
(FPCore (x)
:precision binary64
(let* ((t_0 (/ 1.0 (fabs x)))
(t_1 (* (* t_0 t_0) t_0))
(t_2 (* (* t_1 t_0) t_0)))
(*
(* (/ 1.0 (sqrt (PI))) (exp (* (fabs x) (fabs x))))
(+
(+ (+ t_0 (* (/ 1.0 2.0) t_1)) (* (/ 3.0 4.0) t_2))
(* (/ 15.0 8.0) (* (* t_2 t_0) t_0))))))\begin{array}{l}
\\
\begin{array}{l}
t_0 := \frac{1}{\left|x\right|}\\
t_1 := \left(t\_0 \cdot t\_0\right) \cdot t\_0\\
t_2 := \left(t\_1 \cdot t\_0\right) \cdot t\_0\\
\left(\frac{1}{\sqrt{\mathsf{PI}\left(\right)}} \cdot e^{\left|x\right| \cdot \left|x\right|}\right) \cdot \left(\left(\left(t\_0 + \frac{1}{2} \cdot t\_1\right) + \frac{3}{4} \cdot t\_2\right) + \frac{15}{8} \cdot \left(\left(t\_2 \cdot t\_0\right) \cdot t\_0\right)\right)
\end{array}
\end{array}
Sampling outcomes in binary64 precision:
Herbie found 3 alternatives:
| Alternative | Accuracy | Speedup |
|---|
(FPCore (x)
:precision binary64
(let* ((t_0 (/ 1.0 (fabs x)))
(t_1 (* (* t_0 t_0) t_0))
(t_2 (* (* t_1 t_0) t_0)))
(*
(* (/ 1.0 (sqrt (PI))) (exp (* (fabs x) (fabs x))))
(+
(+ (+ t_0 (* (/ 1.0 2.0) t_1)) (* (/ 3.0 4.0) t_2))
(* (/ 15.0 8.0) (* (* t_2 t_0) t_0))))))\begin{array}{l}
\\
\begin{array}{l}
t_0 := \frac{1}{\left|x\right|}\\
t_1 := \left(t\_0 \cdot t\_0\right) \cdot t\_0\\
t_2 := \left(t\_1 \cdot t\_0\right) \cdot t\_0\\
\left(\frac{1}{\sqrt{\mathsf{PI}\left(\right)}} \cdot e^{\left|x\right| \cdot \left|x\right|}\right) \cdot \left(\left(\left(t\_0 + \frac{1}{2} \cdot t\_1\right) + \frac{3}{4} \cdot t\_2\right) + \frac{15}{8} \cdot \left(\left(t\_2 \cdot t\_0\right) \cdot t\_0\right)\right)
\end{array}
\end{array}
(FPCore (x)
:precision binary64
(*
(+
(* (pow (fabs x) -7.0) (/ 15.0 8.0))
(-
(/ 1.0 (* (fabs x) (fma -0.5 (pow x -2.0) 1.0)))
(-
(/ (* (pow (fabs x) -6.0) 0.25) (/ (- 1.0 (/ 0.5 (* x x))) (fabs x)))
(* 0.75 (pow (fabs x) -5.0)))))
(/ (pow (exp x) x) (sqrt (PI)))))\begin{array}{l}
\\
\left({\left(\left|x\right|\right)}^{-7} \cdot \frac{15}{8} + \left(\frac{1}{\left|x\right| \cdot \mathsf{fma}\left(-0.5, {x}^{-2}, 1\right)} - \left(\frac{{\left(\left|x\right|\right)}^{-6} \cdot 0.25}{\frac{1 - \frac{0.5}{x \cdot x}}{\left|x\right|}} - 0.75 \cdot {\left(\left|x\right|\right)}^{-5}\right)\right)\right) \cdot \frac{{\left(e^{x}\right)}^{x}}{\sqrt{\mathsf{PI}\left(\right)}}
\end{array}
Initial program 100.0%
Applied rewrites49.6%
lift-/.f64N/A
clear-numN/A
lower-/.f64N/A
lift-/.f64N/A
div-invN/A
lift-/.f64N/A
associate-/l*N/A
lift-/.f64N/A
inv-powN/A
lift-pow.f64N/A
pow-divN/A
metadata-evalN/A
metadata-evalN/A
pow-flipN/A
inv-powN/A
clear-numN/A
/-rgt-identityN/A
lower-*.f64100.0
Applied rewrites100.0%
lift-*.f64N/A
lift-*.f64N/A
associate-*l*N/A
Applied rewrites100.0%
lift-*.f64N/A
*-commutativeN/A
lift-/.f64N/A
un-div-invN/A
lower-/.f64100.0
lift-exp.f64N/A
lift-*.f64N/A
lift-fabs.f64N/A
lift-fabs.f64N/A
sqr-absN/A
exp-prodN/A
lower-pow.f64N/A
lower-exp.f64100.0
Applied rewrites100.0%
Final simplification100.0%
(FPCore (x)
:precision binary64
(let* ((t_0 (/ -1.0 (fabs x))))
(*
(+
(-
(/ (- (/ 0.5 (* x x)) -1.0) (fabs x))
(* (* (* t_0 (* t_0 (/ -1.0 (* x x)))) (/ 1.0 (fabs x))) (/ 3.0 4.0)))
(* (pow (fabs x) -7.0) (/ 15.0 8.0)))
(/ (pow (exp x) x) (sqrt (PI))))))\begin{array}{l}
\\
\begin{array}{l}
