Logistic function from Lakshay Garg

Percentage Accurate: 54.3% → 100.0%

Time: 3.2s

Alternatives: 13

Speedup: 1.4×

Specification

Math

\[\begin{array}{l} \\ \frac{2}{1 + e^{-2 \cdot x}} - 1 \end{array} \]

FPCore

(FPCore (x) :precision binary64 (- (/ 2.0 (+ 1.0 (exp (* -2.0 x)))) 1.0))

C

double code(double x) {
	return (2.0 / (1.0 + exp((-2.0 * x)))) - 1.0;
}

Fortran

module fmin_fmax_functions
    implicit none
    private
    public fmax
    public fmin

    interface fmax
        module procedure fmax88
        module procedure fmax44
        module procedure fmax84
        module procedure fmax48
    end interface
    interface fmin
        module procedure fmin88
        module procedure fmin44
        module procedure fmin84
        module procedure fmin48
    end interface
contains
    real(8) function fmax88(x, y) result (res)
        real(8), intent (in) :: x
        real(8), intent (in) :: y
        res = merge(y, merge(x, max(x, y), y /= y), x /= x)
    end function
    real(4) function fmax44(x, y) result (res)
        real(4), intent (in) :: x
        real(4), intent (in) :: y
        res = merge(y, merge(x, max(x, y), y /= y), x /= x)
    end function
    real(8) function fmax84(x, y) result(res)
        real(8), intent (in) :: x
        real(4), intent (in) :: y
        res = merge(dble(y), merge(x, max(x, dble(y)), y /= y), x /= x)
    end function
    real(8) function fmax48(x, y) result(res)
        real(4), intent (in) :: x
        real(8), intent (in) :: y
        res = merge(y, merge(dble(x), max(dble(x), y), y /= y), x /= x)
    end function
    real(8) function fmin88(x, y) result (res)
        real(8), intent (in) :: x
        real(8), intent (in) :: y
        res = merge(y, merge(x, min(x, y), y /= y), x /= x)
    end function
    real(4) function fmin44(x, y) result (res)
        real(4), intent (in) :: x
        real(4), intent (in) :: y
        res = merge(y, merge(x, min(x, y), y /= y), x /= x)
    end function
    real(8) function fmin84(x, y) result(res)
        real(8), intent (in) :: x
        real(4), intent (in) :: y
        res = merge(dble(y), merge(x, min(x, dble(y)), y /= y), x /= x)
    end function
    real(8) function fmin48(x, y) result(res)
        real(4), intent (in) :: x
        real(8), intent (in) :: y
        res = merge(y, merge(dble(x), min(dble(x), y), y /= y), x /= x)
    end function
end module

real(8) function code(x)
use fmin_fmax_functions
    real(8), intent (in) :: x
    code = (2.0d0 / (1.0d0 + exp(((-2.0d0) * x)))) - 1.0d0
end function

Java

public static double code(double x) {
	return (2.0 / (1.0 + Math.exp((-2.0 * x)))) - 1.0;
}

Python

def code(x):
	return (2.0 / (1.0 + math.exp((-2.0 * x)))) - 1.0

Julia

function code(x)
	return Float64(Float64(2.0 / Float64(1.0 + exp(Float64(-2.0 * x)))) - 1.0)
end

MATLAB

function tmp = code(x)
	tmp = (2.0 / (1.0 + exp((-2.0 * x)))) - 1.0;
end

Wolfram

code[x_] := N[(N[(2.0 / N[(1.0 + N[Exp[N[(-2.0 * x), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]), $MachinePrecision] - 1.0), $MachinePrecision]

Initial Program: 54.3% accurate, 1.0× speedup

Math

\[\begin{array}{l} \\ \frac{2}{1 + e^{-2 \cdot x}} - 1 \end{array} \]

FPCore

(FPCore (x) :precision binary64 (- (/ 2.0 (+ 1.0 (exp (* -2.0 x)))) 1.0))

C

double code(double x) {
	return (2.0 / (1.0 + exp((-2.0 * x)))) - 1.0;
}

Fortran

module fmin_fmax_functions
    implicit none
    private
    public fmax
    public fmin

    interface fmax
        module procedure fmax88
        module procedure fmax44
        module procedure fmax84
        module procedure fmax48
    end interface
    interface fmin
        module procedure fmin88
        module procedure fmin44
        module procedure fmin84
        module procedure fmin48
    end interface
contains
    real(8) function fmax88(x, y) result (res)
        real(8), intent (in) :: x
        real(8), intent (in) :: y
        res = merge(y, merge(x, max(x, y), y /= y), x /= x)
    end function
    real(4) function fmax44(x, y) result (res)
        real(4), intent (in) :: x
        real(4), intent (in) :: y
        res = merge(y, merge(x, max(x, y), y /= y), x /= x)
    end function
    real(8) function fmax84(x, y) result(res)
        real(8), intent (in) :: x
        real(4), intent (in) :: y
        res = merge(dble(y), merge(x, max(x, dble(y)), y /= y), x /= x)
    end function
    real(8) function fmax48(x, y) result(res)
        real(4), intent (in) :: x
        real(8), intent (in) :: y
        res = merge(y, merge(dble(x), max(dble(x), y), y /= y), x /= x)
    end function
    real(8) function fmin88(x, y) result (res)
        real(8), intent (in) :: x
        real(8), intent (in) :: y
        res = merge(y, merge(x, min(x, y), y /= y), x /= x)
    end function
    real(4) function fmin44(x, y) result (res)
        real(4), intent (in) :: x
        real(4), intent (in) :: y
        res = merge(y, merge(x, min(x, y), y /= y), x /= x)
    end function
    real(8) function fmin84(x, y) result(res)
        real(8), intent (in) :: x
        real(4), intent (in) :: y
        res = merge(dble(y), merge(x, min(x, dble(y)), y /= y), x /= x)
    end function
    real(8) function fmin48(x, y) result(res)
        real(4), intent (in) :: x
        real(8), intent (in) :: y
        res = merge(y, merge(dble(x), min(dble(x), y), y /= y), x /= x)
    end function
end module

real(8) function code(x)
use fmin_fmax_functions
    real(8), intent (in) :: x
    code = (2.0d0 / (1.0d0 + exp(((-2.0d0) * x)))) - 1.0d0
end function

Java

public static double code(double x) {
	return (2.0 / (1.0 + Math.exp((-2.0 * x)))) - 1.0;
}

Python

def code(x):
	return (2.0 / (1.0 + math.exp((-2.0 * x)))) - 1.0

Julia

function code(x)
	return Float64(Float64(2.0 / Float64(1.0 + exp(Float64(-2.0 * x)))) - 1.0)
end

MATLAB

function tmp = code(x)
	tmp = (2.0 / (1.0 + exp((-2.0 * x)))) - 1.0;
end

Wolfram

code[x_] := N[(N[(2.0 / N[(1.0 + N[Exp[N[(-2.0 * x), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]), $MachinePrecision] - 1.0), $MachinePrecision]

Alternative 1: 100.0% accurate, 0.3× speedup

Math

\[\begin{array}{l} \\ \begin{array}{l} t_0 := e^{x \cdot -2}\\ t_1 := \frac{-2}{-1 - t\_0}\\ \mathbf{if}\;x \leq -0.0074:\\ \;\;\;\;\frac{1}{\frac{t\_1 - -1}{{t\_1}^{2} - 1}}\\ \mathbf{elif}\;x \leq 0.007:\\ \;\;\;\;\mathsf{fma}\left(\mathsf{fma}\left(0.13333333333333333, x \cdot x, -0.3333333333333333\right), x \cdot x, 1\right) \cdot x\\ \mathbf{else}:\\ \;\;\;\;\frac{2}{t\_0 - -1} - 1\\ \end{array} \end{array} \]

FPCore

(FPCore (x)
 :precision binary64
 (let* ((t_0 (exp (* x -2.0))) (t_1 (/ -2.0 (- -1.0 t_0))))
   (if (<= x -0.0074)
     (/ 1.0 (/ (- t_1 -1.0) (- (pow t_1 2.0) 1.0)))
     (if (<= x 0.007)
       (*
        (fma (fma 0.13333333333333333 (* x x) -0.3333333333333333) (* x x) 1.0)
        x)
       (- (/ 2.0 (- t_0 -1.0)) 1.0)))))

C

double code(double x) {
	double t_0 = exp((x * -2.0));
	double t_1 = -2.0 / (-1.0 - t_0);
	double tmp;
	if (x <= -0.0074) {
		tmp = 1.0 / ((t_1 - -1.0) / (pow(t_1, 2.0) - 1.0));
	} else if (x <= 0.007) {
		tmp = fma(fma(0.13333333333333333, (x * x), -0.3333333333333333), (x * x), 1.0) * x;
	} else {
		tmp = (2.0 / (t_0 - -1.0)) - 1.0;
	}
	return tmp;
}

Julia

function code(x)
	t_0 = exp(Float64(x * -2.0))
	t_1 = Float64(-2.0 / Float64(-1.0 - t_0))
	tmp = 0.0
	if (x <= -0.0074)
		tmp = Float64(1.0 / Float64(Float64(t_1 - -1.0) / Float64((t_1 ^ 2.0) - 1.0)));
	elseif (x <= 0.007)
		tmp = Float64(fma(fma(0.13333333333333333, Float64(x * x), -0.3333333333333333), Float64(x * x), 1.0) * x);
	else
		tmp = Float64(Float64(2.0 / Float64(t_0 - -1.0)) - 1.0);
	end
	return tmp
end

Wolfram

code[x_] := Block[{t$95$0 = N[Exp[N[(x * -2.0), $MachinePrecision]], $MachinePrecision]}, Block[{t$95$1 = N[(-2.0 / N[(-1.0 - t$95$0), $MachinePrecision]), $MachinePrecision]}, If[LessEqual[x, -0.0074], N[(1.0 / N[(N[(t$95$1 - -1.0), $MachinePrecision] / N[(N[Power[t$95$1, 2.0], $MachinePrecision] - 1.0), $MachinePrecision]), $MachinePrecision]), $MachinePrecision], If[LessEqual[x, 0.007], N[(N[(N[(0.13333333333333333 * N[(x * x), $MachinePrecision] + -0.3333333333333333), $MachinePrecision] * N[(x * x), $MachinePrecision] + 1.0), $MachinePrecision] * x), $MachinePrecision], N[(N[(2.0 / N[(t$95$0 - -1.0), $MachinePrecision]), $MachinePrecision] - 1.0), $MachinePrecision]]]]]

Derivation

1. Split input into 3 regimes

2. if x < -0.0074000000000000003

   1. Initial program 100.0%

      \[\frac{2}{1 + e^{-2 \cdot x}} - 1 \]
   2. Step-by-step derivation

      1. lift--.f64 N/A

         \[\leadsto \color{blue}{\frac{2}{1 + e^{-2 \cdot x}} - 1} \]

      2. lift-/.f64 N/A

         \[\leadsto \color{blue}{\frac{2}{1 + e^{-2 \cdot x}}} - 1 \]

      3. lift-+.f64 N/A

         \[\leadsto \frac{2}{\color{blue}{1 + e^{-2 \cdot x}}} - 1 \]

      4. lift-*.f64 N/A

         \[\leadsto \frac{2}{1 + e^{\color{blue}{-2 \cdot x}}} - 1 \]

      5. lift-exp.f64 N/A

         \[\leadsto \frac{2}{1 + \color{blue}{e^{-2 \cdot x}}} - 1 \]

      6. flip-- N/A

         \[\leadsto \color{blue}{\frac{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}{\frac{2}{1 + e^{-2 \cdot x}} + 1}} \]

      7. division-flip N/A

         \[\leadsto \color{blue}{\frac{1}{\frac{\frac{2}{1 + e^{-2 \cdot x}} + 1}{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}}} \]

      8. lower-/.f64 N/A

         \[\leadsto \color{blue}{\frac{1}{\frac{\frac{2}{1 + e^{-2 \cdot x}} + 1}{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}}} \]

      9. lower-/.f64 N/A

         \[\leadsto \frac{1}{\color{blue}{\frac{\frac{2}{1 + e^{-2 \cdot x}} + 1}{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}}} \]

   3. Applied rewrites 100.0%

      \[\leadsto \color{blue}{\frac{1}{\frac{\frac{-2}{-1 - e^{x \cdot -2}} - -1}{{\left(\frac{-2}{-1 - e^{x \cdot -2}}\right)}^{2} - 1}}} \]

   if -0.0074000000000000003 < x < 0.00700000000000000015

   1. Initial program 7.8%

      \[\frac{2}{1 + e^{-2 \cdot x}} - 1 \]

   2. Taylor expanded in x around 0

      \[\leadsto \color{blue}{x \cdot \left(1 + {x}^{2} \cdot \left(\frac{2}{15} \cdot {x}^{2} - \frac{1}{3}\right)\right)} \]
   3. Step-by-step derivation

      1. *-commutative N/A

         \[\leadsto \left(1 + {x}^{2} \cdot \left(\frac{2}{15} \cdot {x}^{2} - \frac{1}{3}\right)\right) \cdot \color{blue}{x} \]

      2. lower-*.f64 N/A

         \[\leadsto \left(1 + {x}^{2} \cdot \left(\frac{2}{15} \cdot {x}^{2} - \frac{1}{3}\right)\right) \cdot \color{blue}{x} \]

      3. +-commutative N/A

         \[\leadsto \left({x}^{2} \cdot \left(\frac{2}{15} \cdot {x}^{2} - \frac{1}{3}\right) + 1\right) \cdot x \]

      4. *-commutative N/A

         \[\leadsto \left(\left(\frac{2}{15} \cdot {x}^{2} - \frac{1}{3}\right) \cdot {x}^{2} + 1\right) \cdot x \]

      5. lower-fma.f64 N/A

         \[\leadsto \mathsf{fma}\left(\frac{2}{15} \cdot {x}^{2} - \frac{1}{3}, {x}^{2}, 1\right) \cdot x \]

      6. sub-flip N/A

         \[\leadsto \mathsf{fma}\left(\frac{2}{15} \cdot {x}^{2} + \left(\mathsf{neg}\left(\frac{1}{3}\right)\right), {x}^{2}, 1\right) \cdot x \]

      7. metadata-eval N/A

         \[\leadsto \mathsf{fma}\left(\frac{2}{15} \cdot {x}^{2} + \frac{-1}{3}, {x}^{2}, 1\right) \cdot x \]

      8. lower-fma.f64 N/A

         \[\leadsto \mathsf{fma}\left(\mathsf{fma}\left(\frac{2}{15}, {x}^{2}, \frac{-1}{3}\right), {x}^{2}, 1\right) \cdot x \]

      9. unpow2 N/A

         \[\leadsto \mathsf{fma}\left(\mathsf{fma}\left(\frac{2}{15}, x \cdot x, \frac{-1}{3}\right), {x}^{2}, 1\right) \cdot x \]

      10. lower-*.f64 N/A

          \[\leadsto \mathsf{fma}\left(\mathsf{fma}\left(\frac{2}{15}, x \cdot x, \frac{-1}{3}\right), {x}^{2}, 1\right) \cdot x \]

      11. unpow2 N/A

          \[\leadsto \mathsf{fma}\left(\mathsf{fma}\left(\frac{2}{15}, x \cdot x, \frac{-1}{3}\right), x \cdot x, 1\right) \cdot x \]

      12. lower-*.f64 100.0

          \[\leadsto \mathsf{fma}\left(\mathsf{fma}\left(0.13333333333333333, x \cdot x, -0.3333333333333333\right), x \cdot x, 1\right) \cdot x \]

