Numeric.SpecFunctions:invIncompleteBetaWorker from math-functions-0.1.5.2, F

Average Error: 11.5 → 0.9

Time: 9.8s

Precision: binary64

Cost: 60432

Math

\[\frac{e^{x \cdot \log \left(\frac{x}{x + y}\right)}}{x} \]

↓

\[\begin{array}{l} t_0 := \frac{e^{-y}}{x}\\ t_1 := \log \left(\frac{x}{x + y}\right)\\ t_2 := \frac{e^{x \cdot t_1}}{x}\\ t_3 := \frac{{\left(e^{x}\right)}^{t_1}}{x}\\ \mathbf{if}\;t_2 \leq -200000:\\ \;\;\;\;t_3\\ \mathbf{elif}\;t_2 \leq -5 \cdot 10^{-298}:\\ \;\;\;\;t_0\\ \mathbf{elif}\;t_2 \leq 0:\\ \;\;\;\;t_3\\ \mathbf{elif}\;t_2 \leq 10^{-107}:\\ \;\;\;\;t_0\\ \mathbf{else}:\\ \;\;\;\;\frac{1}{x}\\ \end{array} \]

FPCore

(FPCore (x y) :precision binary64 (/ (exp (* x (log (/ x (+ x y))))) x))

↓

(FPCore (x y)
 :precision binary64
 (let* ((t_0 (/ (exp (- y)) x))
        (t_1 (log (/ x (+ x y))))
        (t_2 (/ (exp (* x t_1)) x))
        (t_3 (/ (pow (exp x) t_1) x)))
   (if (<= t_2 -200000.0)
     t_3
     (if (<= t_2 -5e-298)
       t_0
       (if (<= t_2 0.0) t_3 (if (<= t_2 1e-107) t_0 (/ 1.0 x)))))))

C

double code(double x, double y) {
	return exp((x * log((x / (x + y))))) / x;
}

↓

double code(double x, double y) {
	double t_0 = exp(-y) / x;
	double t_1 = log((x / (x + y)));
	double t_2 = exp((x * t_1)) / x;
	double t_3 = pow(exp(x), t_1) / x;
	double tmp;
	if (t_2 <= -200000.0) {
		tmp = t_3;
	} else if (t_2 <= -5e-298) {
		tmp = t_0;
	} else if (t_2 <= 0.0) {
		tmp = t_3;
	} else if (t_2 <= 1e-107) {
		tmp = t_0;
	} else {
		tmp = 1.0 / x;
	}
	return tmp;
}

Fortran

real(8) function code(x, y)
    real(8), intent (in) :: x
    real(8), intent (in) :: y
    code = exp((x * log((x / (x + y))))) / x
end function

↓

real(8) function code(x, y)
    real(8), intent (in) :: x
    real(8), intent (in) :: y
    real(8) :: t_0
    real(8) :: t_1
    real(8) :: t_2
    real(8) :: t_3
    real(8) :: tmp
    t_0 = exp(-y) / x
    t_1 = log((x / (x + y)))
    t_2 = exp((x * t_1)) / x
    t_3 = (exp(x) ** t_1) / x
    if (t_2 <= (-200000.0d0)) then
        tmp = t_3
    else if (t_2 <= (-5d-298)) then
        tmp = t_0
    else if (t_2 <= 0.0d0) then
        tmp = t_3
    else if (t_2 <= 1d-107) then
        tmp = t_0
    else
        tmp = 1.0d0 / x
    end if
    code = tmp
end function

Java

public static double code(double x, double y) {
	return Math.exp((x * Math.log((x / (x + y))))) / x;
}

↓

public static double code(double x, double y) {
	double t_0 = Math.exp(-y) / x;
	double t_1 = Math.log((x / (x + y)));
	double t_2 = Math.exp((x * t_1)) / x;
	double t_3 = Math.pow(Math.exp(x), t_1) / x;
	double tmp;
	if (t_2 <= -200000.0) {
		tmp = t_3;
	} else if (t_2 <= -5e-298) {
		tmp = t_0;
	} else if (t_2 <= 0.0) {
		tmp = t_3;
	} else if (t_2 <= 1e-107) {
		tmp = t_0;
	} else {
		tmp = 1.0 / x;
	}
	return tmp;
}

Python

def code(x, y):
	return math.exp((x * math.log((x / (x + y))))) / x

↓

def code(x, y):
	t_0 = math.exp(-y) / x
	t_1 = math.log((x / (x + y)))
	t_2 = math.exp((x * t_1)) / x
	t_3 = math.pow(math.exp(x), t_1) / x
	tmp = 0
	if t_2 <= -200000.0:
		tmp = t_3
	elif t_2 <= -5e-298:
		tmp = t_0
	elif t_2 <= 0.0:
		tmp = t_3
	elif t_2 <= 1e-107:
		tmp = t_0
	else:
		tmp = 1.0 / x
	return tmp

Julia

function code(x, y)
	return Float64(exp(Float64(x * log(Float64(x / Float64(x + y))))) / x)
end

