
(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 13 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)) (* s (* (PI) 6.0))) r) (* (/ (exp (/ (- r) s)) (* (* (PI) s) r)) 0.125)))
\begin{array}{l}
\\
\mathsf{fma}\left(0.75, \frac{\frac{e^{\frac{\frac{-r}{3}}{s}}}{s \cdot \left(\mathsf{PI}\left(\right) \cdot 6\right)}}{r}, \frac{e^{\frac{-r}{s}}}{\left(\mathsf{PI}\left(\right) \cdot s\right) \cdot r} \cdot 0.125\right)
\end{array}
Initial program 99.3%
Applied rewrites99.3%
lift-/.f32N/A
lift-exp.f32N/A
lift-/.f32N/A
lift-neg.f32N/A
lift-/.f32N/A
lift-*.f32N/A
associate-/r*N/A
lower-/.f32N/A
Applied rewrites99.4%
Taylor expanded in s around 0
*-commutativeN/A
lower-*.f32N/A
mul-1-negN/A
distribute-frac-negN/A
lower-/.f32N/A
lift-/.f32N/A
lift-neg.f32N/A
lift-exp.f32N/A
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lift-PI.f3299.4
Applied rewrites99.4%
(FPCore (s r) :precision binary32 (+ (/ (* 0.25 (exp (/ (- r) s))) (* (* (* 2.0 (PI)) s) r)) (/ (* 0.75 (exp (/ (- r) (* 3.0 s)))) (* (* (* (PI) s) r) 6.0))))
\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(\mathsf{PI}\left(\right) \cdot s\right) \cdot r\right) \cdot 6}
\end{array}
Initial program 99.3%
Taylor expanded in s around 0
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lift-PI.f3299.3
Applied rewrites99.3%
(FPCore (s r) :precision binary32 (+ (* (/ (exp (/ (- r) s)) (* (* (PI) s) r)) 0.125) (/ (* 0.75 (exp (/ (- r) (* 3.0 s)))) (* (* (* 6.0 (PI)) s) r))))
\begin{array}{l}
\\
\frac{e^{\frac{-r}{s}}}{\left(\mathsf{PI}\left(\right) \cdot s\right) \cdot r} \cdot 0.125 + \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}
Initial program 99.3%
Taylor expanded in s around 0
*-commutativeN/A
lower-*.f32N/A
mul-1-negN/A
distribute-frac-negN/A
lower-/.f32N/A
lift-/.f32N/A
lift-neg.f32N/A
lift-exp.f32N/A
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lift-PI.f3299.3
Applied rewrites99.3%
Final simplification99.3%
(FPCore (s r)
:precision binary32
(fma
0.75
(/
(/
(fma
(/ (fma 0.3333333333333333 r (* -0.05555555555555555 (* r (/ r s)))) s)
-1.0
1.0)
(* s (* (PI) 6.0)))
r)
(* 0.25 (/ (exp (/ (- r) s)) (* (* (* (PI) 2.0) s) r)))))\begin{array}{l}
\\
\mathsf{fma}\left(0.75, \frac{\frac{\mathsf{fma}\left(\frac{\mathsf{fma}\left(0.3333333333333333, r, -0.05555555555555555 \cdot \left(r \cdot \frac{r}{s}\right)\right)}{s}, -1, 1\right)}{s \cdot \left(\mathsf{PI}\left(\right) \cdot 6\right)}}{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 99.3%
Applied rewrites99.3%
lift-/.f32N/A
lift-exp.f32N/A
lift-/.f32N/A
lift-neg.f32N/A
lift-/.f32N/A
lift-*.f32N/A
associate-/r*N/A
lower-/.f32N/A
Applied rewrites99.4%
Taylor expanded in s around -inf
+-commutativeN/A
*-commutativeN/A
lower-fma.f32N/A
lower-/.f32N/A
+-commutativeN/A
lower-fma.f32N/A
lower-*.f32N/A
pow2N/A