   4. Applied rewrites 100.0%

      \[\leadsto \color{blue}{\mathsf{fma}\left(\mathsf{fma}\left(0.13333333333333333, x \cdot x, -0.3333333333333333\right), x \cdot x, 1\right) \cdot x} \]

   if 0.00700000000000000015 < x

   1. Initial program 100.0%

      \[\frac{2}{1 + e^{-2 \cdot x}} - 1 \]
   2. Step-by-step derivation

      1. lift-+.f64 N/A

         \[\leadsto \frac{2}{\color{blue}{1 + e^{-2 \cdot x}}} - 1 \]

      2. lift-*.f64 N/A

         \[\leadsto \frac{2}{1 + e^{\color{blue}{-2 \cdot x}}} - 1 \]

      3. lift-exp.f64 N/A

         \[\leadsto \frac{2}{1 + \color{blue}{e^{-2 \cdot x}}} - 1 \]

      4. add-flip N/A

         \[\leadsto \frac{2}{\color{blue}{\mathsf{neg}\left(\left(\left(\mathsf{neg}\left(1\right)\right) - e^{-2 \cdot x}\right)\right)}} - 1 \]

      5. metadata-eval N/A

         \[\leadsto \frac{2}{\mathsf{neg}\left(\left(\color{blue}{-1} - e^{-2 \cdot x}\right)\right)} - 1 \]

      6. sub-negate-rev N/A

         \[\leadsto \frac{2}{\color{blue}{e^{-2 \cdot x} - -1}} - 1 \]

      7. lower--.f64 N/A

         \[\leadsto \frac{2}{\color{blue}{e^{-2 \cdot x} - -1}} - 1 \]

      8. lift-exp.f64 N/A

         \[\leadsto \frac{2}{\color{blue}{e^{-2 \cdot x}} - -1} - 1 \]

      9. *-commutative N/A

         \[\leadsto \frac{2}{e^{\color{blue}{x \cdot -2}} - -1} - 1 \]

      10. lower-*.f64 100.0

          \[\leadsto \frac{2}{e^{\color{blue}{x \cdot -2}} - -1} - 1 \]

   3. Applied rewrites 100.0%

      \[\leadsto \frac{2}{\color{blue}{e^{x \cdot -2} - -1}} - 1 \]
3. Recombined 3 regimes into one program.
4. Add Preprocessing

Alternative 2: 100.0% accurate, 0.7× speedup

Math

\[\begin{array}{l} \\ \begin{array}{l} t_0 := \frac{2}{e^{x \cdot -2} - -1} - 1\\ \mathbf{if}\;x \leq -0.0074:\\ \;\;\;\;\frac{1}{\frac{1}{t\_0}}\\ \mathbf{elif}\;x \leq 0.007:\\ \;\;\;\;\mathsf{fma}\left(\mathsf{fma}\left(0.13333333333333333, x \cdot x, -0.3333333333333333\right), x \cdot x, 1\right) \cdot x\\ \mathbf{else}:\\ \;\;\;\;t\_0\\ \end{array} \end{array} \]

FPCore

(FPCore (x)
 :precision binary64
 (let* ((t_0 (- (/ 2.0 (- (exp (* x -2.0)) -1.0)) 1.0)))
   (if (<= x -0.0074)
     (/ 1.0 (/ 1.0 t_0))
     (if (<= x 0.007)
       (*
        (fma (fma 0.13333333333333333 (* x x) -0.3333333333333333) (* x x) 1.0)
        x)
       t_0))))

C

double code(double x) {
	double t_0 = (2.0 / (exp((x * -2.0)) - -1.0)) - 1.0;
	double tmp;
	if (x <= -0.0074) {
		tmp = 1.0 / (1.0 / t_0);
	} else if (x <= 0.007) {
		tmp = fma(fma(0.13333333333333333, (x * x), -0.3333333333333333), (x * x), 1.0) * x;
	} else {
		tmp = t_0;
	}
	return tmp;
}

Julia

function code(x)
	t_0 = Float64(Float64(2.0 / Float64(exp(Float64(x * -2.0)) - -1.0)) - 1.0)
	tmp = 0.0
	if (x <= -0.0074)
		tmp = Float64(1.0 / Float64(1.0 / t_0));
	elseif (x <= 0.007)
		tmp = Float64(fma(fma(0.13333333333333333, Float64(x * x), -0.3333333333333333), Float64(x * x), 1.0) * x);
	else
		tmp = t_0;
	end
	return tmp
end

Wolfram

code[x_] := Block[{t$95$0 = N[(N[(2.0 / N[(N[Exp[N[(x * -2.0), $MachinePrecision]], $MachinePrecision] - -1.0), $MachinePrecision]), $MachinePrecision] - 1.0), $MachinePrecision]}, If[LessEqual[x, -0.0074], N[(1.0 / N[(1.0 / t$95$0), $MachinePrecision]), $MachinePrecision], If[LessEqual[x, 0.007], N[(N[(N[(0.13333333333333333 * N[(x * x), $MachinePrecision] + -0.3333333333333333), $MachinePrecision] * N[(x * x), $MachinePrecision] + 1.0), $MachinePrecision] * x), $MachinePrecision], t$95$0]]]

Derivation

1. Split input into 3 regimes

2. if x < -0.0074000000000000003

   1. Initial program 100.0%

      \[\frac{2}{1 + e^{-2 \cdot x}} - 1 \]
   2. Step-by-step derivation

      1. lift--.f64 N/A

         \[\leadsto \color{blue}{\frac{2}{1 + e^{-2 \cdot x}} - 1} \]

      2. lift-/.f64 N/A

         \[\leadsto \color{blue}{\frac{2}{1 + e^{-2 \cdot x}}} - 1 \]

      3. lift-+.f64 N/A

         \[\leadsto \frac{2}{\color{blue}{1 + e^{-2 \cdot x}}} - 1 \]

      4. lift-*.f64 N/A

         \[\leadsto \frac{2}{1 + e^{\color{blue}{-2 \cdot x}}} - 1 \]

      5. lift-exp.f64 N/A

         \[\leadsto \frac{2}{1 + \color{blue}{e^{-2 \cdot x}}} - 1 \]

      6. flip-- N/A

         \[\leadsto \color{blue}{\frac{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}{\frac{2}{1 + e^{-2 \cdot x}} + 1}} \]

      7. division-flip N/A

         \[\leadsto \color{blue}{\frac{1}{\frac{\frac{2}{1 + e^{-2 \cdot x}} + 1}{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}}} \]

      8. lower-/.f64 N/A

         \[\leadsto \color{blue}{\frac{1}{\frac{\frac{2}{1 + e^{-2 \cdot x}} + 1}{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}}} \]

      9. lower-/.f64 N/A

         \[\leadsto \frac{1}{\color{blue}{\frac{\frac{2}{1 + e^{-2 \cdot x}} + 1}{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}}} \]

   3. Applied rewrites 100.0%

      \[\leadsto \color{blue}{\frac{1}{\frac{\frac{-2}{-1 - e^{x \cdot -2}} - -1}{{\left(\frac{-2}{-1 - e^{x \cdot -2}}\right)}^{2} - 1}}} \]
   4. Step-by-step derivation

      1. lift-/.f64 N/A

         \[\leadsto \frac{1}{\color{blue}{\frac{\frac{-2}{-1 - e^{x \cdot -2}} - -1}{{\left(\frac{-2}{-1 - e^{x \cdot -2}}\right)}^{2} - 1}}} \]

      2. lift--.f64 N/A

         \[\leadsto \frac{1}{\frac{\color{blue}{\frac{-2}{-1 - e^{x \cdot -2}} - -1}}{{\left(\frac{-2}{-1 - e^{x \cdot -2}}\right)}^{2} - 1}} \]

      3. lift-/.f64 N/A

         \[\leadsto \frac{1}{\frac{\color{blue}{\frac{-2}{-1 - e^{x \cdot -2}}} - -1}{{\left(\frac{-2}{-1 - e^{x \cdot -2}}\right)}^{2} - 1}} \]

      4. lift--.f64 N/A

         \[\leadsto \frac{1}{\frac{\frac{-2}{\color{blue}{-1 - e^{x \cdot -2}}} - -1}{{\left(\frac{-2}{-1 - e^{x \cdot -2}}\right)}^{2} - 1}} \]

      5. lift-*.f64 N/A

         \[\leadsto \frac{1}{\frac{\frac{-2}{-1 - e^{\color{blue}{x \cdot -2}}} - -1}{{\left(\frac{-2}{-1 - e^{x \cdot -2}}\right)}^{2} - 1}} \]

      6. lift-exp.f64 N/A

         \[\leadsto \frac{1}{\frac{\frac{-2}{-1 - \color{blue}{e^{x \cdot -2}}} - -1}{{\left(\frac{-2}{-1 - e^{x \cdot -2}}\right)}^{2} - 1}} \]

      7. lift--.f64 N/A

         \[\leadsto \frac{1}{\frac{\frac{-2}{-1 - e^{x \cdot -2}} - -1}{\color{blue}{{\left(\frac{-2}{-1 - e^{x \cdot -2}}\right)}^{2} - 1}}} \]

      8. lift-pow.f64 N/A

         \[\leadsto \frac{1}{\frac{\frac{-2}{-1 - e^{x \cdot -2}} - -1}{\color{blue}{{\left(\frac{-2}{-1 - e^{x \cdot -2}}\right)}^{2}} - 1}} \]

      9. lift-/.f64 N/A

         \[\leadsto \frac{1}{\frac{\frac{-2}{-1 - e^{x \cdot -2}} - -1}{{\color{blue}{\left(\frac{-2}{-1 - e^{x \cdot -2}}\right)}}^{2} - 1}} \]

      10. lift--.f64 N/A

          \[\leadsto \frac{1}{\frac{\frac{-2}{-1 - e^{x \cdot -2}} - -1}{{\left(\frac{-2}{\color{blue}{-1 - e^{x \cdot -2}}}\right)}^{2} - 1}} \]

      11. lift-*.f64 N/A

          \[\leadsto \frac{1}{\frac{\frac{-2}{-1 - e^{x \cdot -2}} - -1}{{\left(\frac{-2}{-1 - e^{\color{blue}{x \cdot -2}}}\right)}^{2} - 1}} \]

      12. lift-exp.f64 N/A

          \[\leadsto \frac{1}{\frac{\frac{-2}{-1 - e^{x \cdot -2}} - -1}{{\left(\frac{-2}{-1 - \color{blue}{e^{x \cdot -2}}}\right)}^{2} - 1}} \]

      13. division-flip N/A

          \[\leadsto \frac{1}{\color{blue}{\frac{1}{\frac{{\left(\frac{-2}{-1 - e^{x \cdot -2}}\right)}^{2} - 1}{\frac{-2}{-1 - e^{x \cdot -2}} - -1}}}} \]

   5. Applied rewrites 100.0%

      \[\leadsto \frac{1}{\color{blue}{\frac{1}{\frac{2}{e^{x \cdot -2} - -1} - 1}}} \]

   if -0.0074000000000000003 < x < 0.00700000000000000015

   1. Initial program 7.8%

      \[\frac{2}{1 + e^{-2 \cdot x}} - 1 \]

   2. Taylor expanded in x around 0

      \[\leadsto \color{blue}{x \cdot \left(1 + {x}^{2} \cdot \left(\frac{2}{15} \cdot {x}^{2} - \frac{1}{3}\right)\right)} \]
   3. Step-by-step derivation

      1. *-commutative N/A

         \[\leadsto \left(1 + {x}^{2} \cdot \left(\frac{2}{15} \cdot {x}^{2} - \frac{1}{3}\right)\right) \cdot \color{blue}{x} \]

      2. lower-*.f64 N/A

         \[\leadsto \left(1 + {x}^{2} \cdot \left(\frac{2}{15} \cdot {x}^{2} - \frac{1}{3}\right)\right) \cdot \color{blue}{x} \]

      3. +-commutative N/A

         \[\leadsto \left({x}^{2} \cdot \left(\frac{2}{15} \cdot {x}^{2} - \frac{1}{3}\right) + 1\right) \cdot x \]

      4. *-commutative N/A

         \[\leadsto \left(\left(\frac{2}{15} \cdot {x}^{2} - \frac{1}{3}\right) \cdot {x}^{2} + 1\right) \cdot x \]

      5. lower-fma.f64 N/A

         \[\leadsto \mathsf{fma}\left(\frac{2}{15} \cdot {x}^{2} - \frac{1}{3}, {x}^{2}, 1\right) \cdot x \]

      6. sub-flip N/A

         \[\leadsto \mathsf{fma}\left(\frac{2}{15} \cdot {x}^{2} + \left(\mathsf{neg}\left(\frac{1}{3}\right)\right), {x}^{2}, 1\right) \cdot x \]

      7. metadata-eval N/A

         \[\leadsto \mathsf{fma}\left(\frac{2}{15} \cdot {x}^{2} + \frac{-1}{3}, {x}^{2}, 1\right) \cdot x \]

      8. lower-fma.f64 N/A

         \[\leadsto \mathsf{fma}\left(\mathsf{fma}\left(\frac{2}{15}, {x}^{2}, \frac{-1}{3}\right), {x}^{2}, 1\right) \cdot x \]

      9. unpow2 N/A

         \[\leadsto \mathsf{fma}\left(\mathsf{fma}\left(\frac{2}{15}, x \cdot x, \frac{-1}{3}\right), {x}^{2}, 1\right) \cdot x \]

      10. lower-*.f64 N/A

          \[\leadsto \mathsf{fma}\left(\mathsf{fma}\left(\frac{2}{15}, x \cdot x, \frac{-1}{3}\right), {x}^{2}, 1\right) \cdot x \]

      11. unpow2 N/A

          \[\leadsto \mathsf{fma}\left(\mathsf{fma}\left(\frac{2}{15}, x \cdot x, \frac{-1}{3}\right), x \cdot x, 1\right) \cdot x \]

      12. lower-*.f64 100.0

          \[\leadsto \mathsf{fma}\left(\mathsf{fma}\left(0.13333333333333333, x \cdot x, -0.3333333333333333\right), x \cdot x, 1\right) \cdot x \]

   4. Applied rewrites 100.0%

      \[\leadsto \color{blue}{\mathsf{fma}\left(\mathsf{fma}\left(0.13333333333333333, x \cdot x, -0.3333333333333333\right), x \cdot x, 1\right) \cdot x} \]

   if 0.00700000000000000015 < x

   1. Initial program 100.0%

      \[\frac{2}{1 + e^{-2 \cdot x}} - 1 \]
   2. Step-by-step derivation

      1. lift-+.f64 N/A

         \[\leadsto \frac{2}{\color{blue}{1 + e^{-2 \cdot x}}} - 1 \]

      2. lift-*.f64 N/A

         \[\leadsto \frac{2}{1 + e^{\color{blue}{-2 \cdot x}}} - 1 \]

      3. lift-exp.f64 N/A

         \[\leadsto \frac{2}{1 + \color{blue}{e^{-2 \cdot x}}} - 1 \]

      4. add-flip N/A

         \[\leadsto \frac{2}{\color{blue}{\mathsf{neg}\left(\left(\left(\mathsf{neg}\left(1\right)\right) - e^{-2 \cdot x}\right)\right)}} - 1 \]

      5. metadata-eval N/A

         \[\leadsto \frac{2}{\mathsf{neg}\left(\left(\color{blue}{-1} - e^{-2 \cdot x}\right)\right)} - 1 \]

      6. sub-negate-rev N/A

         \[\leadsto \frac{2}{\color{blue}{e^{-2 \cdot x} - -1}} - 1 \]

