
(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 15 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 (- (/ (* (exp (/ (- r) (* 3.0 s))) 0.75) (* (* (* 6.0 (PI)) r) s)) (/ (* (/ -1.0 (exp (/ r s))) 0.25) (* (* (* (PI) 2.0) s) r))))
\begin{array}{l}
\\
\frac{e^{\frac{-r}{3 \cdot s}} \cdot 0.75}{\left(\left(6 \cdot \mathsf{PI}\left(\right)\right) \cdot r\right) \cdot s} - \frac{\frac{-1}{e^{\frac{r}{s}}} \cdot 0.25}{\left(\left(\mathsf{PI}\left(\right) \cdot 2\right) \cdot s\right) \cdot r}
\end{array}
Initial program 99.8%
lift-*.f32N/A
*-commutativeN/A
lift-*.f32N/A
associate-*r*N/A
lower-*.f32N/A
lower-*.f3299.8
Applied rewrites99.8%
lift-exp.f32N/A
lift-/.f32N/A
lift-neg.f32N/A
distribute-frac-negN/A
lift-/.f32N/A
rec-expN/A
lift-exp.f32N/A
lower-/.f3299.8
Applied rewrites99.8%
Final simplification99.8%
(FPCore (s r)
:precision binary32
(if (<=
(+
(/ (* (exp (/ (- r) (* 3.0 s))) 0.75) (* (* (* 6.0 (PI)) s) r))
(/ (* (exp (/ (- r) s)) 0.25) (* (* (* (PI) 2.0) s) r)))
2.0000000233721948e-7)
(fma
(/ (fma -0.3333333333333333 (/ r s) 1.0) (- r))
(/ -0.125 (* (PI) s))
(/ (/ (/ (/ 0.125 s) (PI)) r) (exp (/ r s))))
(/
(-
(/
(-
(/ -0.16666666666666666 (PI))
(/
(*
(-
(/ -0.06944444444444445 (PI))
(* (/ -0.021604938271604937 s) (/ r (PI))))
r)
s))
s)
(/ -0.25 (* (PI) r)))
s)))\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;\frac{e^{\frac{-r}{3 \cdot s}} \cdot 0.75}{\left(\left(6 \cdot \mathsf{PI}\left(\right)\right) \cdot s\right) \cdot r} + \frac{e^{\frac{-r}{s}} \cdot 0.25}{\left(\left(\mathsf{PI}\left(\right) \cdot 2\right) \cdot s\right) \cdot r} \leq 2.0000000233721948 \cdot 10^{-7}:\\
\;\;\;\;\mathsf{fma}\left(\frac{\mathsf{fma}\left(-0.3333333333333333, \frac{r}{s}, 1\right)}{-r}, \frac{-0.125}{\mathsf{PI}\left(\right) \cdot s}, \frac{\frac{\frac{\frac{0.125}{s}}{\mathsf{PI}\left(\right)}}{r}}{e^{\frac{r}{s}}}\right)\\
\mathbf{else}:\\
\;\;\;\;\frac{\frac{\frac{-0.16666666666666666}{\mathsf{PI}\left(\right)} - \frac{\left(\frac{-0.06944444444444445}{\mathsf{PI}\left(\right)} - \frac{-0.021604938271604937}{s} \cdot \frac{r}{\mathsf{PI}\left(\right)}\right) \cdot r}{s}}{s} - \frac{-0.25}{\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))) < 2.00000002e-7Initial program 99.9%
Applied rewrites99.8%
Taylor expanded in s around inf
+-commutativeN/A
lower-fma.f32N/A
lower-/.f324.6
Applied rewrites4.6%
Applied rewrites4.6%
lift--.f32N/A
sub-negN/A
+-commutativeN/A
lift-*.f32N/A
*-commutativeN/A
distribute-lft-neg-inN/A
lower-fma.f32N/A
Applied rewrites96.0%
if 2.00000002e-7 < (+.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 97.6%
Taylor expanded in s around -inf
Applied rewrites78.3%
Final simplification90.6%
(FPCore (s r)
:precision binary32
(let* ((t_0 (exp (/ (- r) s))) (t_1 (* (* (* (PI) 2.0) s) r)))
(if (<=
(+
(/ (* (exp (/ (- r) (* 3.0 s))) 0.75) (* (* (* 6.0 (PI)) s) r))
(/ (* t_0 0.25) t_1))
2.0000000233721948e-7)
(fma
t_0
(* (/ 1.0 t_1) 0.25)
(* (/ (fma -0.3333333333333333 (/ r s) 1.0) r) (/ (/ 0.125 s) (PI))))
(/
(-
(/
(-
(/ -0.16666666666666666 (PI))
(/
(*
(-
(/ -0.06944444444444445 (PI))
(* (/ -0.021604938271604937 s) (/ r (PI))))
r)
s))
s)
(/ -0.25 (* (PI) r)))
