VandenBroeck and Keller, Equation (20)

Percentage Accurate: 6.7% → 99.0%

Time: 30.5s

Alternatives: 4

Speedup: 4.8×

• could not determine a ground truth

  1. f = 2.00000000000000007e154

Specification

Math

\[\begin{array}{l} \\ \begin{array}{l} t_0 := \frac{\pi}{4} \cdot f\\ t_1 := e^{t\_0}\\ t_2 := e^{-t\_0}\\ -\frac{1}{\frac{\pi}{4}} \cdot \log \left(\frac{t\_1 + t\_2}{t\_1 - t\_2}\right) \end{array} \end{array} \]

FPCore

(FPCore (f)
 :precision binary64
 (let* ((t_0 (* (/ PI 4.0) f)) (t_1 (exp t_0)) (t_2 (exp (- t_0))))
   (- (* (/ 1.0 (/ PI 4.0)) (log (/ (+ t_1 t_2) (- t_1 t_2)))))))

C

double code(double f) {
	double t_0 = (((double) M_PI) / 4.0) * f;
	double t_1 = exp(t_0);
	double t_2 = exp(-t_0);
	return -((1.0 / (((double) M_PI) / 4.0)) * log(((t_1 + t_2) / (t_1 - t_2))));
}

Java

public static double code(double f) {
	double t_0 = (Math.PI / 4.0) * f;
	double t_1 = Math.exp(t_0);
	double t_2 = Math.exp(-t_0);
	return -((1.0 / (Math.PI / 4.0)) * Math.log(((t_1 + t_2) / (t_1 - t_2))));
}

Python

def code(f):
	t_0 = (math.pi / 4.0) * f
	t_1 = math.exp(t_0)
	t_2 = math.exp(-t_0)
	return -((1.0 / (math.pi / 4.0)) * math.log(((t_1 + t_2) / (t_1 - t_2))))

Julia

function code(f)
	t_0 = Float64(Float64(pi / 4.0) * f)
	t_1 = exp(t_0)
	t_2 = exp(Float64(-t_0))
	return Float64(-Float64(Float64(1.0 / Float64(pi / 4.0)) * log(Float64(Float64(t_1 + t_2) / Float64(t_1 - t_2)))))
end

MATLAB

function tmp = code(f)
	t_0 = (pi / 4.0) * f;
	t_1 = exp(t_0);
	t_2 = exp(-t_0);
	tmp = -((1.0 / (pi / 4.0)) * log(((t_1 + t_2) / (t_1 - t_2))));
end

Wolfram

code[f_] := Block[{t$95$0 = N[(N[(Pi / 4.0), $MachinePrecision] * f), $MachinePrecision]}, Block[{t$95$1 = N[Exp[t$95$0], $MachinePrecision]}, Block[{t$95$2 = N[Exp[(-t$95$0)], $MachinePrecision]}, (-N[(N[(1.0 / N[(Pi / 4.0), $MachinePrecision]), $MachinePrecision] * N[Log[N[(N[(t$95$1 + t$95$2), $MachinePrecision] / N[(t$95$1 - t$95$2), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision])]]]

Initial Program: 6.7% accurate, 1.0× speedup

Math

\[\begin{array}{l} \\ \begin{array}{l} t_0 := \frac{\pi}{4} \cdot f\\ t_1 := e^{t\_0}\\ t_2 := e^{-t\_0}\\ -\frac{1}{\frac{\pi}{4}} \cdot \log \left(\frac{t\_1 + t\_2}{t\_1 - t\_2}\right) \end{array} \end{array} \]

FPCore

(FPCore (f)
 :precision binary64
 (let* ((t_0 (* (/ PI 4.0) f)) (t_1 (exp t_0)) (t_2 (exp (- t_0))))
   (- (* (/ 1.0 (/ PI 4.0)) (log (/ (+ t_1 t_2) (- t_1 t_2)))))))

C

double code(double f) {
	double t_0 = (((double) M_PI) / 4.0) * f;
	double t_1 = exp(t_0);
	double t_2 = exp(-t_0);
	return -((1.0 / (((double) M_PI) / 4.0)) * log(((t_1 + t_2) / (t_1 - t_2))));
}

