
(FPCore (x s) :precision binary32 (let* ((t_0 (exp (/ (- (fabs x)) s))) (t_1 (+ 1.0 t_0))) (/ t_0 (* (* s t_1) t_1))))
float code(float x, float s) {
float t_0 = expf((-fabsf(x) / s));
float t_1 = 1.0f + t_0;
return t_0 / ((s * t_1) * t_1);
}
real(4) function code(x, s)
real(4), intent (in) :: x
real(4), intent (in) :: s
real(4) :: t_0
real(4) :: t_1
t_0 = exp((-abs(x) / s))
t_1 = 1.0e0 + t_0
code = t_0 / ((s * t_1) * t_1)
end function
function code(x, s) t_0 = exp(Float32(Float32(-abs(x)) / s)) t_1 = Float32(Float32(1.0) + t_0) return Float32(t_0 / Float32(Float32(s * t_1) * t_1)) end
function tmp = code(x, s) t_0 = exp((-abs(x) / s)); t_1 = single(1.0) + t_0; tmp = t_0 / ((s * t_1) * t_1); end
\begin{array}{l}
\\
\begin{array}{l}
t_0 := e^{\frac{-\left|x\right|}{s}}\\
t_1 := 1 + t\_0\\
\frac{t\_0}{\left(s \cdot t\_1\right) \cdot t\_1}
\end{array}
\end{array}
Sampling outcomes in binary32 precision:
Herbie found 8 alternatives:
| Alternative | Accuracy | Speedup |
|---|
(FPCore (x s) :precision binary32 (let* ((t_0 (exp (/ (- (fabs x)) s))) (t_1 (+ 1.0 t_0))) (/ t_0 (* (* s t_1) t_1))))
float code(float x, float s) {
float t_0 = expf((-fabsf(x) / s));
float t_1 = 1.0f + t_0;
return t_0 / ((s * t_1) * t_1);
}
real(4) function code(x, s)
real(4), intent (in) :: x
real(4), intent (in) :: s
real(4) :: t_0
real(4) :: t_1
t_0 = exp((-abs(x) / s))
t_1 = 1.0e0 + t_0
code = t_0 / ((s * t_1) * t_1)
end function
function code(x, s) t_0 = exp(Float32(Float32(-abs(x)) / s)) t_1 = Float32(Float32(1.0) + t_0) return Float32(t_0 / Float32(Float32(s * t_1) * t_1)) end
function tmp = code(x, s) t_0 = exp((-abs(x) / s)); t_1 = single(1.0) + t_0; tmp = t_0 / ((s * t_1) * t_1); end
\begin{array}{l}
\\
\begin{array}{l}
t_0 := e^{\frac{-\left|x\right|}{s}}\\
t_1 := 1 + t\_0\\
\frac{t\_0}{\left(s \cdot t\_1\right) \cdot t\_1}
\end{array}
\end{array}
(FPCore (x s) :precision binary32 (let* ((t_0 (exp (/ (- (fabs x)) s)))) (/ t_0 (* (+ t_0 1.0) (+ s (/ s (exp (/ (fabs x) s))))))))
float code(float x, float s) {
float t_0 = expf((-fabsf(x) / s));
return t_0 / ((t_0 + 1.0f) * (s + (s / expf((fabsf(x) / s)))));
}
real(4) function code(x, s)
real(4), intent (in) :: x
real(4), intent (in) :: s
real(4) :: t_0
t_0 = exp((-abs(x) / s))
code = t_0 / ((t_0 + 1.0e0) * (s + (s / exp((abs(x) / s)))))
end function
function code(x, s) t_0 = exp(Float32(Float32(-abs(x)) / s)) return Float32(t_0 / Float32(Float32(t_0 + Float32(1.0)) * Float32(s + Float32(s / exp(Float32(abs(x) / s)))))) end
function tmp = code(x, s) t_0 = exp((-abs(x) / s)); tmp = t_0 / ((t_0 + single(1.0)) * (s + (s / exp((abs(x) / s))))); end
\begin{array}{l}
\\
\begin{array}{l}
t_0 := e^{\frac{-\left|x\right|}{s}}\\
\frac{t\_0}{\left(t\_0 + 1\right) \cdot \left(s + \frac{s}{e^{\frac{\left|x\right|}{s}}}\right)}
