
(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 11 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(\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}
\end{array}
Initial program 99.6%
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-eval99.6
Applied rewrites99.6%
Final simplification99.6%
(FPCore (s r)
:precision binary32
(if (<=
(+
(/ (* (exp (/ (- r) (* 3.0 s))) 0.75) (* (* (* 6.0 (PI)) s) r))
(/ (* (exp (/ (- r) s)) 0.25) (* (* (* (PI) 2.0) s) r)))
5.000000097707407e-25)
(/
(fma
(/
(/
(fma (/ 0.06944444444444445 s) (/ r (PI)) (/ -0.16666666666666666 (PI)))
s)
s)
r
(fma -1.0 (/ -0.25 (* (PI) s)) 0.0))
r)
(*
(-
(/ 0.06944444444444445 (* (pow s 3.0) (PI)))
(/ (/ (- (/ (/ 0.16666666666666666 (PI)) s) (/ 0.25 (* (PI) r))) s) r))
r)))\begin{array}{l}
\\
\begin{array}{l}
\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 5.000000097707407 \cdot 10^{-25}:\\
\;\;\;\;\frac{\mathsf{fma}\left(\frac{\frac{\mathsf{fma}\left(\frac{0.06944444444444445}{s}, \frac{r}{\mathsf{PI}\left(\right)}, \frac{-0.16666666666666666}{\mathsf{PI}\left(\right)}\right)}{s}}{s}, r, \mathsf{fma}\left(-1, \frac{-0.25}{\mathsf{PI}\left(\right) \cdot s}, 0\right)\right)}{r}\\
\mathbf{else}:\\
\;\;\;\;\left(\frac{0.06944444444444445}{{s}^{3} \cdot \mathsf{PI}\left(\right)} - \frac{\frac{\frac{\frac{0.16666666666666666}{\mathsf{PI}\left(\right)}}{s} - \frac{0.25}{\mathsf{PI}\left(\right) \cdot r}}{s}}{r}\right) \cdot r\\
\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))) < 5.0000001e-25Initial program 99.8%
Taylor expanded in r around 0
Applied rewrites4.7%
Applied rewrites4.7%
Applied rewrites4.7%
Applied rewrites99.0%
if 5.0000001e-25 < (+.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 r around 0
Applied rewrites38.6%
Taylor expanded in r around inf
Applied rewrites56.7%
Final simplification91.1%
(FPCore (s r)
:precision binary32
(let* ((t_0 (/ r (PI))) (t_1 (/ -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)))
9.999999747378752e-5)
(/
(fma
(/ (/ (fma (/ 0.06944444444444445 s) t_0 t_1) s) s)
r
(fma -1.0 (/ -0.25 (* (PI) s)) 0.0))
r)
(/
(-
(/
(-
t_1
(/
(*
(-
(/ -0.06944444444444445 (PI))
(* (/ -0.021604938271604937 s) t_0))
r)
s))
s)
(/ -0.25 (* (PI) r)))
s))))\begin{array}{l}
\\
\begin{array}{l}
t_0 := \frac{r}{\mathsf{PI}\left(\right)}\\
t_1 := \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 9.999999747378752 \cdot 10^{-5}:\\
\;\;\;\;\frac{\mathsf{fma}\left(\frac{\frac{\mathsf{fma}\left(\frac{0.06944444444444445}{s}, t\_0, t\_1\right)}{s}}{s}, r, \mathsf{fma}\left(-1, \frac{-0.25}{\mathsf{PI}\left(\right) \cdot s}, 0\right)\right)}{r}\\
\mathbf{else}:\\
\;\;\;\;\frac{\frac{t\_1 - \frac{\left(\frac{-0.06944444444444445}{\mathsf{PI}\left(\right)} - \frac{-0.021604938271604937}{s} \cdot t\_0\right) \cdot r}{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))) < 9.99999975e-5Initial program 99.8%
Taylor expanded in r around 0
Applied rewrites5.0%
Applied rewrites5.0%
Applied rewrites5.0%
Applied rewrites96.7%
if 9.99999975e-5 < (+.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 98.1%
Taylor expanded in s around -inf
Applied rewrites70.6%
Final simplification91.0%
(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)))
9.999999747378752e-5)
(/
(fma
(/ (/ (fma (/ 0.06944444444444445 s) (/ r (PI)) t_0) s) s)
r
(fma -1.0 (/ -0.25 (* (PI) s)) 0.0))
r)
(/
(+
(/ (fma (/ 0.06944444444444445 (PI)) (/ r s) t_0) 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 9.999999747378752 \cdot 10^{-5}:\\
\;\;\;\;\frac{\mathsf{fma}\left(\frac{\frac{\mathsf{fma}\left(\frac{0.06944444444444445}{s}, \frac{r}{\mathsf{PI}\left(\right)}, t\_0\right)}{s}}{s}, r, \mathsf{fma}\left(-1, \frac{-0.25}{\mathsf{PI}\left(\right) \cdot s}, 0\right)\right)}{r}\\
