
(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 5 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 (+ (/ (* 0.25 (exp (/ (- r) s))) (* (* (+ s s) (PI)) r)) (/ (* 0.75 (exp (/ (- r) (* 3.0 s)))) (* (* s r) (* 6.0 (PI))))))
\begin{array}{l}
\\
\frac{0.25 \cdot e^{\frac{-r}{s}}}{\left(\left(s + s\right) \cdot \mathsf{PI}\left(\right)\right) \cdot r} + \frac{0.75 \cdot e^{\frac{-r}{3 \cdot s}}}{\left(s \cdot r\right) \cdot \left(6 \cdot \mathsf{PI}\left(\right)\right)}
\end{array}
Initial program 99.6%
lift-literalN/A
lift-PI.f32N/A
lift-*.f32N/A
lift-varN/A
lift-*.f32N/A
lift-varN/A
lift-*.f32N/A
lower-*.f32N/A
lower-*.f32N/A
lift-varN/A
lift-varN/A
lift-*.f32N/A
lift-literalN/A
lift-PI.f3299.6
Applied rewrites99.6%
Taylor expanded in s around 0
Applied rewrites99.6%
(FPCore (s r) :precision binary32 (+ (/ (* 0.25 (exp (/ (- r) s))) (* (* (+ s s) (PI)) 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(s + s\right) \cdot \mathsf{PI}\left(\right)\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}
Initial program 99.6%
Taylor expanded in s around 0
Applied rewrites99.6%
Final simplification99.6%
(FPCore (s r)
:precision binary32
(/
(/
(fma
0.75
(/ (exp (/ (- r) (* 3.0 s))) 6.0)
(* (/ (exp (/ (- r) s)) 2.0) 0.25))
(PI))
(* s r)))\begin{array}{l}
\\
\frac{\frac{\mathsf{fma}\left(0.75, \frac{e^{\frac{-r}{3 \cdot s}}}{6}, \frac{e^{\frac{-r}{s}}}{2} \cdot 0.25\right)}{\mathsf{PI}\left(\right)}}{s \cdot r}
\end{array}
Initial program 99.6%
lift-literalN/A
lift-PI.f32N/A
lift-*.f32N/A
lift-varN/A
lift-*.f32N/A
lift-varN/A
lift-*.f32N/A
lower-*.f32N/A
lower-*.f32N/A
lift-varN/A
lift-varN/A
lift-*.f32N/A
lift-literalN/A
lift-PI.f3299.6
Applied rewrites99.6%
Applied rewrites98.6%
Applied rewrites99.5%
lift-varN/A
lift-neg.f32N/A
lift-varN/A
lift-/.f32N/A
lift-literalN/A
lift-/.f32N/A
lift-/.f32N/A
lift-neg.f32N/A
lift-varN/A
lift-*.f32N/A
lift-literalN/A
lift-var99.5
Applied rewrites99.5%
(FPCore (s r) :precision binary32 (+ (/ (* 0.25 (exp (/ (- r) s))) (* (+ (PI) (PI)) r)) (/ (* 0.75 (exp (/ (- r) (* 3.0 s)))) (* (* r 6.0) (* (PI) s)))))
\begin{array}{l}
\\
\frac{0.25 \cdot e^{\frac{-r}{s}}}{\left(\mathsf{PI}\left(\right) + \mathsf{PI}\left(\right)\right) \cdot r} + \frac{0.75 \cdot e^{\frac{-r}{3 \cdot s}}}{\left(r \cdot 6\right) \cdot \left(\mathsf{PI}\left(\right) \cdot s\right)}
\end{array}
Initial program 99.6%
lift-literalN/A
lift-PI.f32N/A
lift-*.f32N/A
lift-varN/A
lift-*.f32N/A
lift-varN/A
lift-*.f32N/A
lower-*.f32N/A
lower-*.f32N/A
lift-varN/A
lift-literalN/A
lower-*.f32N/A
lift-PI.f32N/A
lift-var99.6
Applied rewrites99.6%
lift-literalN/A
lift-PI.f32N/A
lift-*.f32N/A
lift-varN/A
lift-*.f32N/A
Applied rewrites93.5%
(FPCore (s r) :precision binary32 (+ (* (exp (/ (- r) s)) (/ 0.25 (* 2.0 r))) (/ (* 0.75 (exp (/ (- r) (* 3.0 s)))) (* (* r 6.0) (* (PI) s)))))
\begin{array}{l}
\\
e^{\frac{-r}{s}} \cdot \frac{0.25}{2 \cdot r} + \frac{0.75 \cdot e^{\frac{-r}{3 \cdot s}}}{\left(r \cdot 6\right) \cdot \left(\mathsf{PI}\left(\right) \cdot s\right)}
\end{array}
Initial program 99.6%
lift-literalN/A
lift-PI.f32N/A
lift-*.f32N/A
lift-varN/A
lift-*.f32N/A
lift-varN/A
lift-*.f32N/A
lower-*.f32N/A
lower-*.f32N/A
lift-varN/A
lift-literalN/A
lower-*.f32N/A
lift-PI.f32N/A
lift-var99.6
Applied rewrites99.6%
lift-literalN/A
lift-PI.f32N/A
lift-*.f32N/A
lift-varN/A
lift-*.f32N/A
Applied rewrites93.5%
Applied rewrites93.5%
herbie shell --seed 2025021
(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))))