s))))\begin{array}{l}
\\
\begin{array}{l}
t_0 := e^{\frac{-r}{s}}\\
t_1 := \left(\left(\mathsf{PI}\left(\right) \cdot 2\right) \cdot s\right) \cdot r\\
\mathbf{if}\;\frac{e^{\frac{-r}{3 \cdot s}} \cdot 0.75}{\left(\left(6 \cdot \mathsf{PI}\left(\right)\right) \cdot s\right) \cdot r} + \frac{t\_0 \cdot 0.25}{t\_1} \leq 2.0000000233721948 \cdot 10^{-7}:\\
\;\;\;\;\mathsf{fma}\left(t\_0, \frac{1}{t\_1} \cdot 0.25, \frac{\mathsf{fma}\left(-0.3333333333333333, \frac{r}{s}, 1\right)}{r} \cdot \frac{\frac{0.125}{s}}{\mathsf{PI}\left(\right)}\right)\\
\mathbf{else}:\\
\;\;\;\;\frac{\frac{\frac{-0.16666666666666666}{\mathsf{PI}\left(\right)} - \frac{\left(\frac{-0.06944444444444445}{\mathsf{PI}\left(\right)} - \frac{-0.021604938271604937}{s} \cdot \frac{r}{\mathsf{PI}\left(\right)}\right) \cdot r}{s}}{s} - \frac{-0.25}{\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))) < 2.00000002e-7Initial program 99.9%
Applied rewrites99.8%
Taylor expanded in s around inf
+-commutativeN/A
lower-fma.f32N/A
lower-/.f324.6
Applied rewrites4.6%
Applied rewrites9.3%
if 2.00000002e-7 < (+.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 97.6%
Taylor expanded in s around -inf
Applied rewrites78.3%
Final simplification13.1%
(FPCore (s r) :precision binary32 (+ (/ (* (exp (/ (- r) s)) 0.25) (* (* (* (PI) 2.0) s) r)) (/ (* (exp (/ (- r) (* 3.0 s))) 0.75) (* (* (* 6.0 (PI)) r) s))))
\begin{array}{l}
\\
\frac{e^{\frac{-r}{s}} \cdot 0.25}{\left(\left(\mathsf{PI}\left(\right) \cdot 2\right) \cdot s\right) \cdot r} + \frac{e^{\frac{-r}{3 \cdot s}} \cdot 0.75}{\left(\left(6 \cdot \mathsf{PI}\left(\right)\right) \cdot r\right) \cdot s}
\end{array}
Initial program 99.8%
lift-*.f32N/A
*-commutativeN/A
lift-*.f32N/A
associate-*r*N/A
lower-*.f32N/A
lower-*.f3299.8
Applied rewrites99.8%
Final simplification99.8%
(FPCore (s r) :precision binary32 (/ (- (/ (/ (/ 0.125 s) (PI)) (exp (/ r s))) (* (exp (* -0.3333333333333333 (/ r s))) (/ -0.125 (* (PI) s)))) r))
\begin{array}{l}
\\
\frac{\frac{\frac{\frac{0.125}{s}}{\mathsf{PI}\left(\right)}}{e^{\frac{r}{s}}} - e^{-0.3333333333333333 \cdot \frac{r}{s}} \cdot \frac{-0.125}{\mathsf{PI}\left(\right) \cdot s}}{r}
\end{array}
Initial program 99.8%
lift-*.f32N/A
*-commutativeN/A
lift-*.f32N/A
associate-*r*N/A
lower-*.f32N/A
lower-*.f3299.8
Applied rewrites99.8%
lift-exp.f32N/A
lift-/.f32N/A
lift-neg.f32N/A
distribute-frac-negN/A
lift-/.f32N/A
rec-expN/A
lift-exp.f32N/A
lower-/.f3299.8
Applied rewrites99.8%
lift-/.f32N/A
lift-exp.f32N/A
rec-expN/A
lift-/.f32N/A
distribute-frac-negN/A
clear-numN/A
div-invN/A
clear-numN/A
exp-prodN/A
lower-pow.f32N/A
exp-1-eN/A
lower-E.f32N/A
lower-/.f32N/A
lift-neg.f3299.8
Applied rewrites99.8%
Applied rewrites99.8%
Final simplification99.8%
(FPCore (s r) :precision binary32 (+ (/ (* (exp (/ (* -0.3333333333333333 r) s)) 0.75) (* (* (* 6.0 (PI)) r) s)) (/ (* (exp (/ (- r) s)) 0.25) (* (* (* (PI) 2.0) s) r))))
\begin{array}{l}
\\
\frac{e^{\frac{-0.3333333333333333 \cdot r}{s}} \cdot 0.75}{\left(\left(6 \cdot \mathsf{PI}\left(\right)\right) \cdot r\right) \cdot s} + \frac{e^{\frac{-r}{s}} \cdot 0.25}{\left(\left(\mathsf{PI}\left(\right) \cdot 2\right) \cdot s\right) \cdot r}