associate-/l*N/A
lower-*.f32N/A
lift-/.f329.9
Applied rewrites9.9%
(FPCore (s r)
:precision binary32
(fma
0.75
(/
(fma
(/ (fma (/ (* r r) s) -0.05555555555555555 (* 0.3333333333333333 r)) s)
-1.0
1.0)
(* (* (* (PI) 6.0) s) r))
(* 0.25 (/ (exp (/ (- r) s)) (* (* (* (PI) 2.0) s) r)))))\begin{array}{l}
\\
\mathsf{fma}\left(0.75, \frac{\mathsf{fma}\left(\frac{\mathsf{fma}\left(\frac{r \cdot r}{s}, -0.05555555555555555, 0.3333333333333333 \cdot r\right)}{s}, -1, 1\right)}{\left(\left(\mathsf{PI}\left(\right) \cdot 6\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 99.3%
Applied rewrites99.3%
Taylor expanded in s around -inf
+-commutativeN/A
*-commutativeN/A
lower-fma.f32N/A
lower-/.f32N/A
*-commutativeN/A
lower-fma.f32N/A
lower-/.f32N/A
unpow2N/A
lower-*.f32N/A
lower-*.f329.9
Applied rewrites9.9%
(FPCore (s r)
:precision binary32
(+
(/ (* 0.25 (exp (/ (- r) s))) (* (* (* 2.0 (PI)) s) r))
(/
(*
0.75
(fma
(- (* (/ r (* s s)) 0.05555555555555555) (/ 0.3333333333333333 s))
r
1.0))
(* (* (* 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 \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}
\end{array}
Initial program 99.3%
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
unpow2N/A
lower-*.f32N/A
associate-*r/N/A
metadata-evalN/A
lower-/.f329.9
Applied rewrites9.9%
Final simplification9.9%
(FPCore (s r)
:precision binary32
(fma
0.75
(/
(/
(-
1.0
(/ (fma -0.05555555555555555 (/ (* r r) s) (* 0.3333333333333333 r)) s))
(* s (* (PI) 6.0)))
r)
(* (/ (exp (/ (- r) s)) (* (* (PI) s) r)) 0.125)))\begin{array}{l}
\\
\mathsf{fma}\left(0.75, \frac{\frac{1 - \frac{\mathsf{fma}\left(-0.05555555555555555, \frac{r \cdot r}{s}, 0.3333333333333333 \cdot r\right)}{s}}{s \cdot \left(\mathsf{PI}\left(\right) \cdot 6\right)}}{r}, \frac{e^{\frac{-r}{s}}}{\left(\mathsf{PI}\left(\right) \cdot s\right) \cdot r} \cdot 0.125\right)
\end{array}
Initial program 99.3%
Applied rewrites99.3%
lift-/.f32N/A
lift-exp.f32N/A
lift-/.f32N/A
lift-neg.f32N/A
lift-/.f32N/A
lift-*.f32N/A
associate-/r*N/A
lower-/.f32N/A
Applied rewrites99.4%
Taylor expanded in s around 0
*-commutativeN/A
lower-*.f32N/A
mul-1-negN/A
distribute-frac-negN/A
lower-/.f32N/A
lift-/.f32N/A
lift-neg.f32N/A
lift-exp.f32N/A
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lift-PI.f3299.4
Applied rewrites99.4%
Taylor expanded in s around -inf
lower-+.f32N/A
mul-1-negN/A
lower-neg.f32N/A
lower-/.f32N/A
pow2N/A
lift-/.f32N/A
lift-*.f32N/A
lower-fma.f32N/A
lower-*.f329.9
Applied rewrites9.9%
Final simplification9.9%
(FPCore (s r) :precision binary32 (+ (/ (* 0.25 (exp (/ (- r) s))) (* (* (* 2.0 (PI)) s) r)) (/ (fma (- (* (/ r (* s s)) 0.041666666666666664) (/ 0.25 s)) r 0.75) (* (* (* 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{\mathsf{fma}\left(\frac{r}{s \cdot s} \cdot 0.041666666666666664 - \frac{0.25}{s}, r, 0.75\right)}{\left(\left(6 \cdot \mathsf{PI}\left(\right)\right) \cdot s\right) \cdot r}
