
(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 7 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
(let* ((t_0 (cbrt (PI))) (t_1 (- (log (- 1.0 u1)))))
(if (<= t_1 0.0001500000071246177)
(*
(sqrt (- (- u1)))
(-
(pow (cos (* (pow t_0 2.0) (* t_0 u2))) 2.0)
(pow (sin (* u2 (PI))) 2.0)))
(* (sqrt t_1) (cos (* (PI) (+ u2 u2)))))))\begin{array}{l}
\\
\begin{array}{l}
t_0 := \sqrt[3]{\mathsf{PI}\left(\right)}\\
t_1 := -\log \left(1 - u1\right)\\
\mathbf{if}\;t\_1 \leq 0.0001500000071246177:\\
\;\;\;\;\sqrt{-\left(-u1\right)} \cdot \left({\cos \left({t\_0}^{2} \cdot \left(t\_0 \cdot u2\right)\right)}^{2} - {\sin \left(u2 \cdot \mathsf{PI}\left(\right)\right)}^{2}\right)\\
\mathbf{else}:\\
\;\;\;\;\sqrt{t\_1} \cdot \cos \left(\mathsf{PI}\left(\right) \cdot \left(u2 + u2\right)\right)\\
\end{array}
\end{array}
if (neg.f32 (log.f32 (-.f32 #s(literal 1 binary32) u1))) < 1.50000007e-4Initial program 38.4%
Taylor expanded in u1 around 0
mul-1-negN/A
lower-neg.f3292.6
Applied rewrites92.6%
lift-cos.f32N/A
lift-*.f32N/A
lift-*.f32N/A
associate-*l*N/A
count-2-revN/A
*-commutativeN/A
lift-*.f32N/A
cos-sumN/A
lower--.f32N/A
lift-*.f32N/A
*-commutativeN/A
pow2N/A
lower-pow.f32N/A
lower-cos.f32N/A
*-commutativeN/A
lift-*.f32N/A
lift-*.f32N/A
*-commutativeN/A
Applied rewrites92.4%
lift-*.f32N/A
*-commutativeN/A
lift-PI.f32N/A
add-cube-cbrtN/A
associate-*l*N/A
lower-*.f32N/A
pow2N/A
lower-pow.f32N/A
lift-PI.f32N/A
lower-cbrt.f32N/A
lower-*.f32N/A
lift-PI.f32N/A
lower-cbrt.f3292.6
Applied rewrites92.6%
if 1.50000007e-4 < (neg.f32 (log.f32 (-.f32 #s(literal 1 binary32) u1))) Initial program 90.1%
lift-*.f32N/A
lift-*.f32N/A
associate-*l*N/A
count-2-revN/A
lower-fma.f32N/A
*-commutativeN/A
lower-*.f3273.6
Applied rewrites73.6%
lift-*.f32N/A
*-commutativeN/A
lower-fma.f32N/A
distribute-lft-outN/A
lower-*.f32N/A
lower-+.f3290.1
Applied rewrites90.1%
(FPCore (cosTheta_i u1 u2)
:precision binary32
(let* ((t_0 (cos (* (* 2.0 (PI)) u2))))
(if (<= (* (sqrt (- (log (- 1.0 u1)))) t_0) 0.020999999716877937)
(* (sqrt u1) t_0)
(*
(sqrt (log (/ 1.0 (- 1.0 u1))))
(fma (* -2.0 (* u2 u2)) (* (PI) (PI)) 1.0)))))\begin{array}{l}
\\
\begin{array}{l}
t_0 := \cos \left(\left(2 \cdot \mathsf{PI}\left(\right)\right) \cdot u2\right)\\
\mathbf{if}\;\sqrt{-\log \left(1 - u1\right)} \cdot t\_0 \leq 0.020999999716877937:\\
\;\;\;\;\sqrt{u1} \cdot t\_0\\
\mathbf{else}:\\
\;\;\;\;\sqrt{\log \left(\frac{1}{1 - u1}\right)} \cdot \mathsf{fma}\left(-2 \cdot \left(u2 \cdot u2\right), \mathsf{PI}\left(\right) \cdot \mathsf{PI}\left(\right), 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))) < 0.0209999997Initial program 43.2%
lift-neg.f32N/A
lift-log.f32N/A
neg-logN/A
lower-log.f32N/A
lower-/.f3240.4
Applied rewrites40.4%