\end{array}
\end{array}
Initial program 99.7%
*-commutative99.7%
fabs-neg99.7%
+-commutative99.7%
fabs-neg99.7%
distribute-lft-in99.7%
*-rgt-identity99.7%
+-commutative99.7%
Simplified99.7%
Final simplification99.7%
(FPCore (x s) :precision binary32 (if (<= (fabs x) 0.004999999888241291) (/ (exp (+ (/ x s) (* -2.0 (log1p (exp (/ x s)))))) s) (/ (exp (/ x (- s))) (* s 4.0))))
float code(float x, float s) {
float tmp;
if (fabsf(x) <= 0.004999999888241291f) {
tmp = expf(((x / s) + (-2.0f * log1pf(expf((x / s)))))) / s;
} else {
tmp = expf((x / -s)) / (s * 4.0f);
}
return tmp;
}
function code(x, s) tmp = Float32(0.0) if (abs(x) <= Float32(0.004999999888241291)) tmp = Float32(exp(Float32(Float32(x / s) + Float32(Float32(-2.0) * log1p(exp(Float32(x / s)))))) / s); else tmp = Float32(exp(Float32(x / Float32(-s))) / Float32(s * Float32(4.0))); end return tmp end
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;\left|x\right| \leq 0.004999999888241291:\\
\;\;\;\;\frac{e^{\frac{x}{s} + -2 \cdot \mathsf{log1p}\left(e^{\frac{x}{s}}\right)}}{s}\\
\mathbf{else}:\\
\;\;\;\;\frac{e^{\frac{x}{-s}}}{s \cdot 4}\\
\end{array}
\end{array}
if (fabs.f32 x) < 0.00499999989Initial program 99.3%
fabs-neg99.3%
distribute-frac-neg99.3%
distribute-frac-neg299.3%
fabs-neg99.3%
*-commutative99.3%
fabs-neg99.3%
+-commutative99.3%
fabs-neg99.3%
Simplified99.2%
add-exp-log94.9%
log-div94.7%
add-log-exp94.7%
add-sqr-sqrt-0.0%
add-sqr-sqrt-0.0%
fabs-sqr-0.0%
add-sqr-sqrt-0.0%
sqrt-unprod61.3%
sqr-neg61.3%
sqrt-unprod71.7%
add-sqr-sqrt71.7%
*-commutative71.7%
Applied egg-rr94.3%
associate--r+94.5%
exp-diff95.4%
cancel-sign-sub-inv95.4%
metadata-eval95.4%
add-exp-log99.3%
Applied egg-rr99.3%
if 0.00499999989 < (fabs.f32 x) Initial program 100.0%
*-commutative100.0%
fabs-neg100.0%
+-commutative100.0%
fabs-neg100.0%
distribute-lft-in100.0%
*-rgt-identity100.0%
+-commutative100.0%
Simplified100.0%
Taylor expanded in s around 0 100.0%
rec-exp100.0%
mul-1-neg100.0%
unpow2100.0%
associate-*r/100.0%
mul-1-neg100.0%
Simplified100.0%
distribute-frac-neg100.0%
exp-neg100.0%
add-sqr-sqrt55.1%
fabs-sqr55.1%
add-sqr-sqrt100.0%
add-sqr-sqrt55.1%
sqrt-unprod100.0%
add-sqr-sqrt55.1%
fabs-sqr55.1%
add-sqr-sqrt55.1%
add-sqr-sqrt55.1%
fabs-sqr55.1%
add-sqr-sqrt100.0%
sqr-neg100.0%
distribute-frac-neg100.0%
distribute-frac-neg100.0%
sqrt-unprod-0.0%
add-sqr-sqrt100.0%
Applied egg-rr100.0%
rec-exp100.0%
mul-1-neg100.0%
associate-*r/100.0%
mul-1-neg100.0%
Simplified100.0%
distribute-frac-neg100.0%
exp-neg100.0%
add-sqr-sqrt55.1%
fabs-sqr55.1%
add-sqr-sqrt100.0%
add-sqr-sqrt55.1%
sqrt-unprod100.0%
add-sqr-sqrt55.1%
fabs-sqr55.1%
add-sqr-sqrt55.1%
add-sqr-sqrt55.1%
fabs-sqr55.1%
add-sqr-sqrt100.0%
sqr-neg100.0%
distribute-frac-neg100.0%
distribute-frac-neg100.0%
