
(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 (* x x)) t_0) (/ 1.0 2.0)) t_0)
(* (* (/ (/ -1.0 (* x x)) (* x x)) t_0) (/ 3.0 4.0)))
(* (* (* (* (/ -1.0 (* (* x x) (* x x))) t_0) t_0) t_0) (/ 15.0 8.0)))
(exp (- (* x x) (log (sqrt (PI))))))))\begin{array}{l}
\\
\begin{array}{l}
t_0 := \frac{1}{\left|x\right|}\\
\left(\left(\left(\left(\frac{1}{x \cdot x} \cdot t\_0\right) \cdot \frac{1}{2} + t\_0\right) - \left(\frac{\frac{-1}{x \cdot x}}{x \cdot x} \cdot t\_0\right) \cdot \frac{3}{4}\right) - \left(\left(\left(\frac{-1}{\left(x \cdot x\right) \cdot \left(x \cdot x\right)} \cdot t\_0\right) \cdot t\_0\right) \cdot t\_0\right) \cdot \frac{15}{8}\right) \cdot e^{x \cdot x - \log \left(\sqrt{\mathsf{PI}\left(\right)}\right)}
\end{array}
\end{array}
Initial program 100.0%
lift-*.f64N/A
lift-/.f64N/A
lift-*.f64N/A
lift-/.f64N/A
un-div-invN/A
frac-timesN/A
*-rgt-identityN/A
frac-2negN/A
distribute-lft-neg-inN/A
lower-/.f64N/A
Applied rewrites100.0%
lift-*.f64N/A
lift-*.f64N/A
associate-*l*N/A
lift-*.f64N/A
pow2N/A
pow2N/A
lift-/.f64N/A
inv-powN/A
pow-powN/A
lift-/.f64N/A
inv-powN/A
pow-powN/A
pow-prod-downN/A
lift-fabs.f64N/A
lift-fabs.f64N/A
sqr-absN/A
lift-*.f64N/A
metadata-evalN/A
metadata-evalN/A
Applied rewrites100.0%
lift-*.f64N/A
*-commutativeN/A
lift-/.f64N/A
un-div-invN/A
lift-exp.f64N/A
lift-*.f64N/A
lift-fabs.f64N/A
lift-fabs.f64N/A
sqr-absN/A
lift-*.f64N/A
lift-sqrt.f64N/A
pow1/2N/A
metadata-evalN/A
lift-/.f64N/A
pow-to-expN/A
div-expN/A
lower-exp.f64N/A
lower--.f64N/A
rem-log-expN/A
pow-to-expN/A
lift-/.f64N/A
metadata-evalN/A
pow1/2N/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%
Final simplification100.0%
(FPCore (x) :precision binary64 (* (+ (/ (+ (/ 0.5 (* x x)) (+ (/ (/ 0.75 (* x x)) (* x x)) 1.0)) (fabs x)) (/ 1.875 (pow (fabs x) 7.0))) (* (exp (* x x)) (/ 1.0 (sqrt (PI))))))
\begin{array}{l}
\\
\left(\frac{\frac{0.5}{x \cdot x} + \left(\frac{\frac{0.75}{x \cdot x}}{x \cdot x} + 1\right)}{\left|x\right|} + \frac{1.875}{{\left(\left|x\right|\right)}^{7}}\right) \cdot \left(e^{x \cdot x} \cdot \frac{1}{\sqrt{\mathsf{PI}\left(\right)}}\right)
\end{array}
Initial program 100.0%
lift-*.f64N/A
lift-/.f64N/A
lift-*.f64N/A
lift-/.f64N/A
un-div-invN/A
frac-timesN/A
*-rgt-identityN/A
frac-2negN/A
distribute-lft-neg-inN/A
lower-/.f64N/A
Applied rewrites100.0%
Taylor expanded in x around 0
Applied rewrites100.0%
Applied rewrites100.0%
lift-*.f64N/A
lift-fabs.f64N/A
lift-fabs.f64N/A
sqr-absN/A
lift-*.f64100.0
Applied rewrites100.0%
Final simplification100.0%
(FPCore (x) :precision binary64 (* (+ (/ (+ (/ 0.5 (* x x)) 1.0) (fabs x)) (* (pow (fabs x) -7.0) 1.875)) (* (exp (* x x)) (/ 1.0 (sqrt (PI))))))
\begin{array}{l}
\\
\left(\frac{\frac{0.5}{x \cdot x} + 1}{\left|x\right|} + {\left(\left|x\right|\right)}^{-7} \cdot 1.875\right) \cdot \left(e^{x \cdot x} \cdot \frac{1}{\sqrt{\mathsf{PI}\left(\right)}}\right)
