
(FPCore (cosTheta_i u1 u2) :precision binary32 (* (sqrt (- (log (- 1.0 u1)))) (sin (* (* 2.0 (PI)) u2))))
\begin{array}{l}
\\
\sqrt{-\log \left(1 - u1\right)} \cdot \sin \left(\left(2 \cdot \mathsf{PI}\left(\right)\right) \cdot u2\right)
\end{array}
Sampling outcomes in binary32 precision:
Herbie found 5 alternatives:
| Alternative | Accuracy | Speedup |
|---|
(FPCore (cosTheta_i u1 u2) :precision binary32 (* (sqrt (- (log (- 1.0 u1)))) (sin (* (* 2.0 (PI)) u2))))
\begin{array}{l}
\\
\sqrt{-\log \left(1 - u1\right)} \cdot \sin \left(\left(2 \cdot \mathsf{PI}\left(\right)\right) \cdot u2\right)
\end{array}
(FPCore (cosTheta_i u1 u2) :precision binary32 (if (<= (- 1.0 u1) 0.9998499751091003) (* (sqrt (- (log (- 1.0 u1)))) (sin (* (* 2.0 (PI)) u2))) (* (sin (* (* (PI) 2.0) u2)) (sqrt u1))))
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;1 - u1 \leq 0.9998499751091003:\\
\;\;\;\;\sqrt{-\log \left(1 - u1\right)} \cdot \sin \left(\left(2 \cdot \mathsf{PI}\left(\right)\right) \cdot u2\right)\\
\mathbf{else}:\\
\;\;\;\;\sin \left(\left(\mathsf{PI}\left(\right) \cdot 2\right) \cdot u2\right) \cdot \sqrt{u1}\\
\end{array}
\end{array}
if (-.f32 #s(literal 1 binary32) u1) < 0.999849975Initial program 88.4%
if 0.999849975 < (-.f32 #s(literal 1 binary32) u1) Initial program 37.5%
Applied rewrites40.3%
Taylor expanded in u1 around 0
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
associate-*r*N/A
*-commutativeN/A
lower-sin.f32N/A
*-commutativeN/A
associate-*r*N/A
*-commutativeN/A
*-commutativeN/A
associate-*r*N/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-PI.f32N/A
lower-sqrt.f3293.2
Applied rewrites93.2%
(FPCore (cosTheta_i u1 u2)
:precision binary32
(if (<= (- (log (- 1.0 u1))) 0.0003209999995306134)
(* (sin (* (* (PI) 2.0) u2)) (sqrt u1))
(*
(* 2.0 (* (* (sqrt 2.0) (PI)) u2))
(sqrt (log (sqrt (/ 1.0 (- 1.0 u1))))))))\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;-\log \left(1 - u1\right) \leq 0.0003209999995306134:\\
\;\;\;\;\sin \left(\left(\mathsf{PI}\left(\right) \cdot 2\right) \cdot u2\right) \cdot \sqrt{u1}\\
\mathbf{else}:\\
\;\;\;\;\left(2 \cdot \left(\left(\sqrt{2} \cdot \mathsf{PI}\left(\right)\right) \cdot u2\right)\right) \cdot \sqrt{\log \left(\sqrt{\frac{1}{1 - u1}}\right)}\\
\end{array}
\end{array}
if (neg.f32 (log.f32 (-.f32 #s(literal 1 binary32) u1))) < 3.21e-4Initial program 39.8%
Applied rewrites38.8%
Taylor expanded in u1 around 0
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
associate-*r*N/A
*-commutativeN/A
lower-sin.f32N/A
*-commutativeN/A
associate-*r*N/A
*-commutativeN/A
*-commutativeN/A
associate-*r*N/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-PI.f32N/A
lower-sqrt.f3291.7
Applied rewrites91.7%
if 3.21e-4 < (neg.f32 (log.f32 (-.f32 #s(literal 1 binary32) u1))) Initial program 89.9%
lift-neg.f32N/A
lift-log.f32N/A
neg-logN/A
inv-powN/A
sqr-powN/A
log-prodN/A
lower-+.f32N/A
lower-log.f32N/A
lower-pow.f32N/A
metadata-evalN/A
lower-log.f32N/A
lower-pow.f32N/A
metadata-eval85.1
Applied rewrites85.1%
Taylor expanded in u2 around 0
associate-*r*N/A