Taylor expanded in u1 around 0
lower-sqrt.f3289.4
Applied rewrites89.4%
if 0.0209999997 < (*.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 92.8%
lift-neg.f32N/A
lift-log.f32N/A
neg-logN/A
lower-log.f32N/A
lower-/.f3290.4
Applied rewrites90.4%
Taylor expanded in u2 around 0
+-commutativeN/A
associate-*r*N/A
lower-fma.f32N/A
lower-*.f32N/A
unpow2N/A
lower-*.f32N/A
unpow2N/A
lower-*.f32N/A
lower-PI.f32N/A
lower-PI.f3256.5
Applied rewrites56.0%
(FPCore (cosTheta_i u1 u2)
:precision binary32
(let* ((t_0 (cos (* (* 2.0 (PI)) u2))))
(if (<= (* (sqrt (- (log (- 1.0 u1)))) t_0) 0.020999999716877937)
(* (sqrt u1) t_0)
(sqrt (log (/ (+ u1 1.0) (- 1.0 (* u1 u1))))))))\begin{array}{l}
\\
\begin{array}{l}
t_0 := \cos \left(\left(2 \cdot \mathsf{PI}\left(\right)\right) \cdot u2\right)\\
\mathbf{if}\;\sqrt{-\log \left(1 - u1\right)} \cdot t\_0 \leq 0.020999999716877937:\\
\;\;\;\;\sqrt{u1} \cdot t\_0\\
\mathbf{else}:\\
\;\;\;\;\sqrt{\log \left(\frac{u1 + 1}{1 - u1 \cdot u1}\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))) < 0.0209999997Initial program 43.2%
lift-neg.f32N/A
lift-log.f32N/A
neg-logN/A
lower-log.f32N/A
lower-/.f3240.4
Applied rewrites40.4%
Taylor expanded in u1 around 0
lower-sqrt.f3289.4
Applied rewrites89.4%
if 0.0209999997 < (*.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 92.8%
lift-neg.f32N/A
lift-log.f32N/A
neg-logN/A
lower-log.f32N/A
lower-/.f3290.4
Applied rewrites90.4%
lift-/.f32N/A
lift--.f32N/A
sub-negN/A
lift-neg.f32N/A
flip-+N/A
clear-num-revN/A
lift-neg.f32N/A
lift-neg.f32N/A
sqr-neg-revN/A
lower-/.f32N/A
lift-neg.f32N/A
neg-sub0N/A
associate--r-N/A
metadata-evalN/A
+-commutativeN/A
lower-+.f32N/A
metadata-evalN/A
lower--.f32N/A
lower-*.f3289.7
Applied rewrites89.7%
Taylor expanded in u2 around 0
lower-sqrt.f32N/A
lower-log.f32N/A
lower-/.f32N/A
+-commutativeN/A
lower-+.f32N/A
lower--.f32N/A
unpow2N/A
lower-*.f3275.4
Applied rewrites75.4%
(FPCore (cosTheta_i u1 u2)
:precision binary32
(let* ((t_0 (- (log (- 1.0 u1)))))
(if (<= t_0 0.0001500000071246177)
(* (sqrt u1) (cos (* (* 2.0 (PI)) u2)))
(* (sqrt t_0) (cos (* (PI) (+ u2 u2)))))))\begin{array}{l}
\\
\begin{array}{l}
t_0 := -\log \left(1 - u1\right)\\
\mathbf{if}\;t\_0 \leq 0.0001500000071246177:\\
\;\;\;\;\sqrt{u1} \cdot \cos \left(\left(2 \cdot \mathsf{PI}\left(\right)\right) \cdot u2\right)\\
\mathbf{else}:\\
\;\;\;\;\sqrt{t\_0} \cdot \cos \left(\mathsf{PI}\left(\right) \cdot \left(u2 + u2\right)\right)\\
\end{array}
\end{array}
if (neg.f32 (log.f32 (-.f32 #s(literal 1 binary32) u1))) < 1.50000007e-4Initial program 38.4%
lift-neg.f32N/A
lift-log.f32N/A
neg-logN/A
lower-log.f32N/A
lower-/.f3235.8
Applied rewrites35.8%
Taylor expanded in u1 around 0
lower-sqrt.f3292.6