      7. lower--.f64 N/A

         \[\leadsto \frac{2}{\color{blue}{e^{-2 \cdot x} - -1}} - 1 \]

      8. lift-exp.f64 N/A

         \[\leadsto \frac{2}{\color{blue}{e^{-2 \cdot x}} - -1} - 1 \]

      9. *-commutative N/A

         \[\leadsto \frac{2}{e^{\color{blue}{x \cdot -2}} - -1} - 1 \]

      10. lower-*.f64 100.0

          \[\leadsto \frac{2}{e^{\color{blue}{x \cdot -2}} - -1} - 1 \]

   3. Applied rewrites 100.0%

      \[\leadsto \frac{2}{\color{blue}{e^{x \cdot -2} - -1}} - 1 \]
3. Recombined 3 regimes into one program.
4. Add Preprocessing

Alternative 3: 100.0% accurate, 0.8× speedup

Math

\[\begin{array}{l} \\ \begin{array}{l} t_0 := \frac{2}{e^{x \cdot -2} - -1} - 1\\ \mathbf{if}\;x \leq -0.0074:\\ \;\;\;\;t\_0\\ \mathbf{elif}\;x \leq 0.007:\\ \;\;\;\;\mathsf{fma}\left(\mathsf{fma}\left(0.13333333333333333, x \cdot x, -0.3333333333333333\right), x \cdot x, 1\right) \cdot x\\ \mathbf{else}:\\ \;\;\;\;t\_0\\ \end{array} \end{array} \]

FPCore

(FPCore (x)
 :precision binary64
 (let* ((t_0 (- (/ 2.0 (- (exp (* x -2.0)) -1.0)) 1.0)))
   (if (<= x -0.0074)
     t_0
     (if (<= x 0.007)
       (*
        (fma (fma 0.13333333333333333 (* x x) -0.3333333333333333) (* x x) 1.0)
        x)
       t_0))))

C

double code(double x) {
	double t_0 = (2.0 / (exp((x * -2.0)) - -1.0)) - 1.0;
	double tmp;
	if (x <= -0.0074) {
		tmp = t_0;
	} else if (x <= 0.007) {
		tmp = fma(fma(0.13333333333333333, (x * x), -0.3333333333333333), (x * x), 1.0) * x;
	} else {
		tmp = t_0;
	}
	return tmp;
}

Julia

function code(x)
	t_0 = Float64(Float64(2.0 / Float64(exp(Float64(x * -2.0)) - -1.0)) - 1.0)
	tmp = 0.0
	if (x <= -0.0074)
		tmp = t_0;
	elseif (x <= 0.007)
		tmp = Float64(fma(fma(0.13333333333333333, Float64(x * x), -0.3333333333333333), Float64(x * x), 1.0) * x);
	else
		tmp = t_0;
	end
	return tmp
end

Wolfram

code[x_] := Block[{t$95$0 = N[(N[(2.0 / N[(N[Exp[N[(x * -2.0), $MachinePrecision]], $MachinePrecision] - -1.0), $MachinePrecision]), $MachinePrecision] - 1.0), $MachinePrecision]}, If[LessEqual[x, -0.0074], t$95$0, If[LessEqual[x, 0.007], N[(N[(N[(0.13333333333333333 * N[(x * x), $MachinePrecision] + -0.3333333333333333), $MachinePrecision] * N[(x * x), $MachinePrecision] + 1.0), $MachinePrecision] * x), $MachinePrecision], t$95$0]]]

Derivation

1. Split input into 2 regimes

2. if x < -0.0074000000000000003 or 0.00700000000000000015 < x

   1. Initial program 100.0%

      \[\frac{2}{1 + e^{-2 \cdot x}} - 1 \]
   2. Step-by-step derivation

      1. lift-+.f64 N/A

         \[\leadsto \frac{2}{\color{blue}{1 + e^{-2 \cdot x}}} - 1 \]

      2. lift-*.f64 N/A

         \[\leadsto \frac{2}{1 + e^{\color{blue}{-2 \cdot x}}} - 1 \]

      3. lift-exp.f64 N/A

         \[\leadsto \frac{2}{1 + \color{blue}{e^{-2 \cdot x}}} - 1 \]

      4. add-flip N/A

         \[\leadsto \frac{2}{\color{blue}{\mathsf{neg}\left(\left(\left(\mathsf{neg}\left(1\right)\right) - e^{-2 \cdot x}\right)\right)}} - 1 \]

      5. metadata-eval N/A

         \[\leadsto \frac{2}{\mathsf{neg}\left(\left(\color{blue}{-1} - e^{-2 \cdot x}\right)\right)} - 1 \]

      6. sub-negate-rev N/A

         \[\leadsto \frac{2}{\color{blue}{e^{-2 \cdot x} - -1}} - 1 \]

      7. lower--.f64 N/A

         \[\leadsto \frac{2}{\color{blue}{e^{-2 \cdot x} - -1}} - 1 \]

      8. lift-exp.f64 N/A

         \[\leadsto \frac{2}{\color{blue}{e^{-2 \cdot x}} - -1} - 1 \]

      9. *-commutative N/A

         \[\leadsto \frac{2}{e^{\color{blue}{x \cdot -2}} - -1} - 1 \]

      10. lower-*.f64 100.0

          \[\leadsto \frac{2}{e^{\color{blue}{x \cdot -2}} - -1} - 1 \]

   3. Applied rewrites 100.0%

      \[\leadsto \frac{2}{\color{blue}{e^{x \cdot -2} - -1}} - 1 \]

   if -0.0074000000000000003 < x < 0.00700000000000000015

   1. Initial program 7.8%

      \[\frac{2}{1 + e^{-2 \cdot x}} - 1 \]

   2. Taylor expanded in x around 0

      \[\leadsto \color{blue}{x \cdot \left(1 + {x}^{2} \cdot \left(\frac{2}{15} \cdot {x}^{2} - \frac{1}{3}\right)\right)} \]
   3. Step-by-step derivation

      1. *-commutative N/A

         \[\leadsto \left(1 + {x}^{2} \cdot \left(\frac{2}{15} \cdot {x}^{2} - \frac{1}{3}\right)\right) \cdot \color{blue}{x} \]

      2. lower-*.f64 N/A

         \[\leadsto \left(1 + {x}^{2} \cdot \left(\frac{2}{15} \cdot {x}^{2} - \frac{1}{3}\right)\right) \cdot \color{blue}{x} \]

      3. +-commutative N/A

         \[\leadsto \left({x}^{2} \cdot \left(\frac{2}{15} \cdot {x}^{2} - \frac{1}{3}\right) + 1\right) \cdot x \]

      4. *-commutative N/A

         \[\leadsto \left(\left(\frac{2}{15} \cdot {x}^{2} - \frac{1}{3}\right) \cdot {x}^{2} + 1\right) \cdot x \]

      5. lower-fma.f64 N/A

         \[\leadsto \mathsf{fma}\left(\frac{2}{15} \cdot {x}^{2} - \frac{1}{3}, {x}^{2}, 1\right) \cdot x \]

      6. sub-flip N/A

         \[\leadsto \mathsf{fma}\left(\frac{2}{15} \cdot {x}^{2} + \left(\mathsf{neg}\left(\frac{1}{3}\right)\right), {x}^{2}, 1\right) \cdot x \]

      7. metadata-eval N/A

         \[\leadsto \mathsf{fma}\left(\frac{2}{15} \cdot {x}^{2} + \frac{-1}{3}, {x}^{2}, 1\right) \cdot x \]

      8. lower-fma.f64 N/A

         \[\leadsto \mathsf{fma}\left(\mathsf{fma}\left(\frac{2}{15}, {x}^{2}, \frac{-1}{3}\right), {x}^{2}, 1\right) \cdot x \]

      9. unpow2 N/A

         \[\leadsto \mathsf{fma}\left(\mathsf{fma}\left(\frac{2}{15}, x \cdot x, \frac{-1}{3}\right), {x}^{2}, 1\right) \cdot x \]

      10. lower-*.f64 N/A

          \[\leadsto \mathsf{fma}\left(\mathsf{fma}\left(\frac{2}{15}, x \cdot x, \frac{-1}{3}\right), {x}^{2}, 1\right) \cdot x \]

      11. unpow2 N/A

          \[\leadsto \mathsf{fma}\left(\mathsf{fma}\left(\frac{2}{15}, x \cdot x, \frac{-1}{3}\right), x \cdot x, 1\right) \cdot x \]

      12. lower-*.f64 100.0

          \[\leadsto \mathsf{fma}\left(\mathsf{fma}\left(0.13333333333333333, x \cdot x, -0.3333333333333333\right), x \cdot x, 1\right) \cdot x \]

   4. Applied rewrites 100.0%

      \[\leadsto \color{blue}{\mathsf{fma}\left(\mathsf{fma}\left(0.13333333333333333, x \cdot x, -0.3333333333333333\right), x \cdot x, 1\right) \cdot x} \]
3. Recombined 2 regimes into one program.
4. Add Preprocessing

Alternative 4: 75.9% accurate, 0.9× speedup

Math

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;x \leq -1.5:\\ \;\;\;\;\frac{2}{\mathsf{fma}\left(\mathsf{fma}\left(\mathsf{fma}\left(-1.3333333333333333, x, 2\right), x, -2\right), x, 2\right)} - 1\\ \mathbf{else}:\\ \;\;\;\;\frac{1}{\mathsf{fma}\left(0.3333333333333333, x, \frac{1}{x}\right)}\\ \end{array} \end{array} \]

FPCore

(FPCore (x)
 :precision binary64
 (if (<= x -1.5)
   (- (/ 2.0 (fma (fma (fma -1.3333333333333333 x 2.0) x -2.0) x 2.0)) 1.0)
   (/ 1.0 (fma 0.3333333333333333 x (/ 1.0 x)))))

C

double code(double x) {
	double tmp;
	if (x <= -1.5) {
		tmp = (2.0 / fma(fma(fma(-1.3333333333333333, x, 2.0), x, -2.0), x, 2.0)) - 1.0;
	} else {
		tmp = 1.0 / fma(0.3333333333333333, x, (1.0 / x));
	}
	return tmp;
}

Julia

function code(x)
	tmp = 0.0
	if (x <= -1.5)
		tmp = Float64(Float64(2.0 / fma(fma(fma(-1.3333333333333333, x, 2.0), x, -2.0), x, 2.0)) - 1.0);
	else
		tmp = Float64(1.0 / fma(0.3333333333333333, x, Float64(1.0 / x)));
	end
	return tmp
end

Wolfram

code[x_] := If[LessEqual[x, -1.5], N[(N[(2.0 / N[(N[(N[(-1.3333333333333333 * x + 2.0), $MachinePrecision] * x + -2.0), $MachinePrecision] * x + 2.0), $MachinePrecision]), $MachinePrecision] - 1.0), $MachinePrecision], N[(1.0 / N[(0.3333333333333333 * x + N[(1.0 / x), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]]

Derivation

1. Split input into 2 regimes

2. if x < -1.5

   1. Initial program 100.0%

      \[\frac{2}{1 + e^{-2 \cdot x}} - 1 \]

   2. Taylor expanded in x around 0

      \[\leadsto \frac{2}{\color{blue}{2 + x \cdot \left(x \cdot \left(2 + \frac{-4}{3} \cdot x\right) - 2\right)}} - 1 \]
   3. Step-by-step derivation

      1. +-commutative N/A

         \[\leadsto \frac{2}{x \cdot \left(x \cdot \left(2 + \frac{-4}{3} \cdot x\right) - 2\right) + \color{blue}{2}} - 1 \]

      2. *-commutative N/A

         \[\leadsto \frac{2}{\left(x \cdot \left(2 + \frac{-4}{3} \cdot x\right) - 2\right) \cdot x + 2} - 1 \]

      3. lower-fma.f64 N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(x \cdot \left(2 + \frac{-4}{3} \cdot x\right) - 2, \color{blue}{x}, 2\right)} - 1 \]

      4. sub-flip N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(x \cdot \left(2 + \frac{-4}{3} \cdot x\right) + \left(\mathsf{neg}\left(2\right)\right), x, 2\right)} - 1 \]

      5. *-commutative N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(\left(2 + \frac{-4}{3} \cdot x\right) \cdot x + \left(\mathsf{neg}\left(2\right)\right), x, 2\right)} - 1 \]

      6. metadata-eval N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(\left(2 + \frac{-4}{3} \cdot x\right) \cdot x + -2, x, 2\right)} - 1 \]

      7. lower-fma.f64 N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(\mathsf{fma}\left(2 + \frac{-4}{3} \cdot x, x, -2\right), x, 2\right)} - 1 \]

      8. +-commutative N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(\mathsf{fma}\left(\frac{-4}{3} \cdot x + 2, x, -2\right), x, 2\right)} - 1 \]

      9. lower-fma.f64 99.3

         \[\leadsto \frac{2}{\mathsf{fma}\left(\mathsf{fma}\left(\mathsf{fma}\left(-1.3333333333333333, x, 2\right), x, -2\right), x, 2\right)} - 1 \]

   4. Applied rewrites 99.3%

      \[\leadsto \frac{2}{\color{blue}{\mathsf{fma}\left(\mathsf{fma}\left(\mathsf{fma}\left(-1.3333333333333333, x, 2\right), x, -2\right), x, 2\right)}} - 1 \]

   if -1.5 < x

   1. Initial program 38.9%

      \[\frac{2}{1 + e^{-2 \cdot x}} - 1 \]
   2. Step-by-step derivation

      1. lift--.f64 N/A

         \[\leadsto \color{blue}{\frac{2}{1 + e^{-2 \cdot x}} - 1} \]

      2. lift-/.f64 N/A

         \[\leadsto \color{blue}{\frac{2}{1 + e^{-2 \cdot x}}} - 1 \]

      3. lift-+.f64 N/A

         \[\leadsto \frac{2}{\color{blue}{1 + e^{-2 \cdot x}}} - 1 \]

      4. lift-*.f64 N/A

         \[\leadsto \frac{2}{1 + e^{\color{blue}{-2 \cdot x}}} - 1 \]

      5. lift-exp.f64 N/A

         \[\leadsto \frac{2}{1 + \color{blue}{e^{-2 \cdot x}}} - 1 \]

      6. flip-- N/A

         \[\leadsto \color{blue}{\frac{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}{\frac{2}{1 + e^{-2 \cdot x}} + 1}} \]

      7. division-flip N/A

         \[\leadsto \color{blue}{\frac{1}{\frac{\frac{2}{1 + e^{-2 \cdot x}} + 1}{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}}} \]

      8. lower-/.f64 N/A

         \[\leadsto \color{blue}{\frac{1}{\frac{\frac{2}{1 + e^{-2 \cdot x}} + 1}{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}}} \]

      9. lower-/.f64 N/A

         \[\leadsto \frac{1}{\color{blue}{\frac{\frac{2}{1 + e^{-2 \cdot x}} + 1}{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}}} \]

   3. Applied rewrites 38.9%

      \[\leadsto \color{blue}{\frac{1}{\frac{\frac{-2}{-1 - e^{x \cdot -2}} - -1}{{\left(\frac{-2}{-1 - e^{x \cdot -2}}\right)}^{2} - 1}}} \]

   4. Taylor expanded in x around 0

      \[\leadsto \frac{1}{\color{blue}{\frac{1 + \frac{1}{3} \cdot {x}^{2}}{x}}} \]
   5. Step-by-step derivation

      1. lower-/.f64 N/A

         \[\leadsto \frac{1}{\frac{1 + \frac{1}{3} \cdot {x}^{2}}{\color{blue}{x}}} \]