\end{array}
Initial program 99.8%
lift-*.f32N/A
*-commutativeN/A
lift-*.f32N/A
associate-*r*N/A
lower-*.f32N/A
lower-*.f3299.8
Applied rewrites99.8%
lift-/.f32N/A
lift-neg.f32N/A
neg-mul-1N/A
lift-*.f32N/A
times-fracN/A
metadata-evalN/A
associate-*r/N/A
lower-/.f32N/A
lower-*.f3299.8
Applied rewrites99.8%
Final simplification99.8%
(FPCore (s r) :precision binary32 (+ (/ (* (exp (* -0.3333333333333333 (/ r s))) 0.75) (* (* (* s r) 6.0) (PI))) (/ (* (exp (/ (- r) s)) 0.25) (* (* (* (PI) 2.0) s) r))))
\begin{array}{l}
\\
\frac{e^{-0.3333333333333333 \cdot \frac{r}{s}} \cdot 0.75}{\left(\left(s \cdot r\right) \cdot 6\right) \cdot \mathsf{PI}\left(\right)} + \frac{e^{\frac{-r}{s}} \cdot 0.25}{\left(\left(\mathsf{PI}\left(\right) \cdot 2\right) \cdot s\right) \cdot r}
\end{array}
Initial program 99.8%
lift-/.f32N/A
lift-neg.f32N/A
neg-mul-1N/A
lift-*.f32N/A
times-fracN/A
lower-*.f32N/A
metadata-evalN/A
lower-/.f3299.8
Applied rewrites99.8%
lift-*.f32N/A
lift-*.f32N/A
associate-*l*N/A
lift-*.f32N/A
*-commutativeN/A
associate-*l*N/A
lower-*.f32N/A
lower-*.f32N/A
lower-*.f3299.8
Applied rewrites99.8%
Final simplification99.8%
(FPCore (s r) :precision binary32 (+ (/ (* (exp (* -0.3333333333333333 (/ r s))) 0.75) (* (* (* (PI) r) s) 6.0)) (/ (* (exp (/ (- r) s)) 0.25) (* (* (* (PI) 2.0) s) r))))
\begin{array}{l}
\\
\frac{e^{-0.3333333333333333 \cdot \frac{r}{s}} \cdot 0.75}{\left(\left(\mathsf{PI}\left(\right) \cdot r\right) \cdot s\right) \cdot 6} + \frac{e^{\frac{-r}{s}} \cdot 0.25}{\left(\left(\mathsf{PI}\left(\right) \cdot 2\right) \cdot s\right) \cdot r}
\end{array}
Initial program 99.8%
lift-/.f32N/A
lift-neg.f32N/A
neg-mul-1N/A
lift-*.f32N/A
times-fracN/A
lower-*.f32N/A
metadata-evalN/A
lower-/.f3299.8
Applied rewrites99.8%
lift-*.f32N/A
lift-*.f32N/A
associate-*l*N/A
lift-*.f32N/A
associate-*l*N/A
associate-*l*N/A
lift-*.f32N/A
lower-*.f32N/A
lift-*.f32N/A
*-commutativeN/A
associate-*r*N/A
lift-*.f32N/A
*-commutativeN/A
lower-*.f3299.8
Applied rewrites99.8%
Final simplification99.8%
(FPCore (s r)
:precision binary32
(if (<= s 2.000000047484456e-33)
(-
(/ (* (exp (/ (- r) (* 3.0 s))) 0.75) (* (* (* 6.0 (PI)) r) s))
(/
(* (/ -1.0 (- 1.0 (/ (- (* -0.5 (* (/ r s) r)) r) s))) 0.25)
(* (* (* (PI) 2.0) s) r)))
(fma
(/ (fma -0.3333333333333333 (/ r s) 1.0) (- r))
(/ -0.125 (* (PI) s))
(/ (/ (/ (/ 0.125 s) (PI)) r) (exp (/ r s))))))\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;s \leq 2.000000047484456 \cdot 10^{-33}:\\
\;\;\;\;\frac{e^{\frac{-r}{3 \cdot s}} \cdot 0.75}{\left(\left(6 \cdot \mathsf{PI}\left(\right)\right) \cdot r\right) \cdot s} - \frac{\frac{-1}{1 - \frac{-0.5 \cdot \left(\frac{r}{s} \cdot r\right) - r}{s}} \cdot 0.25}{\left(\left(\mathsf{PI}\left(\right) \cdot 2\right) \cdot s\right) \cdot r}\\
\mathbf{else}:\\
\;\;\;\;\mathsf{fma}\left(\frac{\mathsf{fma}\left(-0.3333333333333333, \frac{r}{s}, 1\right)}{-r}, \frac{-0.125}{\mathsf{PI}\left(\right) \cdot s}, \frac{\frac{\frac{\frac{0.125}{s}}{\mathsf{PI}\left(\right)}}{r}}{e^{\frac{r}{s}}}\right)\\
\end{array}
\end{array}
if s < 2.00000005e-33Initial program 100.0%
lift-*.f32N/A
*-commutativeN/A
lift-*.f32N/A
associate-*r*N/A
