
(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 20 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
(/ (exp (/ r (* s -3.0))) (PI))
0.125
(* (/ (exp (/ (- r) s)) (PI)) 0.125))
s)
r))\begin{array}{l}
\\
\frac{\frac{\mathsf{fma}\left(\frac{e^{\frac{r}{s \cdot -3}}}{\mathsf{PI}\left(\right)}, 0.125, \frac{e^{\frac{-r}{s}}}{\mathsf{PI}\left(\right)} \cdot 0.125\right)}{s}}{r}
\end{array}
Initial program 99.6%
Applied rewrites99.6%
lift-/.f32N/A
lift-/.f32N/A
associate-/l/N/A
metadata-evalN/A
distribute-lft-neg-inN/A
lift-*.f32N/A
lower-/.f32N/A
lift-*.f32N/A
*-commutativeN/A
distribute-rgt-neg-inN/A
metadata-evalN/A
lower-*.f3299.7
Applied rewrites99.7%
(FPCore (s r) :precision binary32 (* (/ 0.125 s) (/ (/ (+ (exp (/ (/ r -3.0) s)) (exp (/ (- r) s))) (PI)) r)))
\begin{array}{l}
\\
\frac{0.125}{s} \cdot \frac{\frac{e^{\frac{\frac{r}{-3}}{s}} + e^{\frac{-r}{s}}}{\mathsf{PI}\left(\right)}}{r}
\end{array}
Initial program 99.6%
Applied rewrites99.6%
lift-/.f32N/A
lift-/.f32N/A
associate-/l/N/A
lift-fma.f32N/A
lift-*.f32N/A
distribute-rgt-outN/A
times-fracN/A
lower-*.f32N/A
lower-/.f32N/A
Applied rewrites99.6%
(FPCore (s r) :precision binary32 (/ (* (/ (+ (exp (/ (/ r -3.0) s)) (exp (/ (- r) s))) (PI)) 0.125) (* s r)))
\begin{array}{l}
\\
\frac{\frac{e^{\frac{\frac{r}{-3}}{s}} + e^{\frac{-r}{s}}}{\mathsf{PI}\left(\right)} \cdot 0.125}{s \cdot r}
\end{array}
Initial program 99.6%
Applied rewrites99.6%
lift-/.f32N/A
lift-/.f32N/A
associate-/l/N/A
lower-/.f32N/A
Applied rewrites99.6%
(FPCore (s r) :precision binary32 (* (/ (+ (exp (/ (- r) s)) (exp (/ (/ r -3.0) s))) (* (PI) r)) (/ 0.125 s)))
\begin{array}{l}
\\
\frac{e^{\frac{-r}{s}} + e^{\frac{\frac{r}{-3}}{s}}}{\mathsf{PI}\left(\right) \cdot r} \cdot \frac{0.125}{s}
\end{array}
Initial program 99.6%
Applied rewrites99.6%
lift-/.f32N/A
lift-/.f32N/A
associate-/l/N/A
lift-fma.f32N/A
lift-*.f32N/A
distribute-rgt-outN/A
times-fracN/A
lower-*.f32N/A
lower-/.f32N/A
Applied rewrites99.6%
lift-*.f32N/A
*-commutativeN/A
lower-*.f3299.6
lift-/.f32N/A
lift-/.f32N/A
associate-/l/N/A
lift-*.f32N/A
lower-/.f3299.6
lift-+.f32N/A
+-commutativeN/A
lower-+.f3299.6
Applied rewrites99.6%
(FPCore (s r) :precision binary32 (/ (* (+ (exp (/ (- r) s)) (exp (/ (/ r -3.0) s))) 0.125) (* (* (PI) r) s)))
\begin{array}{l}
\\
\frac{\left(e^{\frac{-r}{s}} + e^{\frac{\frac{r}{-3}}{s}}\right) \cdot 0.125}{\left(\mathsf{PI}\left(\right) \cdot r\right) \cdot s}
\end{array}
Initial program 99.6%
Applied rewrites99.6%
lift-/.f32N/A
lift-/.f32N/A
associate-/l/N/A
lift-fma.f32N/A
lift-*.f32N/A
distribute-rgt-outN/A
times-fracN/A
lower-*.f32N/A
lower-/.f32N/A
Applied rewrites99.6%
lift-*.f32N/A
*-commutativeN/A
lift-/.f32N/A
lift-/.f32N/A
associate-/l/N/A
lift-*.f32N/A
lift-/.f32N/A
frac-timesN/A
lift-*.f32N/A
lower-/.f32N/A
Applied rewrites99.6%
(FPCore (s r)
:precision binary32
(let* ((t_0 (* (PI) s)))
(fma
(-
(fma (/ r (* s s)) 0.05555555555555555 (/ 1.0 r))