      2. +-commutative N/A

         \[\leadsto \frac{1}{\frac{\frac{1}{3} \cdot {x}^{2} + 1}{x}} \]

      3. lower-fma.f64 N/A

         \[\leadsto \frac{1}{\frac{\mathsf{fma}\left(\frac{1}{3}, {x}^{2}, 1\right)}{x}} \]

      4. pow2 N/A

         \[\leadsto \frac{1}{\frac{\mathsf{fma}\left(\frac{1}{3}, x \cdot x, 1\right)}{x}} \]

      5. lift-*.f64 68.0

         \[\leadsto \frac{1}{\frac{\mathsf{fma}\left(0.3333333333333333, x \cdot x, 1\right)}{x}} \]

   6. Applied rewrites 68.0%

      \[\leadsto \frac{1}{\color{blue}{\frac{\mathsf{fma}\left(0.3333333333333333, x \cdot x, 1\right)}{x}}} \]

   7. Taylor expanded in x around inf

      \[\leadsto \frac{1}{x \cdot \color{blue}{\left(\frac{1}{3} + \frac{1}{{x}^{2}}\right)}} \]
   8. Step-by-step derivation

      1. distribute-rgt-in N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + \frac{1}{{x}^{2}} \cdot \color{blue}{x}} \]

      2. pow-flip N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + {x}^{\left(\mathsf{neg}\left(2\right)\right)} \cdot x} \]

      3. metadata-eval N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + {x}^{-2} \cdot x} \]

      4. pow-plus N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + {x}^{\left(-2 + \color{blue}{1}\right)}} \]

      5. metadata-eval N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + {x}^{-1}} \]

      6. inv-pow N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + \frac{1}{x}} \]

      7. lower-fma.f64 N/A

         \[\leadsto \frac{1}{\mathsf{fma}\left(\frac{1}{3}, x, \frac{1}{x}\right)} \]

      8. lower-/.f64 68.1

         \[\leadsto \frac{1}{\mathsf{fma}\left(0.3333333333333333, x, \frac{1}{x}\right)} \]

   9. Applied rewrites 68.1%

      \[\leadsto \frac{1}{\mathsf{fma}\left(0.3333333333333333, \color{blue}{x}, \frac{1}{x}\right)} \]
3. Recombined 2 regimes into one program.
4. Add Preprocessing

Alternative 5: 75.9% accurate, 0.9× speedup

Math

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;x \leq -1.8:\\ \;\;\;\;\frac{2}{\left(\frac{2}{x} - 1.3333333333333333\right) \cdot \left(\left(x \cdot x\right) \cdot x\right)} - 1\\ \mathbf{else}:\\ \;\;\;\;\frac{1}{\mathsf{fma}\left(0.3333333333333333, x, \frac{1}{x}\right)}\\ \end{array} \end{array} \]

FPCore

(FPCore (x)
 :precision binary64
 (if (<= x -1.8)
   (- (/ 2.0 (* (- (/ 2.0 x) 1.3333333333333333) (* (* x x) x))) 1.0)
   (/ 1.0 (fma 0.3333333333333333 x (/ 1.0 x)))))

C

double code(double x) {
	double tmp;
	if (x <= -1.8) {
		tmp = (2.0 / (((2.0 / x) - 1.3333333333333333) * ((x * x) * x))) - 1.0;
	} else {
		tmp = 1.0 / fma(0.3333333333333333, x, (1.0 / x));
	}
	return tmp;
}

Julia

function code(x)
	tmp = 0.0
	if (x <= -1.8)
		tmp = Float64(Float64(2.0 / Float64(Float64(Float64(2.0 / x) - 1.3333333333333333) * Float64(Float64(x * x) * x))) - 1.0);
	else
		tmp = Float64(1.0 / fma(0.3333333333333333, x, Float64(1.0 / x)));
	end
	return tmp
end

Wolfram

code[x_] := If[LessEqual[x, -1.8], N[(N[(2.0 / N[(N[(N[(2.0 / x), $MachinePrecision] - 1.3333333333333333), $MachinePrecision] * N[(N[(x * x), $MachinePrecision] * x), $MachinePrecision]), $MachinePrecision]), $MachinePrecision] - 1.0), $MachinePrecision], N[(1.0 / N[(0.3333333333333333 * x + N[(1.0 / x), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]]

Derivation

1. Split input into 2 regimes

2. if x < -1.80000000000000004

   1. Initial program 100.0%

      \[\frac{2}{1 + e^{-2 \cdot x}} - 1 \]

   2. Taylor expanded in x around 0

      \[\leadsto \frac{2}{\color{blue}{2 + x \cdot \left(x \cdot \left(2 + \frac{-4}{3} \cdot x\right) - 2\right)}} - 1 \]
   3. Step-by-step derivation

      1. +-commutative N/A

         \[\leadsto \frac{2}{x \cdot \left(x \cdot \left(2 + \frac{-4}{3} \cdot x\right) - 2\right) + \color{blue}{2}} - 1 \]

      2. *-commutative N/A

         \[\leadsto \frac{2}{\left(x \cdot \left(2 + \frac{-4}{3} \cdot x\right) - 2\right) \cdot x + 2} - 1 \]

      3. lower-fma.f64 N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(x \cdot \left(2 + \frac{-4}{3} \cdot x\right) - 2, \color{blue}{x}, 2\right)} - 1 \]

      4. sub-flip N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(x \cdot \left(2 + \frac{-4}{3} \cdot x\right) + \left(\mathsf{neg}\left(2\right)\right), x, 2\right)} - 1 \]

      5. *-commutative N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(\left(2 + \frac{-4}{3} \cdot x\right) \cdot x + \left(\mathsf{neg}\left(2\right)\right), x, 2\right)} - 1 \]

      6. metadata-eval N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(\left(2 + \frac{-4}{3} \cdot x\right) \cdot x + -2, x, 2\right)} - 1 \]

      7. lower-fma.f64 N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(\mathsf{fma}\left(2 + \frac{-4}{3} \cdot x, x, -2\right), x, 2\right)} - 1 \]

      8. +-commutative N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(\mathsf{fma}\left(\frac{-4}{3} \cdot x + 2, x, -2\right), x, 2\right)} - 1 \]

      9. lower-fma.f64 99.3

         \[\leadsto \frac{2}{\mathsf{fma}\left(\mathsf{fma}\left(\mathsf{fma}\left(-1.3333333333333333, x, 2\right), x, -2\right), x, 2\right)} - 1 \]

   4. Applied rewrites 99.3%

      \[\leadsto \frac{2}{\color{blue}{\mathsf{fma}\left(\mathsf{fma}\left(\mathsf{fma}\left(-1.3333333333333333, x, 2\right), x, -2\right), x, 2\right)}} - 1 \]

   5. Taylor expanded in x around inf

      \[\leadsto \frac{2}{{x}^{3} \cdot \color{blue}{\left(2 \cdot \frac{1}{x} - \frac{4}{3}\right)}} - 1 \]
   6. Step-by-step derivation

      1. *-commutative N/A

         \[\leadsto \frac{2}{\left(2 \cdot \frac{1}{x} - \frac{4}{3}\right) \cdot {x}^{\color{blue}{3}}} - 1 \]

      2. lower-*.f64 N/A

         \[\leadsto \frac{2}{\left(2 \cdot \frac{1}{x} - \frac{4}{3}\right) \cdot {x}^{\color{blue}{3}}} - 1 \]

      3. lower--.f64 N/A

         \[\leadsto \frac{2}{\left(2 \cdot \frac{1}{x} - \frac{4}{3}\right) \cdot {x}^{3}} - 1 \]

      4. mult-flip-rev N/A

         \[\leadsto \frac{2}{\left(\frac{2}{x} - \frac{4}{3}\right) \cdot {x}^{3}} - 1 \]

      5. lower-/.f64 N/A

         \[\leadsto \frac{2}{\left(\frac{2}{x} - \frac{4}{3}\right) \cdot {x}^{3}} - 1 \]

      6. unpow3 N/A

         \[\leadsto \frac{2}{\left(\frac{2}{x} - \frac{4}{3}\right) \cdot \left(\left(x \cdot x\right) \cdot x\right)} - 1 \]

      7. pow2 N/A

         \[\leadsto \frac{2}{\left(\frac{2}{x} - \frac{4}{3}\right) \cdot \left({x}^{2} \cdot x\right)} - 1 \]

      8. lower-*.f64 N/A

         \[\leadsto \frac{2}{\left(\frac{2}{x} - \frac{4}{3}\right) \cdot \left({x}^{2} \cdot x\right)} - 1 \]

      9. pow2 N/A

         \[\leadsto \frac{2}{\left(\frac{2}{x} - \frac{4}{3}\right) \cdot \left(\left(x \cdot x\right) \cdot x\right)} - 1 \]

      10. lift-*.f64 99.3

          \[\leadsto \frac{2}{\left(\frac{2}{x} - 1.3333333333333333\right) \cdot \left(\left(x \cdot x\right) \cdot x\right)} - 1 \]

   7. Applied rewrites 99.3%

      \[\leadsto \frac{2}{\left(\frac{2}{x} - 1.3333333333333333\right) \cdot \color{blue}{\left(\left(x \cdot x\right) \cdot x\right)}} - 1 \]

   if -1.80000000000000004 < x

   1. Initial program 38.9%

      \[\frac{2}{1 + e^{-2 \cdot x}} - 1 \]
   2. Step-by-step derivation

      1. lift--.f64 N/A

         \[\leadsto \color{blue}{\frac{2}{1 + e^{-2 \cdot x}} - 1} \]

      2. lift-/.f64 N/A

         \[\leadsto \color{blue}{\frac{2}{1 + e^{-2 \cdot x}}} - 1 \]

      3. lift-+.f64 N/A

         \[\leadsto \frac{2}{\color{blue}{1 + e^{-2 \cdot x}}} - 1 \]

      4. lift-*.f64 N/A

         \[\leadsto \frac{2}{1 + e^{\color{blue}{-2 \cdot x}}} - 1 \]

      5. lift-exp.f64 N/A

         \[\leadsto \frac{2}{1 + \color{blue}{e^{-2 \cdot x}}} - 1 \]

      6. flip-- N/A

         \[\leadsto \color{blue}{\frac{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}{\frac{2}{1 + e^{-2 \cdot x}} + 1}} \]

      7. division-flip N/A

         \[\leadsto \color{blue}{\frac{1}{\frac{\frac{2}{1 + e^{-2 \cdot x}} + 1}{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}}} \]

      8. lower-/.f64 N/A

         \[\leadsto \color{blue}{\frac{1}{\frac{\frac{2}{1 + e^{-2 \cdot x}} + 1}{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}}} \]

      9. lower-/.f64 N/A

         \[\leadsto \frac{1}{\color{blue}{\frac{\frac{2}{1 + e^{-2 \cdot x}} + 1}{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}}} \]

   3. Applied rewrites 38.9%

      \[\leadsto \color{blue}{\frac{1}{\frac{\frac{-2}{-1 - e^{x \cdot -2}} - -1}{{\left(\frac{-2}{-1 - e^{x \cdot -2}}\right)}^{2} - 1}}} \]

   4. Taylor expanded in x around 0

      \[\leadsto \frac{1}{\color{blue}{\frac{1 + \frac{1}{3} \cdot {x}^{2}}{x}}} \]
   5. Step-by-step derivation

      1. lower-/.f64 N/A

         \[\leadsto \frac{1}{\frac{1 + \frac{1}{3} \cdot {x}^{2}}{\color{blue}{x}}} \]

      2. +-commutative N/A

         \[\leadsto \frac{1}{\frac{\frac{1}{3} \cdot {x}^{2} + 1}{x}} \]

      3. lower-fma.f64 N/A

         \[\leadsto \frac{1}{\frac{\mathsf{fma}\left(\frac{1}{3}, {x}^{2}, 1\right)}{x}} \]

      4. pow2 N/A

         \[\leadsto \frac{1}{\frac{\mathsf{fma}\left(\frac{1}{3}, x \cdot x, 1\right)}{x}} \]

      5. lift-*.f64 68.0

         \[\leadsto \frac{1}{\frac{\mathsf{fma}\left(0.3333333333333333, x \cdot x, 1\right)}{x}} \]

   6. Applied rewrites 68.0%

      \[\leadsto \frac{1}{\color{blue}{\frac{\mathsf{fma}\left(0.3333333333333333, x \cdot x, 1\right)}{x}}} \]

   7. Taylor expanded in x around inf

      \[\leadsto \frac{1}{x \cdot \color{blue}{\left(\frac{1}{3} + \frac{1}{{x}^{2}}\right)}} \]
   8. Step-by-step derivation

      1. distribute-rgt-in N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + \frac{1}{{x}^{2}} \cdot \color{blue}{x}} \]

      2. pow-flip N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + {x}^{\left(\mathsf{neg}\left(2\right)\right)} \cdot x} \]

      3. metadata-eval N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + {x}^{-2} \cdot x} \]

      4. pow-plus N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + {x}^{\left(-2 + \color{blue}{1}\right)}} \]

      5. metadata-eval N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + {x}^{-1}} \]

      6. inv-pow N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + \frac{1}{x}} \]

      7. lower-fma.f64 N/A

         \[\leadsto \frac{1}{\mathsf{fma}\left(\frac{1}{3}, x, \frac{1}{x}\right)} \]

      8. lower-/.f64 68.1

         \[\leadsto \frac{1}{\mathsf{fma}\left(0.3333333333333333, x, \frac{1}{x}\right)} \]

   9. Applied rewrites 68.1%

      \[\leadsto \frac{1}{\mathsf{fma}\left(0.3333333333333333, \color{blue}{x}, \frac{1}{x}\right)} \]
3. Recombined 2 regimes into one program.
4. Add Preprocessing

Alternative 6: 75.9% accurate, 1.0× speedup

Math

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;x \leq -1.9:\\ \;\;\;\;\frac{2}{\mathsf{fma}\left(\mathsf{fma}\left(-1.3333333333333333 \cdot x, x, -2\right), x, 2\right)} - 1\\ \mathbf{else}:\\ \;\;\;\;\frac{1}{\mathsf{fma}\left(0.3333333333333333, x, \frac{1}{x}\right)}\\ \end{array} \end{array} \]

FPCore

(FPCore (x)
 :precision binary64
 (if (<= x -1.9)
   (- (/ 2.0 (fma (fma (* -1.3333333333333333 x) x -2.0) x 2.0)) 1.0)
   (/ 1.0 (fma 0.3333333333333333 x (/ 1.0 x)))))

C

double code(double x) {
	double tmp;
	if (x <= -1.9) {
		tmp = (2.0 / fma(fma((-1.3333333333333333 * x), x, -2.0), x, 2.0)) - 1.0;
	} else {
		tmp = 1.0 / fma(0.3333333333333333, x, (1.0 / x));
	}
	return tmp;
}

Julia

function code(x)
	tmp = 0.0
	if (x <= -1.9)
		tmp = Float64(Float64(2.0 / fma(fma(Float64(-1.3333333333333333 * x), x, -2.0), x, 2.0)) - 1.0);
	else
		tmp = Float64(1.0 / fma(0.3333333333333333, x, Float64(1.0 / x)));
	end
	return tmp
end

Wolfram

code[x_] := If[LessEqual[x, -1.9], N[(N[(2.0 / N[(N[(N[(-1.3333333333333333 * x), $MachinePrecision] * x + -2.0), $MachinePrecision] * x + 2.0), $MachinePrecision]), $MachinePrecision] - 1.0), $MachinePrecision], N[(1.0 / N[(0.3333333333333333 * x + N[(1.0 / x), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]]

