
(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 6 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
(let* ((t_0 (/ 1.0 (fabs x))))
(*
(* (/ 1.0 (sqrt (PI))) (exp (* x x)))
(+
(+
(+ t_0 (/ (/ 0.5 (* x x)) (fabs x)))
(* (/ 3.0 4.0) (/ (/ -1.0 (* x x)) (* (* (- x) x) x))))
(*
(/ 15.0 8.0)
(* (* (* (/ -1.0 (* (* x x) (* x x))) (- t_0)) t_0) t_0))))))\begin{array}{l}
\\
\begin{array}{l}
t_0 := \frac{1}{\left|x\right|}\\
\left(\frac{1}{\sqrt{\mathsf{PI}\left(\right)}} \cdot e^{x \cdot x}\right) \cdot \left(\left(\left(t\_0 + \frac{\frac{0.5}{x \cdot x}}{\left|x\right|}\right) + \frac{3}{4} \cdot \frac{\frac{-1}{x \cdot x}}{\left(\left(-x\right) \cdot x\right) \cdot x}\right) + \frac{15}{8} \cdot \left(\left(\left(\frac{-1}{\left(x \cdot x\right) \cdot \left(x \cdot x\right)} \cdot \left(-t\_0\right)\right) \cdot t\_0\right) \cdot t\_0\right)\right)
\end{array}
\end{array}
Initial program 100.0%
lift-*.f64N/A
lift-/.f64N/A
lift-*.f64N/A
lift-/.f64N/A
lift-fabs.f64N/A
associate-*r/N/A
*-rgt-identityN/A
associate-*r/N/A
lower-/.f64N/A
Applied rewrites100.0%
lift-*.f64N/A
lift-*.f64N/A
lift-*.f64N/A
lift-/.f64N/A
lift-fabs.f64N/A
lift-/.f64N/A
lift-fabs.f64N/A
lift-/.f64N/A
lift-fabs.f64N/A
lift-/.f64N/A
lift-fabs.f64N/A
associate-*l*N/A
frac-timesN/A
metadata-evalN/A
sqr-abs-revN/A
pow2N/A
frac-timesN/A
Applied rewrites100.0%
Applied rewrites100.0%
Final simplification100.0%
(FPCore (x) :precision binary64 (/ (/ (pow (exp x) x) (sqrt (PI))) x))
\begin{array}{l}
\\
\frac{\frac{{\left(e^{x}\right)}^{x}}{\sqrt{\mathsf{PI}\left(\right)}}}{x}
\end{array}
Initial program 100.0%
lift-*.f64N/A
lift-/.f64N/A
lift-*.f64N/A
lift-/.f64N/A
lift-fabs.f64N/A
associate-*r/N/A
*-rgt-identityN/A
associate-*r/N/A
lower-/.f64N/A
Applied rewrites100.0%
lift-*.f64N/A
lift-*.f64N/A
lift-*.f64N/A
lift-/.f64N/A
lift-fabs.f64N/A
lift-/.f64N/A
lift-fabs.f64N/A
lift-/.f64N/A
lift-fabs.f64N/A
lift-/.f64N/A
lift-fabs.f64N/A
associate-*l*N/A
frac-timesN/A
metadata-evalN/A
sqr-abs-revN/A
pow2N/A
frac-timesN/A
Applied rewrites100.0%
Applied rewrites100.0%
Taylor expanded in x around inf
associate-*r/N/A
rem-sqrt-square-revN/A
pow2N/A
sqrt-pow1N/A
metadata-evalN/A
unpow1N/A
lower-/.f64N/A
Applied rewrites99.7%
(FPCore (x) :precision binary64 (* (/ (fma (fma (fma 0.16666666666666666 (* x x) 0.5) (* x x) 1.0) (* x x) 1.0) (sqrt (PI))) (pow x -1.0)))
\begin{array}{l}
\\
\frac{\mathsf{fma}\left(\mathsf{fma}\left(\mathsf{fma}\left(0.16666666666666666, x \cdot x, 0.5\right), x \cdot x, 1\right), x \cdot x, 1\right)}{\sqrt{\mathsf{PI}\left(\right)}} \cdot {x}^{-1}
\end{array}
Initial program 100.0%
lift-/.f64N/A
lift-fabs.f64N/A
inv-powN/A
rem-sqrt-square-revN/A
sqr-absN/A
sqrt-pow2N/A
metadata-evalN/A
metadata-evalN/A
metadata-evalN/A
lower-pow.f64N/A
sqr-absN/A
lower-*.f64N/A
metadata-evalN/A
metadata-eval48.8
Applied rewrites48.8%
Taylor expanded in x around 0
Applied rewrites99.7%
lift-*.f64N/A
lift-/.f64N/A
lift-exp.f64N/A
lift-*.f64N/A
lift-fabs.f64N/A
lift-fabs.f64N/A
associate-*l/N/A
lower-/.f64N/A
1-expN/A
sqr-abs-revN/A
pow2N/A
prod-expN/A
lower-exp.f64N/A
lower-+.f64N/A
pow2N/A
lift-*.f6499.7
Applied rewrites99.7%
Taylor expanded in x around 0
