
(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 6 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 (sin (* PI u2))) (t_1 (cos (* PI (* 2.0 u2)))))
(*
(sqrt (- (log1p (- u1))))
(+ t_1 (fma (- t_0) t_0 (- 0.5 (* t_1 0.5)))))))
float code(float cosTheta_i, float u1, float u2) {
float t_0 = sinf((((float) M_PI) * u2));
float t_1 = cosf((((float) M_PI) * (2.0f * u2)));
return sqrtf(-log1pf(-u1)) * (t_1 + fmaf(-t_0, t_0, (0.5f - (t_1 * 0.5f))));
}
function code(cosTheta_i, u1, u2) t_0 = sin(Float32(Float32(pi) * u2)) t_1 = cos(Float32(Float32(pi) * Float32(Float32(2.0) * u2))) return Float32(sqrt(Float32(-log1p(Float32(-u1)))) * Float32(t_1 + fma(Float32(-t_0), t_0, Float32(Float32(0.5) - Float32(t_1 * Float32(0.5)))))) end
\begin{array}{l}
\\
\begin{array}{l}
t_0 := \sin \left(\pi \cdot u2\right)\\
t_1 := \cos \left(\pi \cdot \left(2 \cdot u2\right)\right)\\
\sqrt{-\mathsf{log1p}\left(-u1\right)} \cdot \left(t\_1 + \mathsf{fma}\left(-t\_0, t\_0, 0.5 - t\_1 \cdot 0.5\right)\right)
\end{array}
\end{array}
Initial program 56.4%
sub-neg56.4%
log1p-define99.0%
Simplified99.0%
associate-*l*99.0%
cos-298.9%
prod-diff98.9%
fma-neg98.9%
cos-299.0%
associate-*l*99.0%
*-commutative99.0%
associate-*l*99.0%
sqr-sin-a99.1%
associate-*l*99.1%
Applied egg-rr99.1%
Final simplification99.1%
(FPCore (cosTheta_i u1 u2)
:precision binary32
(*
(sqrt (- (log1p (- u1))))
(+
(cos (* PI (* 2.0 u2)))
(*
(pow u2 6.0)
(fma
(pow PI 6.0)
-0.044444444444444446
(* (pow PI 6.0) 0.044444444444444446))))))
float code(float cosTheta_i, float u1, float u2) {
return sqrtf(-log1pf(-u1)) * (cosf((((float) M_PI) * (2.0f * u2))) + (powf(u2, 6.0f) * fmaf(powf(((float) M_PI), 6.0f), -0.044444444444444446f, (powf(((float) M_PI), 6.0f) * 0.044444444444444446f))));
}
function code(cosTheta_i, u1, u2) return Float32(sqrt(Float32(-log1p(Float32(-u1)))) * Float32(cos(Float32(Float32(pi) * Float32(Float32(2.0) * u2))) + Float32((u2 ^ Float32(6.0)) * fma((Float32(pi) ^ Float32(6.0)), Float32(-0.044444444444444446), Float32((Float32(pi) ^ Float32(6.0)) * Float32(0.044444444444444446)))))) end
\begin{array}{l}
\\
\sqrt{-\mathsf{log1p}\left(-u1\right)} \cdot \left(\cos \left(\pi \cdot \left(2 \cdot u2\right)\right) + {u2}^{6} \cdot \mathsf{fma}\left({\pi}^{6}, -0.044444444444444446, {\pi}^{6} \cdot 0.044444444444444446\right)\right)
\end{array}
Initial program 56.4%
sub-neg56.4%
log1p-define99.0%
Simplified99.0%
associate-*l*99.0%
cos-298.9%
prod-diff98.9%
fma-neg98.9%
cos-299.0%
associate-*l*99.0%
*-commutative99.0%
associate-*l*99.0%
sqr-sin-a99.1%
associate-*l*99.1%
Applied egg-rr99.1%
associate-*r*99.1%
*-commutative99.1%
add-cbrt-cube99.1%
pow1/399.1%
pow399.0%
*-commutative99.0%
*-commutative99.0%
Applied egg-rr99.0%
Taylor expanded in u2 around inf 99.0%
Taylor expanded in u2 around 0 99.0%
mul-1-neg99.0%
distribute-rgt-out99.0%
metadata-eval99.0%
metadata-eval99.0%
distribute-rgt-neg-in99.0%
metadata-eval99.0%
metadata-eval99.0%
*-commutative99.0%
metadata-eval99.0%
metadata-eval99.0%
distribute-rgt-neg-in99.0%
metadata-eval99.0%
metadata-eval99.0%
distribute-rgt-out99.0%
mul-1-neg99.0%