Derivation

1. Split input into 2 regimes

2. if x < -1.8999999999999999

   1. Initial program 100.0%

      \[\frac{2}{1 + e^{-2 \cdot x}} - 1 \]

   2. Taylor expanded in x around 0

      \[\leadsto \frac{2}{\color{blue}{2 + x \cdot \left(x \cdot \left(2 + \frac{-4}{3} \cdot x\right) - 2\right)}} - 1 \]
   3. Step-by-step derivation

      1. +-commutative N/A

         \[\leadsto \frac{2}{x \cdot \left(x \cdot \left(2 + \frac{-4}{3} \cdot x\right) - 2\right) + \color{blue}{2}} - 1 \]

      2. *-commutative N/A

         \[\leadsto \frac{2}{\left(x \cdot \left(2 + \frac{-4}{3} \cdot x\right) - 2\right) \cdot x + 2} - 1 \]

      3. lower-fma.f64 N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(x \cdot \left(2 + \frac{-4}{3} \cdot x\right) - 2, \color{blue}{x}, 2\right)} - 1 \]

      4. sub-flip N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(x \cdot \left(2 + \frac{-4}{3} \cdot x\right) + \left(\mathsf{neg}\left(2\right)\right), x, 2\right)} - 1 \]

      5. *-commutative N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(\left(2 + \frac{-4}{3} \cdot x\right) \cdot x + \left(\mathsf{neg}\left(2\right)\right), x, 2\right)} - 1 \]

      6. metadata-eval N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(\left(2 + \frac{-4}{3} \cdot x\right) \cdot x + -2, x, 2\right)} - 1 \]

      7. lower-fma.f64 N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(\mathsf{fma}\left(2 + \frac{-4}{3} \cdot x, x, -2\right), x, 2\right)} - 1 \]

      8. +-commutative N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(\mathsf{fma}\left(\frac{-4}{3} \cdot x + 2, x, -2\right), x, 2\right)} - 1 \]

      9. lower-fma.f64 99.3

         \[\leadsto \frac{2}{\mathsf{fma}\left(\mathsf{fma}\left(\mathsf{fma}\left(-1.3333333333333333, x, 2\right), x, -2\right), x, 2\right)} - 1 \]

   4. Applied rewrites 99.3%

      \[\leadsto \frac{2}{\color{blue}{\mathsf{fma}\left(\mathsf{fma}\left(\mathsf{fma}\left(-1.3333333333333333, x, 2\right), x, -2\right), x, 2\right)}} - 1 \]

   5. Taylor expanded in x around inf

      \[\leadsto \frac{2}{\mathsf{fma}\left(\mathsf{fma}\left(\frac{-4}{3} \cdot x, x, -2\right), x, 2\right)} - 1 \]
   6. Step-by-step derivation

      1. lower-*.f64 99.3

         \[\leadsto \frac{2}{\mathsf{fma}\left(\mathsf{fma}\left(-1.3333333333333333 \cdot x, x, -2\right), x, 2\right)} - 1 \]

   7. Applied rewrites 99.3%

      \[\leadsto \frac{2}{\mathsf{fma}\left(\mathsf{fma}\left(-1.3333333333333333 \cdot x, x, -2\right), x, 2\right)} - 1 \]

   if -1.8999999999999999 < x

   1. Initial program 38.9%

      \[\frac{2}{1 + e^{-2 \cdot x}} - 1 \]
   2. Step-by-step derivation

      1. lift--.f64 N/A

         \[\leadsto \color{blue}{\frac{2}{1 + e^{-2 \cdot x}} - 1} \]

      2. lift-/.f64 N/A

         \[\leadsto \color{blue}{\frac{2}{1 + e^{-2 \cdot x}}} - 1 \]

      3. lift-+.f64 N/A

         \[\leadsto \frac{2}{\color{blue}{1 + e^{-2 \cdot x}}} - 1 \]

      4. lift-*.f64 N/A

         \[\leadsto \frac{2}{1 + e^{\color{blue}{-2 \cdot x}}} - 1 \]

      5. lift-exp.f64 N/A

         \[\leadsto \frac{2}{1 + \color{blue}{e^{-2 \cdot x}}} - 1 \]

      6. flip-- N/A

         \[\leadsto \color{blue}{\frac{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}{\frac{2}{1 + e^{-2 \cdot x}} + 1}} \]

      7. division-flip N/A

         \[\leadsto \color{blue}{\frac{1}{\frac{\frac{2}{1 + e^{-2 \cdot x}} + 1}{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}}} \]

      8. lower-/.f64 N/A

         \[\leadsto \color{blue}{\frac{1}{\frac{\frac{2}{1 + e^{-2 \cdot x}} + 1}{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}}} \]

      9. lower-/.f64 N/A

         \[\leadsto \frac{1}{\color{blue}{\frac{\frac{2}{1 + e^{-2 \cdot x}} + 1}{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}}} \]

   3. Applied rewrites 38.9%

      \[\leadsto \color{blue}{\frac{1}{\frac{\frac{-2}{-1 - e^{x \cdot -2}} - -1}{{\left(\frac{-2}{-1 - e^{x \cdot -2}}\right)}^{2} - 1}}} \]

   4. Taylor expanded in x around 0

      \[\leadsto \frac{1}{\color{blue}{\frac{1 + \frac{1}{3} \cdot {x}^{2}}{x}}} \]
   5. Step-by-step derivation

      1. lower-/.f64 N/A

         \[\leadsto \frac{1}{\frac{1 + \frac{1}{3} \cdot {x}^{2}}{\color{blue}{x}}} \]

      2. +-commutative N/A

         \[\leadsto \frac{1}{\frac{\frac{1}{3} \cdot {x}^{2} + 1}{x}} \]

      3. lower-fma.f64 N/A

         \[\leadsto \frac{1}{\frac{\mathsf{fma}\left(\frac{1}{3}, {x}^{2}, 1\right)}{x}} \]

      4. pow2 N/A

         \[\leadsto \frac{1}{\frac{\mathsf{fma}\left(\frac{1}{3}, x \cdot x, 1\right)}{x}} \]

      5. lift-*.f64 68.0

         \[\leadsto \frac{1}{\frac{\mathsf{fma}\left(0.3333333333333333, x \cdot x, 1\right)}{x}} \]

   6. Applied rewrites 68.0%

      \[\leadsto \frac{1}{\color{blue}{\frac{\mathsf{fma}\left(0.3333333333333333, x \cdot x, 1\right)}{x}}} \]

   7. Taylor expanded in x around inf

      \[\leadsto \frac{1}{x \cdot \color{blue}{\left(\frac{1}{3} + \frac{1}{{x}^{2}}\right)}} \]
   8. Step-by-step derivation

      1. distribute-rgt-in N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + \frac{1}{{x}^{2}} \cdot \color{blue}{x}} \]

      2. pow-flip N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + {x}^{\left(\mathsf{neg}\left(2\right)\right)} \cdot x} \]

      3. metadata-eval N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + {x}^{-2} \cdot x} \]

      4. pow-plus N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + {x}^{\left(-2 + \color{blue}{1}\right)}} \]

      5. metadata-eval N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + {x}^{-1}} \]

      6. inv-pow N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + \frac{1}{x}} \]

      7. lower-fma.f64 N/A

         \[\leadsto \frac{1}{\mathsf{fma}\left(\frac{1}{3}, x, \frac{1}{x}\right)} \]

      8. lower-/.f64 68.1

         \[\leadsto \frac{1}{\mathsf{fma}\left(0.3333333333333333, x, \frac{1}{x}\right)} \]

   9. Applied rewrites 68.1%

      \[\leadsto \frac{1}{\mathsf{fma}\left(0.3333333333333333, \color{blue}{x}, \frac{1}{x}\right)} \]
3. Recombined 2 regimes into one program.
4. Add Preprocessing

Alternative 7: 75.9% accurate, 1.1× speedup

Math

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;x \leq -2:\\ \;\;\;\;\frac{2}{\mathsf{fma}\left(\left(x \cdot x\right) \cdot -1.3333333333333333, x, 2\right)} - 1\\ \mathbf{else}:\\ \;\;\;\;\frac{1}{\mathsf{fma}\left(0.3333333333333333, x, \frac{1}{x}\right)}\\ \end{array} \end{array} \]

FPCore

(FPCore (x)
 :precision binary64
 (if (<= x -2.0)
   (- (/ 2.0 (fma (* (* x x) -1.3333333333333333) x 2.0)) 1.0)
   (/ 1.0 (fma 0.3333333333333333 x (/ 1.0 x)))))

C

double code(double x) {
	double tmp;
	if (x <= -2.0) {
		tmp = (2.0 / fma(((x * x) * -1.3333333333333333), x, 2.0)) - 1.0;
	} else {
		tmp = 1.0 / fma(0.3333333333333333, x, (1.0 / x));
	}
	return tmp;
}

Julia

function code(x)
	tmp = 0.0
	if (x <= -2.0)
		tmp = Float64(Float64(2.0 / fma(Float64(Float64(x * x) * -1.3333333333333333), x, 2.0)) - 1.0);
	else
		tmp = Float64(1.0 / fma(0.3333333333333333, x, Float64(1.0 / x)));
	end
	return tmp
end

Wolfram

code[x_] := If[LessEqual[x, -2.0], N[(N[(2.0 / N[(N[(N[(x * x), $MachinePrecision] * -1.3333333333333333), $MachinePrecision] * x + 2.0), $MachinePrecision]), $MachinePrecision] - 1.0), $MachinePrecision], N[(1.0 / N[(0.3333333333333333 * x + N[(1.0 / x), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]]

Derivation

1. Split input into 2 regimes

2. if x < -2

   1. Initial program 100.0%

      \[\frac{2}{1 + e^{-2 \cdot x}} - 1 \]

   2. Taylor expanded in x around 0

      \[\leadsto \frac{2}{\color{blue}{2 + x \cdot \left(x \cdot \left(2 + \frac{-4}{3} \cdot x\right) - 2\right)}} - 1 \]
   3. Step-by-step derivation

      1. +-commutative N/A

         \[\leadsto \frac{2}{x \cdot \left(x \cdot \left(2 + \frac{-4}{3} \cdot x\right) - 2\right) + \color{blue}{2}} - 1 \]

      2. *-commutative N/A

         \[\leadsto \frac{2}{\left(x \cdot \left(2 + \frac{-4}{3} \cdot x\right) - 2\right) \cdot x + 2} - 1 \]

      3. lower-fma.f64 N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(x \cdot \left(2 + \frac{-4}{3} \cdot x\right) - 2, \color{blue}{x}, 2\right)} - 1 \]

      4. sub-flip N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(x \cdot \left(2 + \frac{-4}{3} \cdot x\right) + \left(\mathsf{neg}\left(2\right)\right), x, 2\right)} - 1 \]

      5. *-commutative N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(\left(2 + \frac{-4}{3} \cdot x\right) \cdot x + \left(\mathsf{neg}\left(2\right)\right), x, 2\right)} - 1 \]

      6. metadata-eval N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(\left(2 + \frac{-4}{3} \cdot x\right) \cdot x + -2, x, 2\right)} - 1 \]

      7. lower-fma.f64 N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(\mathsf{fma}\left(2 + \frac{-4}{3} \cdot x, x, -2\right), x, 2\right)} - 1 \]

      8. +-commutative N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(\mathsf{fma}\left(\frac{-4}{3} \cdot x + 2, x, -2\right), x, 2\right)} - 1 \]

      9. lower-fma.f64 99.3

         \[\leadsto \frac{2}{\mathsf{fma}\left(\mathsf{fma}\left(\mathsf{fma}\left(-1.3333333333333333, x, 2\right), x, -2\right), x, 2\right)} - 1 \]

   4. Applied rewrites 99.3%

      \[\leadsto \frac{2}{\color{blue}{\mathsf{fma}\left(\mathsf{fma}\left(\mathsf{fma}\left(-1.3333333333333333, x, 2\right), x, -2\right), x, 2\right)}} - 1 \]

   5. Taylor expanded in x around inf

      \[\leadsto \frac{2}{\mathsf{fma}\left(\frac{-4}{3} \cdot {x}^{2}, x, 2\right)} - 1 \]
   6. Step-by-step derivation

      1. *-commutative N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left({x}^{2} \cdot \frac{-4}{3}, x, 2\right)} - 1 \]

      2. lower-*.f64 N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left({x}^{2} \cdot \frac{-4}{3}, x, 2\right)} - 1 \]

      3. pow2 N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(\left(x \cdot x\right) \cdot \frac{-4}{3}, x, 2\right)} - 1 \]

      4. lift-*.f64 99.3

         \[\leadsto \frac{2}{\mathsf{fma}\left(\left(x \cdot x\right) \cdot -1.3333333333333333, x, 2\right)} - 1 \]

   7. Applied rewrites 99.3%

      \[\leadsto \frac{2}{\mathsf{fma}\left(\left(x \cdot x\right) \cdot -1.3333333333333333, x, 2\right)} - 1 \]

   if -2 < x

   1. Initial program 38.9%

      \[\frac{2}{1 + e^{-2 \cdot x}} - 1 \]
   2. Step-by-step derivation

      1. lift--.f64 N/A

         \[\leadsto \color{blue}{\frac{2}{1 + e^{-2 \cdot x}} - 1} \]

      2. lift-/.f64 N/A

         \[\leadsto \color{blue}{\frac{2}{1 + e^{-2 \cdot x}}} - 1 \]

      3. lift-+.f64 N/A

         \[\leadsto \frac{2}{\color{blue}{1 + e^{-2 \cdot x}}} - 1 \]

      4. lift-*.f64 N/A

         \[\leadsto \frac{2}{1 + e^{\color{blue}{-2 \cdot x}}} - 1 \]

      5. lift-exp.f64 N/A

         \[\leadsto \frac{2}{1 + \color{blue}{e^{-2 \cdot x}}} - 1 \]

      6. flip-- N/A

         \[\leadsto \color{blue}{\frac{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}{\frac{2}{1 + e^{-2 \cdot x}} + 1}} \]

      7. division-flip N/A

         \[\leadsto \color{blue}{\frac{1}{\frac{\frac{2}{1 + e^{-2 \cdot x}} + 1}{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}}} \]

      8. lower-/.f64 N/A

         \[\leadsto \color{blue}{\frac{1}{\frac{\frac{2}{1 + e^{-2 \cdot x}} + 1}{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}}} \]

      9. lower-/.f64 N/A

         \[\leadsto \frac{1}{\color{blue}{\frac{\frac{2}{1 + e^{-2 \cdot x}} + 1}{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}}} \]

   3. Applied rewrites 38.9%

      \[\leadsto \color{blue}{\frac{1}{\frac{\frac{-2}{-1 - e^{x \cdot -2}} - -1}{{\left(\frac{-2}{-1 - e^{x \cdot -2}}\right)}^{2} - 1}}} \]

   4. Taylor expanded in x around 0

      \[\leadsto \frac{1}{\color{blue}{\frac{1 + \frac{1}{3} \cdot {x}^{2}}{x}}} \]
   5. Step-by-step derivation

      1. lower-/.f64 N/A

         \[\leadsto \frac{1}{\frac{1 + \frac{1}{3} \cdot {x}^{2}}{\color{blue}{x}}} \]

      2. +-commutative N/A

         \[\leadsto \frac{1}{\frac{\frac{1}{3} \cdot {x}^{2} + 1}{x}} \]

      3. lower-fma.f64 N/A

         \[\leadsto \frac{1}{\frac{\mathsf{fma}\left(\frac{1}{3}, {x}^{2}, 1\right)}{x}} \]