Java

public static double code(double f) {
	double t_0 = (Math.PI / 4.0) * f;
	double t_1 = Math.exp(t_0);
	double t_2 = Math.exp(-t_0);
	return -((1.0 / (Math.PI / 4.0)) * Math.log(((t_1 + t_2) / (t_1 - t_2))));
}

Python

def code(f):
	t_0 = (math.pi / 4.0) * f
	t_1 = math.exp(t_0)
	t_2 = math.exp(-t_0)
	return -((1.0 / (math.pi / 4.0)) * math.log(((t_1 + t_2) / (t_1 - t_2))))

Julia

function code(f)
	t_0 = Float64(Float64(pi / 4.0) * f)
	t_1 = exp(t_0)
	t_2 = exp(Float64(-t_0))
	return Float64(-Float64(Float64(1.0 / Float64(pi / 4.0)) * log(Float64(Float64(t_1 + t_2) / Float64(t_1 - t_2)))))
end

MATLAB

function tmp = code(f)
	t_0 = (pi / 4.0) * f;
	t_1 = exp(t_0);
	t_2 = exp(-t_0);
	tmp = -((1.0 / (pi / 4.0)) * log(((t_1 + t_2) / (t_1 - t_2))));
end

Wolfram

code[f_] := Block[{t$95$0 = N[(N[(Pi / 4.0), $MachinePrecision] * f), $MachinePrecision]}, Block[{t$95$1 = N[Exp[t$95$0], $MachinePrecision]}, Block[{t$95$2 = N[Exp[(-t$95$0)], $MachinePrecision]}, (-N[(N[(1.0 / N[(Pi / 4.0), $MachinePrecision]), $MachinePrecision] * N[Log[N[(N[(t$95$1 + t$95$2), $MachinePrecision] / N[(t$95$1 - t$95$2), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision])]]]

Alternative 1: 99.0% accurate, 2.5× speedup

Math

\[\begin{array}{l} \\ \frac{\frac{\log \tanh \left(\pi \cdot \left(f \cdot 0.25\right)\right)}{\pi}}{0.25} \end{array} \]

FPCore

(FPCore (f) :precision binary64 (/ (/ (log (tanh (* PI (* f 0.25)))) PI) 0.25))

C

double code(double f) {
	return (log(tanh((((double) M_PI) * (f * 0.25)))) / ((double) M_PI)) / 0.25;
}

Java

public static double code(double f) {
	return (Math.log(Math.tanh((Math.PI * (f * 0.25)))) / Math.PI) / 0.25;
}

Python

def code(f):
	return (math.log(math.tanh((math.pi * (f * 0.25)))) / math.pi) / 0.25

Julia

function code(f)
	return Float64(Float64(log(tanh(Float64(pi * Float64(f * 0.25)))) / pi) / 0.25)
end

MATLAB

function tmp = code(f)
	tmp = (log(tanh((pi * (f * 0.25)))) / pi) / 0.25;
end

Wolfram

code[f_] := N[(N[(N[Log[N[Tanh[N[(Pi * N[(f * 0.25), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]], $MachinePrecision] / Pi), $MachinePrecision] / 0.25), $MachinePrecision]

Derivation

1. Initial program 6.9%

   \[-\frac{1}{\frac{\pi}{4}} \cdot \log \left(\frac{e^{\frac{\pi}{4} \cdot f} + e^{-\frac{\pi}{4} \cdot f}}{e^{\frac{\pi}{4} \cdot f} - e^{-\frac{\pi}{4} \cdot f}}\right) \]
2. Step-by-step derivation

   1. distribute-lft-neg-in 6.9%

      \[\leadsto \color{blue}{\left(-\frac{1}{\frac{\pi}{4}}\right) \cdot \log \left(\frac{e^{\frac{\pi}{4} \cdot f} + e^{-\frac{\pi}{4} \cdot f}}{e^{\frac{\pi}{4} \cdot f} - e^{-\frac{\pi}{4} \cdot f}}\right)} \]

