
(FPCore (u s)
:precision binary32
(let* ((t_0 (/ 1.0 (+ 1.0 (exp (/ PI s))))))
(*
(- s)
(log
(-
(/ 1.0 (+ (* u (- (/ 1.0 (+ 1.0 (exp (/ (- PI) s)))) t_0)) t_0))
1.0)))))
float code(float u, float s) {
float t_0 = 1.0f / (1.0f + expf((((float) M_PI) / s)));
return -s * logf(((1.0f / ((u * ((1.0f / (1.0f + expf((-((float) M_PI) / s)))) - t_0)) + t_0)) - 1.0f));
}
function code(u, s) t_0 = Float32(Float32(1.0) / Float32(Float32(1.0) + exp(Float32(Float32(pi) / s)))) return Float32(Float32(-s) * log(Float32(Float32(Float32(1.0) / Float32(Float32(u * Float32(Float32(Float32(1.0) / Float32(Float32(1.0) + exp(Float32(Float32(-Float32(pi)) / s)))) - t_0)) + t_0)) - Float32(1.0)))) end
function tmp = code(u, s) t_0 = single(1.0) / (single(1.0) + exp((single(pi) / s))); tmp = -s * log(((single(1.0) / ((u * ((single(1.0) / (single(1.0) + exp((-single(pi) / s)))) - t_0)) + t_0)) - single(1.0))); end
\begin{array}{l}
\\
\begin{array}{l}
t_0 := \frac{1}{1 + e^{\frac{\pi}{s}}}\\
\left(-s\right) \cdot \log \left(\frac{1}{u \cdot \left(\frac{1}{1 + e^{\frac{-\pi}{s}}} - t\_0\right) + t\_0} - 1\right)
\end{array}
\end{array}
Sampling outcomes in binary32 precision:
Herbie found 9 alternatives:
| Alternative | Accuracy | Speedup |
|---|
(FPCore (u s)
:precision binary32
(let* ((t_0 (/ 1.0 (+ 1.0 (exp (/ PI s))))))
(*
(- s)
(log
(-
(/ 1.0 (+ (* u (- (/ 1.0 (+ 1.0 (exp (/ (- PI) s)))) t_0)) t_0))
1.0)))))
float code(float u, float s) {
float t_0 = 1.0f / (1.0f + expf((((float) M_PI) / s)));
return -s * logf(((1.0f / ((u * ((1.0f / (1.0f + expf((-((float) M_PI) / s)))) - t_0)) + t_0)) - 1.0f));
}
function code(u, s) t_0 = Float32(Float32(1.0) / Float32(Float32(1.0) + exp(Float32(Float32(pi) / s)))) return Float32(Float32(-s) * log(Float32(Float32(Float32(1.0) / Float32(Float32(u * Float32(Float32(Float32(1.0) / Float32(Float32(1.0) + exp(Float32(Float32(-Float32(pi)) / s)))) - t_0)) + t_0)) - Float32(1.0)))) end
function tmp = code(u, s) t_0 = single(1.0) / (single(1.0) + exp((single(pi) / s))); tmp = -s * log(((single(1.0) / ((u * ((single(1.0) / (single(1.0) + exp((-single(pi) / s)))) - t_0)) + t_0)) - single(1.0))); end
\begin{array}{l}
\\
\begin{array}{l}
t_0 := \frac{1}{1 + e^{\frac{\pi}{s}}}\\
\left(-s\right) \cdot \log \left(\frac{1}{u \cdot \left(\frac{1}{1 + e^{\frac{-\pi}{s}}} - t\_0\right) + t\_0} - 1\right)
\end{array}
\end{array}
(FPCore (u s)
:precision binary32
(let* ((t_0 (exp (/ PI s))))
(*
(- s)
(log
(+
-1.0
(/
1.0
(*
u
(+
(+ (/ 1.0 (+ 1.0 (exp (/ PI (- s))))) (/ -1.0 (+ 1.0 t_0)))
(/ 1.0 (fma t_0 u u))))))))))
float code(float u, float s) {
