
(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 14 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 0.75 (/ (exp (/ (/ (- r) 3.0) s)) (* (* (* 6.0 (PI)) s) r)) (* 0.25 (/ (exp (/ (- r) s)) (* (* (* (PI) 2.0) s) r)))))
\begin{array}{l}
\\
\mathsf{fma}\left(0.75, \frac{e^{\frac{\frac{-r}{3}}{s}}}{\left(\left(6 \cdot \mathsf{PI}\left(\right)\right) \cdot s\right) \cdot r}, 0.25 \cdot \frac{e^{\frac{-r}{s}}}{\left(\left(\mathsf{PI}\left(\right) \cdot 2\right) \cdot s\right) \cdot r}\right)
\end{array}
Initial program 99.6%
+-commutativeN/A
associate-/l*N/A
lower-fma.f32N/A
Applied rewrites99.7%
(FPCore (s r) :precision binary32 (fma 0.75 (/ (exp (* -0.3333333333333333 (/ r s))) (* (* (* 6.0 (PI)) s) r)) (* (/ (exp (/ (- r) s)) (* (* (PI) s) r)) 0.125)))
\begin{array}{l}
\\
\mathsf{fma}\left(0.75, \frac{e^{-0.3333333333333333 \cdot \frac{r}{s}}}{\left(\left(6 \cdot \mathsf{PI}\left(\right)\right) \cdot s\right) \cdot r}, \frac{e^{\frac{-r}{s}}}{\left(\mathsf{PI}\left(\right) \cdot s\right) \cdot r} \cdot 0.125\right)
\end{array}
Initial program 99.6%
+-commutativeN/A
associate-/l*N/A
lower-fma.f32N/A
Applied rewrites99.7%
Taylor expanded in s around 0
associate-/r*N/A
lower-*.f32N/A
lower-/.f3299.7
Applied rewrites99.7%
Taylor expanded in s around 0
associate-*r/N/A
*-commutativeN/A
*-commutativeN/A
lower-*.f32N/A
Applied rewrites99.7%
(FPCore (s r) :precision binary32 (fma 0.75 (/ (exp (* -0.3333333333333333 (/ r s))) (* (* (PI) 6.0) (* s r))) (* (/ (exp (/ (- r) s)) (* (* (PI) s) r)) 0.125)))
\begin{array}{l}
\\
\mathsf{fma}\left(0.75, \frac{e^{-0.3333333333333333 \cdot \frac{r}{s}}}{\left(\mathsf{PI}\left(\right) \cdot 6\right) \cdot \left(s \cdot r\right)}, \frac{e^{\frac{-r}{s}}}{\left(\mathsf{PI}\left(\right) \cdot s\right) \cdot r} \cdot 0.125\right)
\end{array}
Initial program 99.6%
+-commutativeN/A
associate-/l*N/A
lower-fma.f32N/A
Applied rewrites99.7%
Taylor expanded in s around 0
associate-/r*N/A
lower-*.f32N/A
lower-/.f3299.7
Applied rewrites99.7%
Taylor expanded in s around 0
associate-*r/N/A
*-commutativeN/A
*-commutativeN/A
lower-*.f32N/A
Applied rewrites99.7%
associate-*l*N/A
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-PI.f32N/A
*-commutativeN/A
lower-*.f3299.6
Applied rewrites99.6%
(FPCore (s r)
:precision binary32
(fma
0.75
(/
(fma
(- (* (/ r (* s s)) 0.05555555555555555) (/ 0.3333333333333333 s))
r
1.0)
(* (* (* 6.0 (PI)) s) r))
(* (/ (exp (/ (- r) s)) (* (* (PI) s) r)) 0.125)))\begin{array}{l}
\\
\mathsf{fma}\left(0.75, \frac{\mathsf{fma}\left(\frac{r}{s \cdot s} \cdot 0.05555555555555555 - \frac{0.3333333333333333}{s}, r, 1\right)}{\left(\left(6 \cdot \mathsf{PI}\left(\right)\right) \cdot s\right) \cdot r}, \frac{e^{\frac{-r}{s}}}{\left(\mathsf{PI}\left(\right) \cdot s\right) \cdot r} \cdot 0.125\right)