   2. distribute-neg-frac2 6.9%

      \[\leadsto \color{blue}{\frac{1}{-\frac{\pi}{4}}} \cdot \log \left(\frac{e^{\frac{\pi}{4} \cdot f} + e^{-\frac{\pi}{4} \cdot f}}{e^{\frac{\pi}{4} \cdot f} - e^{-\frac{\pi}{4} \cdot f}}\right) \]

   3. associate-*l/ 6.9%

      \[\leadsto \color{blue}{\frac{1 \cdot \log \left(\frac{e^{\frac{\pi}{4} \cdot f} + e^{-\frac{\pi}{4} \cdot f}}{e^{\frac{\pi}{4} \cdot f} - e^{-\frac{\pi}{4} \cdot f}}\right)}{-\frac{\pi}{4}}} \]

   4. *-lft-identity 6.9%

      \[\leadsto \frac{\color{blue}{\log \left(\frac{e^{\frac{\pi}{4} \cdot f} + e^{-\frac{\pi}{4} \cdot f}}{e^{\frac{\pi}{4} \cdot f} - e^{-\frac{\pi}{4} \cdot f}}\right)}}{-\frac{\pi}{4}} \]

3. Simplified 6.9%

   \[\leadsto \color{blue}{\frac{\log \left(\frac{{\left(e^{\frac{\pi}{-4}}\right)}^{f} + {\left(e^{\frac{\pi}{4}}\right)}^{f}}{{\left(e^{\frac{\pi}{4}}\right)}^{f} - {\left(e^{\frac{\pi}{-4}}\right)}^{f}}\right)}{\frac{\pi}{-4}}} \]
4. Add Preprocessing
5. Step-by-step derivation

   1. add-log-exp 6.9%

      \[\leadsto \color{blue}{\log \left(e^{\frac{\log \left(\frac{{\left(e^{\frac{\pi}{-4}}\right)}^{f} + {\left(e^{\frac{\pi}{4}}\right)}^{f}}{{\left(e^{\frac{\pi}{4}}\right)}^{f} - {\left(e^{\frac{\pi}{-4}}\right)}^{f}}\right)}{\frac{\pi}{-4}}}\right)} \]

   2. div-inv 6.9%

      \[\leadsto \log \left(e^{\color{blue}{\log \left(\frac{{\left(e^{\frac{\pi}{-4}}\right)}^{f} + {\left(e^{\frac{\pi}{4}}\right)}^{f}}{{\left(e^{\frac{\pi}{4}}\right)}^{f} - {\left(e^{\frac{\pi}{-4}}\right)}^{f}}\right) \cdot \frac{1}{\frac{\pi}{-4}}}}\right) \]

   3. clear-num 6.9%

      \[\leadsto \log \left(e^{\log \left(\frac{{\left(e^{\frac{\pi}{-4}}\right)}^{f} + {\left(e^{\frac{\pi}{4}}\right)}^{f}}{{\left(e^{\frac{\pi}{4}}\right)}^{f} - {\left(e^{\frac{\pi}{-4}}\right)}^{f}}\right) \cdot \color{blue}{\frac{-4}{\pi}}}\right) \]

   4. exp-to-pow 6.9%

      \[\leadsto \log \color{blue}{\left({\left(\frac{{\left(e^{\frac{\pi}{-4}}\right)}^{f} + {\left(e^{\frac{\pi}{4}}\right)}^{f}}{{\left(e^{\frac{\pi}{4}}\right)}^{f} - {\left(e^{\frac{\pi}{-4}}\right)}^{f}}\right)}^{\left(\frac{-4}{\pi}\right)}\right)} \]

6. Applied egg-rr 6.9%

   \[\leadsto \color{blue}{\log \left({\left(\frac{{\left(e^{f}\right)}^{\left(\pi \cdot 0.25\right)} + e^{f \cdot \left(\pi \cdot -0.25\right)}}{{\left(e^{f}\right)}^{\left(\pi \cdot 0.25\right)} - e^{f \cdot \left(\pi \cdot -0.25\right)}}\right)}^{\left(\frac{-4}{\pi}\right)}\right)} \]

