (/ (- (* b c) (* d a)) (* d d))))
   (if (<= d -9.5e+139)
     t_0
     (if (<= d -3.3e-76)
       t_1
       (if (<= d 0.28)
         (/ (- b (/ (* d a) c)) c)
         (if (<= d 1e+102) t_1 t_0))))))
double code(double a, double b, double c, double d) {
	double t_0 = -(a / d);
	double t_1 = ((b * c) - (d * a)) / (d * d);
	double tmp;
	if (d <= -9.5e+139) {
		tmp = t_0;
	} else if (d <= -3.3e-76) {
		tmp = t_1;
	} else if (d <= 0.28) {
		tmp = (b - ((d * a) / c)) / c;
	} else if (d <= 1e+102) {
		tmp = t_1;
	} else {
		tmp = t_0;
	}
	return tmp;
}
real(8) function code(a, b, c, d)
    real(8), intent (in) :: a
    real(8), intent (in) :: b
    real(8), intent (in) :: c
    real(8), intent (in) :: d
    real(8) :: t_0
    real(8) :: t_1
    real(8) :: tmp
    t_0 = -(a / d)
    t_1 = ((b * c) - (d * a)) / (d * d)
    if (d <= (-9.5d+139)) then
        tmp = t_0
    else if (d <= (-3.3d-76)) then
        tmp = t_1
    else if (d <= 0.28d0) then
        tmp = (b - ((d * a) / c)) / c
    else if (d <= 1d+102) then
        tmp = t_1
    else
        tmp = t_0
    end if
    code = tmp
end function
public static double code(double a, double b, double c, double d) {
	double t_0 = -(a / d);
	double t_1 = ((b * c) - (d * a)) / (d * d);
	double tmp;
	if (d <= -9.5e+139) {
		tmp = t_0;
	} else if (d <= -3.3e-76) {
		tmp = t_1;
	} else if (d <= 0.28) {
		tmp = (b - ((d * a) / c)) / c;
	} else if (d <= 1e+102) {
		tmp = t_1;
	} else {
		tmp = t_0;
	}
	return tmp;
}
def code(a, b, c, d):
	t_0 = -(a / d)
	t_1 = ((b * c) - (d * a)) / (d * d)
	tmp = 0
	if d <= -9.5e+139:
		tmp = t_0
	elif d <= -3.3e-76:
		tmp = t_1
	elif d <= 0.28:
		tmp = (b - ((d * a) / c)) / c
	elif d <= 1e+102:
		tmp = t_1
	else:
		tmp = t_0
	return tmp
function code(a, b, c, d)
	t_0 = Float64(-Float64(a / d))
	t_1 = Float64(Float64(Float64(b * c) - Float64(d * a)) / Float64(d * d))
	tmp = 0.0
	if (d <= -9.5e+139)
		tmp = t_0;
	elseif (d <= -3.3e-76)
		tmp = t_1;
	elseif (d <= 0.28)
		tmp = Float64(Float64(b - Float64(Float64(d * a) / c)) / c);
	elseif (d <= 1e+102)
		tmp = t_1;
	else
		tmp = t_0;
	end
	return tmp
end
function tmp_2 = code(a, b, c, d)
	t_0 = -(a / d);
	t_1 = ((b * c) - (d * a)) / (d * d);
	tmp = 0.0;
	if (d <= -9.5e+139)
		tmp = t_0;
	elseif (d <= -3.3e-76)
		tmp = t_1;
	elseif (d <= 0.28)
		tmp = (b - ((d * a) / c)) / c;
	elseif (d <= 1e+102)
		tmp = t_1;
	else
		tmp = t_0;
	end
	tmp_2 = tmp;
end
code[a_, b_, c_, d_] := Block[{t$95$0 = (-N[(a / d), $MachinePrecision])}, Block[{t$95$1 = N[(N[(N[(b * c), $MachinePrecision] - N[(d * a), $MachinePrecision]), $MachinePrecision] / N[(d * d), $MachinePrecision]), $MachinePrecision]}, If[LessEqual[d, -9.5e+139], t$95$0, If[LessEqual[d, -3.3e-76], t$95$1, If[LessEqual[d, 0.28], N[(N[(b - N[(N[(d * a), $MachinePrecision] / c), $MachinePrecision]), $MachinePrecision] / c), $MachinePrecision], If[LessEqual[d, 1e+102], t$95$1, t$95$0]]]]]]
\begin{array}{l}

\\
\begin{array}{l}
t_0 := -\frac{a}{d}\\
t_1 := \frac{b \cdot c - d \cdot a}{d \cdot d}\\
\mathbf{if}\;d \leq -9.5 \cdot 10^{+139}:\\
\;\;\;\;t\_0\\

