
(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 (+ (/ PI s) 2.0)))
(*
s
(-
(log
(+
(/
1.0
(+
(/ u (+ 1.0 (exp (- (/ PI s)))))
(/ (- 1.0 u) (+ 1.0 (exp (/ (* (/ PI s) t_0) t_0))))))
-1.0))))))
float code(float u, float s) {
float t_0 = (((float) M_PI) / s) + 2.0f;
return s * -logf(((1.0f / ((u / (1.0f + expf(-(((float) M_PI) / s)))) + ((1.0f - u) / (1.0f + expf((((((float) M_PI) / s) * t_0) / t_0)))))) + -1.0f));
}
function code(u, s) t_0 = Float32(Float32(Float32(pi) / s) + Float32(2.0)) return Float32(s * Float32(-log(Float32(Float32(Float32(1.0) / Float32(Float32(u / Float32(Float32(1.0) + exp(Float32(-Float32(Float32(pi) / s))))) + Float32(Float32(Float32(1.0) - u) / Float32(Float32(1.0) + exp(Float32(Float32(Float32(Float32(pi) / s) * t_0) / t_0)))))) + Float32(-1.0))))) end
function tmp = code(u, s) t_0 = (single(pi) / s) + single(2.0); tmp = s * -log(((single(1.0) / ((u / (single(1.0) + exp(-(single(pi) / s)))) + ((single(1.0) - u) / (single(1.0) + exp((((single(pi) / s) * t_0) / t_0)))))) + single(-1.0))); end
\begin{array}{l}
\\
\begin{array}{l}
t_0 := \frac{\pi}{s} + 2\\
s \cdot \left(-\log \left(\frac{1}{\frac{u}{1 + e^{-\frac{\pi}{s}}} + \frac{1 - u}{1 + e^{\frac{\frac{\pi}{s} \cdot t\_0}{t\_0}}}} + -1\right)\right)
\end{array}
\end{array}
Initial program 98.9%
Simplified98.9%
expm1-log1p-u98.9%
expm1-undefine98.9%
Applied egg-rr98.9%
expm1-define98.9%
Simplified98.9%
expm1-undefine98.9%
flip--98.9%
log1p-undefine98.9%
rem-exp-log98.9%
+-commutative98.9%
log1p-undefine98.9%
rem-exp-log98.9%
+-commutative98.9%
metadata-eval98.9%
log1p-undefine98.9%
rem-exp-log98.9%
+-commutative98.9%
Applied egg-rr98.9%
difference-of-sqr-198.9%
associate-+l+98.9%
metadata-eval98.9%
associate--l+98.9%
metadata-eval98.9%
associate-+l+98.9%
metadata-eval98.9%
Simplified98.9%
Final simplification98.9%
(FPCore (u s)
:precision binary32
(*
(- s)
(log
(+
-1.0
(/
1.0
(+
(/ u (+ 1.0 (exp (- (/ PI s)))))
(/ (- 1.0 u) (+ 1.0 (exp (/ PI s))))))))))
float code(float u, float s) {
return -s * logf((-1.0f + (1.0f / ((u / (1.0f + expf(-(((float) M_PI) / s)))) + ((1.0f - 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(u / Float32(Float32(1.0) + exp(Float32(-Float32(Float32(pi) / s))))) + Float32(Float32(Float32(1.0) - u) / Float32(Float32(1.0) + exp(Float32(Float32(pi) / s))))))))) end
function tmp = code(u, s) tmp = -s * log((single(-1.0) + (single(1.0) / ((u / (single(1.0) + exp(-(single(pi) / s)))) + ((single(1.0) - u) / (single(1.0) + exp((single(pi) / s)))))))); end
\begin{array}{l}
\\
\left(-s\right) \cdot \log \left(-1 + \frac{1}{\frac{u}{1 + e^{-\frac{\pi}{s}}} + \frac{1 - u}{1 + e^{\frac{\pi}{s}}}}\right)
\end{array}
Initial program 98.9%
Simplified98.9%
Final simplification98.9%
(FPCore (u s) :precision binary32 (let* ((t_0 (- (* -0.25 (* u PI)) (* PI -0.25)))) (* s (+ (- (log s) (log (* 4.0 t_0))) (* -0.25 (/ s t_0))))))
float code(float u, float s) {
float t_0 = (-0.25f * (u * ((float) M_PI))) - (((float) M_PI) * -0.25f);
return s * ((logf(s) - logf((4.0f * t_0))) + (-0.25f * (s / t_0)));
}
function code(u, s) t_0 = Float32(Float32(Float32(-0.25) * Float32(u * Float32(pi))) - Float32(Float32(pi) * Float32(-0.25))) return Float32(s * Float32(Float32(log(s) - log(Float32(Float32(4.0) * t_0))) + Float32(Float32(-0.25) * Float32(s / t_0)))) end
function tmp = code(u, s) t_0 = (single(-0.25) * (u * single(pi))) - (single(pi) * single(-0.25)); tmp = s * ((log(s) - log((single(4.0) * t_0))) + (single(-0.25) * (s / t_0))); end
\begin{array}{l}
\\
\begin{array}{l}
t_0 := -0.25 \cdot \left(u \cdot \pi\right) - \pi \cdot -0.25\\
s \cdot \left(\left(\log s - \log \left(4 \cdot t\_0\right)\right) + -0.25 \cdot \frac{s}{t\_0}\right)
\end{array}
\end{array}
Initial program 98.9%
Simplified98.9%
Taylor expanded in s around -inf 25.1%
Taylor expanded in u around 0 25.3%
*-commutative25.3%
Simplified25.3%
Taylor expanded in s around 0 25.3%
Final simplification25.3%
(FPCore (u s) :precision binary32 (* (- s) (log (+ 1.0 (* 4.0 (/ (* PI (- (* u -0.25) -0.25)) s))))))
float code(float u, float s) {
return -s * logf((1.0f + (4.0f * ((((float) M_PI) * ((u * -0.25f) - -0.25f)) / s))));