8. Simplified 79.4%

   \[\leadsto \color{blue}{\log \left({\left(\frac{1}{\tanh \left(f \cdot \left(0.25 \cdot \pi\right)\right)}\right)}^{\left(\frac{-4}{\pi}\right)}\right)} \]
9. Step-by-step derivation

   1. log-pow 98.7%

      \[\leadsto \color{blue}{\frac{-4}{\pi} \cdot \log \left(\frac{1}{\tanh \left(f \cdot \left(0.25 \cdot \pi\right)\right)}\right)} \]

   2. *-commutative 98.7%

      \[\leadsto \frac{-4}{\pi} \cdot \log \left(\frac{1}{\tanh \left(f \cdot \color{blue}{\left(\pi \cdot 0.25\right)}\right)}\right) \]

   3. *-commutative 98.7%

      \[\leadsto \frac{-4}{\pi} \cdot \log \left(\frac{1}{\tanh \color{blue}{\left(\left(\pi \cdot 0.25\right) \cdot f\right)}}\right) \]

   4. neg-log 99.0%

      \[\leadsto \frac{-4}{\pi} \cdot \color{blue}{\left(-\log \tanh \left(\left(\pi \cdot 0.25\right) \cdot f\right)\right)} \]

   5. *-commutative 99.0%

      \[\leadsto \color{blue}{\left(-\log \tanh \left(\left(\pi \cdot 0.25\right) \cdot f\right)\right) \cdot \frac{-4}{\pi}} \]

   6. clear-num 99.0%

      \[\leadsto \left(-\log \tanh \left(\left(\pi \cdot 0.25\right) \cdot f\right)\right) \cdot \color{blue}{\frac{1}{\frac{\pi}{-4}}} \]

   7. un-div-inv 99.1%

      \[\leadsto \color{blue}{\frac{-\log \tanh \left(\left(\pi \cdot 0.25\right) \cdot f\right)}{\frac{\pi}{-4}}} \]

   8. *-commutative 99.1%

      \[\leadsto \frac{-\log \tanh \color{blue}{\left(f \cdot \left(\pi \cdot 0.25\right)\right)}}{\frac{\pi}{-4}} \]

   9. *-commutative 99.1%

      \[\leadsto \frac{-\log \tanh \left(f \cdot \color{blue}{\left(0.25 \cdot \pi\right)}\right)}{\frac{\pi}{-4}} \]

   10. div-inv 99.1%

       \[\leadsto \frac{-\log \tanh \left(f \cdot \left(0.25 \cdot \pi\right)\right)}{\color{blue}{\pi \cdot \frac{1}{-4}}} \]

   11. metadata-eval 99.1%

       \[\leadsto \frac{-\log \tanh \left(f \cdot \left(0.25 \cdot \pi\right)\right)}{\pi \cdot \color{blue}{-0.25}} \]

   12. metadata-eval 99.1%

       \[\leadsto \frac{-\log \tanh \left(f \cdot \left(0.25 \cdot \pi\right)\right)}{\pi \cdot \color{blue}{\left(-0.25\right)}} \]

   13. distribute-rgt-neg-in 99.1%

       \[\leadsto \frac{-\log \tanh \left(f \cdot \left(0.25 \cdot \pi\right)\right)}{\color{blue}{-\pi \cdot 0.25}} \]

10. Applied egg-rr 99.1%

    \[\leadsto \color{blue}{\frac{\frac{\log \tanh \left(\pi \cdot \left(f \cdot 0.25\right)\right)}{\pi}}{0.25}} \]

11. Final simplification 99.1%

    \[\leadsto \frac{\frac{\log \tanh \left(\pi \cdot \left(f \cdot 0.25\right)\right)}{\pi}}{0.25} \]
12. Add Preprocessing

Alternative 2: 96.1% accurate, 2.5× speedup

Math

\[\begin{array}{l} \\ -4 \cdot \frac{\log \left(\frac{4}{\pi}\right) - \log f}{\pi} \end{array} \]