lower-*.f32N/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-sqrt.f32N/A
lower-PI.f32N/A
lower-sqrt.f32N/A
lower-log.f32N/A
lower-sqrt.f32N/A
lower-/.f32N/A
lower--.f3273.4
Applied rewrites73.4%
(FPCore (cosTheta_i u1 u2)
:precision binary32
(let* ((t_0 (- (log (- 1.0 u1)))))
(if (<= t_0 0.019999999552965164)
(* (sin (* (* (PI) 2.0) u2)) (sqrt u1))
(*
(sqrt t_0)
(*
(* (PI) (fma (* (* u2 u2) -1.3333333333333333) (* (PI) (PI)) 2.0))
u2)))))\begin{array}{l}
\\
\begin{array}{l}
t_0 := -\log \left(1 - u1\right)\\
\mathbf{if}\;t\_0 \leq 0.019999999552965164:\\
\;\;\;\;\sin \left(\left(\mathsf{PI}\left(\right) \cdot 2\right) \cdot u2\right) \cdot \sqrt{u1}\\
\mathbf{else}:\\
\;\;\;\;\sqrt{t\_0} \cdot \left(\left(\mathsf{PI}\left(\right) \cdot \mathsf{fma}\left(\left(u2 \cdot u2\right) \cdot -1.3333333333333333, \mathsf{PI}\left(\right) \cdot \mathsf{PI}\left(\right), 2\right)\right) \cdot u2\right)\\
\end{array}
\end{array}
if (neg.f32 (log.f32 (-.f32 #s(literal 1 binary32) u1))) < 0.0199999996Initial program 52.9%
Applied rewrites36.4%
Taylor expanded in u1 around 0
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
associate-*r*N/A
*-commutativeN/A
lower-sin.f32N/A
*-commutativeN/A
associate-*r*N/A
*-commutativeN/A
*-commutativeN/A
associate-*r*N/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-PI.f32N/A
lower-sqrt.f3282.4
Applied rewrites82.4%
if 0.0199999996 < (neg.f32 (log.f32 (-.f32 #s(literal 1 binary32) u1))) Initial program 96.5%
Taylor expanded in u2 around 0
*-commutativeN/A
*-commutativeN/A
associate-*r*N/A
+-commutativeN/A
lower-*.f32N/A
Applied rewrites80.2%
(FPCore (cosTheta_i u1 u2) :precision binary32 (* (sin (* (* (PI) 2.0) u2)) (sqrt u1)))
\begin{array}{l}
\\
\sin \left(\left(\mathsf{PI}\left(\right) \cdot 2\right) \cdot u2\right) \cdot \sqrt{u1}
\end{array}
Initial program 59.6%
Applied rewrites37.8%
Taylor expanded in u1 around 0
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
associate-*r*N/A
*-commutativeN/A
lower-sin.f32N/A
*-commutativeN/A
associate-*r*N/A
*-commutativeN/A
*-commutativeN/A
associate-*r*N/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-PI.f32N/A
lower-sqrt.f3276.1
Applied rewrites76.1%
(FPCore (cosTheta_i u1 u2) :precision binary32 (* (* 2.0 (sqrt u1)) (* u2 (PI))))
\begin{array}{l}
\\
\left(2 \cdot \sqrt{u1}\right) \cdot \left(u2 \cdot \mathsf{PI}\left(\right)\right)
\end{array}
Initial program 59.6%
Applied rewrites14.5%
Taylor expanded in u2 around 0
associate-*r*N/A
*-commutativeN/A
associate-*r*N/A
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
associate-*r*N/A
*-commutativeN/A
*-commutativeN/A
associate-*r*N/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-PI.f32N/A
lower-sqrt.f32N/A
lower-log1p.f3267.4
Applied rewrites67.4%
Taylor expanded in u1 around 0
Applied rewrites67.8%
herbie shell --seed 2024311
(FPCore (cosTheta_i u1 u2)
:name "Beckmann Sample, near normal, slope_y"
:precision binary32
:pre (and (and (and (> cosTheta_i 0.9999) (<= cosTheta_i 1.0)) (and (<= 2.328306437e-10 u1) (<= u1 1.0))) (and (<= 2.328306437e-10 u2) (<= u2 1.0)))
(* (sqrt (- (log (- 1.0 u1)))) (sin (* (* 2.0 (PI)) u2))))