\mathbf{elif}\;d \leq -3.3 \cdot 10^{-76}:\\
\;\;\;\;t\_1\\

\mathbf{elif}\;d \leq 0.28:\\
\;\;\;\;\frac{b - \frac{d \cdot a}{c}}{c}\\

\mathbf{elif}\;d \leq 10^{+102}:\\
\;\;\;\;t\_1\\

\mathbf{else}:\\
\;\;\;\;t\_0\\


\end{array}
\end{array}
Derivation
  1. Split input into 3 regimes
  2. if d < -9.5000000000000002e139 or 9.99999999999999977e101 < d

    1. Initial program 35.2%

      \[\frac{b \cdot c - a \cdot d}{c \cdot c + d \cdot d} \]
    2. Add Preprocessing
    3. Taylor expanded in c around 0

      \[\leadsto \color{blue}{-1 \cdot \frac{a}{d}} \]
    4. Step-by-step derivation
      1. mul-1-negN/A

        \[\leadsto \color{blue}{\mathsf{neg}\left(\frac{a}{d}\right)} \]
      2. distribute-neg-frac2N/A

        \[\leadsto \color{blue}{\frac{a}{\mathsf{neg}\left(d\right)}} \]
      3. mul-1-negN/A

        \[\leadsto \frac{a}{\color{blue}{-1 \cdot d}} \]
      4. lower-/.f64N/A

        \[\leadsto \color{blue}{\frac{a}{-1 \cdot d}} \]
      5. mul-1-negN/A

        \[\leadsto \frac{a}{\color{blue}{\mathsf{neg}\left(d\right)}} \]
      6. lower-neg.f6474.6

        \[\leadsto \frac{a}{\color{blue}{-d}} \]
    5. Applied rewrites74.6%

      \[\leadsto \color{blue}{\frac{a}{-d}} \]

    if -9.5000000000000002e139 < d < -3.29999999999999984e-76 or 0.28000000000000003 < d < 9.99999999999999977e101

    1. Initial program 74.3%

      \[\frac{b \cdot c - a \cdot d}{c \cdot c + d \cdot d} \]
    2. Add Preprocessing
    3. Taylor expanded in c around 0

      \[\leadsto \frac{b \cdot c - a \cdot d}{\color{blue}{{d}^{2}}} \]
    4. Step-by-step derivation
      1. unpow2N/A

        \[\leadsto \frac{b \cdot c - a \cdot d}{\color{blue}{d \cdot d}} \]
      2. lower-*.f6452.6

        \[\leadsto \frac{b \cdot c - a \cdot d}{\color{blue}{d \cdot d}} \]
    5. Applied rewrites52.6%

      \[\leadsto \frac{b \cdot c - a \cdot d}{\color{blue}{d \cdot d}} \]

    if -3.29999999999999984e-76 < d < 0.28000000000000003

    1. Initial program 73.3%

      \[\frac{b \cdot c - a \cdot d}{c \cdot c + d \cdot d} \]
    2. Add Preprocessing
    3. Taylor expanded in c around inf

      \[\leadsto \color{blue}{\frac{b + -1 \cdot \frac{a \cdot d}{c}}{c}} \]
    4. Step-by-step derivation
      1. lower-/.f64N/A

        \[\leadsto \color{blue}{\frac{b + -1 \cdot \frac{a \cdot d}{c}}{c}} \]
      2. mul-1-negN/A

        \[\leadsto \frac{b + \color{blue}{\left(\mathsf{neg}\left(\frac{a \cdot d}{c}\right)\right)}}{c} \]
      3. unsub-negN/A

        \[\leadsto \frac{\color{blue}{b - \frac{a \cdot d}{c}}}{c} \]
      4. lower--.f64N/A

        \[\leadsto \frac{\color{blue}{b - \frac{a \cdot d}{c}}}{c} \]
      5. lower-/.f64N/A

        \[\leadsto \frac{b - \color{blue}{\frac{a \cdot d}{c}}}{c} \]
      6. *-commutativeN/A

        \[\leadsto \frac{b - \frac{\color{blue}{d \cdot a}}{c}}{c} \]
      7. lower-*.f6482.5

        \[\leadsto \frac{b - \frac{\color{blue}{d \cdot a}}{c}}{c} \]
    5. Applied rewrites82.5%

      \[\leadsto \color{blue}{\frac{b - \frac{d \cdot a}{c}}{c}} \]
  3. Recombined 3 regimes into one program.
  4. Final simplification72.5%

    \[\leadsto \begin{array}{l} \mathbf{if}\;d \leq -9.5 \cdot 10^{+139}:\\ \;\;\;\;-\frac{a}{d}\\ \mathbf{elif}\;d \leq -3.3 \cdot 10^{-76}:\\ \;\;\;\;\frac{b \cdot c - d \cdot a}{d \cdot d}\\ \mathbf{elif}\;d \leq 0.28:\\ \;\;\;\;\frac{b - \frac{d \cdot a}{c}}{c}\\ \mathbf{elif}\;d \leq 10^{+102}:\\ \;\;\;\;\frac{b \cdot c - d \cdot a}{d \cdot d}\\ \mathbf{else}:\\ \;\;\;\;-\frac{a}{d}\\ \end{array} \]
  5. Add Preprocessing

Developer Target 1: 99.4% accurate, 0.6× speedup?