FPCore

(FPCore (f) :precision binary64 (* -4.0 (/ (- (log (/ 4.0 PI)) (log f)) PI)))

C

double code(double f) {
	return -4.0 * ((log((4.0 / ((double) M_PI))) - log(f)) / ((double) M_PI));
}

Java

public static double code(double f) {
	return -4.0 * ((Math.log((4.0 / Math.PI)) - Math.log(f)) / Math.PI);
}

Python

def code(f):
	return -4.0 * ((math.log((4.0 / math.pi)) - math.log(f)) / math.pi)

Julia

function code(f)
	return Float64(-4.0 * Float64(Float64(log(Float64(4.0 / pi)) - log(f)) / pi))
end

MATLAB

function tmp = code(f)
	tmp = -4.0 * ((log((4.0 / pi)) - log(f)) / pi);
end

Wolfram

code[f_] := N[(-4.0 * N[(N[(N[Log[N[(4.0 / Pi), $MachinePrecision]], $MachinePrecision] - N[Log[f], $MachinePrecision]), $MachinePrecision] / Pi), $MachinePrecision]), $MachinePrecision]

Derivation

1. Initial program 6.9%

   \[-\frac{1}{\frac{\pi}{4}} \cdot \log \left(\frac{e^{\frac{\pi}{4} \cdot f} + e^{-\frac{\pi}{4} \cdot f}}{e^{\frac{\pi}{4} \cdot f} - e^{-\frac{\pi}{4} \cdot f}}\right) \]

3. Simplified 98.7%

   \[\leadsto \color{blue}{\log \left(\frac{1}{\mathsf{expm1}\left(\left(\pi \cdot f\right) \cdot 0.5\right)} + \frac{-1}{\mathsf{expm1}\left(\left(-0.5 \cdot f\right) \cdot \pi\right)}\right) \cdot \frac{-4}{\pi}} \]
4. Add Preprocessing

5. Taylor expanded in f around 0 94.3%

   \[\leadsto \color{blue}{-4 \cdot \frac{\log \left(\frac{4}{\pi}\right) + -1 \cdot \log f}{\pi}} \]
6. Step-by-step derivation

   1. mul-1-neg 94.3%

      \[\leadsto -4 \cdot \frac{\log \left(\frac{4}{\pi}\right) + \color{blue}{\left(-\log f\right)}}{\pi} \]

   2. unsub-neg 94.3%

      \[\leadsto -4 \cdot \frac{\color{blue}{\log \left(\frac{4}{\pi}\right) - \log f}}{\pi} \]

7. Simplified 94.3%

   \[\leadsto \color{blue}{-4 \cdot \frac{\log \left(\frac{4}{\pi}\right) - \log f}{\pi}} \]

8. Final simplification 94.3%

   \[\leadsto -4 \cdot \frac{\log \left(\frac{4}{\pi}\right) - \log f}{\pi} \]
9. Add Preprocessing

Alternative 3: 96.1% accurate, 4.8× speedup

Math

\[\begin{array}{l} \\ -4 \cdot \frac{\log \left(0.25 \cdot \left(\pi \cdot f\right)\right)}{-\pi} \end{array} \]

FPCore

(FPCore (f) :precision binary64 (* -4.0 (/ (log (* 0.25 (* PI f))) (- PI))))

C

double code(double f) {
	return -4.0 * (log((0.25 * (((double) M_PI) * f))) / -((double) M_PI));
}

Java

public static double code(double f) {
	return -4.0 * (Math.log((0.25 * (Math.PI * f))) / -Math.PI);
}

Python

def code(f):
	return -4.0 * (math.log((0.25 * (math.pi * f))) / -math.pi)

Julia

function code(f)
	return Float64(-4.0 * Float64(log(Float64(0.25 * Float64(pi * f))) / Float64(-pi)))
end

MATLAB

function tmp = code(f)
	tmp = -4.0 * (log((0.25 * (pi * f))) / -pi);
end

Wolfram

code[f_] := N[(-4.0 * N[(N[Log[N[(0.25 * N[(Pi * f), $MachinePrecision]), $MachinePrecision]], $MachinePrecision] / (-Pi)), $MachinePrecision]), $MachinePrecision]

