
(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 16 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 (fma 0.125 (/ (exp (/ (- r) s)) (* (PI) (* s r))) (* 0.125 (/ (exp (/ (/ r -3.0) s)) (* (* (PI) s) r)))))
\begin{array}{l}
\\
\mathsf{fma}\left(0.125, \frac{e^{\frac{-r}{s}}}{\mathsf{PI}\left(\right) \cdot \left(s \cdot r\right)}, 0.125 \cdot \frac{e^{\frac{\frac{r}{-3}}{s}}}{\left(\mathsf{PI}\left(\right) \cdot s\right) \cdot r}\right)
\end{array}
Initial program 99.5%
lift-+.f32N/A
lift-/.f32N/A
lift-*.f32N/A
lift-*.f32N/A
lift-*.f32N/A
associate-*l*N/A
lift-*.f32N/A
associate-*l*N/A
times-fracN/A
lower-fma.f32N/A
Applied rewrites99.6%
(FPCore (s r)
:precision binary32
(let* ((t_0 (exp (/ (- r) s)))
(t_1 (/ (* 0.25 t_0) (* (* (* 2.0 (PI)) s) r))))
(if (<=
(+ t_1 (/ (* 0.75 (exp (/ (- r) (* 3.0 s)))) (* (* (* 6.0 (PI)) s) r)))
0.0020000000949949026)
(* (/ (+ t_0 (exp (/ (/ r -3.0) s))) r) 0.125)
(+
t_1
(/
(-
(/
(+
(/
(/
(fma
(* r (/ r s))
0.0007716049382716049
(* -0.006944444444444444 r))
(PI))
s)
(/ 0.041666666666666664 (PI)))
s)
(/ 0.125 (* (PI) r)))
(- s))))))\begin{array}{l}
\\
\begin{array}{l}
t_0 := e^{\frac{-r}{s}}\\
t_1 := \frac{0.25 \cdot t\_0}{\left(\left(2 \cdot \mathsf{PI}\left(\right)\right) \cdot s\right) \cdot r}\\
\mathbf{if}\;t\_1 + \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 0.0020000000949949026:\\
\;\;\;\;\frac{t\_0 + e^{\frac{\frac{r}{-3}}{s}}}{r} \cdot 0.125\\
\mathbf{else}:\\
\;\;\;\;t\_1 + \frac{\frac{\frac{\frac{\mathsf{fma}\left(r \cdot \frac{r}{s}, 0.0007716049382716049, -0.006944444444444444 \cdot r\right)}{\mathsf{PI}\left(\right)}}{s} + \frac{0.041666666666666664}{\mathsf{PI}\left(\right)}}{s} - \frac{0.125}{\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))) < 0.00200000009Initial program 99.7%
lift-+.f32N/A
lift-/.f32N/A
lift-*.f32N/A
lift-*.f32N/A
lift-*.f32N/A
associate-*l*N/A
lift-*.f32N/A
associate-*l*N/A
times-fracN/A
lower-fma.f32N/A
Applied rewrites99.7%
lift-fma.f32N/A
lift-*.f32N/A
distribute-lft-outN/A
*-commutativeN/A
lower-*.f32N/A
Applied rewrites99.7%
lift-/.f32N/A
lift-*.f32N/A
lift-*.f32N/A
*-commutativeN/A
associate-*r*N/A
*-commutativeN/A
lift-*.f32N/A
associate-/r*N/A
lower-/.f32N/A
lower-/.f3299.7
lift-+.f32N/A
+-commutativeN/A
lower-+.f3299.7
Applied rewrites99.7%
lift-*.f32N/A
lift-/.f32N/A
associate-*l/N/A
associate-/l*N/A
metadata-evalN/A
associate-/r*N/A
lift-*.f32N/A
associate-*l*N/A
lift-*.f32N/A
lift-*.f32N/A
lower-*.f32N/A
Applied rewrites99.3%
if 0.00200000009 < (+.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 97.7%
Taylor expanded in s around -inf
mul-1-negN/A
distribute-neg-frac2N/A
lower-/.f32N/A
Applied rewrites70.0%
Final simplification95.9%
(FPCore (s r)
:precision binary32
(let* ((t_0 (exp (/ (- r) s)))
(t_1 (/ (* 0.25 t_0) (* (* (* 2.0 (PI)) s) r))))
(if (<=
(+ t_1 (/ (* 0.75 (exp (/ (- r) (* 3.0 s)))) (* (* (* 6.0 (PI)) s) r)))
0.0020000000949949026)
(* (/ (+ t_0 (exp (/ (/ r -3.0) s))) r) 0.125)
(+
t_1
(/
(+
(/ 0.125 (* (PI) r))
(/
(/ (fma (/ r s) 0.006944444444444444 -0.041666666666666664) (PI))
s))
s)))))\begin{array}{l}