\end{array}
Initial program 99.6%
+-commutativeN/A
associate-/l*N/A
lower-fma.f32N/A
Applied rewrites99.7%
Taylor expanded in s around 0
associate-/r*N/A
lower-*.f32N/A
lower-/.f3299.7
Applied rewrites99.7%
Taylor expanded in s around 0
associate-*r/N/A
*-commutativeN/A
*-commutativeN/A
lower-*.f32N/A
Applied rewrites99.7%
Taylor expanded in r around 0
+-commutativeN/A
*-commutativeN/A
lower-fma.f32N/A
lower--.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-/.f32N/A
pow2N/A
lower-*.f32N/A
associate-*r/N/A
metadata-evalN/A
lower-/.f3210.9
Applied rewrites10.9%
(FPCore (s r)
:precision binary32
(let* ((t_0 (/ r (* (* s s) (PI)))))
(/
(-
(fma t_0 0.006944444444444444 (fma 0.0625 t_0 (/ 0.25 (* (PI) r))))
(/ 0.16666666666666666 (* (PI) s)))
s)))\begin{array}{l}
\\
\begin{array}{l}
t_0 := \frac{r}{\left(s \cdot s\right) \cdot \mathsf{PI}\left(\right)}\\
\frac{\mathsf{fma}\left(t\_0, 0.006944444444444444, \mathsf{fma}\left(0.0625, t\_0, \frac{0.25}{\mathsf{PI}\left(\right) \cdot r}\right)\right) - \frac{0.16666666666666666}{\mathsf{PI}\left(\right) \cdot s}}{s}
\end{array}
\end{array}
Initial program 99.6%
Taylor expanded in s around inf
lower-/.f32N/A
Applied rewrites10.5%
(FPCore (s r)
:precision binary32
(/
(/
(fma
(-
(* 0.06944444444444445 (/ r (* (* s s) (PI))))
(/ (/ 0.16666666666666666 (PI)) s))
r
(/ 0.25 (PI)))
r)
s))\begin{array}{l}
\\
\frac{\frac{\mathsf{fma}\left(0.06944444444444445 \cdot \frac{r}{\left(s \cdot s\right) \cdot \mathsf{PI}\left(\right)} - \frac{\frac{0.16666666666666666}{\mathsf{PI}\left(\right)}}{s}, r, \frac{0.25}{\mathsf{PI}\left(\right)}\right)}{r}}{s}
\end{array}
Initial program 99.6%
+-commutativeN/A
associate-/l*N/A
lower-fma.f32N/A
Applied rewrites99.7%
Taylor expanded in s around 0
associate-/r*N/A
lower-*.f32N/A
lower-/.f3299.7
Applied rewrites99.7%
Taylor expanded in s around inf
Applied rewrites10.5%
Taylor expanded in r around 0
lower-/.f32N/A
Applied rewrites10.5%
Final simplification10.5%
(FPCore (s r)
:precision binary32
(/
(-
(/
(+ (/ (* (/ r (PI)) -0.06944444444444445) s) (/ 0.16666666666666666 (PI)))
s)
(/ 0.25 (* (PI) r)))
(- s)))\begin{array}{l}
\\
\frac{\frac{\frac{\frac{r}{\mathsf{PI}\left(\right)} \cdot -0.06944444444444445}{s} + \frac{0.16666666666666666}{\mathsf{PI}\left(\right)}}{s} - \frac{0.25}{\mathsf{PI}\left(\right) \cdot r}}{-s}
\end{array}
Initial program 99.6%
Taylor expanded in s around -inf
mul-1-negN/A
lower-neg.f32N/A
lower-/.f32N/A
Applied rewrites10.5%
Final simplification10.5%
(FPCore (s r) :precision binary32 (/ (- (/ (fma (/ (* r r) (* (* s s) (PI))) 0.06944444444444445 (/ 0.25 (PI))) r) (/ 0.16666666666666666 (* (PI) s))) s))
\begin{array}{l}
\\