Simplified99.0%
Final simplification99.0%
(FPCore (cosTheta_i u1 u2) :precision binary32 (* (sqrt (- (log1p (- u1)))) (cos (* u2 (* PI 2.0)))))
float code(float cosTheta_i, float u1, float u2) {
return sqrtf(-log1pf(-u1)) * cosf((u2 * (((float) M_PI) * 2.0f)));
}
function code(cosTheta_i, u1, u2) return Float32(sqrt(Float32(-log1p(Float32(-u1)))) * cos(Float32(u2 * Float32(Float32(pi) * Float32(2.0))))) end
\begin{array}{l}
\\
\sqrt{-\mathsf{log1p}\left(-u1\right)} \cdot \cos \left(u2 \cdot \left(\pi \cdot 2\right)\right)
\end{array}
Initial program 56.4%
sub-neg56.4%
log1p-define99.0%
Simplified99.0%
Final simplification99.0%
(FPCore (cosTheta_i u1 u2)
:precision binary32
(let* ((t_0 (* u2 (* PI 2.0))))
(if (<= t_0 0.00800000037997961)
(sqrt (- (log1p (- u1))))
(* (cos t_0) (sqrt u1)))))
float code(float cosTheta_i, float u1, float u2) {
float t_0 = u2 * (((float) M_PI) * 2.0f);
float tmp;
if (t_0 <= 0.00800000037997961f) {
tmp = sqrtf(-log1pf(-u1));
} else {
tmp = cosf(t_0) * sqrtf(u1);
}
return tmp;
}
function code(cosTheta_i, u1, u2) t_0 = Float32(u2 * Float32(Float32(pi) * Float32(2.0))) tmp = Float32(0.0) if (t_0 <= Float32(0.00800000037997961)) tmp = sqrt(Float32(-log1p(Float32(-u1)))); else tmp = Float32(cos(t_0) * sqrt(u1)); end return tmp end
\begin{array}{l}
\\
\begin{array}{l}
t_0 := u2 \cdot \left(\pi \cdot 2\right)\\
\mathbf{if}\;t\_0 \leq 0.00800000037997961:\\
\;\;\;\;\sqrt{-\mathsf{log1p}\left(-u1\right)}\\
\mathbf{else}:\\
\;\;\;\;\cos t\_0 \cdot \sqrt{u1}\\
\end{array}
\end{array}
if (*.f32 (*.f32 2 (PI.f32)) u2) < 0.00800000038Initial program 55.6%
sub-neg55.6%
log1p-define99.5%
Simplified99.5%
Taylor expanded in u2 around 0 97.1%
if 0.00800000038 < (*.f32 (*.f32 2 (PI.f32)) u2) Initial program 58.0%
sub-neg58.0%
log1p-define98.1%
Simplified98.1%
add-cbrt-cube41.2%
pow1/341.2%
Applied egg-rr75.2%
Taylor expanded in u1 around 0 78.8%
Final simplification91.4%
(FPCore (cosTheta_i u1 u2) :precision binary32 (sqrt (- (log1p (- u1)))))
float code(float cosTheta_i, float u1, float u2) {
return sqrtf(-log1pf(-u1));
}
function code(cosTheta_i, u1, u2) return sqrt(Float32(-log1p(Float32(-u1)))) end
\begin{array}{l}
\\
\sqrt{-\mathsf{log1p}\left(-u1\right)}
\end{array}
Initial program 56.4%
sub-neg56.4%
log1p-define99.0%
Simplified99.0%
Taylor expanded in u2 around 0 79.6%
Final simplification79.6%
(FPCore (cosTheta_i u1 u2) :precision binary32 (sqrt u1))
float code(float cosTheta_i, float u1, float u2) {
return sqrtf(u1);
}
real(4) function code(costheta_i, u1, u2)
real(4), intent (in) :: costheta_i
real(4), intent (in) :: u1
real(4), intent (in) :: u2
code = sqrt(u1)
end function
function code(cosTheta_i, u1, u2) return sqrt(u1) end
function tmp = code(cosTheta_i, u1, u2) tmp = sqrt(u1); end
\begin{array}{l}
\\
\sqrt{u1}
\end{array}
Initial program 56.4%
sub-neg56.4%
log1p-define99.0%
Simplified99.0%
Taylor expanded in u2 around 0 79.6%
add-cbrt-cube79.6%
pow1/377.4%
Applied egg-rr63.6%
Taylor expanded in u1 around 0 66.4%
Final simplification66.4%
herbie shell --seed 2024043
(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))))