
(FPCore (s r) :precision binary32 (+ (/ (* 0.25 (exp (/ (- r) s))) (* (* (* 2.0 (PI)) s) r)) (/ (* 0.75 (exp (/ (- r) (* 3.0 s)))) (* (* (* 6.0 (PI)) s) r))))
\begin{array}{l}
\\
\frac{0.25 \cdot e^{\frac{-r}{s}}}{\left(\left(2 \cdot \mathsf{PI}\left(\right)\right) \cdot s\right) \cdot r} + \frac{0.75 \cdot e^{\frac{-r}{3 \cdot s}}}{\left(\left(6 \cdot \mathsf{PI}\left(\right)\right) \cdot s\right) \cdot r}
\end{array}
Sampling outcomes in binary32 precision:
Herbie found 9 alternatives:
| Alternative | Accuracy | Speedup |
|---|
(FPCore (s r) :precision binary32 (+ (/ (* 0.25 (exp (/ (- r) s))) (* (* (* 2.0 (PI)) s) r)) (/ (* 0.75 (exp (/ (- r) (* 3.0 s)))) (* (* (* 6.0 (PI)) s) r))))
\begin{array}{l}
\\
\frac{0.25 \cdot e^{\frac{-r}{s}}}{\left(\left(2 \cdot \mathsf{PI}\left(\right)\right) \cdot s\right) \cdot r} + \frac{0.75 \cdot e^{\frac{-r}{3 \cdot s}}}{\left(\left(6 \cdot \mathsf{PI}\left(\right)\right) \cdot s\right) \cdot r}
\end{array}
(FPCore (s r) :precision binary32 (+ (/ (* 0.25 (exp (/ (- r) s))) (* (* (* 2.0 (PI)) s) r)) (/ (* 0.75 (exp (/ (- r) (* 3.0 s)))) (* (* s r) (* 6.0 (PI))))))
\begin{array}{l}
\\
\frac{0.25 \cdot e^{\frac{-r}{s}}}{\left(\left(2 \cdot \mathsf{PI}\left(\right)\right) \cdot s\right) \cdot r} + \frac{0.75 \cdot e^{\frac{-r}{3 \cdot s}}}{\left(s \cdot r\right) \cdot \left(6 \cdot \mathsf{PI}\left(\right)\right)}
\end{array}
Initial program 99.4%
lift-*.f32N/A
lift-*.f32N/A
associate-*l*N/A
*-commutativeN/A
lower-*.f32N/A
lower-*.f3299.5
Applied rewrites99.5%
(FPCore (s r)
:precision binary32
(let* ((t_0 (/ -0.16666666666666666 (PI))))
(if (<=
(+
(/ (* 0.25 (exp (/ (- r) s))) (* (* (* 2.0 (PI)) s) r))
(/ (* 0.75 (exp (/ (- r) (* 3.0 s)))) (* (* (* 6.0 (PI)) s) r)))
3.999999989900971e-6)
(/
(fma
(/ (/ (fma r (pow (* (PI) (* s 14.4)) -1.0) t_0) s) s)
r
(/ 0.25 (* (PI) s)))
r)
(/
(-
(/
(-
t_0
(/
(*
r
(-
(/ -0.06944444444444445 (PI))
(* (/ r (PI)) (/ -0.021604938271604937 s))))
s))
s)
(/ -0.25 (* (PI) r)))
s))))\begin{array}{l}
\\
\begin{array}{l}
t_0 := \frac{-0.16666666666666666}{\mathsf{PI}\left(\right)}\\
\mathbf{if}\;\frac{0.25 \cdot e^{\frac{-r}{s}}}{\left(\left(2 \cdot \mathsf{PI}\left(\right)\right) \cdot s\right) \cdot r} + \frac{0.75 \cdot e^{\frac{-r}{3 \cdot s}}}{\left(\left(6 \cdot \mathsf{PI}\left(\right)\right) \cdot s\right) \cdot r} \leq 3.999999989900971 \cdot 10^{-6}:\\
\;\;\;\;\frac{\mathsf{fma}\left(\frac{\frac{\mathsf{fma}\left(r, {\left(\mathsf{PI}\left(\right) \cdot \left(s \cdot 14.4\right)\right)}^{-1}, t\_0\right)}{s}}{s}, r, \frac{0.25}{\mathsf{PI}\left(\right) \cdot s}\right)}{r}\\
\mathbf{else}:\\
\;\;\;\;\frac{\frac{t\_0 - \frac{r \cdot \left(\frac{-0.06944444444444445}{\mathsf{PI}\left(\right)} - \frac{r}{\mathsf{PI}\left(\right)} \cdot \frac{-0.021604938271604937}{s}\right)}{s}}{s} - \frac{-0.25}{\mathsf{PI}\left(\right) \cdot r}}{s}\\
\end{array}
\end{array}
if (+.f32 (/.f32 (*.f32 #s(literal 1/4 binary32) (exp.f32 (/.f32 (neg.f32 r) s))) (*.f32 (*.f32 (*.f32 #s(literal 2 binary32) (PI.f32)) s) r)) (/.f32 (*.f32 #s(literal 3/4 binary32) (exp.f32 (/.f32 (neg.f32 r) (*.f32 #s(literal 3 binary32) s)))) (*.f32 (*.f32 (*.f32 #s(literal 6 binary32) (PI.f32)) s) r))) < 3.99999999e-6Initial program 99.6%