      4. pow2 N/A

         \[\leadsto \frac{1}{\frac{\mathsf{fma}\left(\frac{1}{3}, x \cdot x, 1\right)}{x}} \]

      5. lift-*.f64 68.0

         \[\leadsto \frac{1}{\frac{\mathsf{fma}\left(0.3333333333333333, x \cdot x, 1\right)}{x}} \]

   6. Applied rewrites 68.0%

      \[\leadsto \frac{1}{\color{blue}{\frac{\mathsf{fma}\left(0.3333333333333333, x \cdot x, 1\right)}{x}}} \]

   7. Taylor expanded in x around inf

      \[\leadsto \frac{1}{x \cdot \color{blue}{\left(\frac{1}{3} + \frac{1}{{x}^{2}}\right)}} \]
   8. Step-by-step derivation

      1. distribute-rgt-in N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + \frac{1}{{x}^{2}} \cdot \color{blue}{x}} \]

      2. pow-flip N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + {x}^{\left(\mathsf{neg}\left(2\right)\right)} \cdot x} \]

      3. metadata-eval N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + {x}^{-2} \cdot x} \]

      4. pow-plus N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + {x}^{\left(-2 + \color{blue}{1}\right)}} \]

      5. metadata-eval N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + {x}^{-1}} \]

      6. inv-pow N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + \frac{1}{x}} \]

      7. lower-fma.f64 N/A

         \[\leadsto \frac{1}{\mathsf{fma}\left(\frac{1}{3}, x, \frac{1}{x}\right)} \]

      8. lower-/.f64 68.1

         \[\leadsto \frac{1}{\mathsf{fma}\left(0.3333333333333333, x, \frac{1}{x}\right)} \]

   9. Applied rewrites 68.1%

      \[\leadsto \frac{1}{\mathsf{fma}\left(0.3333333333333333, \color{blue}{x}, \frac{1}{x}\right)} \]
3. Recombined 2 regimes into one program.
4. Add Preprocessing

Alternative 8: 75.9% accurate, 0.6× speedup

Math

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;\frac{2}{1 + e^{-2 \cdot x}} - 1 \leq -0.5:\\ \;\;\;\;\frac{2}{\left(\left(x \cdot x\right) \cdot x\right) \cdot -1.3333333333333333} - 1\\ \mathbf{else}:\\ \;\;\;\;\frac{1}{\mathsf{fma}\left(0.3333333333333333, x, \frac{1}{x}\right)}\\ \end{array} \end{array} \]

FPCore

(FPCore (x)
 :precision binary64
 (if (<= (- (/ 2.0 (+ 1.0 (exp (* -2.0 x)))) 1.0) -0.5)
   (- (/ 2.0 (* (* (* x x) x) -1.3333333333333333)) 1.0)
   (/ 1.0 (fma 0.3333333333333333 x (/ 1.0 x)))))

C

double code(double x) {
	double tmp;
	if (((2.0 / (1.0 + exp((-2.0 * x)))) - 1.0) <= -0.5) {
		tmp = (2.0 / (((x * x) * x) * -1.3333333333333333)) - 1.0;
	} else {
		tmp = 1.0 / fma(0.3333333333333333, x, (1.0 / x));
	}
	return tmp;
}

Julia

function code(x)
	tmp = 0.0
	if (Float64(Float64(2.0 / Float64(1.0 + exp(Float64(-2.0 * x)))) - 1.0) <= -0.5)
		tmp = Float64(Float64(2.0 / Float64(Float64(Float64(x * x) * x) * -1.3333333333333333)) - 1.0);
	else
		tmp = Float64(1.0 / fma(0.3333333333333333, x, Float64(1.0 / x)));
	end
	return tmp
end

Wolfram

code[x_] := If[LessEqual[N[(N[(2.0 / N[(1.0 + N[Exp[N[(-2.0 * x), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]), $MachinePrecision] - 1.0), $MachinePrecision], -0.5], N[(N[(2.0 / N[(N[(N[(x * x), $MachinePrecision] * x), $MachinePrecision] * -1.3333333333333333), $MachinePrecision]), $MachinePrecision] - 1.0), $MachinePrecision], N[(1.0 / N[(0.3333333333333333 * x + N[(1.0 / x), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]]

Derivation

1. Split input into 2 regimes

2. if (-.f64 (/.f64 #s(literal 2 binary64) (+.f64 #s(literal 1 binary64) (exp.f64 (*.f64 #s(literal -2 binary64) x)))) #s(literal 1 binary64)) < -0.5

   1. Initial program 100.0%

      \[\frac{2}{1 + e^{-2 \cdot x}} - 1 \]

   2. Taylor expanded in x around 0

      \[\leadsto \frac{2}{\color{blue}{2 + x \cdot \left(x \cdot \left(2 + \frac{-4}{3} \cdot x\right) - 2\right)}} - 1 \]
   3. Step-by-step derivation

      1. +-commutative N/A

         \[\leadsto \frac{2}{x \cdot \left(x \cdot \left(2 + \frac{-4}{3} \cdot x\right) - 2\right) + \color{blue}{2}} - 1 \]

      2. *-commutative N/A

         \[\leadsto \frac{2}{\left(x \cdot \left(2 + \frac{-4}{3} \cdot x\right) - 2\right) \cdot x + 2} - 1 \]

      3. lower-fma.f64 N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(x \cdot \left(2 + \frac{-4}{3} \cdot x\right) - 2, \color{blue}{x}, 2\right)} - 1 \]

      4. sub-flip N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(x \cdot \left(2 + \frac{-4}{3} \cdot x\right) + \left(\mathsf{neg}\left(2\right)\right), x, 2\right)} - 1 \]

      5. *-commutative N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(\left(2 + \frac{-4}{3} \cdot x\right) \cdot x + \left(\mathsf{neg}\left(2\right)\right), x, 2\right)} - 1 \]

      6. metadata-eval N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(\left(2 + \frac{-4}{3} \cdot x\right) \cdot x + -2, x, 2\right)} - 1 \]

      7. lower-fma.f64 N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(\mathsf{fma}\left(2 + \frac{-4}{3} \cdot x, x, -2\right), x, 2\right)} - 1 \]

      8. +-commutative N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(\mathsf{fma}\left(\frac{-4}{3} \cdot x + 2, x, -2\right), x, 2\right)} - 1 \]

      9. lower-fma.f64 99.2

         \[\leadsto \frac{2}{\mathsf{fma}\left(\mathsf{fma}\left(\mathsf{fma}\left(-1.3333333333333333, x, 2\right), x, -2\right), x, 2\right)} - 1 \]

   4. Applied rewrites 99.2%

      \[\leadsto \frac{2}{\color{blue}{\mathsf{fma}\left(\mathsf{fma}\left(\mathsf{fma}\left(-1.3333333333333333, x, 2\right), x, -2\right), x, 2\right)}} - 1 \]

   5. Taylor expanded in x around inf

      \[\leadsto \frac{2}{\frac{-4}{3} \cdot \color{blue}{{x}^{3}}} - 1 \]
   6. Step-by-step derivation

      1. *-commutative N/A

         \[\leadsto \frac{2}{{x}^{3} \cdot \frac{-4}{3}} - 1 \]

      2. lower-*.f64 N/A

         \[\leadsto \frac{2}{{x}^{3} \cdot \frac{-4}{3}} - 1 \]

      3. unpow3 N/A

         \[\leadsto \frac{2}{\left(\left(x \cdot x\right) \cdot x\right) \cdot \frac{-4}{3}} - 1 \]

      4. pow2 N/A

         \[\leadsto \frac{2}{\left({x}^{2} \cdot x\right) \cdot \frac{-4}{3}} - 1 \]

      5. lower-*.f64 N/A

         \[\leadsto \frac{2}{\left({x}^{2} \cdot x\right) \cdot \frac{-4}{3}} - 1 \]

      6. pow2 N/A

         \[\leadsto \frac{2}{\left(\left(x \cdot x\right) \cdot x\right) \cdot \frac{-4}{3}} - 1 \]

      7. lift-*.f64 99.2

         \[\leadsto \frac{2}{\left(\left(x \cdot x\right) \cdot x\right) \cdot -1.3333333333333333} - 1 \]

   7. Applied rewrites 99.2%

      \[\leadsto \frac{2}{\left(\left(x \cdot x\right) \cdot x\right) \cdot \color{blue}{-1.3333333333333333}} - 1 \]

   if -0.5 < (-.f64 (/.f64 #s(literal 2 binary64) (+.f64 #s(literal 1 binary64) (exp.f64 (*.f64 #s(literal -2 binary64) x)))) #s(literal 1 binary64))

   1. Initial program 38.9%

      \[\frac{2}{1 + e^{-2 \cdot x}} - 1 \]
   2. Step-by-step derivation

      1. lift--.f64 N/A

         \[\leadsto \color{blue}{\frac{2}{1 + e^{-2 \cdot x}} - 1} \]

      2. lift-/.f64 N/A

         \[\leadsto \color{blue}{\frac{2}{1 + e^{-2 \cdot x}}} - 1 \]

      3. lift-+.f64 N/A

         \[\leadsto \frac{2}{\color{blue}{1 + e^{-2 \cdot x}}} - 1 \]

      4. lift-*.f64 N/A

         \[\leadsto \frac{2}{1 + e^{\color{blue}{-2 \cdot x}}} - 1 \]

      5. lift-exp.f64 N/A

         \[\leadsto \frac{2}{1 + \color{blue}{e^{-2 \cdot x}}} - 1 \]

      6. flip-- N/A

         \[\leadsto \color{blue}{\frac{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}{\frac{2}{1 + e^{-2 \cdot x}} + 1}} \]

      7. division-flip N/A

         \[\leadsto \color{blue}{\frac{1}{\frac{\frac{2}{1 + e^{-2 \cdot x}} + 1}{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}}} \]

      8. lower-/.f64 N/A

         \[\leadsto \color{blue}{\frac{1}{\frac{\frac{2}{1 + e^{-2 \cdot x}} + 1}{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}}} \]

      9. lower-/.f64 N/A

         \[\leadsto \frac{1}{\color{blue}{\frac{\frac{2}{1 + e^{-2 \cdot x}} + 1}{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}}} \]

   3. Applied rewrites 38.8%

      \[\leadsto \color{blue}{\frac{1}{\frac{\frac{-2}{-1 - e^{x \cdot -2}} - -1}{{\left(\frac{-2}{-1 - e^{x \cdot -2}}\right)}^{2} - 1}}} \]

   4. Taylor expanded in x around 0

      \[\leadsto \frac{1}{\color{blue}{\frac{1 + \frac{1}{3} \cdot {x}^{2}}{x}}} \]
   5. Step-by-step derivation

      1. lower-/.f64 N/A

         \[\leadsto \frac{1}{\frac{1 + \frac{1}{3} \cdot {x}^{2}}{\color{blue}{x}}} \]

      2. +-commutative N/A

         \[\leadsto \frac{1}{\frac{\frac{1}{3} \cdot {x}^{2} + 1}{x}} \]

      3. lower-fma.f64 N/A

         \[\leadsto \frac{1}{\frac{\mathsf{fma}\left(\frac{1}{3}, {x}^{2}, 1\right)}{x}} \]

      4. pow2 N/A

         \[\leadsto \frac{1}{\frac{\mathsf{fma}\left(\frac{1}{3}, x \cdot x, 1\right)}{x}} \]

      5. lift-*.f64 68.0

         \[\leadsto \frac{1}{\frac{\mathsf{fma}\left(0.3333333333333333, x \cdot x, 1\right)}{x}} \]

   6. Applied rewrites 68.0%

      \[\leadsto \frac{1}{\color{blue}{\frac{\mathsf{fma}\left(0.3333333333333333, x \cdot x, 1\right)}{x}}} \]

   7. Taylor expanded in x around inf

      \[\leadsto \frac{1}{x \cdot \color{blue}{\left(\frac{1}{3} + \frac{1}{{x}^{2}}\right)}} \]
   8. Step-by-step derivation

      1. distribute-rgt-in N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + \frac{1}{{x}^{2}} \cdot \color{blue}{x}} \]

      2. pow-flip N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + {x}^{\left(\mathsf{neg}\left(2\right)\right)} \cdot x} \]

      3. metadata-eval N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + {x}^{-2} \cdot x} \]

      4. pow-plus N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + {x}^{\left(-2 + \color{blue}{1}\right)}} \]

      5. metadata-eval N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + {x}^{-1}} \]

      6. inv-pow N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + \frac{1}{x}} \]

      7. lower-fma.f64 N/A

         \[\leadsto \frac{1}{\mathsf{fma}\left(\frac{1}{3}, x, \frac{1}{x}\right)} \]

      8. lower-/.f64 68.1

         \[\leadsto \frac{1}{\mathsf{fma}\left(0.3333333333333333, x, \frac{1}{x}\right)} \]

   9. Applied rewrites 68.1%

      \[\leadsto \frac{1}{\mathsf{fma}\left(0.3333333333333333, \color{blue}{x}, \frac{1}{x}\right)} \]
3. Recombined 2 regimes into one program.
4. Add Preprocessing

Alternative 9: 75.9% accurate, 1.2× speedup

Math

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;x \leq -2.3:\\ \;\;\;\;\frac{2}{\mathsf{fma}\left(x + x, x, 2\right)} - 1\\ \mathbf{else}:\\ \;\;\;\;\frac{1}{\mathsf{fma}\left(0.3333333333333333, x, \frac{1}{x}\right)}\\ \end{array} \end{array} \]

FPCore

(FPCore (x)
 :precision binary64
 (if (<= x -2.3)
   (- (/ 2.0 (fma (+ x x) x 2.0)) 1.0)
   (/ 1.0 (fma 0.3333333333333333 x (/ 1.0 x)))))

C

double code(double x) {
	double tmp;
	if (x <= -2.3) {
		tmp = (2.0 / fma((x + x), x, 2.0)) - 1.0;
	} else {
		tmp = 1.0 / fma(0.3333333333333333, x, (1.0 / x));
	}
	return tmp;
}

Julia

function code(x)
	tmp = 0.0
	if (x <= -2.3)
		tmp = Float64(Float64(2.0 / fma(Float64(x + x), x, 2.0)) - 1.0);
	else
		tmp = Float64(1.0 / fma(0.3333333333333333, x, Float64(1.0 / x)));
	end
	return tmp
end

Wolfram

code[x_] := If[LessEqual[x, -2.3], N[(N[(2.0 / N[(N[(x + x), $MachinePrecision] * x + 2.0), $MachinePrecision]), $MachinePrecision] - 1.0), $MachinePrecision], N[(1.0 / N[(0.3333333333333333 * x + N[(1.0 / x), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]]

Derivation

1. Split input into 2 regimes

2. if x < -2.2999999999999998

   1. Initial program 100.0%

      \[\frac{2}{1 + e^{-2 \cdot x}} - 1 \]

   2. Taylor expanded in x around 0

      \[\leadsto \frac{2}{\color{blue}{2 + x \cdot \left(2 \cdot x - 2\right)}} - 1 \]
   3. Step-by-step derivation

      1. +-commutative N/A

         \[\leadsto \frac{2}{x \cdot \left(2 \cdot x - 2\right) + \color{blue}{2}} - 1 \]

      2. *-commutative N/A

         \[\leadsto \frac{2}{\left(2 \cdot x - 2\right) \cdot x + 2} - 1 \]

      3. lower-fma.f64 N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(2 \cdot x - 2, \color{blue}{x}, 2\right)} - 1 \]