↓

function code(x, y)
	t_0 = Float64(exp(Float64(-y)) / x)
	t_1 = log(Float64(x / Float64(x + y)))
	t_2 = Float64(exp(Float64(x * t_1)) / x)
	t_3 = Float64((exp(x) ^ t_1) / x)
	tmp = 0.0
	if (t_2 <= -200000.0)
		tmp = t_3;
	elseif (t_2 <= -5e-298)
		tmp = t_0;
	elseif (t_2 <= 0.0)
		tmp = t_3;
	elseif (t_2 <= 1e-107)
		tmp = t_0;
	else
		tmp = Float64(1.0 / x);
	end
	return tmp
end

MATLAB

function tmp = code(x, y)
	tmp = exp((x * log((x / (x + y))))) / x;
end

↓

function tmp_2 = code(x, y)
	t_0 = exp(-y) / x;
	t_1 = log((x / (x + y)));
	t_2 = exp((x * t_1)) / x;
	t_3 = (exp(x) ^ t_1) / x;
	tmp = 0.0;
	if (t_2 <= -200000.0)
		tmp = t_3;
	elseif (t_2 <= -5e-298)
		tmp = t_0;
	elseif (t_2 <= 0.0)
		tmp = t_3;
	elseif (t_2 <= 1e-107)
		tmp = t_0;
	else
		tmp = 1.0 / x;
	end
	tmp_2 = tmp;
end

Wolfram

code[x_, y_] := N[(N[Exp[N[(x * N[Log[N[(x / N[(x + y), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]], $MachinePrecision] / x), $MachinePrecision]

↓

code[x_, y_] := Block[{t$95$0 = N[(N[Exp[(-y)], $MachinePrecision] / x), $MachinePrecision]}, Block[{t$95$1 = N[Log[N[(x / N[(x + y), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]}, Block[{t$95$2 = N[(N[Exp[N[(x * t$95$1), $MachinePrecision]], $MachinePrecision] / x), $MachinePrecision]}, Block[{t$95$3 = N[(N[Power[N[Exp[x], $MachinePrecision], t$95$1], $MachinePrecision] / x), $MachinePrecision]}, If[LessEqual[t$95$2, -200000.0], t$95$3, If[LessEqual[t$95$2, -5e-298], t$95$0, If[LessEqual[t$95$2, 0.0], t$95$3, If[LessEqual[t$95$2, 1e-107], t$95$0, N[(1.0 / x), $MachinePrecision]]]]]]]]]

Target

Original	11.5
Target	8.1
Herbie	0.9

\[\begin{array}{l} \mathbf{if}\;y < -3.7311844206647956 \cdot 10^{+94}:\\ \;\;\;\;\frac{e^{\frac{-1}{y}}}{x}\\ \mathbf{elif}\;y < 2.817959242728288 \cdot 10^{+37}:\\ \;\;\;\;\frac{{\left(\frac{x}{y + x}\right)}^{x}}{x}\\ \mathbf{elif}\;y < 2.347387415166998 \cdot 10^{+178}:\\ \;\;\;\;\log \left(e^{\frac{{\left(\frac{x}{y + x}\right)}^{x}}{x}}\right)\\ \mathbf{else}:\\ \;\;\;\;\frac{e^{\frac{-1}{y}}}{x}\\ \end{array} \]

Derivation

1. Split input into 3 regimes

2. if (/.f64 (exp.f64 (*.f64 x (log.f64 (/.f64 x (+.f64 x y))))) x) < -2e5 or -5.0000000000000002e-298 < (/.f64 (exp.f64 (*.f64 x (log.f64 (/.f64 x (+.f64 x y))))) x) < 0.0

   1. Initial program 16.3

      \[\frac{e^{x \cdot \log \left(\frac{x}{x + y}\right)}}{x} \]

   2. Simplified 0.6

      \[\leadsto \color{blue}{\frac{{\left(e^{x}\right)}^{\log \left(\frac{x}{x + y}\right)}}{x}} \]
      Proof
      (/.f64 (pow.f64 (exp.f64 x) (log.f64 (/.f64 x (+.f64 x y)))) x): 0 points increase in error, 0 points decrease in error
      (/.f64 (Rewrite<= exp-prod_binary64 (exp.f64 (*.f64 x (log.f64 (/.f64 x (+.f64 x y)))))) x): 18 points increase in error, 1 points decrease in error

   if -2e5 < (/.f64 (exp.f64 (*.f64 x (log.f64 (/.f64 x (+.f64 x y))))) x) < -5.0000000000000002e-298 or 0.0 < (/.f64 (exp.f64 (*.f64 x (log.f64 (/.f64 x (+.f64 x y))))) x) < 1e-107

   1. Initial program 13.7

      \[\frac{e^{x \cdot \log \left(\frac{x}{x + y}\right)}}{x} \]