\\
\begin{array}{l}
t_0 := e^{\frac{-r}{s}}\\
t_1 := \frac{0.25 \cdot t\_0}{\left(\left(2 \cdot \mathsf{PI}\left(\right)\right) \cdot s\right) \cdot r}\\
\mathbf{if}\;t\_1 + \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 0.0020000000949949026:\\
\;\;\;\;\frac{t\_0 + e^{\frac{\frac{r}{-3}}{s}}}{r} \cdot 0.125\\
\mathbf{else}:\\
\;\;\;\;t\_1 + \frac{\frac{0.125}{\mathsf{PI}\left(\right) \cdot r} + \frac{\frac{\mathsf{fma}\left(\frac{r}{s}, 0.006944444444444444, -0.041666666666666664\right)}{\mathsf{PI}\left(\right)}}{s}}{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))) < 0.00200000009Initial program 99.7%
lift-+.f32N/A
lift-/.f32N/A
lift-*.f32N/A
lift-*.f32N/A
lift-*.f32N/A
associate-*l*N/A
lift-*.f32N/A
associate-*l*N/A
times-fracN/A
lower-fma.f32N/A
Applied rewrites99.7%
lift-fma.f32N/A
lift-*.f32N/A
distribute-lft-outN/A
*-commutativeN/A
lower-*.f32N/A
Applied rewrites99.7%
lift-/.f32N/A
lift-*.f32N/A
lift-*.f32N/A
*-commutativeN/A
associate-*r*N/A
*-commutativeN/A
lift-*.f32N/A
associate-/r*N/A
lower-/.f32N/A
lower-/.f3299.7
lift-+.f32N/A
+-commutativeN/A
lower-+.f3299.7
Applied rewrites99.7%
lift-*.f32N/A
lift-/.f32N/A
associate-*l/N/A
associate-/l*N/A
metadata-evalN/A
associate-/r*N/A
lift-*.f32N/A
associate-*l*N/A
lift-*.f32N/A
lift-*.f32N/A
lower-*.f32N/A
Applied rewrites99.3%
if 0.00200000009 < (+.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 97.7%
Taylor expanded in s around inf
lower-/.f32N/A
Applied rewrites67.2%
(FPCore (s r) :precision binary32 (* (/ (+ (exp (/ (- r) s)) (exp (/ (/ r -3.0) s))) (* (* s r) (PI))) 0.125))
\begin{array}{l}
\\
\frac{e^{\frac{-r}{s}} + e^{\frac{\frac{r}{-3}}{s}}}{\left(s \cdot r\right) \cdot \mathsf{PI}\left(\right)} \cdot 0.125
\end{array}
Initial program 99.5%
lift-+.f32N/A
lift-/.f32N/A
lift-*.f32N/A
lift-*.f32N/A
lift-*.f32N/A
associate-*l*N/A
lift-*.f32N/A
associate-*l*N/A
times-fracN/A
lower-fma.f32N/A
Applied rewrites99.6%
lift-fma.f32N/A
lift-*.f32N/A
distribute-lft-outN/A
*-commutativeN/A
lower-*.f32N/A
Applied rewrites99.6%
(FPCore (s r) :precision binary32 (* (/ (+ (exp (/ (- r) s)) (exp (/ r (* -3.0 s)))) (* (* s r) (PI))) 0.125))
\begin{array}{l}
\\
\frac{e^{\frac{-r}{s}} + e^{\frac{r}{-3 \cdot s}}}{\left(s \cdot r\right) \cdot \mathsf{PI}\left(\right)} \cdot 0.125
\end{array}
Initial program 99.5%
lift-+.f32N/A
lift-/.f32N/A
lift-*.f32N/A
lift-*.f32N/A
lift-*.f32N/A
associate-*l*N/A
lift-*.f32N/A
associate-*l*N/A
times-fracN/A
lower-fma.f32N/A
Applied rewrites99.6%
lift-fma.f32N/A
lift-*.f32N/A
distribute-lft-outN/A
*-commutativeN/A
lower-*.f32N/A
Applied rewrites99.6%
lift-/.f32N/A
lift-/.f32N/A
associate-/l/N/A
metadata-evalN/A
distribute-lft-neg-inN/A
lower-/.f32N/A
distribute-lft-neg-inN/A
metadata-evalN/A
lower-*.f3299.5
Applied rewrites99.5%
(FPCore (s r) :precision binary32 (* (/ (+ (exp (/ (- r) s)) (exp (* -0.3333333333333333 (/ r s)))) (* (* s r) (PI))) 0.125))
\begin{array}{l}
\\
\frac{e^{\frac{-r}{s}} + e^{-0.3333333333333333 \cdot \frac{r}{s}}}{\left(s \cdot r\right) \cdot \mathsf{PI}\left(\right)} \cdot 0.125
\end{array}
Initial program 99.5%