\frac{\frac{\mathsf{fma}\left(\frac{r \cdot r}{\left(s \cdot s\right) \cdot \mathsf{PI}\left(\right)}, 0.06944444444444445, \frac{0.25}{\mathsf{PI}\left(\right)}\right)}{r} - \frac{0.16666666666666666}{\mathsf{PI}\left(\right) \cdot s}}{s}
\end{array}
Initial program 99.6%
+-commutativeN/A
associate-/l*N/A
lower-fma.f32N/A
Applied rewrites99.7%
Taylor expanded in s around 0
associate-/r*N/A
lower-*.f32N/A
lower-/.f3299.7
Applied rewrites99.7%
Taylor expanded in s around inf
Applied rewrites10.5%
Taylor expanded in r around 0
lower-/.f32N/A
Applied rewrites10.5%
Final simplification10.5%
(FPCore (s r) :precision binary32 (/ (fma -0.16666666666666666 (/ r (* (* s s) (PI))) (/ 0.25 (* (PI) s))) r))
\begin{array}{l}
\\
\frac{\mathsf{fma}\left(-0.16666666666666666, \frac{r}{\left(s \cdot s\right) \cdot \mathsf{PI}\left(\right)}, \frac{0.25}{\mathsf{PI}\left(\right) \cdot s}\right)}{r}
\end{array}
Initial program 99.6%
Taylor expanded in r around 0
lower-/.f32N/A
Applied rewrites9.7%
(FPCore (s r) :precision binary32 (/ (- (/ 0.25 (* (PI) r)) (/ 0.16666666666666666 (* (PI) s))) s))
\begin{array}{l}
\\
\frac{\frac{0.25}{\mathsf{PI}\left(\right) \cdot r} - \frac{0.16666666666666666}{\mathsf{PI}\left(\right) \cdot s}}{s}
\end{array}
Initial program 99.6%
Taylor expanded in s around inf
lower-/.f32N/A
Applied rewrites9.7%
(FPCore (s r) :precision binary32 (/ (/ (/ 0.25 r) (PI)) s))
\begin{array}{l}
\\
\frac{\frac{\frac{0.25}{r}}{\mathsf{PI}\left(\right)}}{s}
\end{array}
Initial program 99.6%
Taylor expanded in s around inf
lower-/.f32N/A
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-PI.f329.4
Applied rewrites9.4%
*-commutativeN/A
*-commutativeN/A
associate-/r*N/A
lower-/.f32N/A
lower-/.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-PI.f329.4
Applied rewrites9.4%
Applied rewrites9.4%
Final simplification9.4%
(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 99.6%
Taylor expanded in s around inf
lower-/.f32N/A
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-PI.f329.4
Applied rewrites9.4%
*-commutativeN/A
*-commutativeN/A
associate-/r*N/A
lower-/.f32N/A
lower-/.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-PI.f329.4
Applied rewrites9.4%
(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 99.6%
Taylor expanded in s around inf
lower-/.f32N/A
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-PI.f329.4
Applied rewrites9.4%
(FPCore (s r) :precision binary32 (/ 0.25 (* (* r s) (PI))))
\begin{array}{l}
\\
\frac{0.25}{\left(r \cdot s\right) \cdot \mathsf{PI}\left(\right)}
\end{array}
Initial program 99.6%
Taylor expanded in s around inf
lower-/.f32N/A
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-PI.f329.4
Applied rewrites9.4%
*-commutativeN/A
*-commutativeN/A
associate-*r*N/A
lower-*.f32N/A
lower-*.f32N/A
lower-PI.f329.4
Applied rewrites9.4%
herbie shell --seed 2025043
(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))))