
(FPCore (u1 u2) :precision binary64 (+ (* (* (/ 1.0 6.0) (pow (* -2.0 (log u1)) 0.5)) (cos (* (* 2.0 (PI)) u2))) 0.5))
\begin{array}{l}
\\
\left(\frac{1}{6} \cdot {\left(-2 \cdot \log u1\right)}^{0.5}\right) \cdot \cos \left(\left(2 \cdot \mathsf{PI}\left(\right)\right) \cdot u2\right) + 0.5
\end{array}
Sampling outcomes in binary64 precision:
Herbie found 5 alternatives:
| Alternative | Accuracy | Speedup |
|---|
(FPCore (u1 u2) :precision binary64 (+ (* (* (/ 1.0 6.0) (pow (* -2.0 (log u1)) 0.5)) (cos (* (* 2.0 (PI)) u2))) 0.5))
\begin{array}{l}
\\
\left(\frac{1}{6} \cdot {\left(-2 \cdot \log u1\right)}^{0.5}\right) \cdot \cos \left(\left(2 \cdot \mathsf{PI}\left(\right)\right) \cdot u2\right) + 0.5
\end{array}
(FPCore (u1 u2) :precision binary64 (+ (* (* (* 0.16666666666666666 (sqrt 2.0)) (sqrt (- (log u1)))) (cos (* (* 2.0 (PI)) u2))) 0.5))
\begin{array}{l}
\\
\left(\left(0.16666666666666666 \cdot \sqrt{2}\right) \cdot \sqrt{-\log u1}\right) \cdot \cos \left(\left(2 \cdot \mathsf{PI}\left(\right)\right) \cdot u2\right) + 0.5
\end{array}
Initial program 99.4%
lift-*.f64N/A
*-commutativeN/A
lift-pow.f64N/A
sqr-powN/A
associate-*l*N/A
lower-*.f64N/A
metadata-evalN/A
metadata-evalN/A
lower-pow.f64N/A
lift-*.f64N/A
*-commutativeN/A
lower-*.f64N/A
metadata-evalN/A
lower-*.f64N/A
metadata-evalN/A
metadata-evalN/A
lower-pow.f64N/A
lift-*.f64N/A
*-commutativeN/A
lower-*.f64N/A
metadata-eval99.2
lift-/.f64N/A
metadata-eval99.2
Applied rewrites99.2%
Taylor expanded in u1 around inf
*-commutativeN/A
associate-*r*N/A
lower-*.f64N/A
lower-*.f64N/A
lower-sqrt.f64N/A
lower-sqrt.f64N/A
log-recN/A
lower-neg.f64N/A
lower-log.f6499.6
Applied rewrites99.6%
(FPCore (u1 u2) :precision binary64 (+ (* (* 0.16666666666666666 (* (sqrt 2.0) (sqrt (- (log u1))))) (fma (* (* (PI) (PI)) -2.0) (* u2 u2) 1.0)) 0.5))
\begin{array}{l}
\\
\left(0.16666666666666666 \cdot \left(\sqrt{2} \cdot \sqrt{-\log u1}\right)\right) \cdot \mathsf{fma}\left(\left(\mathsf{PI}\left(\right) \cdot \mathsf{PI}\left(\right)\right) \cdot -2, u2 \cdot u2, 1\right) + 0.5
\end{array}
Initial program 99.4%
Taylor expanded in u1 around inf
*-commutativeN/A
lower-*.f64N/A
lower-sqrt.f64N/A
lower-sqrt.f64N/A
log-recN/A
lower-neg.f64N/A
lower-log.f6499.5
Applied rewrites99.5%
Taylor expanded in u2 around 0
+-commutativeN/A
rem-square-sqrtN/A
unpow2N/A
*-commutativeN/A
associate-*r*N/A
*-commutativeN/A
unpow2N/A
rem-square-sqrtN/A
*-commutativeN/A
lower-fma.f64N/A
Applied rewrites99.4%
lift-/.f64N/A
metadata-eval99.4
Applied rewrites99.4%
(FPCore (u1 u2) :precision binary64 (fma (* (fma (* u2 u2) (* (* (PI) (PI)) -2.0) 1.0) (sqrt (* (- (log u1)) 2.0))) 0.16666666666666666 0.5))