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;\left|d\right| < \left|c\right|:\\ \;\;\;\;\frac{b - a \cdot \frac{d}{c}}{c + d \cdot \frac{d}{c}}\\ \mathbf{else}:\\ \;\;\;\;\frac{\left(-a\right) + b \cdot \frac{c}{d}}{d + c \cdot \frac{c}{d}}\\ \end{array} \end{array} \]
(FPCore (a b c d)
 :precision binary64
 (if (< (fabs d) (fabs c))
   (/ (- b (* a (/ d c))) (+ c (* d (/ d c))))
   (/ (+ (- a) (* b (/ c d))) (+ d (* c (/ c d))))))
double code(double a, double b, double c, double d) {
	double tmp;
	if (fabs(d) < fabs(c)) {
		tmp = (b - (a * (d / c))) / (c + (d * (d / c)));
	} else {
		tmp = (-a + (b * (c / d))) / (d + (c * (c / d)));
	}
	return tmp;
}
real(8) function code(a, b, c, d)
    real(8), intent (in) :: a
    real(8), intent (in) :: b
    real(8), intent (in) :: c
    real(8), intent (in) :: d
    real(8) :: tmp
    if (abs(d) < abs(c)) then
        tmp = (b - (a * (d / c))) / (c + (d * (d / c)))
    else
        tmp = (-a + (b * (c / d))) / (d + (c * (c / d)))
    end if
    code = tmp
end function
public static double code(double a, double b, double c, double d) {
	double tmp;
	if (Math.abs(d) < Math.abs(c)) {
		tmp = (b - (a * (d / c))) / (c + (d * (d / c)));
	} else {
		tmp = (-a + (b * (c / d))) / (d + (c * (c / d)));
	}
	return tmp;
}
def code(a, b, c, d):
	tmp = 0
	if math.fabs(d) < math.fabs(c):
		tmp = (b - (a * (d / c))) / (c + (d * (d / c)))
	else:
		tmp = (-a + (b * (c / d))) / (d + (c * (c / d)))
	return tmp
function code(a, b, c, d)
	tmp = 0.0
	if (abs(d) < abs(c))
		tmp = Float64(Float64(b - Float64(a * Float64(d / c))) / Float64(c + Float64(d * Float64(d / c))));
	else
		tmp = Float64(Float64(Float64(-a) + Float64(b * Float64(c / d))) / Float64(d + Float64(c * Float64(c / d))));
	end
	return tmp
end
function tmp_2 = code(a, b, c, d)
	tmp = 0.0;
	if (abs(d) < abs(c))
		tmp = (b - (a * (d / c))) / (c + (d * (d / c)));
	else
		tmp = (-a + (b * (c / d))) / (d + (c * (c / d)));
	end
	tmp_2 = tmp;
end
code[a_, b_, c_, d_] := If[Less[N[Abs[d], $MachinePrecision], N[Abs[c], $MachinePrecision]], N[(N[(b - N[(a * N[(d / c), $MachinePrecision]), $MachinePrecision]), $MachinePrecision] / N[(c + N[(d * N[(d / c), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]), $MachinePrecision], N[(N[((-a) + N[(b * N[(c / d), $MachinePrecision]), $MachinePrecision]), $MachinePrecision] / N[(d + N[(c * N[(c / d), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]]
\begin{array}{l}

\\
\begin{array}{l}
\mathbf{if}\;\left|d\right| < \left|c\right|:\\
\;\;\;\;\frac{b - a \cdot \frac{d}{c}}{c + d \cdot \frac{d}{c}}\\

\mathbf{else}:\\
\;\;\;\;\frac{\left(-a\right) + b \cdot \frac{c}{d}}{d + c \cdot \frac{c}{d}}\\


\end{array}
\end{array}

Reproduce

?
herbie shell --seed 2024228 
(FPCore (a b c d)
  :name "Complex division, imag part"
  :precision binary64

  :alt
  (! :herbie-platform default (if (< (fabs d) (fabs c)) (/ (- b (* a (/ d c))) (+ c (* d (/ d c)))) (/ (+ (- a) (* b (/ c d))) (+ d (* c (/ c d))))))

  (/ (- (* b c) (* a d)) (+ (* c c) (* d d))))