\end{array}
Initial program 99.3%
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
unpow2N/A
lower-*.f32N/A
associate-*r/N/A
metadata-evalN/A
lower-/.f329.9
Applied rewrites9.9%
(FPCore (s r)
:precision binary32
(+
(/
(fma (- (* (/ r (* s s)) 0.125) (/ 0.25 s)) r 0.25)
(* (* (* 2.0 (PI)) s) r))
(/
(+
(/
(-
(* (/ (/ r s) (PI)) 0.006944444444444444)
(/ 0.041666666666666664 (PI)))
s)
(/ 0.125 (* (PI) r)))
s)))\begin{array}{l}
\\
\frac{\mathsf{fma}\left(\frac{r}{s \cdot s} \cdot 0.125 - \frac{0.25}{s}, r, 0.25\right)}{\left(\left(2 \cdot \mathsf{PI}\left(\right)\right) \cdot s\right) \cdot r} + \frac{\frac{\frac{\frac{r}{s}}{\mathsf{PI}\left(\right)} \cdot 0.006944444444444444 - \frac{0.041666666666666664}{\mathsf{PI}\left(\right)}}{s} + \frac{0.125}{\mathsf{PI}\left(\right) \cdot r}}{s}
\end{array}
Initial program 99.3%
Taylor expanded in s around -inf
mul-1-negN/A
lower-neg.f32N/A
lower-/.f32N/A
Applied rewrites9.9%
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
unpow2N/A
lower-*.f32N/A
associate-*r/N/A
metadata-evalN/A
lower-/.f329.3
Applied rewrites9.3%
Final simplification9.3%
(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 99.3%
Taylor expanded in s around -inf
mul-1-negN/A
lower-neg.f32N/A
lower-/.f32N/A
Applied rewrites9.3%
Final simplification9.3%
(FPCore (s r) :precision binary32 (+ (/ (* 0.25 1.0) (* (* (* 2.0 (PI)) s) r)) (/ (/ -0.125 (* r (PI))) (- s))))
\begin{array}{l}
\\
\frac{0.25 \cdot 1}{\left(\left(2 \cdot \mathsf{PI}\left(\right)\right) \cdot s\right) \cdot r} + \frac{\frac{-0.125}{r \cdot \mathsf{PI}\left(\right)}}{-s}
\end{array}
Initial program 99.3%
Taylor expanded in s around -inf
Applied rewrites9.6%
Taylor expanded in s around inf
Applied rewrites7.1%
Taylor expanded in s around inf
lower-/.f32N/A
lower-*.f32N/A
lift-PI.f328.6
Applied rewrites8.6%
Final simplification8.6%
(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 99.3%
Taylor expanded in s around inf
lower-/.f32N/A
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lift-PI.f328.6
Applied rewrites8.6%
lift-/.f32N/A
lift-*.f32N/A
lift-PI.f32N/A
lift-*.f32N/A
*-commutativeN/A
*-commutativeN/A
associate-/r*N/A
lower-/.f32N/A
lower-/.f32N/A
*-commutativeN/A
lift-*.f32N/A
lift-PI.f328.6
Applied rewrites8.6%
(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 99.3%
Taylor expanded in s around inf
lower-/.f32N/A
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lift-PI.f328.6
Applied rewrites8.6%
lift-*.f32N/A
lift-PI.f32N/A
lift-*.f32N/A
*-commutativeN/A
*-commutativeN/A
associate-*r*N/A
lower-*.f32N/A
lower-*.f32N/A
lift-PI.f328.6
Applied rewrites8.6%
herbie shell --seed 2025051
(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))))