float t_0 = expf((((float) M_PI) / s));
return -s * logf((-1.0f + (1.0f / (u * (((1.0f / (1.0f + expf((((float) M_PI) / -s)))) + (-1.0f / (1.0f + t_0))) + (1.0f / fmaf(t_0, u, u)))))));
}
function code(u, s) t_0 = exp(Float32(Float32(pi) / s)) return Float32(Float32(-s) * log(Float32(Float32(-1.0) + Float32(Float32(1.0) / Float32(u * Float32(Float32(Float32(Float32(1.0) / Float32(Float32(1.0) + exp(Float32(Float32(pi) / Float32(-s))))) + Float32(Float32(-1.0) / Float32(Float32(1.0) + t_0))) + Float32(Float32(1.0) / fma(t_0, u, u)))))))) end
\begin{array}{l}
\\
\begin{array}{l}
t_0 := e^{\frac{\pi}{s}}\\
\left(-s\right) \cdot \log \left(-1 + \frac{1}{u \cdot \left(\left(\frac{1}{1 + e^{\frac{\pi}{-s}}} + \frac{-1}{1 + t\_0}\right) + \frac{1}{\mathsf{fma}\left(t\_0, u, u\right)}\right)}\right)
\end{array}
\end{array}
Initial program 98.8%
Taylor expanded in u around inf
lower-*.f32N/A
associate--l+N/A
+-commutativeN/A
lower-+.f32N/A
Applied rewrites98.8%
Final simplification98.8%
(FPCore (u s)
:precision binary32
(let* ((t_0 (exp (/ PI s))))
(*
(- s)
(log
(+
-1.0
(/
1.0
(+
(/ 1.0 (+ 1.0 t_0))
(+ (/ u (- -1.0 t_0)) (/ u (+ 1.0 (exp (/ PI (- s)))))))))))))
float code(float u, float s) {
float t_0 = expf((((float) M_PI) / s));
return -s * logf((-1.0f + (1.0f / ((1.0f / (1.0f + t_0)) + ((u / (-1.0f - t_0)) + (u / (1.0f + expf((((float) M_PI) / -s)))))))));
}
function code(u, s) t_0 = exp(Float32(Float32(pi) / s)) return Float32(Float32(-s) * log(Float32(Float32(-1.0) + Float32(Float32(1.0) / Float32(Float32(Float32(1.0) / Float32(Float32(1.0) + t_0)) + Float32(Float32(u / Float32(Float32(-1.0) - t_0)) + Float32(u / Float32(Float32(1.0) + exp(Float32(Float32(pi) / Float32(-s))))))))))) end
function tmp = code(u, s) t_0 = exp((single(pi) / s)); tmp = -s * log((single(-1.0) + (single(1.0) / ((single(1.0) / (single(1.0) + t_0)) + ((u / (single(-1.0) - t_0)) + (u / (single(1.0) + exp((single(pi) / -s))))))))); end
\begin{array}{l}
\\
\begin{array}{l}
t_0 := e^{\frac{\pi}{s}}\\
\left(-s\right) \cdot \log \left(-1 + \frac{1}{\frac{1}{1 + t\_0} + \left(\frac{u}{-1 - t\_0} + \frac{u}{1 + e^{\frac{\pi}{-s}}}\right)}\right)
\end{array}
\end{array}
Initial program 98.8%
Applied rewrites98.7%
Applied rewrites98.8%
Final simplification98.8%
(FPCore (u s)
:precision binary32
(*
(- s)
(log
(+
-1.0
(/
1.0
(+ (/ 1.0 (+ 1.0 (exp (/ PI s)))) (/ u (+ 1.0 (exp (/ PI (- s)))))))))))
float code(float u, float s) {
return -s * logf((-1.0f + (1.0f / ((1.0f / (1.0f + expf((((float) M_PI) / s)))) + (u / (1.0f + expf((((float) M_PI) / -s))))))));
}