Derivation

1. Initial program 6.9%

   \[-\frac{1}{\frac{\pi}{4}} \cdot \log \left(\frac{e^{\frac{\pi}{4} \cdot f} + e^{-\frac{\pi}{4} \cdot f}}{e^{\frac{\pi}{4} \cdot f} - e^{-\frac{\pi}{4} \cdot f}}\right) \]
2. Add Preprocessing

3. Taylor expanded in f around 0 93.8%

   \[\leadsto -\frac{1}{\frac{\pi}{4}} \cdot \log \color{blue}{\left(\frac{2}{f \cdot \left(0.25 \cdot \pi - -0.25 \cdot \pi\right)}\right)} \]
4. Step-by-step derivation

   1. distribute-rgt-out-- 93.8%

      \[\leadsto -\frac{1}{\frac{\pi}{4}} \cdot \log \left(\frac{2}{f \cdot \color{blue}{\left(\pi \cdot \left(0.25 - -0.25\right)\right)}}\right) \]

   2. metadata-eval 93.8%

      \[\leadsto -\frac{1}{\frac{\pi}{4}} \cdot \log \left(\frac{2}{f \cdot \left(\pi \cdot \color{blue}{0.5}\right)}\right) \]

5. Simplified 93.8%

   \[\leadsto -\frac{1}{\frac{\pi}{4}} \cdot \log \color{blue}{\left(\frac{2}{f \cdot \left(\pi \cdot 0.5\right)}\right)} \]
6. Step-by-step derivation

   1. *-commutative 93.8%

      \[\leadsto -\color{blue}{\log \left(\frac{2}{f \cdot \left(\pi \cdot 0.5\right)}\right) \cdot \frac{1}{\frac{\pi}{4}}} \]

   2. div-inv 93.8%

      \[\leadsto -\log \left(\frac{2}{f \cdot \left(\pi \cdot 0.5\right)}\right) \cdot \frac{1}{\color{blue}{\pi \cdot \frac{1}{4}}} \]

   3. metadata-eval 93.8%

      \[\leadsto -\log \left(\frac{2}{f \cdot \left(\pi \cdot 0.5\right)}\right) \cdot \frac{1}{\pi \cdot \color{blue}{0.25}} \]

   4. div-inv 93.9%

      \[\leadsto -\color{blue}{\frac{\log \left(\frac{2}{f \cdot \left(\pi \cdot 0.5\right)}\right)}{\pi \cdot 0.25}} \]

   5. clear-num 93.9%

      \[\leadsto -\frac{\log \color{blue}{\left(\frac{1}{\frac{f \cdot \left(\pi \cdot 0.5\right)}{2}}\right)}}{\pi \cdot 0.25} \]

   6. log-rec 94.3%

      \[\leadsto -\frac{\color{blue}{-\log \left(\frac{f \cdot \left(\pi \cdot 0.5\right)}{2}\right)}}{\pi \cdot 0.25} \]

   7. associate-*r* 94.3%

      \[\leadsto -\frac{-\log \left(\frac{\color{blue}{\left(f \cdot \pi\right) \cdot 0.5}}{2}\right)}{\pi \cdot 0.25} \]

   8. associate-/l* 94.3%

      \[\leadsto -\frac{-\log \color{blue}{\left(\left(f \cdot \pi\right) \cdot \frac{0.5}{2}\right)}}{\pi \cdot 0.25} \]

   9. metadata-eval 94.3%

      \[\leadsto -\frac{-\log \left(\left(f \cdot \pi\right) \cdot \color{blue}{0.25}\right)}{\pi \cdot 0.25} \]

   10. associate-*r* 94.3%

       \[\leadsto -\frac{-\log \color{blue}{\left(f \cdot \left(\pi \cdot 0.25\right)\right)}}{\pi \cdot 0.25} \]

   11. *-commutative 94.3%

       \[\leadsto -\frac{-\log \left(f \cdot \color{blue}{\left(0.25 \cdot \pi\right)}\right)}{\pi \cdot 0.25} \]

