
(FPCore (cosTheta_i u1 u2) :precision binary32 (* (sqrt (- (log (- 1.0 u1)))) (cos (* (* 2.0 (PI)) u2))))
\begin{array}{l}
\\
\sqrt{-\log \left(1 - u1\right)} \cdot \cos \left(\left(2 \cdot \mathsf{PI}\left(\right)\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))))
\begin{array}{l}
\\
\sqrt{-\log \left(1 - u1\right)} \cdot \cos \left(\left(2 \cdot \mathsf{PI}\left(\right)\right) \cdot u2\right)
\end{array}
(FPCore (cosTheta_i u1 u2)
:precision binary32
(if (<= (- 1.0 u1) 0.9998800158500671)
(* (cos (* u2 (* (PI) 2.0))) (sqrt (- (log (- 1.0 u1)))))
(*
(sqrt u1)
(cos
(*
(* (* (* (sqrt (PI)) u2) (pow (PI) 0.16666666666666666)) (cbrt (PI)))
2.0)))))\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;1 - u1 \leq 0.9998800158500671:\\
\;\;\;\;\cos \left(u2 \cdot \left(\mathsf{PI}\left(\right) \cdot 2\right)\right) \cdot \sqrt{-\log \left(1 - u1\right)}\\
\mathbf{else}:\\
\;\;\;\;\sqrt{u1} \cdot \cos \left(\left(\left(\left(\sqrt{\mathsf{PI}\left(\right)} \cdot u2\right) \cdot {\mathsf{PI}\left(\right)}^{0.16666666666666666}\right) \cdot \sqrt[3]{\mathsf{PI}\left(\right)}\right) \cdot 2\right)\\
\end{array}
\end{array}
if (-.f32 #s(literal 1 binary32) u1) < 0.999880016Initial program 88.8%
if 0.999880016 < (-.f32 #s(literal 1 binary32) u1) Initial program 36.7%
Applied rewrites60.9%
Taylor expanded in u1 around 0
*-commutativeN/A
lower-*.f32N/A
lower-cos.f32N/A
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-PI.f32N/A
lower-sqrt.f3293.3
Applied rewrites93.3%
Applied rewrites93.3%
Final simplification91.6%
(FPCore (cosTheta_i u1 u2) :precision binary32 (if (<= (- 1.0 u1) 0.9998800158500671) (* (cos (* u2 (* (PI) 2.0))) (sqrt (- (log (- 1.0 u1))))) (* (/ (* (sqrt u1) u1) u1) (cos (* (* u2 (PI)) 2.0)))))
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;1 - u1 \leq 0.9998800158500671:\\
\;\;\;\;\cos \left(u2 \cdot \left(\mathsf{PI}\left(\right) \cdot 2\right)\right) \cdot \sqrt{-\log \left(1 - u1\right)}\\
\mathbf{else}:\\
\;\;\;\;\frac{\sqrt{u1} \cdot u1}{u1} \cdot \cos \left(\left(u2 \cdot \mathsf{PI}\left(\right)\right) \cdot 2\right)\\
\end{array}
\end{array}
if (-.f32 #s(literal 1 binary32) u1) < 0.999880016Initial program 88.8%
if 0.999880016 < (-.f32 #s(literal 1 binary32) u1) Initial program 36.7%
Applied rewrites62.7%
Taylor expanded in u1 around 0
*-commutativeN/A
lower-*.f32N/A
lower-cos.f32N/A
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-PI.f32N/A
lower-sqrt.f3293.3
Applied rewrites93.3%
Applied rewrites93.0%
Applied rewrites93.3%
Final simplification91.6%
(FPCore (cosTheta_i u1 u2) :precision binary32 (* (/ (* (sqrt u1) u1) u1) (cos (* (* u2 (PI)) 2.0))))
\begin{array}{l}
\\
\frac{\sqrt{u1} \cdot u1}{u1} \cdot \cos \left(\left(u2 \cdot \mathsf{PI}\left(\right)\right) \cdot 2\right)
\end{array}
Initial program 56.3%
Applied rewrites54.9%
Taylor expanded in u1 around 0
*-commutativeN/A
lower-*.f32N/A
lower-cos.f32N/A
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-PI.f32N/A
lower-sqrt.f3278.1
Applied rewrites78.1%
Applied rewrites77.9%
Applied rewrites78.1%
Final simplification78.1%
(FPCore (cosTheta_i u1 u2) :precision binary32 (* (cos (* (* u2 (PI)) 2.0)) (sqrt u1)))
\begin{array}{l}
\\
\cos \left(\left(u2 \cdot \mathsf{PI}\left(\right)\right) \cdot 2\right) \cdot \sqrt{u1}
\end{array}
Initial program 56.3%
Applied rewrites54.4%
Taylor expanded in u1 around 0
*-commutativeN/A
lower-*.f32N/A
lower-cos.f32N/A
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-PI.f32N/A
lower-sqrt.f3278.1
Applied rewrites78.1%
Final simplification78.1%
(FPCore (cosTheta_i u1 u2) :precision binary32 (* 1.0 (sqrt u1)))
float code(float cosTheta_i, float u1, float u2) {
return 1.0f * 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 = 1.0e0 * sqrt(u1)
end function
function code(cosTheta_i, u1, u2) return Float32(Float32(1.0) * sqrt(u1)) end
function tmp = code(cosTheta_i, u1, u2) tmp = single(1.0) * sqrt(u1); end
\begin{array}{l}
\\
1 \cdot \sqrt{u1}
\end{array}
Initial program 56.3%
Applied rewrites53.5%
Taylor expanded in u1 around 0
*-commutativeN/A
lower-*.f32N/A
lower-cos.f32N/A
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-PI.f32N/A
lower-sqrt.f3278.1
Applied rewrites78.1%
Taylor expanded in u2 around 0
Applied rewrites68.4%
herbie shell --seed 2024304
(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))))