(/ 0.3333333333333333 s))
(/ 0.125 t_0)
(* 0.125 (/ (exp (/ (- r) s)) (* t_0 r))))))\begin{array}{l}
\\
\begin{array}{l}
t_0 := \mathsf{PI}\left(\right) \cdot s\\
\mathsf{fma}\left(\mathsf{fma}\left(\frac{r}{s \cdot s}, 0.05555555555555555, \frac{1}{r}\right) - \frac{0.3333333333333333}{s}, \frac{0.125}{t\_0}, 0.125 \cdot \frac{e^{\frac{-r}{s}}}{t\_0 \cdot r}\right)
\end{array}
\end{array}
Initial program 99.6%
Applied rewrites99.6%
Taylor expanded in s around inf
Applied rewrites11.3%
(FPCore (s r)
:precision binary32
(*
(/ 0.125 s)
(/
(/
(+
(fma
(/ (fma -0.05555555555555555 (/ (* r r) s) (* 0.3333333333333333 r)) s)
-1.0
1.0)
(exp (/ (- r) s)))
(PI))
r)))\begin{array}{l}
\\
\frac{0.125}{s} \cdot \frac{\frac{\mathsf{fma}\left(\frac{\mathsf{fma}\left(-0.05555555555555555, \frac{r \cdot r}{s}, 0.3333333333333333 \cdot r\right)}{s}, -1, 1\right) + e^{\frac{-r}{s}}}{\mathsf{PI}\left(\right)}}{r}
\end{array}
Initial program 99.6%
Applied rewrites99.6%
lift-/.f32N/A
lift-/.f32N/A
associate-/l/N/A
lift-fma.f32N/A
lift-*.f32N/A
distribute-rgt-outN/A
times-fracN/A
lower-*.f32N/A
lower-/.f32N/A
Applied rewrites99.6%
Taylor expanded in s around -inf
Applied rewrites11.3%
(FPCore (s r)
:precision binary32
(*
(/ 0.125 s)
(/
(/
(+
(fma
(- (* (/ r (* s s)) 0.05555555555555555) (/ 0.3333333333333333 s))
r
1.0)
(exp (/ (- r) s)))
(PI))
r)))\begin{array}{l}
\\
\frac{0.125}{s} \cdot \frac{\frac{\mathsf{fma}\left(\frac{r}{s \cdot s} \cdot 0.05555555555555555 - \frac{0.3333333333333333}{s}, r, 1\right) + e^{\frac{-r}{s}}}{\mathsf{PI}\left(\right)}}{r}
\end{array}
Initial program 99.6%
Applied rewrites99.6%
lift-/.f32N/A
lift-/.f32N/A
associate-/l/N/A
lift-fma.f32N/A
lift-*.f32N/A
distribute-rgt-outN/A
times-fracN/A
lower-*.f32N/A
lower-/.f32N/A
Applied rewrites99.6%
Taylor expanded in r around 0
Applied rewrites11.3%
(FPCore (s r)
:precision binary32
(/
(/
(+
(/
(fma
(/ (* (/ r s) r) (PI))
0.06944444444444445
(* (/ r (PI)) -0.16666666666666666))
s)
(/ 0.25 (PI)))
s)
r))\begin{array}{l}
\\
\frac{\frac{\frac{\mathsf{fma}\left(\frac{\frac{r}{s} \cdot r}{\mathsf{PI}\left(\right)}, 0.06944444444444445, \frac{r}{\mathsf{PI}\left(\right)} \cdot -0.16666666666666666\right)}{s} + \frac{0.25}{\mathsf{PI}\left(\right)}}{s}}{r}
\end{array}
Initial program 99.6%
Applied rewrites99.6%
Taylor expanded in s around -inf
Applied rewrites11.0%
Final simplification11.0%
(FPCore (s r)
:precision binary32
(/
(/
(fma
(-
(* 0.06944444444444445 (/ r (* (* s s) (PI))))
(/ 0.16666666666666666 (* (PI) s)))
r
(/ 0.25 (PI)))
s)
r))\begin{array}{l}
\\
\frac{\frac{\mathsf{fma}\left(0.06944444444444445 \cdot \frac{r}{\left(s \cdot s\right) \cdot \mathsf{PI}\left(\right)} - \frac{0.16666666666666666}{\mathsf{PI}\left(\right) \cdot s}, r, \frac{0.25}{\mathsf{PI}\left(\right)}\right)}{s}}{r}
\end{array}
Initial program 99.6%
Applied rewrites99.6%
Taylor expanded in s around inf
Applied rewrites9.9%
Taylor expanded in s around 0