lower-*.f32N/A
lower-*.f32100.0
Applied rewrites100.0%
lift-exp.f32N/A
lift-/.f32N/A
lift-neg.f32N/A
distribute-frac-negN/A
lift-/.f32N/A
rec-expN/A
lift-exp.f32N/A
lower-/.f32100.0
Applied rewrites100.0%
Taylor expanded in s around -inf
mul-1-negN/A
unsub-negN/A
lower--.f32N/A
lower-/.f32N/A
+-commutativeN/A
*-commutativeN/A
metadata-evalN/A
distribute-rgt-outN/A
mul-1-negN/A
unsub-negN/A
lower--.f32N/A
distribute-rgt-outN/A
metadata-evalN/A
lower-*.f32N/A
unpow2N/A
associate-/l*N/A
lower-*.f32N/A
lower-/.f32100.0
Applied rewrites100.0%
if 2.00000005e-33 < s Initial program 99.7%
Applied rewrites99.7%
Taylor expanded in s around inf
+-commutativeN/A
lower-fma.f32N/A
lower-/.f325.8
Applied rewrites5.3%
Applied rewrites5.6%
lift--.f32N/A
sub-negN/A
+-commutativeN/A
lift-*.f32N/A
*-commutativeN/A
distribute-lft-neg-inN/A
lower-fma.f32N/A
Applied rewrites92.6%
Final simplification93.9%
(FPCore (s r)
:precision binary32
(/
(-
(/
(/
(-
-0.16666666666666666
(* (fma (/ 0.021604938271604937 s) r -0.06944444444444445) (/ r s)))
(PI))
s)
(/ -0.25 (* (PI) r)))
s))\begin{array}{l}
\\
\frac{\frac{\frac{-0.16666666666666666 - \mathsf{fma}\left(\frac{0.021604938271604937}{s}, r, -0.06944444444444445\right) \cdot \frac{r}{s}}{\mathsf{PI}\left(\right)}}{s} - \frac{-0.25}{\mathsf{PI}\left(\right) \cdot r}}{s}
\end{array}
Initial program 99.8%
Taylor expanded in s around -inf
Applied rewrites7.5%
Applied rewrites7.5%
Applied rewrites6.3%
(FPCore (s r)
:precision binary32
(/
(-
(/
(- (/ -0.16666666666666666 (PI)) (/ (* (/ -0.06944444444444445 (PI)) r) s))
s)
(/ -0.25 (* (PI) r)))
s))\begin{array}{l}
\\
\frac{\frac{\frac{-0.16666666666666666}{\mathsf{PI}\left(\right)} - \frac{\frac{-0.06944444444444445}{\mathsf{PI}\left(\right)} \cdot r}{s}}{s} - \frac{-0.25}{\mathsf{PI}\left(\right) \cdot r}}{s}
\end{array}
Initial program 99.8%
Taylor expanded in s around -inf
Applied rewrites7.5%
Taylor expanded in s around inf
Applied rewrites7.6%
Final simplification7.6%
(FPCore (s r) :precision binary32 (/ (/ (/ 0.25 (PI)) s) r))
\begin{array}{l}
\\
\frac{\frac{\frac{0.25}{\mathsf{PI}\left(\right)}}{s}}{r}
\end{array}
Initial program 99.8%
Taylor expanded in s around inf
associate-/l/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.f327.1
Applied rewrites7.1%
Applied rewrites7.1%
(FPCore (s r) :precision binary32 (/ (/ (/ 0.25 s) (PI)) r))
\begin{array}{l}
\\
\frac{\frac{\frac{0.25}{s}}{\mathsf{PI}\left(\right)}}{r}
\end{array}
Initial program 99.8%
Taylor expanded in s around inf
associate-/l/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.f327.1
Applied rewrites7.1%
Applied rewrites7.1%
(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 99.8%
Taylor expanded in s around inf
associate-/l/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.f327.1
Applied rewrites7.1%
Applied rewrites7.1%
Applied rewrites7.1%
(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 99.8%
Taylor expanded in s around inf
associate-/l/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.f327.1
Applied rewrites7.1%
Applied rewrites7.1%
Applied rewrites7.1%
herbie shell --seed 2024273
(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))))