Taylor expanded in r around 0
Applied rewrites4.8%
Applied rewrites8.8%
if 3.99999999e-6 < (+.f32 (/.f32 (*.f32 #s(literal 1/4 binary32) (exp.f32 (/.f32 (neg.f32 r) s))) (*.f32 (*.f32 (*.f32 #s(literal 2 binary32) (PI.f32)) s) r)) (/.f32 (*.f32 #s(literal 3/4 binary32) (exp.f32 (/.f32 (neg.f32 r) (*.f32 #s(literal 3 binary32) s)))) (*.f32 (*.f32 (*.f32 #s(literal 6 binary32) (PI.f32)) s) r))) Initial program 97.9%
Taylor expanded in s around -inf
Applied rewrites57.5%
(FPCore (s r) :precision binary32 (+ (/ (* (exp (/ (- r) s)) 0.125) (* (* (PI) s) r)) (/ (* 0.75 (exp (* (/ -0.3333333333333333 s) r))) (* (* s r) (* 6.0 (PI))))))
\begin{array}{l}
\\
\frac{e^{\frac{-r}{s}} \cdot 0.125}{\left(\mathsf{PI}\left(\right) \cdot s\right) \cdot r} + \frac{0.75 \cdot e^{\frac{-0.3333333333333333}{s} \cdot r}}{\left(s \cdot r\right) \cdot \left(6 \cdot \mathsf{PI}\left(\right)\right)}
\end{array}
Initial program 99.4%
lift-*.f32N/A
lift-*.f32N/A
associate-*l*N/A
*-commutativeN/A
lower-*.f32N/A
lower-*.f3299.5
Applied rewrites99.5%
lift-/.f32N/A
lift-neg.f32N/A
lift-*.f32N/A
metadata-evalN/A
distribute-lft-neg-inN/A
lift-*.f32N/A
frac-2negN/A
div-invN/A
*-commutativeN/A
lower-*.f32N/A
lift-*.f32N/A
associate-/r*N/A
metadata-evalN/A
metadata-evalN/A
lower-/.f32N/A
metadata-eval99.5
Applied rewrites99.5%
Taylor expanded in s around 0
associate-*r/N/A
lower-/.f32N/A
mul-1-negN/A
exp-negN/A
associate-*r/N/A
metadata-evalN/A
lower-/.f32N/A
lower-exp.f32N/A
lower-/.f32N/A
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-PI.f3299.4
Applied rewrites99.4%
Applied rewrites99.5%
(FPCore (s r) :precision binary32 (+ (/ (/ 0.125 (+ (/ (fma 0.5 (* r (/ r s)) r) s) 1.0)) (* (* (PI) s) r)) (/ (* 0.75 (exp (* (/ -0.3333333333333333 s) r))) (* (* s r) (* 6.0 (PI))))))
\begin{array}{l}
\\
\frac{\frac{0.125}{\frac{\mathsf{fma}\left(0.5, r \cdot \frac{r}{s}, r\right)}{s} + 1}}{\left(\mathsf{PI}\left(\right) \cdot s\right) \cdot r} + \frac{0.75 \cdot e^{\frac{-0.3333333333333333}{s} \cdot r}}{\left(s \cdot r\right) \cdot \left(6 \cdot \mathsf{PI}\left(\right)\right)}
\end{array}
Initial program 99.4%
lift-*.f32N/A
lift-*.f32N/A
associate-*l*N/A
*-commutativeN/A
lower-*.f32N/A
lower-*.f3299.5
Applied rewrites99.5%
lift-/.f32N/A
lift-neg.f32N/A
lift-*.f32N/A
metadata-evalN/A
distribute-lft-neg-inN/A
lift-*.f32N/A
frac-2negN/A
div-invN/A
*-commutativeN/A
lower-*.f32N/A
lift-*.f32N/A
associate-/r*N/A
metadata-evalN/A
metadata-evalN/A
lower-/.f32N/A
metadata-eval99.5
Applied rewrites99.5%
Taylor expanded in s around 0
associate-*r/N/A
lower-/.f32N/A
mul-1-negN/A
exp-negN/A
associate-*r/N/A
metadata-evalN/A
lower-/.f32N/A
lower-exp.f32N/A
lower-/.f32N/A
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-PI.f3299.4
Applied rewrites99.4%
Taylor expanded in s around -inf
Applied rewrites15.4%
(FPCore (s r) :precision binary32 (+ (/ (/ 0.125 (+ (/ r s) 1.0)) (* (* (PI) s) r)) (/ (* 0.75 (exp (* (/ -0.3333333333333333 s) r))) (* (* s r) (* 6.0 (PI))))))
\begin{array}{l}
\\
