
(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 10 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 (+ (/ (* (exp (/ r (* -3.0 s))) 0.75) (* (* 6.0 (PI)) (* s r))) (/ (* (exp (/ (- r) s)) 0.25) (* (* (* (PI) 2.0) s) r))))
\begin{array}{l}
\\
\frac{e^{\frac{r}{-3 \cdot s}} \cdot 0.75}{\left(6 \cdot \mathsf{PI}\left(\right)\right) \cdot \left(s \cdot r\right)} + \frac{e^{\frac{-r}{s}} \cdot 0.25}{\left(\left(\mathsf{PI}\left(\right) \cdot 2\right) \cdot s\right) \cdot r}
\end{array}
Initial program 99.2%
lift-*.f32N/A
lift-*.f32N/A
associate-*l*N/A
*-commutativeN/A
lower-*.f32N/A
lower-*.f3299.3
Applied rewrites99.3%
lift-/.f32N/A
lift-*.f32N/A
lift-neg.f32N/A
metadata-evalN/A
distribute-lft-neg-inN/A
lift-*.f32N/A
frac-2negN/A
lift-/.f3299.3
Applied rewrites99.3%
Final simplification99.3%
(FPCore (s r)
:precision binary32
(let* ((t_0 (/ -0.16666666666666666 (PI))))
(if (<=
(+
(/ (* (exp (/ (- r) (* 3.0 s))) 0.75) (* (* (* 6.0 (PI)) s) r))
(/ (* (exp (/ (- r) s)) 0.25) (* (* (* (PI) 2.0) s) r)))
4.999999955487895e-38)
(/
(fma
(/ (/ (fma 0.06944444444444445 (pow (* (/ (PI) r) s) -1.0) t_0) s) s)
r
(/ 0.25 (* (PI) s)))
r)
(/
(-
(/ (- t_0 (/ (* (/ r (PI)) -0.06944444444444445) 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{e^{\frac{-r}{3 \cdot s}} \cdot 0.75}{\left(\left(6 \cdot \mathsf{PI}\left(\right)\right) \cdot s\right) \cdot r} + \frac{e^{\frac{-r}{s}} \cdot 0.25}{\left(\left(\mathsf{PI}\left(\right) \cdot 2\right) \cdot s\right) \cdot r} \leq 4.999999955487895 \cdot 10^{-38}:\\
\;\;\;\;\frac{\mathsf{fma}\left(\frac{\frac{\mathsf{fma}\left(0.06944444444444445, {\left(\frac{\mathsf{PI}\left(\right)}{r} \cdot s\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{\frac{r}{\mathsf{PI}\left(\right)} \cdot -0.06944444444444445}{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))) < 4.99999996e-38Initial program 99.6%
Taylor expanded in r around 0
Applied rewrites4.6%
Applied rewrites9.5%
if 4.99999996e-38 < (+.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 96.6%
Taylor expanded in s around -inf
Applied rewrites50.4%
Taylor expanded in s around inf
Applied rewrites52.3%
Final simplification14.2%
(FPCore (s r)
:precision binary32
(let* ((t_0 (/ -0.16666666666666666 (PI))))
(if (<=
(+
(/ (* (exp (/ (- r) (* 3.0 s))) 0.75) (* (* (* 6.0 (PI)) s) r))
(/ (* (exp (/ (- r) s)) 0.25) (* (* (* (PI) 2.0) s) r)))
0.0)
(/
(fma
(/ (/ (fma r (pow (* (* 14.4 s) (PI)) -1.0) t_0) s) s)
r
(/ 0.25 (* (PI) s)))
r)
(/
(-
(/ (- t_0 (/ (* (/ r (PI)) -0.06944444444444445) 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{e^{\frac{-r}{3 \cdot s}} \cdot 0.75}{\left(\left(6 \cdot \mathsf{PI}\left(\right)\right) \cdot s\right) \cdot r} + \frac{e^{\frac{-r}{s}} \cdot 0.25}{\left(\left(\mathsf{PI}\left(\right) \cdot 2\right) \cdot s\right) \cdot r} \leq 0:\\
\;\;\;\;\frac{\mathsf{fma}\left(\frac{\frac{\mathsf{fma}\left(r, {\left(\left(14.4 \cdot s\right) \cdot \mathsf{PI}\left(\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{\frac{r}{\mathsf{PI}\left(\right)} \cdot -0.06944444444444445}{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))) < 0.0Initial program 99.6%
Taylor expanded in r around 0
Applied rewrites4.6%
Applied rewrites9.3%
if 0.0 < (+.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 96.3%
Taylor expanded in s around -inf
Applied rewrites48.9%
Taylor expanded in s around inf
Applied rewrites50.8%
Final simplification13.9%
(FPCore (s r) :precision binary32 (+ (/ (/ 0.125 (exp (/ r s))) (* (* (PI) s) r)) (/ (* (exp (/ r (* -3.0 s))) 0.75) (* (* 6.0 (PI)) (* s r)))))
\begin{array}{l}
\\
\frac{\frac{0.125}{e^{\frac{r}{s}}}}{\left(\mathsf{PI}\left(\right) \cdot s\right) \cdot r} + \frac{e^{\frac{r}{-3 \cdot s}} \cdot 0.75}{\left(6 \cdot \mathsf{PI}\left(\right)\right) \cdot \left(s \cdot r\right)}
\end{array}