   12. associate-*r* 94.3%

       \[\leadsto -\frac{-\log \color{blue}{\left(\left(f \cdot 0.25\right) \cdot \pi\right)}}{\pi \cdot 0.25} \]

   13. *-commutative 94.3%

       \[\leadsto -\frac{-\log \color{blue}{\left(\pi \cdot \left(f \cdot 0.25\right)\right)}}{\pi \cdot 0.25} \]

7. Applied egg-rr 94.3%

   \[\leadsto -\color{blue}{\frac{-\log \left(\pi \cdot \left(f \cdot 0.25\right)\right)}{\pi \cdot 0.25}} \]
8. Step-by-step derivation

   1. neg-mul-1 94.3%

      \[\leadsto -\frac{\color{blue}{-1 \cdot \log \left(\pi \cdot \left(f \cdot 0.25\right)\right)}}{\pi \cdot 0.25} \]

   2. *-commutative 94.3%

      \[\leadsto -\frac{-1 \cdot \log \left(\pi \cdot \left(f \cdot 0.25\right)\right)}{\color{blue}{0.25 \cdot \pi}} \]

   3. times-frac 94.3%

      \[\leadsto -\color{blue}{\frac{-1}{0.25} \cdot \frac{\log \left(\pi \cdot \left(f \cdot 0.25\right)\right)}{\pi}} \]

   4. metadata-eval 94.3%

      \[\leadsto -\color{blue}{-4} \cdot \frac{\log \left(\pi \cdot \left(f \cdot 0.25\right)\right)}{\pi} \]

   5. *-commutative 94.3%

      \[\leadsto --4 \cdot \frac{\log \color{blue}{\left(\left(f \cdot 0.25\right) \cdot \pi\right)}}{\pi} \]

   6. *-commutative 94.3%

      \[\leadsto --4 \cdot \frac{\log \left(\color{blue}{\left(0.25 \cdot f\right)} \cdot \pi\right)}{\pi} \]

   7. associate-*r* 94.3%

      \[\leadsto --4 \cdot \frac{\log \color{blue}{\left(0.25 \cdot \left(f \cdot \pi\right)\right)}}{\pi} \]

9. Simplified 94.3%

   \[\leadsto -\color{blue}{-4 \cdot \frac{\log \left(0.25 \cdot \left(f \cdot \pi\right)\right)}{\pi}} \]

10. Final simplification 94.3%

    \[\leadsto -4 \cdot \frac{\log \left(0.25 \cdot \left(\pi \cdot f\right)\right)}{-\pi} \]
11. Add Preprocessing

Alternative 4: 0.7% accurate, 5.1× speedup

Math

\[\begin{array}{l} \\ \frac{-4}{\pi} \cdot \log 0 \end{array} \]

FPCore

(FPCore (f) :precision binary64 (* (/ -4.0 PI) (log 0.0)))

C

double code(double f) {
	return (-4.0 / ((double) M_PI)) * log(0.0);
}

Java

public static double code(double f) {
	return (-4.0 / Math.PI) * Math.log(0.0);
}

Python

def code(f):
	return (-4.0 / math.pi) * math.log(0.0)

Julia

function code(f)
	return Float64(Float64(-4.0 / pi) * log(0.0))
end

MATLAB

function tmp = code(f)
	tmp = (-4.0 / pi) * log(0.0);
end

Wolfram

code[f_] := N[(N[(-4.0 / Pi), $MachinePrecision] * N[Log[0.0], $MachinePrecision]), $MachinePrecision]

Derivation

1. Initial program 6.9%

   \[-\frac{1}{\frac{\pi}{4}} \cdot \log \left(\frac{e^{\frac{\pi}{4} \cdot f} + e^{-\frac{\pi}{4} \cdot f}}{e^{\frac{\pi}{4} \cdot f} - e^{-\frac{\pi}{4} \cdot f}}\right) \]
2. Step-by-step derivation