function code(u, s) return Float32(Float32(-s) * log(Float32(Float32(-1.0) + Float32(Float32(1.0) / Float32(Float32(Float32(1.0) / Float32(Float32(1.0) + exp(Float32(Float32(pi) / s)))) + Float32(u / Float32(Float32(1.0) + exp(Float32(Float32(pi) / Float32(-s)))))))))) end
function tmp = code(u, s) tmp = -s * log((single(-1.0) + (single(1.0) / ((single(1.0) / (single(1.0) + exp((single(pi) / s)))) + (u / (single(1.0) + exp((single(pi) / -s)))))))); end
\begin{array}{l}
\\
\left(-s\right) \cdot \log \left(-1 + \frac{1}{\frac{1}{1 + e^{\frac{\pi}{s}}} + \frac{u}{1 + e^{\frac{\pi}{-s}}}}\right)
\end{array}
Initial program 98.8%
Applied rewrites98.8%
Taylor expanded in s around -inf
mul-1-negN/A
unsub-negN/A
lower--.f32N/A
lower-/.f32N/A
Applied rewrites97.7%
Taylor expanded in s around 0
lower-+.f32N/A
lower-/.f32N/A
lower-+.f32N/A
lower-exp.f32N/A
lower-/.f32N/A
lower-PI.f32N/A
lower-/.f32N/A
lower-+.f32N/A
lower-exp.f32N/A
mul-1-negN/A
distribute-neg-frac2N/A
mul-1-negN/A
lower-/.f32N/A
lower-PI.f32N/A
mul-1-negN/A
lower-neg.f3298.7
Applied rewrites98.7%
Final simplification98.7%
(FPCore (u s)
:precision binary32
(*
(- s)
(log
(+
-1.0
(/
1.0
(*
u
(+
(/ 1.0 (+ 1.0 (exp (/ PI (- s)))))
(/
-1.0
(+
2.0
(/
(+
PI
(fma
0.16666666666666666
(/ (* PI (* PI PI)) (* s s))
(* 0.5 (/ (* PI PI) s))))
s))))))))))
float code(float u, float s) {
return -s * logf((-1.0f + (1.0f / (u * ((1.0f / (1.0f + expf((((float) M_PI) / -s)))) + (-1.0f / (2.0f + ((((float) M_PI) + fmaf(0.16666666666666666f, ((((float) M_PI) * (((float) M_PI) * ((float) M_PI))) / (s * s)), (0.5f * ((((float) M_PI) * ((float) M_PI)) / s)))) / s))))))));
}
function code(u, s) return Float32(Float32(-s) * log(Float32(Float32(-1.0) + Float32(Float32(1.0) / Float32(u * Float32(Float32(Float32(1.0) / Float32(Float32(1.0) + exp(Float32(Float32(pi) / Float32(-s))))) + Float32(Float32(-1.0) / Float32(Float32(2.0) + Float32(Float32(Float32(pi) + fma(Float32(0.16666666666666666), Float32(Float32(Float32(pi) * Float32(Float32(pi) * Float32(pi))) / Float32(s * s)), Float32(Float32(0.5) * Float32(Float32(Float32(pi) * Float32(pi)) / s)))) / s))))))))) end
\begin{array}{l}
\\
\left(-s\right) \cdot \log \left(-1 + \frac{1}{u \cdot \left(\frac{1}{1 + e^{\frac{\pi}{-s}}} + \frac{-1}{2 + \frac{\pi + \mathsf{fma}\left(0.16666666666666666, \frac{\pi \cdot \left(\pi \cdot \pi\right)}{s \cdot s}, 0.5 \cdot \frac{\pi \cdot \pi}{s}\right)}{s}}\right)}\right)
\end{array}
Initial program 98.8%
Applied rewrites98.8%
Taylor expanded in s around -inf
mul-1-negN/A
unsub-negN/A
lower--.f32N/A
lower-/.f32N/A
Applied rewrites97.7%
Taylor expanded in u around inf