Applied rewrites9.8%
Taylor expanded in r around 0
Applied rewrites11.0%
(FPCore (s r)
:precision binary32
(/
(+
(/
(fma (/ (/ r s) (PI)) 0.06944444444444445 (/ -0.16666666666666666 (PI)))
s)
(/ 0.25 (* (PI) r)))
s))\begin{array}{l}
\\
\frac{\frac{\mathsf{fma}\left(\frac{\frac{r}{s}}{\mathsf{PI}\left(\right)}, 0.06944444444444445, \frac{-0.16666666666666666}{\mathsf{PI}\left(\right)}\right)}{s} + \frac{0.25}{\mathsf{PI}\left(\right) \cdot r}}{s}
\end{array}
Initial program 99.6%
Applied rewrites99.6%
Taylor expanded in s around -inf
Applied rewrites10.9%
Final simplification10.9%
(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 99.6%
Applied rewrites99.6%
Taylor expanded in s around inf
Applied rewrites10.9%
(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{\frac{0.25}{\mathsf{PI}\left(\right)}}{s}\right)}{r}
\end{array}
Initial program 99.6%
Applied rewrites99.6%
Taylor expanded in r around 0
Applied rewrites9.9%
(FPCore (s r) :precision binary32 (/ (/ (/ (fma (/ r s) -0.16666666666666666 0.25) (PI)) s) r))
\begin{array}{l}
\\
\frac{\frac{\frac{\mathsf{fma}\left(\frac{r}{s}, -0.16666666666666666, 0.25\right)}{\mathsf{PI}\left(\right)}}{s}}{r}
\end{array}
Initial program 99.6%
Applied rewrites99.6%
Taylor expanded in s around inf
Applied rewrites9.9%
Applied rewrites9.9%
(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%
Applied rewrites99.6%
Taylor expanded in s around inf
Applied rewrites9.9%
(FPCore (s r) :precision binary32 (/ (/ (fma (/ r s) -0.16666666666666666 0.25) (PI)) (* s r)))
\begin{array}{l}
\\
\frac{\frac{\mathsf{fma}\left(\frac{r}{s}, -0.16666666666666666, 0.25\right)}{\mathsf{PI}\left(\right)}}{s \cdot r}
\end{array}
Initial program 99.6%
Applied rewrites99.6%
Taylor expanded in s around inf
Applied rewrites9.9%
lift-/.f32N/A
lift-/.f32N/A
associate-/l/N/A
lower-/.f32N/A
Applied rewrites9.8%
(FPCore (s r) :precision binary32 (* (/ 0.125 s) (/ 2.0 (* (PI) r))))
\begin{array}{l}
\\
\frac{0.125}{s} \cdot \frac{2}{\mathsf{PI}\left(\right) \cdot r}
\end{array}
Initial program 99.6%
Applied rewrites99.6%
lift-/.f32N/A
lift-/.f32N/A
associate-/l/N/A
lift-fma.f32N/A
lift-*.f32N/A
distribute-rgt-outN/A
times-fracN/A
lower-*.f32N/A
lower-/.f32N/A
Applied rewrites99.6%
Taylor expanded in s around inf
Applied rewrites9.8%
(FPCore (s r) :precision binary32 (/ (/ 0.25 s) (* (PI) r)))
\begin{array}{l}
\\
\frac{\frac{0.25}{s}}{\mathsf{PI}\left(\right) \cdot r}
\end{array}
Initial program 99.6%
Taylor expanded in s around inf
Applied rewrites9.8%
Applied rewrites9.8%
Applied rewrites9.8%
(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 99.6%
Taylor expanded in s around inf
Applied rewrites9.8%
Applied rewrites9.8%
(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 99.6%
Taylor expanded in s around inf
Applied rewrites9.8%
Applied rewrites9.8%
Applied rewrites9.8%
herbie shell --seed 2025019
(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))))