
(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 (* (cos (* (* 2.0 PI) u2)) (sqrt (- (log1p (- u1))))))
float code(float cosTheta_i, float u1, float u2) {
return cosf(((2.0f * ((float) M_PI)) * u2)) * sqrtf(-log1pf(-u1));
}
function code(cosTheta_i, u1, u2) return Float32(cos(Float32(Float32(Float32(2.0) * Float32(pi)) * u2)) * sqrt(Float32(-log1p(Float32(-u1))))) end
\begin{array}{l}
\\
\cos \left(\left(2 \cdot \pi\right) \cdot u2\right) \cdot \sqrt{-\mathsf{log1p}\left(-u1\right)}
\end{array}
Initial program 53.9%
sub-neg53.9%
log1p-def99.2%
Simplified99.2%
Final simplification99.2%
(FPCore (cosTheta_i u1 u2)
:precision binary32
(let* ((t_0 (cos (* (* 2.0 PI) u2))))
(if (<= t_0 0.999998927116394)
(* t_0 (sqrt (* u1 (- (* u1 (- -0.5)) -1.0))))
(sqrt (- (log1p (- u1)))))))
float code(float cosTheta_i, float u1, float u2) {
float t_0 = cosf(((2.0f * ((float) M_PI)) * u2));
float tmp;
if (t_0 <= 0.999998927116394f) {
tmp = t_0 * sqrtf((u1 * ((u1 * -(-0.5f)) - -1.0f)));
} else {
tmp = sqrtf(-log1pf(-u1));
}
return tmp;
}
function code(cosTheta_i, u1, u2) t_0 = cos(Float32(Float32(Float32(2.0) * Float32(pi)) * u2)) tmp = Float32(0.0) if (t_0 <= Float32(0.999998927116394)) tmp = Float32(t_0 * sqrt(Float32(u1 * Float32(Float32(u1 * Float32(-Float32(-0.5))) - Float32(-1.0))))); else tmp = sqrt(Float32(-log1p(Float32(-u1)))); end return tmp end
\begin{array}{l}
\\
\begin{array}{l}
t_0 := \cos \left(\left(2 \cdot \pi\right) \cdot u2\right)\\
\mathbf{if}\;t\_0 \leq 0.999998927116394:\\
\;\;\;\;t\_0 \cdot \sqrt{u1 \cdot \left(u1 \cdot \left(--0.5\right) - -1\right)}\\
\mathbf{else}:\\
\;\;\;\;\sqrt{-\mathsf{log1p}\left(-u1\right)}\\
\end{array}
\end{array}
if (cos.f32 (*.f32 (*.f32 2 (PI.f32)) u2)) < 0.999998927Initial program 57.6%
Taylor expanded in u1 around 0 86.4%
*-commutative86.4%
*-commutative86.4%
unpow286.4%
associate-*l*86.4%
distribute-lft-out86.3%
Simplified86.3%
if 0.999998927 < (cos.f32 (*.f32 (*.f32 2 (PI.f32)) u2)) Initial program 51.6%
sub-neg51.6%
log1p-def99.6%
Simplified99.6%
Taylor expanded in u2 around 0 99.1%
Final simplification94.1%
(FPCore (cosTheta_i u1 u2)
:precision binary32
(let* ((t_0 (* (* 2.0 PI) u2)))
(if (<= t_0 0.0044999998062849045)
(sqrt (- (log1p (- u1))))
(* (cos t_0) (sqrt u1)))))
float code(float cosTheta_i, float u1, float u2) {
float t_0 = (2.0f * ((float) M_PI)) * u2;
float tmp;
if (t_0 <= 0.0044999998062849045f) {
tmp = sqrtf(-log1pf(-u1));
} else {
tmp = cosf(t_0) * sqrtf(u1);
}
return tmp;
}
function code(cosTheta_i, u1, u2) t_0 = Float32(Float32(Float32(2.0) * Float32(pi)) * u2) tmp = Float32(0.0) if (t_0 <= Float32(0.0044999998062849045)) 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 := \left(2 \cdot \pi\right) \cdot u2\\
\mathbf{if}\;t\_0 \leq 0.0044999998062849045:\\
\;\;\;\;\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) < 0.00449999981Initial program 52.6%
sub-neg52.6%
log1p-def99.5%
Simplified99.5%
Taylor expanded in u2 around 0 98.1%
if 0.00449999981 < (*.f32 (*.f32 2 (PI.f32)) u2) Initial program 56.4%
sub-neg56.4%
log1p-def98.5%
Simplified98.5%
neg-mul-198.5%
log1p-udef56.4%
sub-neg56.4%
neg-mul-156.4%
add-sqr-sqrt56.2%
pow256.2%
Applied egg-rr74.4%
Taylor expanded in u1 around 0 76.4%
Final simplification90.6%
(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 53.9%
sub-neg53.9%
log1p-def99.2%
Simplified99.2%
Taylor expanded in u2 around 0 78.4%
Final simplification78.4%
(FPCore (cosTheta_i u1 u2) :precision binary32 (sqrt (* u1 (- (* u1 (- -0.5)) -1.0))))
float code(float cosTheta_i, float u1, float u2) {
return sqrtf((u1 * ((u1 * -(-0.5f)) - -1.0f)));
}
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 * ((u1 * -(-0.5e0)) - (-1.0e0))))
end function
function code(cosTheta_i, u1, u2) return sqrt(Float32(u1 * Float32(Float32(u1 * Float32(-Float32(-0.5))) - Float32(-1.0)))) end
function tmp = code(cosTheta_i, u1, u2) tmp = sqrt((u1 * ((u1 * -single(-0.5)) - single(-1.0)))); end
\begin{array}{l}
\\
\sqrt{u1 \cdot \left(u1 \cdot \left(--0.5\right) - -1\right)}
\end{array}
Initial program 53.9%
Taylor expanded in u1 around 0 89.4%
*-commutative89.4%
*-commutative89.4%
unpow289.4%
associate-*l*89.4%
distribute-lft-out89.3%
Simplified89.3%
Taylor expanded in u2 around 0 72.7%
Final simplification72.7%
(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 53.9%
sub-neg53.9%
log1p-def99.2%
Simplified99.2%
expm1-log1p-u98.9%
associate-*l*98.9%
Applied egg-rr98.9%
Taylor expanded in u1 around 0 78.0%
mul-1-neg78.0%
Simplified78.0%
Taylor expanded in u2 around 0 65.1%
Final simplification65.1%
herbie shell --seed 2024039
(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))))