\begin{array}{l}
\\
\mathsf{fma}\left(\mathsf{fma}\left(u2 \cdot u2, \left(\mathsf{PI}\left(\right) \cdot \mathsf{PI}\left(\right)\right) \cdot -2, 1\right) \cdot \sqrt{\left(-\log u1\right) \cdot 2}, 0.16666666666666666, 0.5\right)
\end{array}
Initial program 99.4%
Taylor expanded in u1 around inf
*-commutativeN/A
lower-*.f64N/A
lower-sqrt.f64N/A
lower-sqrt.f64N/A
log-recN/A
lower-neg.f64N/A
lower-log.f6499.5
Applied rewrites99.5%
Taylor expanded in u2 around 0
+-commutativeN/A
rem-square-sqrtN/A
unpow2N/A
*-commutativeN/A
associate-*r*N/A
*-commutativeN/A
unpow2N/A
rem-square-sqrtN/A
*-commutativeN/A
lower-fma.f64N/A
Applied rewrites99.4%
lift-+.f64N/A
Applied rewrites99.3%
(FPCore (u1 u2) :precision binary64 (fma (* 0.16666666666666666 (sqrt 2.0)) (sqrt (- (log u1))) 0.5))
double code(double u1, double u2) {
return fma((0.16666666666666666 * sqrt(2.0)), sqrt(-log(u1)), 0.5);
}
function code(u1, u2) return fma(Float64(0.16666666666666666 * sqrt(2.0)), sqrt(Float64(-log(u1))), 0.5) end
code[u1_, u2_] := N[(N[(0.16666666666666666 * N[Sqrt[2.0], $MachinePrecision]), $MachinePrecision] * N[Sqrt[(-N[Log[u1], $MachinePrecision])], $MachinePrecision] + 0.5), $MachinePrecision]
\begin{array}{l}
\\
\mathsf{fma}\left(0.16666666666666666 \cdot \sqrt{2}, \sqrt{-\log u1}, 0.5\right)
\end{array}
Initial program 99.4%
Taylor expanded in u2 around 0
+-commutativeN/A
*-commutativeN/A
associate-*r*N/A
lower-fma.f64N/A
*-commutativeN/A
lower-*.f64N/A
lower-sqrt.f64N/A
lower-sqrt.f64N/A
lower-log.f640.0
Applied rewrites0.0%
Applied rewrites98.7%
Taylor expanded in u1 around inf
Applied rewrites99.1%
(FPCore (u1 u2) :precision binary64 (fma (sqrt (* (log u1) -2.0)) 0.16666666666666666 0.5))
double code(double u1, double u2) {
return fma(sqrt((log(u1) * -2.0)), 0.16666666666666666, 0.5);
}
function code(u1, u2) return fma(sqrt(Float64(log(u1) * -2.0)), 0.16666666666666666, 0.5) end
code[u1_, u2_] := N[(N[Sqrt[N[(N[Log[u1], $MachinePrecision] * -2.0), $MachinePrecision]], $MachinePrecision] * 0.16666666666666666 + 0.5), $MachinePrecision]
\begin{array}{l}
\\
\mathsf{fma}\left(\sqrt{\log u1 \cdot -2}, 0.16666666666666666, 0.5\right)
\end{array}
Initial program 99.4%
Taylor expanded in u2 around 0
+-commutativeN/A
*-commutativeN/A
associate-*r*N/A
lower-fma.f64N/A
*-commutativeN/A
lower-*.f64N/A
lower-sqrt.f64N/A
lower-sqrt.f64N/A
lower-log.f640.0
Applied rewrites0.0%
Applied rewrites98.9%
herbie shell --seed 2025009
(FPCore (u1 u2)
:name "normal distribution"
:precision binary64
:pre (and (and (<= 0.0 u1) (<= u1 1.0)) (and (<= 0.0 u2) (<= u2 1.0)))
(+ (* (* (/ 1.0 6.0) (pow (* -2.0 (log u1)) 0.5)) (cos (* (* 2.0 (PI)) u2))) 0.5))