
(FPCore (cosTheta_i u1 u2) :precision binary32 (* (sqrt (- (log (- 1.0 u1)))) (cos (* (* 2.0 PI) u2))))
float code(float cosTheta_i, float u1, float u2) {
return sqrtf(-logf((1.0f - u1))) * cosf(((2.0f * ((float) M_PI)) * u2));
}
function code(cosTheta_i, u1, u2) return Float32(sqrt(Float32(-log(Float32(Float32(1.0) - u1)))) * cos(Float32(Float32(Float32(2.0) * Float32(pi)) * u2))) end
function tmp = code(cosTheta_i, u1, u2) tmp = sqrt(-log((single(1.0) - u1))) * cos(((single(2.0) * single(pi)) * u2)); end
\begin{array}{l}
\\
\sqrt{-\log \left(1 - u1\right)} \cdot \cos \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)))) (cos (* (* 2.0 PI) u2))))
float code(float cosTheta_i, float u1, float u2) {
return sqrtf(-logf((1.0f - u1))) * cosf(((2.0f * ((float) M_PI)) * u2));
}
function code(cosTheta_i, u1, u2) return Float32(sqrt(Float32(-log(Float32(Float32(1.0) - u1)))) * cos(Float32(Float32(Float32(2.0) * Float32(pi)) * u2))) end
function tmp = code(cosTheta_i, u1, u2) tmp = sqrt(-log((single(1.0) - u1))) * cos(((single(2.0) * single(pi)) * u2)); end
\begin{array}{l}
\\
\sqrt{-\log \left(1 - u1\right)} \cdot \cos \left(\left(2 \cdot \pi\right) \cdot u2\right)
\end{array}
(FPCore (cosTheta_i u1 u2)
:precision binary32
(let* ((t_0 (* (* PI PI) (* u2 u2)))
(t_1 (* PI (* PI PI)))
(t_2 (* u2 (* u2 u2))))
(*
(sqrt (- (log1p (- u1))))
(cos
(/ (fma t_1 t_2 (* t_1 t_2)) (fma (* PI PI) (* u2 u2) (- t_0 t_0)))))))
float code(float cosTheta_i, float u1, float u2) {
float t_0 = (((float) M_PI) * ((float) M_PI)) * (u2 * u2);
float t_1 = ((float) M_PI) * (((float) M_PI) * ((float) M_PI));
float t_2 = u2 * (u2 * u2);
return sqrtf(-log1pf(-u1)) * cosf((fmaf(t_1, t_2, (t_1 * t_2)) / fmaf((((float) M_PI) * ((float) M_PI)), (u2 * u2), (t_0 - t_0))));
}
function code(cosTheta_i, u1, u2) t_0 = Float32(Float32(Float32(pi) * Float32(pi)) * Float32(u2 * u2)) t_1 = Float32(Float32(pi) * Float32(Float32(pi) * Float32(pi))) t_2 = Float32(u2 * Float32(u2 * u2)) return Float32(sqrt(Float32(-log1p(Float32(-u1)))) * cos(Float32(fma(t_1, t_2, Float32(t_1 * t_2)) / fma(Float32(Float32(pi) * Float32(pi)), Float32(u2 * u2), Float32(t_0 - t_0))))) end
\begin{array}{l}
\\
\begin{array}{l}
t_0 := \left(\pi \cdot \pi\right) \cdot \left(u2 \cdot u2\right)\\
t_1 := \pi \cdot \left(\pi \cdot \pi\right)\\
t_2 := u2 \cdot \left(u2 \cdot u2\right)\\
\sqrt{-\mathsf{log1p}\left(-u1\right)} \cdot \cos \left(\frac{\mathsf{fma}\left(t\_1, t\_2, t\_1 \cdot t\_2\right)}{\mathsf{fma}\left(\pi \cdot \pi, u2 \cdot u2, t\_0 - t\_0\right)}\right)
\end{array}
\end{array}
Initial program 57.5%
lift-log.f32N/A
lift--.f32N/A
sub-negN/A
lower-log1p.f32N/A
lower-neg.f3299.0
Applied rewrites99.0%
lift-*.f32N/A
lift-*.f32N/A
associate-*r*N/A
lift-*.f32N/A
count-2N/A
lift-*.f32N/A
lift-*.f32N/A
distribute-lft-outN/A
lower-*.f32N/A
lower-+.f3299.0
Applied rewrites99.0%
lift-*.f32N/A
lift-+.f32N/A
distribute-lft-inN/A