\mathbf{else}:\\
\;\;\;\;\frac{\frac{\mathsf{fma}\left(\frac{0.06944444444444445}{\mathsf{PI}\left(\right)}, \frac{r}{s}, t\_0\right)}{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))) < 9.99999975e-5Initial program 99.8%
Taylor expanded in r around 0
Applied rewrites5.0%
Applied rewrites5.0%
Applied rewrites5.0%
Applied rewrites96.7%
if 9.99999975e-5 < (+.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 98.1%
Taylor expanded in r around 0
Applied rewrites45.0%
Applied rewrites45.0%
Taylor expanded in s around inf
Applied rewrites58.3%
Final simplification87.7%
(FPCore (s r) :precision binary32 (+ (/ (* (exp (/ r (* -3.0 s))) 0.75) (* (* (* 6.0 (PI)) r) s)) (/ (* (exp (/ (- r) s)) 0.25) (* (* (* (PI) 2.0) r) s))))
\begin{array}{l}
\\
\frac{e^{\frac{r}{-3 \cdot s}} \cdot 0.75}{\left(\left(6 \cdot \mathsf{PI}\left(\right)\right) \cdot r\right) \cdot s} + \frac{e^{\frac{-r}{s}} \cdot 0.25}{\left(\left(\mathsf{PI}\left(\right) \cdot 2\right) \cdot r\right) \cdot s}
\end{array}
Initial program 99.6%
lift-*.f32N/A
*-commutativeN/A
lift-*.f32N/A
associate-*r*N/A
lower-*.f32N/A
lower-*.f3299.6
Applied rewrites99.6%
lift-*.f32N/A
*-commutativeN/A
lift-*.f32N/A
associate-*r*N/A
lower-*.f32N/A
lower-*.f3299.6
lift-*.f32N/A
*-commutativeN/A
lower-*.f3299.6
Applied rewrites99.6%
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-eval99.6
Applied rewrites99.6%
Final simplification99.6%
(FPCore (s r) :precision binary32 (+ (/ (/ 0.125 (exp (/ r s))) (* (* (PI) s) r)) (/ (* (exp (/ r (* -3.0 s))) 0.75) (* (* (* 6.0 (PI)) r) s))))
\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(\left(6 \cdot \mathsf{PI}\left(\right)\right) \cdot r\right) \cdot s}
\end{array}
Initial program 99.6%
lift-*.f32N/A
*-commutativeN/A
lift-*.f32N/A
associate-*r*N/A
lower-*.f32N/A
lower-*.f3299.6
Applied rewrites99.6%
lift-*.f32N/A
*-commutativeN/A
lift-*.f32N/A
associate-*r*N/A
lower-*.f32N/A
lower-*.f3299.6
lift-*.f32N/A
*-commutativeN/A
lower-*.f3299.6
Applied rewrites99.6%
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-eval99.6
Applied rewrites99.6%
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.f3299.6
Applied rewrites99.6%
Final simplification99.6%
(FPCore (s r) :precision binary32 (let* ((t_0 (sqrt (PI)))) (/ (/ 0.25 (* (* t_0 s) t_0)) r)))
\begin{array}{l}
\\
\begin{array}{l}
t_0 := \sqrt{\mathsf{PI}\left(\right)}\\
\frac{\frac{0.25}{\left(t\_0 \cdot s\right) \cdot t\_0}}{r}
\end{array}
\end{array}
Initial program 99.6%
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.f328.4
Applied rewrites8.4%
Applied rewrites8.4%
Final simplification8.4%
(FPCore (s r) :precision binary32 (/ (/ 1.0 (/ s (/ 0.25 (PI)))) r))
\begin{array}{l}
\\
\frac{\frac{1}{\frac{s}{\frac{0.25}{\mathsf{PI}\left(\right)}}}}{r}
\end{array}
Initial program 99.6%
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.f328.4
Applied rewrites8.4%
Applied rewrites8.4%
(FPCore (s r) :precision binary32 (/ (/ 0.25 (* (PI) s)) r))
\begin{array}{l}
\\
\frac{\frac{0.25}{\mathsf{PI}\left(\right) \cdot s}}{r}
\end{array}
Initial program 99.6%
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.f328.4
Applied rewrites8.4%
(FPCore (s r) :precision binary32 (/ 0.25 (* (* (PI) r) s)))
\begin{array}{l}
\\
\frac{0.25}{\left(\mathsf{PI}\left(\right) \cdot r\right) \cdot s}
\end{array}
Initial program 99.6%
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.f328.4
Applied rewrites8.4%
Applied rewrites8.3%
Applied rewrites8.3%
(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 99.6%
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.f328.4
Applied rewrites8.4%
Applied rewrites8.3%
herbie shell --seed 2024332
(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))))