
(FPCore (cosTheta_i u1 u2) :precision binary32 (* (sqrt (- (log (- 1.0 u1)))) (sin (* (* 2.0 PI) u2))))
float code(float cosTheta_i, float u1, float u2) {
return sqrtf(-logf((1.0f - u1))) * sinf(((2.0f * ((float) M_PI)) * u2));
}
function code(cosTheta_i, u1, u2) return Float32(sqrt(Float32(-log(Float32(Float32(1.0) - u1)))) * sin(Float32(Float32(Float32(2.0) * Float32(pi)) * u2))) end
function tmp = code(cosTheta_i, u1, u2) tmp = sqrt(-log((single(1.0) - u1))) * sin(((single(2.0) * single(pi)) * u2)); end
\begin{array}{l}
\\
\sqrt{-\log \left(1 - u1\right)} \cdot \sin \left(\left(2 \cdot \pi\right) \cdot u2\right)
\end{array}
Sampling outcomes in binary32 precision:
Herbie found 18 alternatives:
| Alternative | Accuracy | Speedup |
|---|
(FPCore (cosTheta_i u1 u2) :precision binary32 (* (sqrt (- (log (- 1.0 u1)))) (sin (* (* 2.0 PI) u2))))
float code(float cosTheta_i, float u1, float u2) {
return sqrtf(-logf((1.0f - u1))) * sinf(((2.0f * ((float) M_PI)) * u2));
}
function code(cosTheta_i, u1, u2) return Float32(sqrt(Float32(-log(Float32(Float32(1.0) - u1)))) * sin(Float32(Float32(Float32(2.0) * Float32(pi)) * u2))) end
function tmp = code(cosTheta_i, u1, u2) tmp = sqrt(-log((single(1.0) - u1))) * sin(((single(2.0) * single(pi)) * u2)); end
\begin{array}{l}
\\
\sqrt{-\log \left(1 - u1\right)} \cdot \sin \left(\left(2 \cdot \pi\right) \cdot u2\right)
\end{array}
(FPCore (cosTheta_i u1 u2) :precision binary32 (* (sqrt (- (log1p (- u1)))) (sin (* (* 2.0 PI) u2))))
float code(float cosTheta_i, float u1, float u2) {
return sqrtf(-log1pf(-u1)) * sinf(((2.0f * ((float) M_PI)) * u2));
}
function code(cosTheta_i, u1, u2) return Float32(sqrt(Float32(-log1p(Float32(-u1)))) * sin(Float32(Float32(Float32(2.0) * Float32(pi)) * u2))) end
\begin{array}{l}
\\
\sqrt{-\mathsf{log1p}\left(-u1\right)} \cdot \sin \left(\left(2 \cdot \pi\right) \cdot u2\right)
\end{array}
Initial program 57.6%
lift-log.f32N/A
lift--.f32N/A
sub-negN/A
lower-log1p.f32N/A
lower-neg.f3298.3
Applied rewrites98.3%
(FPCore (cosTheta_i u1 u2)
:precision binary32
(if (<= (- (log (- 1.0 u1))) 0.03500000014901161)
(*
(sqrt (fma (* u1 u1) (fma u1 (fma u1 0.25 0.3333333333333333) 0.5) u1))
(sin (* PI (+ u2 u2))))
(*
(sqrt (- (log1p (- u1))))
(*
2.0
(* u2 (fma (* u2 u2) (* (* PI PI) (* PI -0.6666666666666666)) PI))))))
float code(float cosTheta_i, float u1, float u2) {
float tmp;
if (-logf((1.0f - u1)) <= 0.03500000014901161f) {
tmp = sqrtf(fmaf((u1 * u1), fmaf(u1, fmaf(u1, 0.25f, 0.3333333333333333f), 0.5f), u1)) * sinf((((float) M_PI) * (u2 + u2)));
} else {
tmp = sqrtf(-log1pf(-u1)) * (2.0f * (u2 * fmaf((u2 * u2), ((((float) M_PI) * ((float) M_PI)) * (((float) M_PI) * -0.6666666666666666f)), ((float) M_PI))));