\end{array}
Initial program 100.0%
lift-*.f64N/A
lift-/.f64N/A
lift-*.f64N/A
lift-/.f64N/A
un-div-invN/A
frac-timesN/A
*-rgt-identityN/A
frac-2negN/A
distribute-lft-neg-inN/A
lower-/.f64N/A
Applied rewrites100.0%
Taylor expanded in x around inf
Applied rewrites99.5%
Applied rewrites99.5%
lift-*.f64N/A
lift-fabs.f64N/A
lift-fabs.f64N/A
sqr-absN/A
lift-*.f6499.5
Applied rewrites99.5%
Final simplification99.5%
(FPCore (x) :precision binary64 (* (+ (/ 1.875 (pow (fabs x) 7.0)) (/ 1.0 (fabs x))) (* (exp (* (fabs x) (fabs x))) (/ 1.0 (sqrt (PI))))))
\begin{array}{l}
\\
\left(\frac{1.875}{{\left(\left|x\right|\right)}^{7}} + \frac{1}{\left|x\right|}\right) \cdot \left(e^{\left|x\right| \cdot \left|x\right|} \cdot \frac{1}{\sqrt{\mathsf{PI}\left(\right)}}\right)
\end{array}
Initial program 100.0%
lift-*.f64N/A
lift-/.f64N/A
lift-*.f64N/A
lift-/.f64N/A
un-div-invN/A
frac-timesN/A
*-rgt-identityN/A
frac-2negN/A
distribute-lft-neg-inN/A
lower-/.f64N/A
Applied rewrites100.0%
Taylor expanded in x around inf
Applied rewrites99.5%
Applied rewrites99.5%
Taylor expanded in x around inf
Applied rewrites99.4%
Final simplification99.4%
(FPCore (x) :precision binary64 (* (/ 0.5 (pow (fabs x) 3.0)) (* (exp (* (fabs x) (fabs x))) (/ 1.0 (sqrt (PI))))))
\begin{array}{l}
\\
\frac{0.5}{{\left(\left|x\right|\right)}^{3}} \cdot \left(e^{\left|x\right| \cdot \left|x\right|} \cdot \frac{1}{\sqrt{\mathsf{PI}\left(\right)}}\right)
\end{array}
Initial program 100.0%
lift-*.f64N/A
lift-/.f64N/A
lift-*.f64N/A
lift-/.f64N/A
un-div-invN/A
frac-timesN/A
*-rgt-identityN/A
frac-2negN/A
distribute-lft-neg-inN/A
lower-/.f64N/A
Applied rewrites100.0%
Taylor expanded in x around inf
Applied rewrites99.5%
Applied rewrites99.5%
Taylor expanded in x around 0
Applied rewrites34.9%
Final simplification34.9%
(FPCore (x) :precision binary64 (* (/ (/ (/ 0.75 (* x x)) (* x x)) (fabs x)) (* (exp (* x x)) (/ 1.0 (sqrt (PI))))))
\begin{array}{l}
\\
\frac{\frac{\frac{0.75}{x \cdot x}}{x \cdot x}}{\left|x\right|} \cdot \left(e^{x \cdot x} \cdot \frac{1}{\sqrt{\mathsf{PI}\left(\right)}}\right)
\end{array}
Initial program 100.0%
lift-*.f64N/A
lift-/.f64N/A
lift-*.f64N/A
lift-/.f64N/A
un-div-invN/A
frac-timesN/A
*-rgt-identityN/A
frac-2negN/A
distribute-lft-neg-inN/A
lower-/.f64N/A
Applied rewrites100.0%
Taylor expanded in x around 0
associate-/r*N/A
metadata-evalN/A
associate-*r/N/A
lower-/.f64N/A
associate-*r/N/A
metadata-evalN/A
lower-/.f64N/A
lower-pow.f64N/A
lower-fabs.f6423.9
Applied rewrites23.9%
Applied rewrites23.9%
lift-*.f64N/A
lift-fabs.f64N/A
lift-fabs.f64N/A
sqr-absN/A
lift-*.f6423.9
Applied rewrites23.9%
Final simplification23.9%
herbie shell --seed 2024288
(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)))))))