
(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 15 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 (* PI (+ u2 u2)))))
float code(float cosTheta_i, float u1, float u2) {
return sqrtf(-log1pf(-u1)) * sinf((((float) M_PI) * (u2 + u2)));
}
function code(cosTheta_i, u1, u2) return Float32(sqrt(Float32(-log1p(Float32(-u1)))) * sin(Float32(Float32(pi) * Float32(u2 + u2)))) end
\begin{array}{l}
\\
\sqrt{-\mathsf{log1p}\left(-u1\right)} \cdot \sin \left(\pi \cdot \left(u2 + u2\right)\right)
\end{array}
Initial program 55.7%
lift-log.f32N/A
lift--.f32N/A
sub-negN/A
lower-log1p.f32N/A
lower-neg.f3298.5
Applied rewrites98.5%
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%
lift-*.f32N/A
lift-*.f32N/A
lift-sin.f32N/A
lift-cos.f32N/A
2-sinN/A
lift-*.f32N/A
associate-*l*N/A
lift-PI.f32N/A
lift-PI.f32N/A
lift-*.f32N/A
lift-*.f32N/A
lift-sin.f3298.5
lift-*.f32N/A
lift-*.f32N/A
associate-*l*N/A
lift-*.f32N/A
count-2N/A
lift-*.f32N/A
Applied rewrites98.5%
(FPCore (cosTheta_i u1 u2)
:precision binary32
(if (<= (* u2 (* PI 2.0)) 0.05000000074505806)
(*
(sqrt (- (log1p (- u1))))
(* u2 (fma -1.3333333333333333 (* (* u2 u2) (* PI (* PI PI))) (* PI 2.0))))
(*
(sin (* PI (+ u2 u2)))
(sqrt
(-
(*
u1
(fma u1 (fma u1 (fma u1 -0.25 -0.3333333333333333) -0.5) -1.0)))))))
float code(float cosTheta_i, float u1, float u2) {
float tmp;
if ((u2 * (((float) M_PI) * 2.0f)) <= 0.05000000074505806f) {
tmp = sqrtf(-log1pf(-u1)) * (u2 * fmaf(-1.3333333333333333f, ((u2 * u2) * (((float) M_PI) * (((float) M_PI) * ((float) M_PI)))), (((float) M_PI) * 2.0f)));
} else {
tmp = sinf((((float) M_PI) * (u2 + u2))) * sqrtf(-(u1 * fmaf(u1, fmaf(u1, fmaf(u1, -0.25f, -0.3333333333333333f), -0.5f), -1.0f)));
}
return tmp;
}
function code(cosTheta_i, u1, u2) tmp = Float32(0.0) if (Float32(u2 * Float32(Float32(pi) * Float32(2.0))) <= Float32(0.05000000074505806)) tmp = Float32(sqrt(Float32(-log1p(Float32(-u1)))) * Float32(u2 * fma(Float32(-1.3333333333333333), Float32(Float32(u2 * u2) * Float32(Float32(pi) * Float32(Float32(pi) * Float32(pi)))), Float32(Float32(pi) * Float32(2.0))))); else tmp = Float32(sin(Float32(Float32(pi) * Float32(u2 + u2))) * sqrt(Float32(-Float32(u1 * fma(u1, fma(u1, fma(u1, Float32(-0.25), Float32(-0.3333333333333333)), Float32(-0.5)), Float32(-1.0)))))); end return tmp end
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;u2 \cdot \left(\pi \cdot 2\right) \leq 0.05000000074505806:\\
\;\;\;\;\sqrt{-\mathsf{log1p}\left(-u1\right)} \cdot \left(u2 \cdot \mathsf{fma}\left(-1.3333333333333333, \left(u2 \cdot u2\right) \cdot \left(\pi \cdot \left(\pi \cdot \pi\right)\right), \pi \cdot 2\right)\right)\\
\mathbf{else}:\\
\;\;\;\;\sin \left(\pi \cdot \left(u2 + u2\right)\right) \cdot \sqrt{-u1 \cdot \mathsf{fma}\left(u1, \mathsf{fma}\left(u1, \mathsf{fma}\left(u1, -0.25, -0.3333333333333333\right), -0.5\right), -1\right)}\\
\end{array}
\end{array}
if (*.f32 (*.f32 #s(literal 2 binary32) (PI.f32)) u2) < 0.0500000007Initial program 58.0%
lift-log.f32N/A
lift--.f32N/A
sub-negN/A
lower-log1p.f32N/A
lower-neg.f3298.5
Applied rewrites98.5%
Taylor expanded in u2 around 0
+-commutativeN/A
*-commutativeN/A
associate-*r*N/A
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
associate-*r*N/A
*-commutativeN/A
+-commutativeN/A
lower-fma.f32N/A
Applied rewrites98.5%
if 0.0500000007 < (*.f32 (*.f32 #s(literal 2 binary32) (PI.f32)) u2) Initial program 56.6%
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.f3291.6
Applied rewrites91.6%
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-+.f3291.6
Applied rewrites91.6%
Taylor expanded in u1 around 0
lower-*.f32N/A
sub-negN/A
metadata-evalN/A
lower-fma.f32N/A
sub-negN/A
metadata-evalN/A
lower-fma.f32N/A
sub-negN/A
*-commutativeN/A
metadata-evalN/A
lower-fma.f3293.3
Applied rewrites93.3%
Final simplification97.4%
herbie shell --seed 2024219
(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))))