
(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 5 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 (* (sqrt (- (log1p (- u1)))) (cos (* 2.0 (* PI u2)))))
float code(float cosTheta_i, float u1, float u2) {
return sqrtf(-log1pf(-u1)) * cosf((2.0f * (((float) M_PI) * u2)));
}
function code(cosTheta_i, u1, u2) return Float32(sqrt(Float32(-log1p(Float32(-u1)))) * cos(Float32(Float32(2.0) * Float32(Float32(pi) * u2)))) end
\begin{array}{l}
\\
\sqrt{-\mathsf{log1p}\left(-u1\right)} \cdot \cos \left(2 \cdot \left(\pi \cdot u2\right)\right)
\end{array}
Initial program 58.8%
sub-neg58.8%
log1p-def99.3%
associate-*l*99.3%
Simplified99.3%
Final simplification99.3%
(FPCore (cosTheta_i u1 u2)
:precision binary32
(let* ((t_0 (* u2 (* 2.0 PI))))
(if (<= t_0 0.00800000037997961)
(sqrt (- (log1p (- u1))))
(* (sqrt u1) (cos t_0)))))
float code(float cosTheta_i, float u1, float u2) {
float t_0 = u2 * (2.0f * ((float) M_PI));
float tmp;
if (t_0 <= 0.00800000037997961f) {
tmp = sqrtf(-log1pf(-u1));
} else {
tmp = sqrtf(u1) * cosf(t_0);
}
return tmp;
}
function code(cosTheta_i, u1, u2) t_0 = Float32(u2 * Float32(Float32(2.0) * Float32(pi))) tmp = Float32(0.0) if (t_0 <= Float32(0.00800000037997961)) tmp = sqrt(Float32(-log1p(Float32(-u1)))); else tmp = Float32(sqrt(u1) * cos(t_0)); end return tmp end
\begin{array}{l}
\\
\begin{array}{l}
t_0 := u2 \cdot \left(2 \cdot \pi\right)\\
\mathbf{if}\;t_0 \leq 0.00800000037997961:\\
\;\;\;\;\sqrt{-\mathsf{log1p}\left(-u1\right)}\\
\mathbf{else}:\\
\;\;\;\;\sqrt{u1} \cdot \cos t_0\\
\end{array}
\end{array}
if (*.f32 (*.f32 2 (PI.f32)) u2) < 0.00800000038Initial program 59.3%
sub-neg59.3%
log1p-def99.6%
associate-*l*99.6%
Simplified99.6%
Taylor expanded in u2 around 0 98.1%
if 0.00800000038 < (*.f32 (*.f32 2 (PI.f32)) u2) Initial program 57.5%
add-cube-cbrt57.4%
pow357.4%
add-sqr-sqrt57.4%
sqrt-unprod57.4%
sqr-neg57.4%
sqrt-unprod1.6%
add-sqr-sqrt1.6%
sub-neg1.6%
log1p-udef-0.0%
add-sqr-sqrt-0.0%
sqrt-unprod74.6%
sqr-neg74.6%
sqrt-unprod74.6%
add-sqr-sqrt74.6%
Applied egg-rr74.6%
Taylor expanded in u1 around 0 76.7%
Final simplification92.2%
(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 58.8%
sub-neg58.8%
log1p-def99.3%
associate-*l*99.3%
Simplified99.3%
Taylor expanded in u2 around 0 82.4%
Final simplification82.4%
(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 58.8%
sub-neg58.8%
log1p-def99.3%
associate-*l*99.3%
Simplified99.3%
Taylor expanded in u2 around 0 82.4%
add-sqr-sqrt81.6%
pow281.6%
pow1/281.6%
sqrt-pow181.6%
add-sqr-sqrt81.6%
sqrt-unprod81.6%
sqr-neg81.6%
sqrt-unprod-0.0%
add-sqr-sqrt-0.0%
add-sqr-sqrt-0.0%
sqrt-unprod64.6%
sqr-neg64.6%
sqrt-unprod64.6%
add-sqr-sqrt64.6%
metadata-eval64.6%
Applied egg-rr64.6%
Taylor expanded in u1 around 0 66.5%
Final simplification66.5%
(FPCore (cosTheta_i u1 u2) :precision binary32 (* u1 (* u1 0.5)))
float code(float cosTheta_i, float u1, float u2) {
return u1 * (u1 * 0.5f);
}
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 = u1 * (u1 * 0.5e0)
end function
function code(cosTheta_i, u1, u2) return Float32(u1 * Float32(u1 * Float32(0.5))) end
function tmp = code(cosTheta_i, u1, u2) tmp = u1 * (u1 * single(0.5)); end
\begin{array}{l}
\\
u1 \cdot \left(u1 \cdot 0.5\right)
\end{array}
Initial program 58.8%
sub-neg58.8%
log1p-def99.3%
associate-*l*99.3%
Simplified99.3%
Taylor expanded in u2 around 0 82.4%
Taylor expanded in u1 around 0 79.0%
Taylor expanded in u1 around inf 14.4%
*-commutative14.4%
unpow214.4%
associate-*l*14.4%
Simplified14.4%
Final simplification14.4%
herbie shell --seed 2023268
(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))))