t_0 := \frac{-1}{\left|x\right|}\\
\left(\left(\frac{\frac{0.5}{x \cdot x} - -1}{\left|x\right|} - \left(\left(t\_0 \cdot \left(t\_0 \cdot \frac{-1}{x \cdot x}\right)\right) \cdot \frac{1}{\left|x\right|}\right) \cdot \frac{3}{4}\right) + {\left(\left|x\right|\right)}^{-7} \cdot \frac{15}{8}\right) \cdot \frac{{\left(e^{x}\right)}^{x}}{\sqrt{\mathsf{PI}\left(\right)}}
\end{array}
\end{array}
Initial program 100.0%
Taylor expanded in x around 0
+-commutativeN/A
unpow3N/A
unpow2N/A
associate-/r*N/A
associate-*r/N/A
*-lft-identityN/A
associate-*l/N/A
*-rgt-identityN/A
distribute-lft-inN/A
associate-*l/N/A
*-commutativeN/A
*-rgt-identityN/A
lower-/.f64N/A
Applied rewrites100.0%
lift-*.f64N/A
lift-*.f64N/A
associate-*l*N/A
Applied rewrites100.0%
lift-*.f64N/A
lift-/.f64N/A
lift-/.f64N/A
frac-timesN/A
metadata-evalN/A
lift-fabs.f64N/A
lift-fabs.f64N/A
sqr-absN/A
lift-*.f64N/A
lower-/.f64100.0
Applied rewrites100.0%
lift-*.f64N/A
*-commutativeN/A
lift-/.f64N/A
un-div-invN/A
lower-/.f64100.0
lift-exp.f64N/A
lift-*.f64N/A
lift-fabs.f64N/A
lift-fabs.f64N/A
sqr-absN/A
exp-prodN/A
lower-pow.f64N/A
lower-exp.f64100.0
Applied rewrites100.0%
Final simplification100.0%
(FPCore (x)
:precision binary64
(let* ((t_0 (/ 1.0 (* x x))))
(*
(+
(-
(/ (- (/ 0.5 (* x x)) -1.0) (fabs x))
(* (* (/ -1.0 (fabs x)) (* t_0 t_0)) (/ 3.0 4.0)))
(* (pow (fabs x) -7.0) (/ 15.0 8.0)))
(* (exp (* (fabs x) (fabs x))) (/ 1.0 (sqrt (PI)))))))\begin{array}{l}
\\
\begin{array}{l}
t_0 := \frac{1}{x \cdot x}\\
\left(\left(\frac{\frac{0.5}{x \cdot x} - -1}{\left|x\right|} - \left(\frac{-1}{\left|x\right|} \cdot \left(t\_0 \cdot t\_0\right)\right) \cdot \frac{3}{4}\right) + {\left(\left|x\right|\right)}^{-7} \cdot \frac{15}{8}\right) \cdot \left(e^{\left|x\right| \cdot \left|x\right|} \cdot \frac{1}{\sqrt{\mathsf{PI}\left(\right)}}\right)
\end{array}
\end{array}
Initial program 100.0%
Taylor expanded in x around 0
+-commutativeN/A
unpow3N/A
unpow2N/A
associate-/r*N/A
associate-*r/N/A
*-lft-identityN/A
associate-*l/N/A
*-rgt-identityN/A
distribute-lft-inN/A
associate-*l/N/A
*-commutativeN/A
*-rgt-identityN/A
lower-/.f64N/A
Applied rewrites100.0%
lift-*.f64N/A
lift-*.f64N/A
associate-*l*N/A
Applied rewrites100.0%
lift-*.f64N/A
lift-/.f64N/A
lift-/.f64N/A
frac-timesN/A
metadata-evalN/A
lift-fabs.f64N/A
lift-fabs.f64N/A
sqr-absN/A
lift-*.f64N/A
lower-/.f64100.0
Applied rewrites100.0%
lift-*.f64N/A
lift-*.f64N/A
lift-/.f64N/A
metadata-evalN/A
lift-*.f64N/A
sqr-absN/A
lift-fabs.f64N/A
lift-fabs.f64N/A
frac-timesN/A
lift-/.f64N/A
lift-/.f64N/A
lift-*.f64N/A
associate-*l*N/A
lift-*.f64N/A
pow2N/A
lift-*.f64N/A
Applied rewrites100.0%
Final simplification100.0%
herbie shell --seed 2024257
(FPCore (x)
:name "Jmat.Real.erfi, branch x greater than or equal to 5"
:precision binary64
:pre (>= x 0.5)
(* (* (/ 1.0 (sqrt (PI))) (exp (* (fabs x) (fabs x)))) (+ (+ (+ (/ 1.0 (fabs x)) (* (/ 1.0 2.0) (* (* (/ 1.0 (fabs x)) (/ 1.0 (fabs x))) (/ 1.0 (fabs x))))) (* (/ 3.0 4.0) (* (* (* (* (/ 1.0 (fabs x)) (/ 1.0 (fabs x))) (/ 1.0 (fabs x))) (/ 1.0 (fabs x))) (/ 1.0 (fabs x))))) (* (/ 15.0 8.0) (* (* (* (* (* (* (/ 1.0 (fabs x)) (/ 1.0 (fabs x))) (/ 1.0 (fabs x))) (/ 1.0 (fabs x))) (/ 1.0 (fabs x))) (/ 1.0 (fabs x))) (/ 1.0 (fabs x)))))))