Initial program 99.2%
lift-/.f32N/A
frac-2negN/A
lift-neg.f32N/A
remove-double-negN/A
lower-/.f32N/A
lift-*.f32N/A
distribute-lft-neg-inN/A
lower-*.f32N/A
metadata-eval99.2
Applied rewrites99.2%
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.f3299.3
Applied rewrites99.3%
lift-*.f32N/A
lift-*.f32N/A
associate-*l*N/A
lift-*.f32N/A
*-commutativeN/A
lower-*.f3299.3
Applied rewrites99.3%
Final simplification99.3%
(FPCore (s r) :precision binary32 (+ (/ (* (exp (/ r (* -3.0 s))) 0.75) (* (* (* 6.0 (PI)) s) r)) (/ (* 0.125 (exp (/ (- r) s))) (* (* (PI) s) r))))
\begin{array}{l}
\\
\frac{e^{\frac{r}{-3 \cdot s}} \cdot 0.75}{\left(\left(6 \cdot \mathsf{PI}\left(\right)\right) \cdot s\right) \cdot r} + \frac{0.125 \cdot e^{\frac{-r}{s}}}{\left(\mathsf{PI}\left(\right) \cdot s\right) \cdot r}
\end{array}
Initial program 99.2%
lift-/.f32N/A
frac-2negN/A
lift-neg.f32N/A
remove-double-negN/A
lower-/.f32N/A
lift-*.f32N/A
distribute-lft-neg-inN/A
lower-*.f32N/A
metadata-eval99.2
Applied rewrites99.2%
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.f3299.3
Applied rewrites99.3%
Applied rewrites99.2%
Final simplification99.2%
(FPCore (s r) :precision binary32 (+ (/ (/ 0.125 (- 1.0 (/ (- (* (* (/ r s) r) -0.5) r) s))) (* (* (PI) s) r)) (/ (* (exp (/ r (* -3.0 s))) 0.75) (* (* (* 6.0 (PI)) s) r))))
\begin{array}{l}
\\
\frac{\frac{0.125}{1 - \frac{\left(\frac{r}{s} \cdot r\right) \cdot -0.5 - r}{s}}}{\left(\mathsf{PI}\left(\right) \cdot s\right) \cdot r} + \frac{e^{\frac{r}{-3 \cdot s}} \cdot 0.75}{\left(\left(6 \cdot \mathsf{PI}\left(\right)\right) \cdot s\right) \cdot r}
\end{array}
Initial program 99.2%
lift-/.f32N/A
frac-2negN/A
lift-neg.f32N/A
remove-double-negN/A
lower-/.f32N/A
lift-*.f32N/A
distribute-lft-neg-inN/A
lower-*.f32N/A
metadata-eval99.2
Applied rewrites99.2%
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.f3299.3
Applied rewrites99.3%
Taylor expanded in s around -inf
Applied rewrites59.2%
Final simplification59.2%
(FPCore (s r) :precision binary32 (+ (/ (/ 0.125 (+ 1.0 (/ r s))) (* (* (PI) s) r)) (/ (* (exp (/ r (* -3.0 s))) 0.75) (* (* (* 6.0 (PI)) s) r))))
\begin{array}{l}
\\
\frac{\frac{0.125}{1 + \frac{r}{s}}}{\left(\mathsf{PI}\left(\right) \cdot s\right) \cdot r} + \frac{e^{\frac{r}{-3 \cdot s}} \cdot 0.75}{\left(\left(6 \cdot \mathsf{PI}\left(\right)\right) \cdot s\right) \cdot r}
\end{array}
Initial program 99.2%
lift-/.f32N/A
frac-2negN/A
lift-neg.f32N/A
remove-double-negN/A
lower-/.f32N/A
lift-*.f32N/A
distribute-lft-neg-inN/A
lower-*.f32N/A
metadata-eval99.2
Applied rewrites99.2%
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.f3299.3
Applied rewrites99.3%
Taylor expanded in s around inf
Applied rewrites14.3%
Final simplification14.3%
(FPCore (s r)
:precision binary32
(/
(-
(/
(- (/ -0.16666666666666666 (PI)) (/ (* (/ r (PI)) -0.06944444444444445) s))
s)
(/ -0.25 (* (PI) r)))
s))\begin{array}{l}
\\
\frac{\frac{\frac{-0.16666666666666666}{\mathsf{PI}\left(\right)} - \frac{\frac{r}{\mathsf{PI}\left(\right)} \cdot -0.06944444444444445}{s}}{s} - \frac{-0.25}{\mathsf{PI}\left(\right) \cdot r}}{s}
\end{array}
Initial program 99.2%
Taylor expanded in s around -inf
Applied rewrites8.7%
Taylor expanded in s around inf
Applied rewrites9.1%
(FPCore (s r) :precision binary32 (/ 0.25 (* (* (PI) s) r)))
\begin{array}{l}
\\
\frac{0.25}{\left(\mathsf{PI}\left(\right) \cdot s\right) \cdot r}
\end{array}
Initial program 99.2%
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.f328.6
Applied rewrites8.6%
Applied rewrites8.6%
Applied rewrites8.6%
(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 99.2%
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.f328.6
Applied rewrites8.6%
Applied rewrites8.6%
Applied rewrites8.6%
herbie shell --seed 2024285
(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))))