lift-+.f32N/A
lift-/.f32N/A
lift-*.f32N/A
lift-*.f32N/A
lift-*.f32N/A
associate-*l*N/A
lift-*.f32N/A
associate-*l*N/A
times-fracN/A
lower-fma.f32N/A
Applied rewrites99.6%
lift-fma.f32N/A
lift-*.f32N/A
distribute-lft-outN/A
*-commutativeN/A
lower-*.f32N/A
Applied rewrites99.6%
Taylor expanded in s around 0
lower-*.f32N/A
lower-/.f3299.5
Applied rewrites99.5%
(FPCore (s r)
:precision binary32
(+
(/ (* 0.25 (exp (/ (- r) s))) (* (* (* 2.0 (PI)) s) r))
(/
(+
(/ 0.125 (* (PI) r))
(/ (/ (fma (/ r s) 0.006944444444444444 -0.041666666666666664) (PI)) s))
s)))\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{\frac{0.125}{\mathsf{PI}\left(\right) \cdot r} + \frac{\frac{\mathsf{fma}\left(\frac{r}{s}, 0.006944444444444444, -0.041666666666666664\right)}{\mathsf{PI}\left(\right)}}{s}}{s}
\end{array}
Initial program 99.5%
Taylor expanded in s around inf
lower-/.f32N/A
Applied rewrites11.0%
(FPCore (s r)
:precision binary32
(/
(+
(/
(fma 0.06944444444444445 (/ (/ r s) (PI)) (/ -0.16666666666666666 (PI)))
s)
(/ 0.25 (* (PI) r)))
s))\begin{array}{l}
\\
\frac{\frac{\mathsf{fma}\left(0.06944444444444445, \frac{\frac{r}{s}}{\mathsf{PI}\left(\right)}, \frac{-0.16666666666666666}{\mathsf{PI}\left(\right)}\right)}{s} + \frac{0.25}{\mathsf{PI}\left(\right) \cdot r}}{s}
\end{array}
Initial program 99.5%
Applied rewrites99.5%
Taylor expanded in s around -inf
mul-1-negN/A
distribute-neg-frac2N/A
lower-/.f32N/A
Applied rewrites10.2%
Final simplification10.2%
(FPCore (s r)
:precision binary32
(let* ((t_0 (* (PI) s)))
(/
(-
(fma (/ r s) (/ 0.06944444444444445 t_0) (/ 0.25 (* (PI) r)))
(/ 0.16666666666666666 t_0))
s)))\begin{array}{l}
\\
\begin{array}{l}
t_0 := \mathsf{PI}\left(\right) \cdot s\\
\frac{\mathsf{fma}\left(\frac{r}{s}, \frac{0.06944444444444445}{t\_0}, \frac{0.25}{\mathsf{PI}\left(\right) \cdot r}\right) - \frac{0.16666666666666666}{t\_0}}{s}
\end{array}
\end{array}
Initial program 99.5%
lift-+.f32N/A
lift-/.f32N/A
lift-*.f32N/A
lift-*.f32N/A
lift-*.f32N/A
associate-*l*N/A
lift-*.f32N/A
associate-*l*N/A
times-fracN/A
lower-fma.f32N/A
Applied rewrites99.6%
Taylor expanded in s around inf
lower-/.f32N/A
Applied rewrites10.2%
Applied rewrites10.2%
Final simplification10.2%
(FPCore (s r) :precision binary32 (/ (- (fma 0.06944444444444445 (/ r (* (* s s) (PI))) (/ 0.25 (* (PI) r))) (/ 0.16666666666666666 (* (PI) s))) s))
\begin{array}{l}
\\
\frac{\mathsf{fma}\left(0.06944444444444445, \frac{r}{\left(s \cdot s\right) \cdot \mathsf{PI}\left(\right)}, \frac{0.25}{\mathsf{PI}\left(\right) \cdot r}\right) - \frac{0.16666666666666666}{\mathsf{PI}\left(\right) \cdot s}}{s}
\end{array}
Initial program 99.5%
lift-+.f32N/A
lift-/.f32N/A
lift-*.f32N/A
lift-*.f32N/A
lift-*.f32N/A
associate-*l*N/A
lift-*.f32N/A
associate-*l*N/A
times-fracN/A
lower-fma.f32N/A
Applied rewrites99.6%
Taylor expanded in s around inf
lower-/.f32N/A
Applied rewrites10.2%
Final simplification10.2%
(FPCore (s r)
:precision binary32
(*
(/
(-
2.0
(/ (fma 1.3333333333333333 r (/ (* (* r r) 0.5555555555555556) (- s))) s))
(* (* s r) (PI)))
0.125))\begin{array}{l}
\\