   1. distribute-lft-neg-in 6.9%

      \[\leadsto \color{blue}{\left(-\frac{1}{\frac{\pi}{4}}\right) \cdot \log \left(\frac{e^{\frac{\pi}{4} \cdot f} + e^{-\frac{\pi}{4} \cdot f}}{e^{\frac{\pi}{4} \cdot f} - e^{-\frac{\pi}{4} \cdot f}}\right)} \]

   2. distribute-neg-frac2 6.9%

      \[\leadsto \color{blue}{\frac{1}{-\frac{\pi}{4}}} \cdot \log \left(\frac{e^{\frac{\pi}{4} \cdot f} + e^{-\frac{\pi}{4} \cdot f}}{e^{\frac{\pi}{4} \cdot f} - e^{-\frac{\pi}{4} \cdot f}}\right) \]

   3. associate-*l/ 6.9%

      \[\leadsto \color{blue}{\frac{1 \cdot \log \left(\frac{e^{\frac{\pi}{4} \cdot f} + e^{-\frac{\pi}{4} \cdot f}}{e^{\frac{\pi}{4} \cdot f} - e^{-\frac{\pi}{4} \cdot f}}\right)}{-\frac{\pi}{4}}} \]

   4. *-lft-identity 6.9%

      \[\leadsto \frac{\color{blue}{\log \left(\frac{e^{\frac{\pi}{4} \cdot f} + e^{-\frac{\pi}{4} \cdot f}}{e^{\frac{\pi}{4} \cdot f} - e^{-\frac{\pi}{4} \cdot f}}\right)}}{-\frac{\pi}{4}} \]

3. Simplified 6.9%

   \[\leadsto \color{blue}{\frac{\log \left(\frac{{\left(e^{\frac{\pi}{-4}}\right)}^{f} + {\left(e^{\frac{\pi}{4}}\right)}^{f}}{{\left(e^{\frac{\pi}{4}}\right)}^{f} - {\left(e^{\frac{\pi}{-4}}\right)}^{f}}\right)}{\frac{\pi}{-4}}} \]
4. Add Preprocessing

5. Taylor expanded in f around inf 6.9%

   \[\leadsto \color{blue}{-4 \cdot \frac{\log \left(\frac{e^{-0.25 \cdot \left(f \cdot \pi\right)} + e^{0.25 \cdot \left(f \cdot \pi\right)}}{e^{0.25 \cdot \left(f \cdot \pi\right)} - e^{-0.25 \cdot \left(f \cdot \pi\right)}}\right)}{\pi}} \]

7. Simplified 98.7%

   \[\leadsto \color{blue}{\frac{-4}{\pi} \cdot \log \left(\frac{1}{\tanh \left(f \cdot \left(0.25 \cdot \pi\right)\right)}\right)} \]

9. Applied egg-rr 0.6%

   \[\leadsto \frac{-4}{\pi} \cdot \log \color{blue}{\left(\frac{{\left(e^{\pi}\right)}^{\left(f \cdot 0.25\right)}}{2 \cdot \cosh \left(\pi \cdot \left(f \cdot 0.25\right)\right)} - \frac{{\left(e^{\pi}\right)}^{\left(f \cdot 0.25\right)}}{2 \cdot \cosh \left(\pi \cdot \left(f \cdot 0.25\right)\right)}\right)} \]
10. Step-by-step derivation

    1. +-inverses 0.7%

       \[\leadsto \frac{-4}{\pi} \cdot \log \color{blue}{0} \]

11. Simplified 0.7%

    \[\leadsto \frac{-4}{\pi} \cdot \log \color{blue}{0} \]

12. Final simplification 0.7%

    \[\leadsto \frac{-4}{\pi} \cdot \log 0 \]
13. Add Preprocessing

Reproduce

herbie shell --seed 2024059 
(FPCore (f)
  :name "VandenBroeck and Keller, Equation (20)"
  :precision binary64
  (- (* (/ 1.0 (/ PI 4.0)) (log (/ (+ (exp (* (/ PI 4.0) f)) (exp (- (* (/ PI 4.0) f)))) (- (exp (* (/ PI 4.0) f)) (exp (- (* (/ PI 4.0) f)))))))))