   2. Simplified 13.7

      \[\leadsto \color{blue}{\frac{{\left(\frac{x}{x + y}\right)}^{x}}{x}} \]
      Proof
      (/.f64 (pow.f64 (/.f64 x (+.f64 x y)) x) x): 0 points increase in error, 0 points decrease in error
      (/.f64 (Rewrite<= exp-to-pow_binary64 (exp.f64 (*.f64 (log.f64 (/.f64 x (+.f64 x y))) x))) x): 0 points increase in error, 0 points decrease in error
      (/.f64 (exp.f64 (Rewrite<= *-commutative_binary64 (*.f64 x (log.f64 (/.f64 x (+.f64 x y)))))) x): 0 points increase in error, 0 points decrease in error

   3. Taylor expanded in x around inf 0.3

      \[\leadsto \frac{\color{blue}{e^{-1 \cdot y}}}{x} \]

   4. Simplified 0.3

      \[\leadsto \frac{\color{blue}{e^{-y}}}{x} \]
      Proof
      (exp.f64 (neg.f64 y)): 0 points increase in error, 0 points decrease in error
      (exp.f64 (Rewrite<= mul-1-neg_binary64 (*.f64 -1 y))): 0 points increase in error, 0 points decrease in error

   if 1e-107 < (/.f64 (exp.f64 (*.f64 x (log.f64 (/.f64 x (+.f64 x y))))) x)

   1. Initial program 1.7

      \[\frac{e^{x \cdot \log \left(\frac{x}{x + y}\right)}}{x} \]

   2. Simplified 1.7

      \[\leadsto \color{blue}{\frac{{\left(\frac{x}{x + y}\right)}^{x}}{x}} \]
      Proof
      (/.f64 (pow.f64 (/.f64 x (+.f64 x y)) x) x): 0 points increase in error, 0 points decrease in error
      (/.f64 (Rewrite<= exp-to-pow_binary64 (exp.f64 (*.f64 (log.f64 (/.f64 x (+.f64 x y))) x))) x): 0 points increase in error, 0 points decrease in error
      (/.f64 (exp.f64 (Rewrite<= *-commutative_binary64 (*.f64 x (log.f64 (/.f64 x (+.f64 x y)))))) x): 0 points increase in error, 0 points decrease in error

   3. Taylor expanded in x around 0 2.3

      \[\leadsto \frac{\color{blue}{1}}{x} \]
3. Recombined 3 regimes into one program.

4. Final simplification 0.9

   \[\leadsto \begin{array}{l} \mathbf{if}\;\frac{e^{x \cdot \log \left(\frac{x}{x + y}\right)}}{x} \leq -200000:\\ \;\;\;\;\frac{{\left(e^{x}\right)}^{\log \left(\frac{x}{x + y}\right)}}{x}\\ \mathbf{elif}\;\frac{e^{x \cdot \log \left(\frac{x}{x + y}\right)}}{x} \leq -5 \cdot 10^{-298}:\\ \;\;\;\;\frac{e^{-y}}{x}\\ \mathbf{elif}\;\frac{e^{x \cdot \log \left(\frac{x}{x + y}\right)}}{x} \leq 0:\\ \;\;\;\;\frac{{\left(e^{x}\right)}^{\log \left(\frac{x}{x + y}\right)}}{x}\\ \mathbf{elif}\;\frac{e^{x \cdot \log \left(\frac{x}{x + y}\right)}}{x} \leq 10^{-107}:\\ \;\;\;\;\frac{e^{-y}}{x}\\ \mathbf{else}:\\ \;\;\;\;\frac{1}{x}\\ \end{array} \]

Alternatives

Alternative 1
Error	0.5
Cost	6920

\[\begin{array}{l} t_0 := \frac{e^{-y}}{x}\\ \mathbf{if}\;x \leq -1.85 \cdot 10^{+47}:\\ \;\;\;\;t_0\\ \mathbf{elif}\;x \leq 2.7 \cdot 10^{-5}:\\ \;\;\;\;\frac{1}{x}\\ \mathbf{else}:\\ \;\;\;\;t_0\\ \end{array} \]

Alternative 2
Error	1.4
Cost	580

\[\begin{array}{l} \mathbf{if}\;y \leq 2.4:\\ \;\;\;\;\frac{1}{x}\\ \mathbf{else}:\\ \;\;\;\;\left(1 + \frac{1}{x}\right) + -1\\ \end{array} \]

Alternative 3
Error	9.7
Cost	192

\[\frac{1}{x} \]

Reproduce

herbie shell --seed 2022329 
(FPCore (x y)
  :name "Numeric.SpecFunctions:invIncompleteBetaWorker from math-functions-0.1.5.2, F"
  :precision binary64

  :herbie-target
  (if (< y -3.7311844206647956e+94) (/ (exp (/ -1.0 y)) x) (if (< y 2.817959242728288e+37) (/ (pow (/ x (+ y x)) x) x) (if (< y 2.347387415166998e+178) (log (exp (/ (pow (/ x (+ y x)) x) x))) (/ (exp (/ -1.0 y)) x))))

  (/ (exp (* x (log (/ x (+ x y))))) x))