      4. sub-flip N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(2 \cdot x + \left(\mathsf{neg}\left(2\right)\right), x, 2\right)} - 1 \]

      5. metadata-eval N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(2 \cdot x + -2, x, 2\right)} - 1 \]

      6. *-commutative N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(x \cdot 2 + -2, x, 2\right)} - 1 \]

      7. lower-fma.f64 99.0

         \[\leadsto \frac{2}{\mathsf{fma}\left(\mathsf{fma}\left(x, 2, -2\right), x, 2\right)} - 1 \]

   4. Applied rewrites 99.0%

      \[\leadsto \frac{2}{\color{blue}{\mathsf{fma}\left(\mathsf{fma}\left(x, 2, -2\right), x, 2\right)}} - 1 \]

   5. Taylor expanded in x around inf

      \[\leadsto \frac{2}{\mathsf{fma}\left(2 \cdot x, x, 2\right)} - 1 \]
   6. Step-by-step derivation

      1. count-2-rev N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(x + x, x, 2\right)} - 1 \]

      2. lower-+.f64 99.0

         \[\leadsto \frac{2}{\mathsf{fma}\left(x + x, x, 2\right)} - 1 \]

   7. Applied rewrites 99.0%

      \[\leadsto \frac{2}{\mathsf{fma}\left(x + x, x, 2\right)} - 1 \]

   if -2.2999999999999998 < x

   1. Initial program 38.9%

      \[\frac{2}{1 + e^{-2 \cdot x}} - 1 \]
   2. Step-by-step derivation

      1. lift--.f64 N/A

         \[\leadsto \color{blue}{\frac{2}{1 + e^{-2 \cdot x}} - 1} \]

      2. lift-/.f64 N/A

         \[\leadsto \color{blue}{\frac{2}{1 + e^{-2 \cdot x}}} - 1 \]

      3. lift-+.f64 N/A

         \[\leadsto \frac{2}{\color{blue}{1 + e^{-2 \cdot x}}} - 1 \]

      4. lift-*.f64 N/A

         \[\leadsto \frac{2}{1 + e^{\color{blue}{-2 \cdot x}}} - 1 \]

      5. lift-exp.f64 N/A

         \[\leadsto \frac{2}{1 + \color{blue}{e^{-2 \cdot x}}} - 1 \]

      6. flip-- N/A

         \[\leadsto \color{blue}{\frac{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}{\frac{2}{1 + e^{-2 \cdot x}} + 1}} \]

      7. division-flip N/A

         \[\leadsto \color{blue}{\frac{1}{\frac{\frac{2}{1 + e^{-2 \cdot x}} + 1}{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}}} \]

      8. lower-/.f64 N/A

         \[\leadsto \color{blue}{\frac{1}{\frac{\frac{2}{1 + e^{-2 \cdot x}} + 1}{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}}} \]

      9. lower-/.f64 N/A

         \[\leadsto \frac{1}{\color{blue}{\frac{\frac{2}{1 + e^{-2 \cdot x}} + 1}{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}}} \]

   3. Applied rewrites 38.9%

      \[\leadsto \color{blue}{\frac{1}{\frac{\frac{-2}{-1 - e^{x \cdot -2}} - -1}{{\left(\frac{-2}{-1 - e^{x \cdot -2}}\right)}^{2} - 1}}} \]

   4. Taylor expanded in x around 0

      \[\leadsto \frac{1}{\color{blue}{\frac{1 + \frac{1}{3} \cdot {x}^{2}}{x}}} \]
   5. Step-by-step derivation

      1. lower-/.f64 N/A

         \[\leadsto \frac{1}{\frac{1 + \frac{1}{3} \cdot {x}^{2}}{\color{blue}{x}}} \]

      2. +-commutative N/A

         \[\leadsto \frac{1}{\frac{\frac{1}{3} \cdot {x}^{2} + 1}{x}} \]

      3. lower-fma.f64 N/A

         \[\leadsto \frac{1}{\frac{\mathsf{fma}\left(\frac{1}{3}, {x}^{2}, 1\right)}{x}} \]

      4. pow2 N/A

         \[\leadsto \frac{1}{\frac{\mathsf{fma}\left(\frac{1}{3}, x \cdot x, 1\right)}{x}} \]

      5. lift-*.f64 68.0

         \[\leadsto \frac{1}{\frac{\mathsf{fma}\left(0.3333333333333333, x \cdot x, 1\right)}{x}} \]

   6. Applied rewrites 68.0%

      \[\leadsto \frac{1}{\color{blue}{\frac{\mathsf{fma}\left(0.3333333333333333, x \cdot x, 1\right)}{x}}} \]

   7. Taylor expanded in x around inf

      \[\leadsto \frac{1}{x \cdot \color{blue}{\left(\frac{1}{3} + \frac{1}{{x}^{2}}\right)}} \]
   8. Step-by-step derivation

      1. distribute-rgt-in N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + \frac{1}{{x}^{2}} \cdot \color{blue}{x}} \]

      2. pow-flip N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + {x}^{\left(\mathsf{neg}\left(2\right)\right)} \cdot x} \]

      3. metadata-eval N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + {x}^{-2} \cdot x} \]

      4. pow-plus N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + {x}^{\left(-2 + \color{blue}{1}\right)}} \]

      5. metadata-eval N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + {x}^{-1}} \]

      6. inv-pow N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + \frac{1}{x}} \]

      7. lower-fma.f64 N/A

         \[\leadsto \frac{1}{\mathsf{fma}\left(\frac{1}{3}, x, \frac{1}{x}\right)} \]

      8. lower-/.f64 68.1

         \[\leadsto \frac{1}{\mathsf{fma}\left(0.3333333333333333, x, \frac{1}{x}\right)} \]

   9. Applied rewrites 68.1%

      \[\leadsto \frac{1}{\mathsf{fma}\left(0.3333333333333333, \color{blue}{x}, \frac{1}{x}\right)} \]
3. Recombined 2 regimes into one program.
4. Add Preprocessing

Alternative 10: 75.9% accurate, 1.4× speedup

Math

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;x \leq -2.4:\\ \;\;\;\;\frac{2}{x \cdot \left(x + x\right)} - 1\\ \mathbf{else}:\\ \;\;\;\;\frac{1}{\mathsf{fma}\left(0.3333333333333333, x, \frac{1}{x}\right)}\\ \end{array} \end{array} \]

FPCore

(FPCore (x)
 :precision binary64
 (if (<= x -2.4)
   (- (/ 2.0 (* x (+ x x))) 1.0)
   (/ 1.0 (fma 0.3333333333333333 x (/ 1.0 x)))))

C

double code(double x) {
	double tmp;
	if (x <= -2.4) {
		tmp = (2.0 / (x * (x + x))) - 1.0;
	} else {
		tmp = 1.0 / fma(0.3333333333333333, x, (1.0 / x));
	}
	return tmp;
}

Julia

function code(x)
	tmp = 0.0
	if (x <= -2.4)
		tmp = Float64(Float64(2.0 / Float64(x * Float64(x + x))) - 1.0);
	else
		tmp = Float64(1.0 / fma(0.3333333333333333, x, Float64(1.0 / x)));
	end
	return tmp
end

Wolfram

code[x_] := If[LessEqual[x, -2.4], N[(N[(2.0 / N[(x * N[(x + x), $MachinePrecision]), $MachinePrecision]), $MachinePrecision] - 1.0), $MachinePrecision], N[(1.0 / N[(0.3333333333333333 * x + N[(1.0 / x), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]]

Derivation

1. Split input into 2 regimes

2. if x < -2.39999999999999991

   1. Initial program 100.0%

      \[\frac{2}{1 + e^{-2 \cdot x}} - 1 \]

   2. Taylor expanded in x around 0

      \[\leadsto \frac{2}{\color{blue}{2 + x \cdot \left(2 \cdot x - 2\right)}} - 1 \]
   3. Step-by-step derivation

      1. +-commutative N/A

         \[\leadsto \frac{2}{x \cdot \left(2 \cdot x - 2\right) + \color{blue}{2}} - 1 \]

      2. *-commutative N/A

         \[\leadsto \frac{2}{\left(2 \cdot x - 2\right) \cdot x + 2} - 1 \]

      3. lower-fma.f64 N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(2 \cdot x - 2, \color{blue}{x}, 2\right)} - 1 \]

      4. sub-flip N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(2 \cdot x + \left(\mathsf{neg}\left(2\right)\right), x, 2\right)} - 1 \]

      5. metadata-eval N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(2 \cdot x + -2, x, 2\right)} - 1 \]

      6. *-commutative N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(x \cdot 2 + -2, x, 2\right)} - 1 \]

      7. lower-fma.f64 99.0

         \[\leadsto \frac{2}{\mathsf{fma}\left(\mathsf{fma}\left(x, 2, -2\right), x, 2\right)} - 1 \]

   4. Applied rewrites 99.0%

      \[\leadsto \frac{2}{\color{blue}{\mathsf{fma}\left(\mathsf{fma}\left(x, 2, -2\right), x, 2\right)}} - 1 \]

   5. Taylor expanded in x around inf

      \[\leadsto \frac{2}{2 \cdot \color{blue}{{x}^{2}}} - 1 \]
   6. Step-by-step derivation

      1. *-commutative N/A

         \[\leadsto \frac{2}{{x}^{2} \cdot 2} - 1 \]

      2. lower-*.f64 N/A

         \[\leadsto \frac{2}{{x}^{2} \cdot 2} - 1 \]

      3. pow2 N/A

         \[\leadsto \frac{2}{\left(x \cdot x\right) \cdot 2} - 1 \]

      4. lift-*.f64 99.0

         \[\leadsto \frac{2}{\left(x \cdot x\right) \cdot 2} - 1 \]

   7. Applied rewrites 99.0%

      \[\leadsto \frac{2}{\left(x \cdot x\right) \cdot \color{blue}{2}} - 1 \]
   8. Step-by-step derivation

      1. +-commutative 99.0

         \[\leadsto \frac{2}{\color{blue}{\left(x \cdot x\right)} \cdot 2} - 1 \]

      2. *-commutative 99.0

         \[\leadsto \frac{2}{\left(x \cdot x\right) \cdot 2} - 1 \]

      3. metadata-eval 99.0

         \[\leadsto \frac{2}{\left(x \cdot \color{blue}{x}\right) \cdot 2} - 1 \]

      4. sub-flip 99.0

         \[\leadsto \frac{2}{\color{blue}{\left(x \cdot x\right)} \cdot 2} - 1 \]

      5. lift-*.f64 N/A

         \[\leadsto \frac{2}{\left(x \cdot x\right) \cdot 2} - 1 \]

      6. lift-*.f64 N/A

         \[\leadsto \frac{2}{\left(x \cdot x\right) \cdot 2} - 1 \]

      7. associate-*l* N/A

         \[\leadsto \frac{2}{x \cdot \left(x \cdot \color{blue}{2}\right)} - 1 \]

      8. *-commutative N/A

         \[\leadsto \frac{2}{x \cdot \left(2 \cdot x\right)} - 1 \]

      9. lower-*.f64 N/A

         \[\leadsto \frac{2}{x \cdot \left(2 \cdot \color{blue}{x}\right)} - 1 \]

      10. count-2-rev N/A

          \[\leadsto \frac{2}{x \cdot \left(x + x\right)} - 1 \]

      11. lower-+.f64 99.0

          \[\leadsto \frac{2}{x \cdot \left(x + x\right)} - 1 \]

   9. Applied rewrites 99.0%

      \[\leadsto \frac{2}{\color{blue}{x \cdot \left(x + x\right)}} - 1 \]

   if -2.39999999999999991 < x

   1. Initial program 38.9%

      \[\frac{2}{1 + e^{-2 \cdot x}} - 1 \]
   2. Step-by-step derivation

      1. lift--.f64 N/A

         \[\leadsto \color{blue}{\frac{2}{1 + e^{-2 \cdot x}} - 1} \]

      2. lift-/.f64 N/A

         \[\leadsto \color{blue}{\frac{2}{1 + e^{-2 \cdot x}}} - 1 \]

      3. lift-+.f64 N/A

         \[\leadsto \frac{2}{\color{blue}{1 + e^{-2 \cdot x}}} - 1 \]

      4. lift-*.f64 N/A

         \[\leadsto \frac{2}{1 + e^{\color{blue}{-2 \cdot x}}} - 1 \]

      5. lift-exp.f64 N/A

         \[\leadsto \frac{2}{1 + \color{blue}{e^{-2 \cdot x}}} - 1 \]

      6. flip-- N/A

         \[\leadsto \color{blue}{\frac{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}{\frac{2}{1 + e^{-2 \cdot x}} + 1}} \]

      7. division-flip N/A

         \[\leadsto \color{blue}{\frac{1}{\frac{\frac{2}{1 + e^{-2 \cdot x}} + 1}{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}}} \]

      8. lower-/.f64 N/A

         \[\leadsto \color{blue}{\frac{1}{\frac{\frac{2}{1 + e^{-2 \cdot x}} + 1}{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}}} \]

      9. lower-/.f64 N/A

         \[\leadsto \frac{1}{\color{blue}{\frac{\frac{2}{1 + e^{-2 \cdot x}} + 1}{\frac{2}{1 + e^{-2 \cdot x}} \cdot \frac{2}{1 + e^{-2 \cdot x}} - 1 \cdot 1}}} \]

   3. Applied rewrites 38.9%

      \[\leadsto \color{blue}{\frac{1}{\frac{\frac{-2}{-1 - e^{x \cdot -2}} - -1}{{\left(\frac{-2}{-1 - e^{x \cdot -2}}\right)}^{2} - 1}}} \]

   4. Taylor expanded in x around 0

      \[\leadsto \frac{1}{\color{blue}{\frac{1 + \frac{1}{3} \cdot {x}^{2}}{x}}} \]
   5. Step-by-step derivation

      1. lower-/.f64 N/A

         \[\leadsto \frac{1}{\frac{1 + \frac{1}{3} \cdot {x}^{2}}{\color{blue}{x}}} \]

      2. +-commutative N/A

         \[\leadsto \frac{1}{\frac{\frac{1}{3} \cdot {x}^{2} + 1}{x}} \]

      3. lower-fma.f64 N/A

         \[\leadsto \frac{1}{\frac{\mathsf{fma}\left(\frac{1}{3}, {x}^{2}, 1\right)}{x}} \]

      4. pow2 N/A

         \[\leadsto \frac{1}{\frac{\mathsf{fma}\left(\frac{1}{3}, x \cdot x, 1\right)}{x}} \]

      5. lift-*.f64 68.0

         \[\leadsto \frac{1}{\frac{\mathsf{fma}\left(0.3333333333333333, x \cdot x, 1\right)}{x}} \]

   6. Applied rewrites 68.0%

      \[\leadsto \frac{1}{\color{blue}{\frac{\mathsf{fma}\left(0.3333333333333333, x \cdot x, 1\right)}{x}}} \]

   7. Taylor expanded in x around inf

      \[\leadsto \frac{1}{x \cdot \color{blue}{\left(\frac{1}{3} + \frac{1}{{x}^{2}}\right)}} \]
   8. Step-by-step derivation

      1. distribute-rgt-in N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + \frac{1}{{x}^{2}} \cdot \color{blue}{x}} \]

      2. pow-flip N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + {x}^{\left(\mathsf{neg}\left(2\right)\right)} \cdot x} \]

      3. metadata-eval N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + {x}^{-2} \cdot x} \]

      4. pow-plus N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + {x}^{\left(-2 + \color{blue}{1}\right)}} \]

      5. metadata-eval N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + {x}^{-1}} \]