\frac{2 - \frac{\mathsf{fma}\left(1.3333333333333333, r, \frac{\left(r \cdot r\right) \cdot 0.5555555555555556}{-s}\right)}{s}}{\left(s \cdot r\right) \cdot \mathsf{PI}\left(\right)} \cdot 0.125
\end{array}
Initial program 99.5%
lift-+.f32N/A
lift-/.f32N/A
lift-*.f32N/A
lift-*.f32N/A
lift-*.f32N/A
associate-*l*N/A
lift-*.f32N/A
associate-*l*N/A
times-fracN/A
lower-fma.f32N/A
Applied rewrites99.6%
lift-fma.f32N/A
lift-*.f32N/A
distribute-lft-outN/A
*-commutativeN/A
lower-*.f32N/A
Applied rewrites99.6%
Taylor expanded in s around -inf
fp-cancel-sign-sub-invN/A
metadata-evalN/A
*-lft-identityN/A
lower--.f32N/A
lower-/.f32N/A
Applied rewrites10.2%
(FPCore (s r)
:precision binary32
(*
(/
(fma
(/ (- 1.3333333333333333 (/ (* r 0.5555555555555556) s)) s)
-1.0
(/ 2.0 r))
(* (PI) s))
0.125))\begin{array}{l}
\\
\frac{\mathsf{fma}\left(\frac{1.3333333333333333 - \frac{r \cdot 0.5555555555555556}{s}}{s}, -1, \frac{2}{r}\right)}{\mathsf{PI}\left(\right) \cdot s} \cdot 0.125
\end{array}
Initial program 99.5%
lift-+.f32N/A
lift-/.f32N/A
lift-*.f32N/A
lift-*.f32N/A
lift-*.f32N/A
associate-*l*N/A
lift-*.f32N/A
associate-*l*N/A
times-fracN/A
lower-fma.f32N/A
Applied rewrites99.6%
lift-fma.f32N/A
lift-*.f32N/A
distribute-lft-outN/A
*-commutativeN/A
lower-*.f32N/A
Applied rewrites99.6%
lift-/.f32N/A
lift-*.f32N/A
lift-*.f32N/A
*-commutativeN/A
associate-*r*N/A
*-commutativeN/A
lift-*.f32N/A
associate-/r*N/A
lower-/.f32N/A
lower-/.f3299.5
lift-+.f32N/A
+-commutativeN/A
lower-+.f3299.5
Applied rewrites99.5%
Taylor expanded in s around -inf
*-commutativeN/A
lower-fma.f32N/A
lower-/.f32N/A
fp-cancel-sign-sub-invN/A
metadata-evalN/A
*-lft-identityN/A
lower--.f32N/A
lower-/.f32N/A
distribute-rgt-outN/A
metadata-evalN/A
lower-*.f32N/A
associate-*r/N/A
metadata-evalN/A
lower-/.f3210.1
Applied rewrites10.1%
(FPCore (s r) :precision binary32 (let* ((t_0 (sqrt (PI)))) (/ 0.25 (* (* r t_0) (* t_0 s)))))
\begin{array}{l}
\\
\begin{array}{l}
t_0 := \sqrt{\mathsf{PI}\left(\right)}\\
\frac{0.25}{\left(r \cdot t\_0\right) \cdot \left(t\_0 \cdot s\right)}
\end{array}
\end{array}
Initial program 99.5%
Taylor expanded in s around inf
*-commutativeN/A
associate-/r*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.f329.2
Applied rewrites9.2%
Applied rewrites9.2%
Applied rewrites9.2%
Applied rewrites9.2%
(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 99.5%
Taylor expanded in s around inf
*-commutativeN/A
associate-/r*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.f329.2
Applied rewrites9.2%
Applied rewrites9.2%
Applied rewrites9.2%
(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 99.5%
Taylor expanded in s around inf
*-commutativeN/A
associate-/r*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.f329.2
Applied rewrites9.2%
Applied rewrites9.2%
Applied rewrites9.2%
(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 99.5%
Taylor expanded in s around inf
*-commutativeN/A
associate-/r*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.f329.2
Applied rewrites9.2%
Applied rewrites9.2%
herbie shell --seed 2025009
(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))))