}
return tmp;
}
function code(cosTheta_i, u1, u2) tmp = Float32(0.0) if (Float32(-log(Float32(Float32(1.0) - u1))) <= Float32(0.03500000014901161)) tmp = Float32(sqrt(fma(Float32(u1 * u1), fma(u1, fma(u1, Float32(0.25), Float32(0.3333333333333333)), Float32(0.5)), u1)) * sin(Float32(Float32(pi) * Float32(u2 + u2)))); else tmp = Float32(sqrt(Float32(-log1p(Float32(-u1)))) * Float32(Float32(2.0) * Float32(u2 * fma(Float32(u2 * u2), Float32(Float32(Float32(pi) * Float32(pi)) * Float32(Float32(pi) * Float32(-0.6666666666666666))), Float32(pi))))); end return tmp end
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;-\log \left(1 - u1\right) \leq 0.03500000014901161:\\
\;\;\;\;\sqrt{\mathsf{fma}\left(u1 \cdot u1, \mathsf{fma}\left(u1, \mathsf{fma}\left(u1, 0.25, 0.3333333333333333\right), 0.5\right), u1\right)} \cdot \sin \left(\pi \cdot \left(u2 + u2\right)\right)\\
\mathbf{else}:\\
\;\;\;\;\sqrt{-\mathsf{log1p}\left(-u1\right)} \cdot \left(2 \cdot \left(u2 \cdot \mathsf{fma}\left(u2 \cdot u2, \left(\pi \cdot \pi\right) \cdot \left(\pi \cdot -0.6666666666666666\right), \pi\right)\right)\right)\\
\end{array}
\end{array}
if (neg.f32 (log.f32 (-.f32 #s(literal 1 binary32) u1))) < 0.0350000001Initial program 50.6%
Taylor expanded in u1 around 0
lower-*.f32N/A
sub-negN/A
metadata-evalN/A
lower-fma.f32N/A
sub-negN/A
*-commutativeN/A
metadata-evalN/A
lower-fma.f3297.6
Applied rewrites97.6%
lift-*.f32N/A
lift-*.f32N/A
associate-*l*N/A
lift-*.f32N/A
count-2N/A
lift-*.f32N/A
lift-*.f32N/A
distribute-lft-outN/A
lower-*.f32N/A
lower-+.f3297.6
Applied rewrites97.6%
Taylor expanded in u1 around 0
+-commutativeN/A
distribute-lft-inN/A
associate-*r*N/A
unpow2N/A
*-rgt-identityN/A
lower-fma.f32N/A
unpow2N/A
lower-*.f32N/A
+-commutativeN/A
lower-fma.f32N/A
+-commutativeN/A
*-commutativeN/A
lower-fma.f3298.3
Applied rewrites98.3%
if 0.0350000001 < (neg.f32 (log.f32 (-.f32 #s(literal 1 binary32) u1))) Initial program 97.4%
lift-log.f32N/A
lift--.f32N/A
sub-negN/A
lower-log1p.f32N/A
lower-neg.f3298.4
Applied rewrites98.4%
lift-sin.f32N/A
lift-*.f32N/A
lift-*.f32N/A
associate-*l*N/A
sin-2N/A
lower-*.f32N/A
lower-*.f32N/A
lower-sin.f32N/A
lower-*.f32N/A
lower-cos.f32N/A
lower-*.f3298.3
Applied rewrites98.3%
Taylor expanded in u2 around 0
lower-*.f32N/A
+-commutativeN/A
lower-fma.f32N/A
unpow2N/A
lower-*.f32N/A
distribute-rgt-outN/A
unpow3N/A
associate-*l*N/A
lower-*.f32N/A
lower-*.f32N/A
lower-PI.f32N/A
lower-PI.f32N/A
lower-*.f32N/A
lower-PI.f32N/A
metadata-evalN/A
lower-PI.f3290.1
Applied rewrites90.1%
herbie shell --seed 2024223
(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))))