\frac{\frac{0.125}{\frac{r}{s} + 1}}{\left(\mathsf{PI}\left(\right) \cdot s\right) \cdot r} + \frac{0.75 \cdot e^{\frac{-0.3333333333333333}{s} \cdot r}}{\left(s \cdot r\right) \cdot \left(6 \cdot \mathsf{PI}\left(\right)\right)}
\end{array}
Initial program 99.4%
lift-*.f32N/A
lift-*.f32N/A
associate-*l*N/A
*-commutativeN/A
lower-*.f32N/A
lower-*.f3299.5
Applied rewrites99.5%
lift-/.f32N/A
lift-neg.f32N/A
lift-*.f32N/A
metadata-evalN/A
distribute-lft-neg-inN/A
lift-*.f32N/A
frac-2negN/A
div-invN/A
*-commutativeN/A
lower-*.f32N/A
lift-*.f32N/A
associate-/r*N/A
metadata-evalN/A
metadata-evalN/A
lower-/.f32N/A
metadata-eval99.5
Applied rewrites99.5%
Taylor expanded in s around 0
associate-*r/N/A
lower-/.f32N/A
mul-1-negN/A
exp-negN/A
associate-*r/N/A
metadata-evalN/A
lower-/.f32N/A
lower-exp.f32N/A
lower-/.f32N/A
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-PI.f3299.4
Applied rewrites99.4%
Taylor expanded in s around inf
Applied rewrites13.9%
(FPCore (s r)
:precision binary32
(/
(-
(/
(-
(/ -0.16666666666666666 (PI))
(/
(*
r
(-
(/ -0.06944444444444445 (PI))
(* (/ r (PI)) (/ -0.021604938271604937 s))))
s))
s)
(/ -0.25 (* (PI) r)))
s))\begin{array}{l}
\\
\frac{\frac{\frac{-0.16666666666666666}{\mathsf{PI}\left(\right)} - \frac{r \cdot \left(\frac{-0.06944444444444445}{\mathsf{PI}\left(\right)} - \frac{r}{\mathsf{PI}\left(\right)} \cdot \frac{-0.021604938271604937}{s}\right)}{s}}{s} - \frac{-0.25}{\mathsf{PI}\left(\right) \cdot r}}{s}
\end{array}
Initial program 99.4%
Taylor expanded in s around -inf
Applied rewrites8.1%
(FPCore (s r) :precision binary32 (* (/ 1.0 r) (/ 0.25 (* (PI) s))))
\begin{array}{l}
\\
\frac{1}{r} \cdot \frac{0.25}{\mathsf{PI}\left(\right) \cdot s}
\end{array}
Initial program 99.4%
Taylor expanded in s around inf
associate-/l/N/A
metadata-evalN/A
associate-*r/N/A
lower-/.f32N/A
associate-*r/N/A
metadata-evalN/A
lower-/.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-PI.f327.8
Applied rewrites7.8%
Applied rewrites7.8%
(FPCore (s r) :precision binary32 (/ (/ 0.25 r) (* (PI) s)))
\begin{array}{l}
\\
\frac{\frac{0.25}{r}}{\mathsf{PI}\left(\right) \cdot s}
\end{array}
Initial program 99.4%
Taylor expanded in s around inf
associate-/l/N/A
metadata-evalN/A
associate-*r/N/A
lower-/.f32N/A
associate-*r/N/A
metadata-evalN/A
lower-/.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-PI.f327.8
Applied rewrites7.8%
Applied rewrites7.8%
(FPCore (s r) :precision binary32 (/ 0.25 (* (* s r) (PI))))
\begin{array}{l}
\\
\frac{0.25}{\left(s \cdot r\right) \cdot \mathsf{PI}\left(\right)}
\end{array}
Initial program 99.4%
Taylor expanded in s around inf
associate-/l/N/A
metadata-evalN/A
associate-*r/N/A
lower-/.f32N/A
associate-*r/N/A
metadata-evalN/A
lower-/.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-PI.f327.8
Applied rewrites7.8%
Applied rewrites7.8%
Applied rewrites7.8%
herbie shell --seed 2024309
(FPCore (s r)
:name "Disney BSSRDF, PDF of scattering profile"
:precision binary32
:pre (and (and (<= 0.0 s) (<= s 256.0)) (and (< 1e-6 r) (< r 1000000.0)))
(+ (/ (* 0.25 (exp (/ (- r) s))) (* (* (* 2.0 (PI)) s) r)) (/ (* 0.75 (exp (/ (- r) (* 3.0 s)))) (* (* (* 6.0 (PI)) s) r))))