}
function code(u, s) return Float32(Float32(-s) * log(Float32(Float32(1.0) + Float32(Float32(4.0) * Float32(Float32(Float32(pi) * Float32(Float32(u * Float32(-0.25)) - Float32(-0.25))) / s))))) end
function tmp = code(u, s) tmp = -s * log((single(1.0) + (single(4.0) * ((single(pi) * ((u * single(-0.25)) - single(-0.25))) / s)))); end
\begin{array}{l}
\\
\left(-s\right) \cdot \log \left(1 + 4 \cdot \frac{\pi \cdot \left(u \cdot -0.25 - -0.25\right)}{s}\right)
\end{array}
Initial program 98.9%
Simplified98.9%
Taylor expanded in s around -inf 25.1%
Taylor expanded in u around 0 25.3%
*-commutative25.3%
Simplified25.3%
associate-*r*25.3%
*-commutative25.3%
distribute-rgt-out--25.3%
Applied egg-rr25.3%
Final simplification25.3%
(FPCore (u s) :precision binary32 (- (* u (/ PI (+ 1.0 (/ PI s)))) (* s (log1p (/ PI s)))))
float code(float u, float s) {
return (u * (((float) M_PI) / (1.0f + (((float) M_PI) / s)))) - (s * log1pf((((float) M_PI) / s)));
}
function code(u, s) return Float32(Float32(u * Float32(Float32(pi) / Float32(Float32(1.0) + Float32(Float32(pi) / s)))) - Float32(s * log1p(Float32(Float32(pi) / s)))) end
\begin{array}{l}
\\
u \cdot \frac{\pi}{1 + \frac{\pi}{s}} - s \cdot \mathsf{log1p}\left(\frac{\pi}{s}\right)
\end{array}
Initial program 98.9%
Simplified98.9%
Taylor expanded in s around -inf 25.1%
Taylor expanded in u around 0 25.3%
*-commutative25.3%
Simplified25.3%
Taylor expanded in u around 0 25.3%
+-commutative25.3%
mul-1-neg25.3%
unsub-neg25.3%
associate-/l*25.3%
+-commutative25.3%
log1p-define25.3%
Simplified25.3%
Final simplification25.3%
(FPCore (u s) :precision binary32 (* (- s) (log (+ 1.0 (/ PI s)))))
float code(float u, float s) {
return -s * logf((1.0f + (((float) M_PI) / s)));
}
function code(u, s) return Float32(Float32(-s) * log(Float32(Float32(1.0) + Float32(Float32(pi) / s)))) end
function tmp = code(u, s) tmp = -s * log((single(1.0) + (single(pi) / s))); end
\begin{array}{l}
\\
\left(-s\right) \cdot \log \left(1 + \frac{\pi}{s}\right)
\end{array}
Initial program 98.9%
Simplified98.9%
Taylor expanded in s around -inf 25.1%
Taylor expanded in u around 0 25.3%
*-commutative25.3%
Simplified25.3%
Taylor expanded in u around 0 25.3%
Final simplification25.3%
(FPCore (u s) :precision binary32 (* s (- (log1p (/ PI s)))))
float code(float u, float s) {
return s * -log1pf((((float) M_PI) / s));
}
function code(u, s) return Float32(s * Float32(-log1p(Float32(Float32(pi) / s)))) end
\begin{array}{l}
\\
s \cdot \left(-\mathsf{log1p}\left(\frac{\pi}{s}\right)\right)
\end{array}
Initial program 98.9%
Simplified98.9%
Taylor expanded in s around -inf 25.1%
Taylor expanded in u around 0 25.3%
*-commutative25.3%
Simplified25.3%
Taylor expanded in u around 0 25.3%
mul-1-neg25.3%
*-commutative25.3%
distribute-rgt-neg-in25.3%
log1p-define25.3%
Simplified25.3%
Final simplification25.3%
(FPCore (u s) :precision binary32 (* -4.0 (* (* u PI) 0.5)))
float code(float u, float s) {
return -4.0f * ((u * ((float) M_PI)) * 0.5f);
}
function code(u, s) return Float32(Float32(-4.0) * Float32(Float32(u * Float32(pi)) * Float32(0.5))) end
function tmp = code(u, s) tmp = single(-4.0) * ((u * single(pi)) * single(0.5)); end
\begin{array}{l}
\\
-4 \cdot \left(\left(u \cdot \pi\right) \cdot 0.5\right)
\end{array}
Initial program 98.9%
Simplified98.9%
Taylor expanded in s around -inf 11.0%
associate--r+11.0%
cancel-sign-sub-inv11.0%
metadata-eval11.0%
cancel-sign-sub-inv11.0%
associate-*r*11.0%
distribute-rgt-out11.0%
*-commutative11.0%
metadata-eval11.0%
*-commutative11.0%
associate-*l*11.0%
Simplified11.0%
Taylor expanded in u around inf 5.0%
associate-*r*5.0%
Simplified5.0%
add-sqr-sqrt-0.0%
sqrt-unprod12.1%
pow212.1%
*-commutative12.1%
Applied egg-rr12.1%
Taylor expanded in u around 0 12.1%
*-commutative12.1%
*-commutative12.1%
Simplified12.1%
Final simplification12.1%
(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 98.9%
Simplified98.9%
Taylor expanded in u around 0 10.8%
neg-mul-110.8%
Simplified10.8%
herbie shell --seed 2024092
(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))))