pow2N/A
+-lft-identityN/A
pow2N/A
sqr-abs-revN/A
+-commutativeN/A
*-commutativeN/A
lower-fma.f64N/A
+-commutativeN/A
*-commutativeN/A
lower-fma.f64N/A
+-commutativeN/A
lower-fma.f64N/A
pow2N/A
lift-*.f64N/A
pow2N/A
lift-*.f64N/A
pow2N/A
lift-*.f6484.8
Applied rewrites84.8%
(FPCore (x) :precision binary64 (* (/ (fma (fma (* x x) 0.5 1.0) (* x x) 1.0) (sqrt (PI))) (pow x -1.0)))
\begin{array}{l}
\\
\frac{\mathsf{fma}\left(\mathsf{fma}\left(x \cdot x, 0.5, 1\right), x \cdot x, 1\right)}{\sqrt{\mathsf{PI}\left(\right)}} \cdot {x}^{-1}
\end{array}
Initial program 100.0%
lift-/.f64N/A
lift-fabs.f64N/A
inv-powN/A
rem-sqrt-square-revN/A
sqr-absN/A
sqrt-pow2N/A
metadata-evalN/A
metadata-evalN/A
metadata-evalN/A
lower-pow.f64N/A
sqr-absN/A
lower-*.f64N/A
metadata-evalN/A
metadata-eval48.8
Applied rewrites48.8%
Taylor expanded in x around 0
Applied rewrites99.7%
lift-*.f64N/A
lift-/.f64N/A
lift-exp.f64N/A
lift-*.f64N/A
lift-fabs.f64N/A
lift-fabs.f64N/A
associate-*l/N/A
lower-/.f64N/A
1-expN/A
sqr-abs-revN/A
pow2N/A
prod-expN/A
lower-exp.f64N/A
lower-+.f64N/A
pow2N/A
lift-*.f6499.7
Applied rewrites99.7%
Taylor expanded in x around 0
pow2N/A
+-lft-identityN/A
pow2N/A
sqr-abs-revN/A
+-commutativeN/A
*-commutativeN/A
lower-fma.f64N/A
+-commutativeN/A
*-commutativeN/A
lower-fma.f64N/A
pow2N/A
lift-*.f64N/A
pow2N/A
lift-*.f6475.0
Applied rewrites75.0%
(FPCore (x) :precision binary64 (* (/ (fma x x 1.0) (sqrt (PI))) (pow x -1.0)))
\begin{array}{l}
\\
\frac{\mathsf{fma}\left(x, x, 1\right)}{\sqrt{\mathsf{PI}\left(\right)}} \cdot {x}^{-1}
\end{array}
Initial program 100.0%
lift-/.f64N/A
lift-fabs.f64N/A
inv-powN/A
rem-sqrt-square-revN/A
sqr-absN/A
sqrt-pow2N/A
metadata-evalN/A
metadata-evalN/A
metadata-evalN/A
lower-pow.f64N/A
sqr-absN/A
lower-*.f64N/A
metadata-evalN/A
metadata-eval48.8
Applied rewrites48.8%
Taylor expanded in x around 0
Applied rewrites99.7%
lift-*.f64N/A
lift-/.f64N/A
lift-exp.f64N/A
lift-*.f64N/A
lift-fabs.f64N/A
lift-fabs.f64N/A
associate-*l/N/A
lower-/.f64N/A
1-expN/A
sqr-abs-revN/A
pow2N/A
prod-expN/A
lower-exp.f64N/A
lower-+.f64N/A
pow2N/A
lift-*.f6499.7
Applied rewrites99.7%
Taylor expanded in x around 0
pow2N/A
+-lft-identityN/A
pow2N/A
sqr-abs-revN/A
+-commutativeN/A
pow2N/A
lower-fma.f6453.1
Applied rewrites53.1%
(FPCore (x) :precision binary64 (* (/ 1.0 (sqrt (PI))) (pow x -1.0)))
\begin{array}{l}
\\
\frac{1}{\sqrt{\mathsf{PI}\left(\right)}} \cdot {x}^{-1}
\end{array}
Initial program 100.0%
lift-/.f64N/A
lift-fabs.f64N/A
inv-powN/A
rem-sqrt-square-revN/A
sqr-absN/A
sqrt-pow2N/A
metadata-evalN/A
metadata-evalN/A
metadata-evalN/A
lower-pow.f64N/A
sqr-absN/A
lower-*.f64N/A
metadata-evalN/A
metadata-eval48.8
Applied rewrites48.8%
Taylor expanded in x around 0
Applied rewrites99.7%
lift-*.f64N/A
lift-/.f64N/A
lift-exp.f64N/A
lift-*.f64N/A
lift-fabs.f64N/A
lift-fabs.f64N/A
associate-*l/N/A
lower-/.f64N/A
1-expN/A
sqr-abs-revN/A
pow2N/A
prod-expN/A
lower-exp.f64N/A
lower-+.f64N/A
pow2N/A
lift-*.f6499.7
Applied rewrites99.7%
Taylor expanded in x around 0
pow22.3
+-lft-identity2.3
pow22.3
sqr-abs-rev2.3
Applied rewrites2.3%
herbie shell --seed 2025054
(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)))))))