Applied rewrites96.6%
Final simplification96.6%
(FPCore (u s) :precision binary32 (* 4.0 (* (* PI (log E)) (fma 0.5 u -0.25))))
float code(float u, float s) {
return 4.0f * ((((float) M_PI) * logf(((float) M_E))) * fmaf(0.5f, u, -0.25f));
}
function code(u, s) return Float32(Float32(4.0) * Float32(Float32(Float32(pi) * log(Float32(exp(1)))) * fma(Float32(0.5), u, Float32(-0.25)))) end
\begin{array}{l}
\\
4 \cdot \left(\left(\pi \cdot \log e\right) \cdot \mathsf{fma}\left(0.5, u, -0.25\right)\right)
\end{array}
Initial program 98.8%
Taylor expanded in s around inf
lower-/.f32N/A
distribute-rgt-out--N/A
metadata-evalN/A
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-PI.f323.3
Applied rewrites3.3%
Taylor expanded in s around inf
lower-*.f32N/A
cancel-sign-sub-invN/A
associate-*r*N/A
metadata-evalN/A
distribute-rgt-outN/A
lower-*.f32N/A
lower-PI.f32N/A
lower-fma.f3211.7
Applied rewrites11.7%
add-log-expN/A
*-un-lft-identityN/A
lift-PI.f32N/A
exp-prodN/A
log-powN/A
lower-*.f32N/A
lower-log.f32N/A
exp-1-eN/A
lower-E.f3211.7
Applied rewrites11.7%
(FPCore (u s)
:precision binary32
(let* ((t_0 (fma 0.25 (* u u) 0.0625)))
(*
4.0
(*
PI
(/
(fma (* u (* u u)) 0.125 -0.015625)
(/ (- (* t_0 t_0) (* (* u 0.125) (* u 0.125))) (- t_0 (* u 0.125))))))))
float code(float u, float s) {
float t_0 = fmaf(0.25f, (u * u), 0.0625f);
return 4.0f * (((float) M_PI) * (fmaf((u * (u * u)), 0.125f, -0.015625f) / (((t_0 * t_0) - ((u * 0.125f) * (u * 0.125f))) / (t_0 - (u * 0.125f)))));
}
function code(u, s) t_0 = fma(Float32(0.25), Float32(u * u), Float32(0.0625)) return Float32(Float32(4.0) * Float32(Float32(pi) * Float32(fma(Float32(u * Float32(u * u)), Float32(0.125), Float32(-0.015625)) / Float32(Float32(Float32(t_0 * t_0) - Float32(Float32(u * Float32(0.125)) * Float32(u * Float32(0.125)))) / Float32(t_0 - Float32(u * Float32(0.125))))))) end
\begin{array}{l}
\\
\begin{array}{l}
t_0 := \mathsf{fma}\left(0.25, u \cdot u, 0.0625\right)\\
4 \cdot \left(\pi \cdot \frac{\mathsf{fma}\left(u \cdot \left(u \cdot u\right), 0.125, -0.015625\right)}{\frac{t\_0 \cdot t\_0 - \left(u \cdot 0.125\right) \cdot \left(u \cdot 0.125\right)}{t\_0 - u \cdot 0.125}}\right)
\end{array}
\end{array}
Initial program 98.8%
Taylor expanded in s around inf
lower-/.f32N/A
distribute-rgt-out--N/A
metadata-evalN/A
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-PI.f323.3
Applied rewrites3.3%
Taylor expanded in s around inf
lower-*.f32N/A
cancel-sign-sub-invN/A
associate-*r*N/A
metadata-evalN/A
distribute-rgt-outN/A
lower-*.f32N/A
lower-PI.f32N/A
lower-fma.f3211.7
Applied rewrites11.7%