flip3-+N/A
lower-/.f32N/A
Applied rewrites99.0%
(FPCore (cosTheta_i u1 u2)
:precision binary32
(if (<=
(* (sqrt (- (log (- 1.0 u1)))) (cos (* u2 (* PI 2.0))))
0.19499999284744263)
(*
(cos (* PI (+ u2 u2)))
(sqrt (fma (* u1 u1) (fma u1 (fma u1 0.25 0.3333333333333333) 0.5) u1)))
(* (sqrt (- (log1p (- u1)))) (fma (* PI PI) (* (* u2 u2) -2.0) 1.0))))
float code(float cosTheta_i, float u1, float u2) {
float tmp;
if ((sqrtf(-logf((1.0f - u1))) * cosf((u2 * (((float) M_PI) * 2.0f)))) <= 0.19499999284744263f) {
tmp = cosf((((float) M_PI) * (u2 + u2))) * sqrtf(fmaf((u1 * u1), fmaf(u1, fmaf(u1, 0.25f, 0.3333333333333333f), 0.5f), u1));
} else {
tmp = sqrtf(-log1pf(-u1)) * fmaf((((float) M_PI) * ((float) M_PI)), ((u2 * u2) * -2.0f), 1.0f);
}
return tmp;
}
function code(cosTheta_i, u1, u2) tmp = Float32(0.0) if (Float32(sqrt(Float32(-log(Float32(Float32(1.0) - u1)))) * cos(Float32(u2 * Float32(Float32(pi) * Float32(2.0))))) <= Float32(0.19499999284744263)) tmp = Float32(cos(Float32(Float32(pi) * Float32(u2 + u2))) * sqrt(fma(Float32(u1 * u1), fma(u1, fma(u1, Float32(0.25), Float32(0.3333333333333333)), Float32(0.5)), u1))); else tmp = Float32(sqrt(Float32(-log1p(Float32(-u1)))) * fma(Float32(Float32(pi) * Float32(pi)), Float32(Float32(u2 * u2) * Float32(-2.0)), Float32(1.0))); end return tmp end
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;\sqrt{-\log \left(1 - u1\right)} \cdot \cos \left(u2 \cdot \left(\pi \cdot 2\right)\right) \leq 0.19499999284744263:\\
\;\;\;\;\cos \left(\pi \cdot \left(u2 + u2\right)\right) \cdot \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)}\\
\mathbf{else}:\\
\;\;\;\;\sqrt{-\mathsf{log1p}\left(-u1\right)} \cdot \mathsf{fma}\left(\pi \cdot \pi, \left(u2 \cdot u2\right) \cdot -2, 1\right)\\
\end{array}
\end{array}
if (*.f32 (sqrt.f32 (neg.f32 (log.f32 (-.f32 #s(literal 1 binary32) u1)))) (cos.f32 (*.f32 (*.f32 #s(literal 2 binary32) (PI.f32)) u2))) < 0.194999993Initial program 51.1%
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.f3298.7
Applied rewrites98.7%
lift-*.f32N/A
lift-*.f32N/A
associate-*r*N/A
lift-*.f32N/A
count-2N/A
lift-*.f32N/A
lift-*.f32N/A
distribute-lft-outN/A
lower-*.f32N/A
lower-+.f3298.7
Applied rewrites98.7%
if 0.194999993 < (*.f32 (sqrt.f32 (neg.f32 (log.f32 (-.f32 #s(literal 1 binary32) u1)))) (cos.f32 (*.f32 (*.f32 #s(literal 2 binary32) (PI.f32)) u2))) Initial program 97.8%
lift-log.f32N/A
lift--.f32N/A
sub-negN/A
lower-log1p.f32N/A
lower-neg.f3299.3
Applied rewrites99.3%
Taylor expanded in u2 around 0
+-commutativeN/A
associate-*r*N/A
*-commutativeN/A
lower-fma.f32N/A
unpow2N/A
lower-*.f32N/A
lower-PI.f32N/A
lower-PI.f32N/A
lower-*.f32N/A
unpow2N/A
lower-*.f3294.3
Applied rewrites94.3%
Final simplification98.1%
herbie shell --seed 2024223
(FPCore (cosTheta_i u1 u2)
:name "Beckmann Sample, near normal, slope_x"
: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)))) (cos (* (* 2.0 PI) u2))))