      6. inv-pow N/A

         \[\leadsto \frac{1}{\frac{1}{3} \cdot x + \frac{1}{x}} \]

      7. lower-fma.f64 N/A

         \[\leadsto \frac{1}{\mathsf{fma}\left(\frac{1}{3}, x, \frac{1}{x}\right)} \]

      8. lower-/.f64 68.1

         \[\leadsto \frac{1}{\mathsf{fma}\left(0.3333333333333333, x, \frac{1}{x}\right)} \]

   9. Applied rewrites 68.1%

      \[\leadsto \frac{1}{\mathsf{fma}\left(0.3333333333333333, \color{blue}{x}, \frac{1}{x}\right)} \]
3. Recombined 2 regimes into one program.
4. Add Preprocessing

Alternative 11: 75.7% accurate, 1.2× speedup

Math

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;-2 \cdot x \leq 0.2:\\ \;\;\;\;x\\ \mathbf{else}:\\ \;\;\;\;\frac{2}{x \cdot \left(x + x\right)} - 1\\ \end{array} \end{array} \]

FPCore

(FPCore (x)
 :precision binary64
 (if (<= (* -2.0 x) 0.2) x (- (/ 2.0 (* x (+ x x))) 1.0)))

C

double code(double x) {
	double tmp;
	if ((-2.0 * x) <= 0.2) {
		tmp = x;
	} else {
		tmp = (2.0 / (x * (x + x))) - 1.0;
	}
	return tmp;
}

Fortran

module fmin_fmax_functions
    implicit none
    private
    public fmax
    public fmin

    interface fmax
        module procedure fmax88
        module procedure fmax44
        module procedure fmax84
        module procedure fmax48
    end interface
    interface fmin
        module procedure fmin88
        module procedure fmin44
        module procedure fmin84
        module procedure fmin48
    end interface
contains
    real(8) function fmax88(x, y) result (res)
        real(8), intent (in) :: x
        real(8), intent (in) :: y
        res = merge(y, merge(x, max(x, y), y /= y), x /= x)
    end function
    real(4) function fmax44(x, y) result (res)
        real(4), intent (in) :: x
        real(4), intent (in) :: y
        res = merge(y, merge(x, max(x, y), y /= y), x /= x)
    end function
    real(8) function fmax84(x, y) result(res)
        real(8), intent (in) :: x
        real(4), intent (in) :: y
        res = merge(dble(y), merge(x, max(x, dble(y)), y /= y), x /= x)
    end function
    real(8) function fmax48(x, y) result(res)
        real(4), intent (in) :: x
        real(8), intent (in) :: y
        res = merge(y, merge(dble(x), max(dble(x), y), y /= y), x /= x)
    end function
    real(8) function fmin88(x, y) result (res)
        real(8), intent (in) :: x
        real(8), intent (in) :: y
        res = merge(y, merge(x, min(x, y), y /= y), x /= x)
    end function
    real(4) function fmin44(x, y) result (res)
        real(4), intent (in) :: x
        real(4), intent (in) :: y
        res = merge(y, merge(x, min(x, y), y /= y), x /= x)
    end function
    real(8) function fmin84(x, y) result(res)
        real(8), intent (in) :: x
        real(4), intent (in) :: y
        res = merge(dble(y), merge(x, min(x, dble(y)), y /= y), x /= x)
    end function
    real(8) function fmin48(x, y) result(res)
        real(4), intent (in) :: x
        real(8), intent (in) :: y
        res = merge(y, merge(dble(x), min(dble(x), y), y /= y), x /= x)
    end function
end module

real(8) function code(x)
use fmin_fmax_functions
    real(8), intent (in) :: x
    real(8) :: tmp
    if (((-2.0d0) * x) <= 0.2d0) then
        tmp = x
    else
        tmp = (2.0d0 / (x * (x + x))) - 1.0d0
    end if
    code = tmp
end function

Java

public static double code(double x) {
	double tmp;
	if ((-2.0 * x) <= 0.2) {
		tmp = x;
	} else {
		tmp = (2.0 / (x * (x + x))) - 1.0;
	}
	return tmp;
}

Python

def code(x):
	tmp = 0
	if (-2.0 * x) <= 0.2:
		tmp = x
	else:
		tmp = (2.0 / (x * (x + x))) - 1.0
	return tmp

Julia

function code(x)
	tmp = 0.0
	if (Float64(-2.0 * x) <= 0.2)
		tmp = x;
	else
		tmp = Float64(Float64(2.0 / Float64(x * Float64(x + x))) - 1.0);
	end
	return tmp
end

MATLAB

function tmp_2 = code(x)
	tmp = 0.0;
	if ((-2.0 * x) <= 0.2)
		tmp = x;
	else
		tmp = (2.0 / (x * (x + x))) - 1.0;
	end
	tmp_2 = tmp;
end

Wolfram

code[x_] := If[LessEqual[N[(-2.0 * x), $MachinePrecision], 0.2], x, N[(N[(2.0 / N[(x * N[(x + x), $MachinePrecision]), $MachinePrecision]), $MachinePrecision] - 1.0), $MachinePrecision]]

Derivation

1. Split input into 2 regimes

2. if (*.f64 #s(literal -2 binary64) x) < 0.20000000000000001

   1. Initial program 38.8%

      \[\frac{2}{1 + e^{-2 \cdot x}} - 1 \]

   2. Taylor expanded in x around 0

      \[\leadsto \color{blue}{x} \]
   3. Step-by-step derivation

   4. Applied rewrites 67.9%

      \[\leadsto \color{blue}{x} \]

   if 0.20000000000000001 < (*.f64 #s(literal -2 binary64) x)

   1. Initial program 100.0%

      \[\frac{2}{1 + e^{-2 \cdot x}} - 1 \]

   2. Taylor expanded in x around 0

      \[\leadsto \frac{2}{\color{blue}{2 + x \cdot \left(2 \cdot x - 2\right)}} - 1 \]
   3. Step-by-step derivation

      1. +-commutative N/A

         \[\leadsto \frac{2}{x \cdot \left(2 \cdot x - 2\right) + \color{blue}{2}} - 1 \]

      2. *-commutative N/A

         \[\leadsto \frac{2}{\left(2 \cdot x - 2\right) \cdot x + 2} - 1 \]

      3. lower-fma.f64 N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(2 \cdot x - 2, \color{blue}{x}, 2\right)} - 1 \]

      4. sub-flip N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(2 \cdot x + \left(\mathsf{neg}\left(2\right)\right), x, 2\right)} - 1 \]

      5. metadata-eval N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(2 \cdot x + -2, x, 2\right)} - 1 \]

      6. *-commutative N/A

         \[\leadsto \frac{2}{\mathsf{fma}\left(x \cdot 2 + -2, x, 2\right)} - 1 \]

      7. lower-fma.f64 98.8

         \[\leadsto \frac{2}{\mathsf{fma}\left(\mathsf{fma}\left(x, 2, -2\right), x, 2\right)} - 1 \]

   4. Applied rewrites 98.8%

      \[\leadsto \frac{2}{\color{blue}{\mathsf{fma}\left(\mathsf{fma}\left(x, 2, -2\right), x, 2\right)}} - 1 \]

   5. Taylor expanded in x around inf

      \[\leadsto \frac{2}{2 \cdot \color{blue}{{x}^{2}}} - 1 \]
   6. Step-by-step derivation

      1. *-commutative N/A

         \[\leadsto \frac{2}{{x}^{2} \cdot 2} - 1 \]

      2. lower-*.f64 N/A

         \[\leadsto \frac{2}{{x}^{2} \cdot 2} - 1 \]

      3. pow2 N/A

         \[\leadsto \frac{2}{\left(x \cdot x\right) \cdot 2} - 1 \]

      4. lift-*.f64 98.7

         \[\leadsto \frac{2}{\left(x \cdot x\right) \cdot 2} - 1 \]

   7. Applied rewrites 98.7%

      \[\leadsto \frac{2}{\left(x \cdot x\right) \cdot \color{blue}{2}} - 1 \]
   8. Step-by-step derivation

      1. +-commutative 98.7

         \[\leadsto \frac{2}{\color{blue}{\left(x \cdot x\right)} \cdot 2} - 1 \]

      2. *-commutative 98.7

         \[\leadsto \frac{2}{\left(x \cdot x\right) \cdot 2} - 1 \]

      3. metadata-eval 98.7

         \[\leadsto \frac{2}{\left(x \cdot \color{blue}{x}\right) \cdot 2} - 1 \]

      4. sub-flip 98.7

         \[\leadsto \frac{2}{\color{blue}{\left(x \cdot x\right)} \cdot 2} - 1 \]

      5. lift-*.f64 N/A

         \[\leadsto \frac{2}{\left(x \cdot x\right) \cdot 2} - 1 \]

      6. lift-*.f64 N/A

         \[\leadsto \frac{2}{\left(x \cdot x\right) \cdot 2} - 1 \]

      7. associate-*l* N/A

         \[\leadsto \frac{2}{x \cdot \left(x \cdot \color{blue}{2}\right)} - 1 \]

      8. *-commutative N/A

         \[\leadsto \frac{2}{x \cdot \left(2 \cdot x\right)} - 1 \]

      9. lower-*.f64 N/A

         \[\leadsto \frac{2}{x \cdot \left(2 \cdot \color{blue}{x}\right)} - 1 \]

      10. count-2-rev N/A

          \[\leadsto \frac{2}{x \cdot \left(x + x\right)} - 1 \]

      11. lower-+.f64 98.7

          \[\leadsto \frac{2}{x \cdot \left(x + x\right)} - 1 \]

   9. Applied rewrites 98.7%

      \[\leadsto \frac{2}{\color{blue}{x \cdot \left(x + x\right)}} - 1 \]
3. Recombined 2 regimes into one program.
4. Add Preprocessing

Alternative 12: 75.4% accurate, 1.2× speedup

Math

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;-2 \cdot x \leq 0.2:\\ \;\;\;\;x\\ \mathbf{else}:\\ \;\;\;\;\frac{2}{\mathsf{fma}\left(x, -2, 2\right)} - 1\\ \end{array} \end{array} \]

FPCore

(FPCore (x)
 :precision binary64
 (if (<= (* -2.0 x) 0.2) x (- (/ 2.0 (fma x -2.0 2.0)) 1.0)))

C

double code(double x) {
	double tmp;
	if ((-2.0 * x) <= 0.2) {
		tmp = x;
	} else {
		tmp = (2.0 / fma(x, -2.0, 2.0)) - 1.0;
	}
	return tmp;
}

Julia

function code(x)
	tmp = 0.0
	if (Float64(-2.0 * x) <= 0.2)
		tmp = x;
	else
		tmp = Float64(Float64(2.0 / fma(x, -2.0, 2.0)) - 1.0);
	end
	return tmp
end

Wolfram

code[x_] := If[LessEqual[N[(-2.0 * x), $MachinePrecision], 0.2], x, N[(N[(2.0 / N[(x * -2.0 + 2.0), $MachinePrecision]), $MachinePrecision] - 1.0), $MachinePrecision]]

Derivation

1. Split input into 2 regimes

2. if (*.f64 #s(literal -2 binary64) x) < 0.20000000000000001

   1. Initial program 38.8%

      \[\frac{2}{1 + e^{-2 \cdot x}} - 1 \]

   2. Taylor expanded in x around 0

      \[\leadsto \color{blue}{x} \]
   3. Step-by-step derivation

   4. Applied rewrites 67.9%

      \[\leadsto \color{blue}{x} \]

   if 0.20000000000000001 < (*.f64 #s(literal -2 binary64) x)

   1. Initial program 100.0%

      \[\frac{2}{1 + e^{-2 \cdot x}} - 1 \]

   2. Taylor expanded in x around 0

      \[\leadsto \frac{2}{\color{blue}{2 + -2 \cdot x}} - 1 \]
   3. Step-by-step derivation

      1. +-commutative N/A

         \[\leadsto \frac{2}{-2 \cdot x + \color{blue}{2}} - 1 \]

      2. *-commutative N/A

         \[\leadsto \frac{2}{x \cdot -2 + 2} - 1 \]

      3. lower-fma.f64 97.7

         \[\leadsto \frac{2}{\mathsf{fma}\left(x, \color{blue}{-2}, 2\right)} - 1 \]

   4. Applied rewrites 97.7%

      \[\leadsto \frac{2}{\color{blue}{\mathsf{fma}\left(x, -2, 2\right)}} - 1 \]
3. Recombined 2 regimes into one program.
4. Add Preprocessing

Alternative 13: 52.1% accurate, 22.8× speedup

Math

\[\begin{array}{l} \\ x \end{array} \]

FPCore

(FPCore (x) :precision binary64 x)

C

double code(double x) {
	return x;
}

Fortran

module fmin_fmax_functions
    implicit none
    private
    public fmax
    public fmin

    interface fmax
        module procedure fmax88
        module procedure fmax44
        module procedure fmax84
        module procedure fmax48
    end interface
    interface fmin
        module procedure fmin88
        module procedure fmin44
        module procedure fmin84
        module procedure fmin48
    end interface
contains
    real(8) function fmax88(x, y) result (res)
        real(8), intent (in) :: x
        real(8), intent (in) :: y
        res = merge(y, merge(x, max(x, y), y /= y), x /= x)
    end function
    real(4) function fmax44(x, y) result (res)
        real(4), intent (in) :: x
        real(4), intent (in) :: y
        res = merge(y, merge(x, max(x, y), y /= y), x /= x)
    end function
    real(8) function fmax84(x, y) result(res)
        real(8), intent (in) :: x
        real(4), intent (in) :: y
        res = merge(dble(y), merge(x, max(x, dble(y)), y /= y), x /= x)
    end function
    real(8) function fmax48(x, y) result(res)
        real(4), intent (in) :: x
        real(8), intent (in) :: y
        res = merge(y, merge(dble(x), max(dble(x), y), y /= y), x /= x)
    end function
    real(8) function fmin88(x, y) result (res)
        real(8), intent (in) :: x
        real(8), intent (in) :: y
        res = merge(y, merge(x, min(x, y), y /= y), x /= x)
    end function
    real(4) function fmin44(x, y) result (res)
        real(4), intent (in) :: x
        real(4), intent (in) :: y
        res = merge(y, merge(x, min(x, y), y /= y), x /= x)
    end function
    real(8) function fmin84(x, y) result(res)
        real(8), intent (in) :: x
        real(4), intent (in) :: y
        res = merge(dble(y), merge(x, min(x, dble(y)), y /= y), x /= x)
    end function
    real(8) function fmin48(x, y) result(res)
        real(4), intent (in) :: x
        real(8), intent (in) :: y
        res = merge(y, merge(dble(x), min(dble(x), y), y /= y), x /= x)
    end function
end module

real(8) function code(x)
use fmin_fmax_functions
    real(8), intent (in) :: x
    code = x
end function

Java

public static double code(double x) {
	return x;
}

Python

def code(x):
	return x

Julia

function code(x)
	return x
end

MATLAB

function tmp = code(x)
	tmp = x;
end

Wolfram

code[x_] := x

Derivation

1. Initial program 54.3%

   \[\frac{2}{1 + e^{-2 \cdot x}} - 1 \]

2. Taylor expanded in x around 0

   \[\leadsto \color{blue}{x} \]
3. Step-by-step derivation

4. Applied rewrites 52.1%

   \[\leadsto \color{blue}{x} \]
5. Add Preprocessing

Reproduce

herbie shell --seed 2025127 
(FPCore (x)
  :name "Logistic function from Lakshay Garg"
  :precision binary64
  (- (/ 2.0 (+ 1.0 (exp (* -2.0 x)))) 1.0))