
(FPCore (cosTheta alpha)
:precision binary32
(let* ((t_0 (- (* alpha alpha) 1.0)))
(/
t_0
(* (* PI (log (* alpha alpha))) (+ 1.0 (* (* t_0 cosTheta) cosTheta))))))
float code(float cosTheta, float alpha) {
float t_0 = (alpha * alpha) - 1.0f;
return t_0 / ((((float) M_PI) * logf((alpha * alpha))) * (1.0f + ((t_0 * cosTheta) * cosTheta)));
}
function code(cosTheta, alpha) t_0 = Float32(Float32(alpha * alpha) - Float32(1.0)) return Float32(t_0 / Float32(Float32(Float32(pi) * log(Float32(alpha * alpha))) * Float32(Float32(1.0) + Float32(Float32(t_0 * cosTheta) * cosTheta)))) end
function tmp = code(cosTheta, alpha) t_0 = (alpha * alpha) - single(1.0); tmp = t_0 / ((single(pi) * log((alpha * alpha))) * (single(1.0) + ((t_0 * cosTheta) * cosTheta))); end
\begin{array}{l}
\\
\begin{array}{l}
t_0 := \alpha \cdot \alpha - 1\\
\frac{t\_0}{\left(\pi \cdot \log \left(\alpha \cdot \alpha\right)\right) \cdot \left(1 + \left(t\_0 \cdot cosTheta\right) \cdot cosTheta\right)}
\end{array}
\end{array}
Sampling outcomes in binary32 precision:
Herbie found 7 alternatives:
| Alternative | Accuracy | Speedup |
|---|
(FPCore (cosTheta alpha)
:precision binary32
(let* ((t_0 (- (* alpha alpha) 1.0)))
(/
t_0
(* (* PI (log (* alpha alpha))) (+ 1.0 (* (* t_0 cosTheta) cosTheta))))))
float code(float cosTheta, float alpha) {
float t_0 = (alpha * alpha) - 1.0f;
return t_0 / ((((float) M_PI) * logf((alpha * alpha))) * (1.0f + ((t_0 * cosTheta) * cosTheta)));
}
function code(cosTheta, alpha) t_0 = Float32(Float32(alpha * alpha) - Float32(1.0)) return Float32(t_0 / Float32(Float32(Float32(pi) * log(Float32(alpha * alpha))) * Float32(Float32(1.0) + Float32(Float32(t_0 * cosTheta) * cosTheta)))) end
function tmp = code(cosTheta, alpha) t_0 = (alpha * alpha) - single(1.0); tmp = t_0 / ((single(pi) * log((alpha * alpha))) * (single(1.0) + ((t_0 * cosTheta) * cosTheta))); end
\begin{array}{l}
\\
\begin{array}{l}
t_0 := \alpha \cdot \alpha - 1\\
\frac{t\_0}{\left(\pi \cdot \log \left(\alpha \cdot \alpha\right)\right) \cdot \left(1 + \left(t\_0 \cdot cosTheta\right) \cdot cosTheta\right)}
\end{array}
\end{array}
(FPCore (cosTheta alpha) :precision binary32 (/ (fma alpha alpha -1.0) (* (* PI (* (log alpha) 2.0)) (fma (fma alpha alpha -1.0) (* cosTheta cosTheta) 1.0))))
float code(float cosTheta, float alpha) {
return fmaf(alpha, alpha, -1.0f) / ((((float) M_PI) * (logf(alpha) * 2.0f)) * fmaf(fmaf(alpha, alpha, -1.0f), (cosTheta * cosTheta), 1.0f));
}
function code(cosTheta, alpha) return Float32(fma(alpha, alpha, Float32(-1.0)) / Float32(Float32(Float32(pi) * Float32(log(alpha) * Float32(2.0))) * fma(fma(alpha, alpha, Float32(-1.0)), Float32(cosTheta * cosTheta), Float32(1.0)))) end
\begin{array}{l}
\\
\frac{\mathsf{fma}\left(\alpha, \alpha, -1\right)}{\left(\pi \cdot \left(\log \alpha \cdot 2\right)\right) \cdot \mathsf{fma}\left(\mathsf{fma}\left(\alpha, \alpha, -1\right), cosTheta \cdot cosTheta, 1\right)}
\end{array}
Initial program 98.5%
lift-+.f32N/A
+-commutativeN/A
lift-*.f32N/A
lift-*.f32N/A
associate-*l*N/A
lower-fma.f32N/A
lift--.f32N/A
sub-negN/A
lift-*.f32N/A
lower-fma.f32N/A
metadata-evalN/A
lower-*.f3298.5
Applied rewrites98.5%
Taylor expanded in alpha around 0
*-commutativeN/A
lower-*.f32N/A
lower-log.f3298.5
Applied rewrites98.5%
Taylor expanded in alpha around 0
sub-negN/A
unpow2N/A
metadata-evalN/A
lower-fma.f3298.5
Applied rewrites98.5%
(FPCore (cosTheta alpha) :precision binary32 (/ (+ -1.0 (* alpha alpha)) (* (* PI (log alpha)) (* 2.0 (- 1.0 (* cosTheta cosTheta))))))
float code(float cosTheta, float alpha) {
return (-1.0f + (alpha * alpha)) / ((((float) M_PI) * logf(alpha)) * (2.0f * (1.0f - (cosTheta * cosTheta))));
}
function code(cosTheta, alpha) return Float32(Float32(Float32(-1.0) + Float32(alpha * alpha)) / Float32(Float32(Float32(pi) * log(alpha)) * Float32(Float32(2.0) * Float32(Float32(1.0) - Float32(cosTheta * cosTheta))))) end
function tmp = code(cosTheta, alpha) tmp = (single(-1.0) + (alpha * alpha)) / ((single(pi) * log(alpha)) * (single(2.0) * (single(1.0) - (cosTheta * cosTheta)))); end
\begin{array}{l}
\\
\frac{-1 + \alpha \cdot \alpha}{\left(\pi \cdot \log \alpha\right) \cdot \left(2 \cdot \left(1 - cosTheta \cdot cosTheta\right)\right)}
\end{array}
Initial program 98.5%
lift-+.f32N/A
flip-+N/A
clear-numN/A
clear-numN/A
flip-+N/A
lift-+.f32N/A
lower-/.f32N/A
lower-/.f3298.5
lift-+.f32N/A
+-commutativeN/A
lift-*.f32N/A
lift-*.f32N/A
associate-*l*N/A
Applied rewrites98.5%
Taylor expanded in alpha around 0
*-commutativeN/A
associate-*r*N/A
associate-*l*N/A
lower-*.f32N/A
lower-*.f32N/A
lower-PI.f32N/A
lower-log.f32N/A
lower-*.f32N/A
mul-1-negN/A
unsub-negN/A
lower--.f32N/A
unpow2N/A
lower-*.f3297.5
Applied rewrites97.5%
Final simplification97.5%
herbie shell --seed 2024223
(FPCore (cosTheta alpha)
:name "GTR1 distribution"
:precision binary32
:pre (and (and (<= 0.0 cosTheta) (<= cosTheta 1.0)) (and (<= 0.0001 alpha) (<= alpha 1.0)))
(/ (- (* alpha alpha) 1.0) (* (* PI (log (* alpha alpha))) (+ 1.0 (* (* (- (* alpha alpha) 1.0) cosTheta) cosTheta)))))