Applied rewrites92.6%
if 1.50000007e-4 < (neg.f32 (log.f32 (-.f32 #s(literal 1 binary32) u1))) Initial program 90.1%
lift-*.f32N/A
lift-*.f32N/A
associate-*l*N/A
count-2-revN/A
lower-fma.f32N/A
*-commutativeN/A
lower-*.f3273.6
Applied rewrites73.6%
lift-*.f32N/A
*-commutativeN/A
lower-fma.f32N/A
distribute-lft-outN/A
lower-*.f32N/A
lower-+.f3290.1
Applied rewrites90.1%
(FPCore (cosTheta_i u1 u2) :precision binary32 (* (sqrt u1) (cos (* (* 2.0 (PI)) u2))))
\begin{array}{l}
\\
\sqrt{u1} \cdot \cos \left(\left(2 \cdot \mathsf{PI}\left(\right)\right) \cdot u2\right)
\end{array}
Initial program 60.6%
lift-neg.f32N/A
lift-log.f32N/A
neg-logN/A
lower-log.f32N/A
lower-/.f3257.9
Applied rewrites57.9%
Taylor expanded in u1 around 0
lower-sqrt.f3275.1
Applied rewrites75.1%
(FPCore (cosTheta_i u1 u2) :precision binary32 (* (sqrt u1) (+ 1.0 (* (* (* (* u2 u2) -2.0) (PI)) (PI)))))
\begin{array}{l}
\\
\sqrt{u1} \cdot \left(1 + \left(\left(\left(u2 \cdot u2\right) \cdot -2\right) \cdot \mathsf{PI}\left(\right)\right) \cdot \mathsf{PI}\left(\right)\right)
\end{array}
Initial program 60.6%
lift-neg.f32N/A
lift-log.f32N/A
neg-logN/A
lower-log.f32N/A
lower-/.f3257.9
Applied rewrites57.9%
Taylor expanded in u1 around 0
lower-sqrt.f3275.1
Applied rewrites75.1%
Taylor expanded in u2 around 0
+-commutativeN/A
associate-*r*N/A
lower-fma.f32N/A
lower-*.f32N/A
unpow2N/A
lower-*.f32N/A
unpow2N/A
lower-*.f32N/A
lower-PI.f32N/A
lower-PI.f3265.5
Applied rewrites65.2%
Applied rewrites69.9%
Final simplification69.9%
(FPCore (cosTheta_i u1 u2) :precision binary32 (* (sqrt (- (- u1))) 1.0))
float code(float cosTheta_i, float u1, float u2) {
return sqrtf(-(-u1)) * 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)) * 1.0e0
end function
function code(cosTheta_i, u1, u2) return Float32(sqrt(Float32(-Float32(-u1))) * Float32(1.0)) end
function tmp = code(cosTheta_i, u1, u2) tmp = sqrt(-(-u1)) * single(1.0); end
\begin{array}{l}
\\
\sqrt{-\left(-u1\right)} \cdot 1
\end{array}
Initial program 60.6%
Taylor expanded in u1 around 0
mul-1-negN/A
lower-neg.f3275.1
Applied rewrites75.1%
lift-cos.f32N/A
lift-*.f32N/A
lift-*.f32N/A
associate-*l*N/A
count-2-revN/A
*-commutativeN/A
lift-*.f32N/A
cos-sumN/A
lower--.f32N/A
lift-*.f32N/A
*-commutativeN/A
pow2N/A
lower-pow.f32N/A
lower-cos.f32N/A
*-commutativeN/A
lift-*.f32N/A
lift-*.f32N/A
*-commutativeN/A
Applied rewrites75.0%
lift-*.f32N/A
*-commutativeN/A
lift-PI.f32N/A
add-cube-cbrtN/A
associate-*l*N/A
lower-*.f32N/A
pow2N/A
lower-pow.f32N/A
lift-PI.f32N/A
lower-cbrt.f32N/A
lower-*.f32N/A
lift-PI.f32N/A
lower-cbrt.f3275.1
Applied rewrites75.1%
Taylor expanded in u2 around 0
Applied rewrites65.5%
herbie shell --seed 2024305
(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))))