flip3-+N/A
lower-/.f32N/A
*-commutativeN/A
unpow-prod-downN/A
lower-fma.f32N/A
unpow3N/A
lower-*.f32N/A
lower-*.f32N/A
metadata-evalN/A
metadata-evalN/A
associate-+r-N/A
lower--.f32N/A
swap-sqrN/A
metadata-evalN/A
metadata-evalN/A
lower-fma.f32N/A
metadata-evalN/A
lower-*.f32N/A
metadata-evalN/A
*-commutativeN/A
associate-*l*N/A
lower-*.f32N/A
metadata-eval11.7
Applied rewrites11.7%
lift-*.f32N/A
lift-fma.f32N/A
lift-*.f32N/A
sub-negN/A
flip-+N/A
lower-/.f32N/A
Applied rewrites11.7%
Final simplification11.7%
(FPCore (u s) :precision binary32 (* PI (fma 2.0 u -1.0)))
float code(float u, float s) {
return ((float) M_PI) * fmaf(2.0f, u, -1.0f);
}
function code(u, s) return Float32(Float32(pi) * fma(Float32(2.0), u, Float32(-1.0))) end
\begin{array}{l}
\\
\pi \cdot \mathsf{fma}\left(2, u, -1\right)
\end{array}
Initial program 98.8%
Taylor expanded in s around inf
lower-/.f32N/A
distribute-rgt-out--N/A
metadata-evalN/A
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-PI.f323.3
Applied rewrites3.3%
Taylor expanded in s around inf
lower-*.f32N/A
cancel-sign-sub-invN/A
associate-*r*N/A
metadata-evalN/A
distribute-rgt-outN/A
lower-*.f32N/A
lower-PI.f32N/A
lower-fma.f3211.7
Applied rewrites11.7%
Taylor expanded in u around 0
+-commutativeN/A
associate-*r*N/A
distribute-rgt-outN/A
lower-*.f32N/A
lower-PI.f32N/A
lower-fma.f3211.7
Applied rewrites11.7%
(FPCore (u s) :precision binary32 (- PI))
float code(float u, float s) {
return -((float) M_PI);
}
function code(u, s) return Float32(-Float32(pi)) end
function tmp = code(u, s) tmp = -single(pi); end
\begin{array}{l}
\\
-\pi
\end{array}
Initial program 98.8%
Taylor expanded in u around 0
mul-1-negN/A
lower-neg.f32N/A
lower-PI.f3211.5
Applied rewrites11.5%
(FPCore (u s) :precision binary32 PI)
float code(float u, float s) {
return (float) M_PI;
}
function code(u, s) return Float32(pi) end
function tmp = code(u, s) tmp = single(pi); end
\begin{array}{l}
\\
\pi
\end{array}
Initial program 98.8%
Taylor expanded in s around inf
lower-/.f32N/A
distribute-rgt-out--N/A
metadata-evalN/A
*-commutativeN/A
lower-*.f32N/A
*-commutativeN/A
lower-*.f32N/A
lower-PI.f323.3
Applied rewrites3.3%
Applied rewrites0.6%
Taylor expanded in u around 0
lower-PI.f324.7
Applied rewrites4.7%
herbie shell --seed 2024220
(FPCore (u s)
:name "Sample trimmed logistic on [-pi, pi]"
:precision binary32
:pre (and (and (<= 2.328306437e-10 u) (<= u 1.0)) (and (<= 0.0 s) (<= s 1.0651631)))
(* (- s) (log (- (/ 1.0 (+ (* u (- (/ 1.0 (+ 1.0 (exp (/ (- PI) s)))) (/ 1.0 (+ 1.0 (exp (/ PI s)))))) (/ 1.0 (+ 1.0 (exp (/ PI s)))))) 1.0))))