sqrt-unprod-0.0%
add-sqr-sqrt100.0%
Applied egg-rr55.1%
rec-exp100.0%
mul-1-neg100.0%
associate-*r/100.0%
mul-1-neg100.0%
Simplified55.1%
Taylor expanded in x around 0 56.5%
Final simplification76.2%
(FPCore (x s) :precision binary32 (let* ((t_0 (exp (/ x (- s))))) (/ t_0 (* s (pow (+ 1.0 t_0) 2.0)))))
float code(float x, float s) {
float t_0 = expf((x / -s));
return t_0 / (s * powf((1.0f + t_0), 2.0f));
}
real(4) function code(x, s)
real(4), intent (in) :: x
real(4), intent (in) :: s
real(4) :: t_0
t_0 = exp((x / -s))
code = t_0 / (s * ((1.0e0 + t_0) ** 2.0e0))
end function
function code(x, s) t_0 = exp(Float32(x / Float32(-s))) return Float32(t_0 / Float32(s * (Float32(Float32(1.0) + t_0) ^ Float32(2.0)))) end
function tmp = code(x, s) t_0 = exp((x / -s)); tmp = t_0 / (s * ((single(1.0) + t_0) ^ single(2.0))); end
\begin{array}{l}
\\
\begin{array}{l}
t_0 := e^{\frac{x}{-s}}\\
\frac{t\_0}{s \cdot {\left(1 + t\_0\right)}^{2}}
\end{array}
\end{array}
Initial program 99.7%
*-commutative99.7%
fabs-neg99.7%
+-commutative99.7%
fabs-neg99.7%
distribute-lft-in99.7%
*-rgt-identity99.7%
+-commutative99.7%
Simplified99.7%
Taylor expanded in s around 0 99.7%
rec-exp99.7%
mul-1-neg99.7%
unpow299.7%
associate-*r/99.7%
mul-1-neg99.7%
Simplified99.7%
distribute-frac-neg99.7%
exp-neg99.6%
add-sqr-sqrt52.6%
fabs-sqr52.6%
add-sqr-sqrt95.8%
add-sqr-sqrt52.6%
sqrt-unprod99.6%
add-sqr-sqrt52.6%
fabs-sqr52.6%
add-sqr-sqrt54.2%
add-sqr-sqrt52.6%
fabs-sqr52.6%
add-sqr-sqrt99.6%
sqr-neg99.6%
distribute-frac-neg99.6%
distribute-frac-neg99.6%
sqrt-unprod-0.0%
add-sqr-sqrt93.9%
Applied egg-rr95.8%
rec-exp95.8%
mul-1-neg95.8%
associate-*r/95.8%
mul-1-neg95.8%
Simplified95.8%
distribute-frac-neg99.7%
exp-neg99.6%
add-sqr-sqrt52.6%
fabs-sqr52.6%
add-sqr-sqrt95.8%
add-sqr-sqrt52.6%
sqrt-unprod99.6%
add-sqr-sqrt52.6%
fabs-sqr52.6%
add-sqr-sqrt54.2%
add-sqr-sqrt52.6%
fabs-sqr52.6%
add-sqr-sqrt99.6%
sqr-neg99.6%
distribute-frac-neg99.6%
distribute-frac-neg99.6%
sqrt-unprod-0.0%
add-sqr-sqrt93.9%
Applied egg-rr66.9%
rec-exp95.8%
mul-1-neg95.8%
associate-*r/95.8%
mul-1-neg95.8%
Simplified67.0%
Final simplification67.0%
(FPCore (x s) :precision binary32 (* (/ 1.0 (fma s (exp (/ x s)) s)) 0.5))
float code(float x, float s) {
return (1.0f / fmaf(s, expf((x / s)), s)) * 0.5f;
}
function code(x, s) return Float32(Float32(Float32(1.0) / fma(s, exp(Float32(x / s)), s)) * Float32(0.5)) end
\begin{array}{l}
\\
\frac{1}{\mathsf{fma}\left(s, e^{\frac{x}{s}}, s\right)} \cdot 0.5
\end{array}
Initial program 99.7%
fabs-neg99.7%
distribute-frac-neg99.7%
distribute-frac-neg299.7%
fabs-neg99.7%
*-commutative99.7%
fabs-neg99.7%
+-commutative99.7%
fabs-neg99.7%
Simplified99.7%
*-un-lft-identity99.7%
associate-*r*99.7%
times-frac99.6%
Applied egg-rr60.6%
Taylor expanded in x around 0 64.0%
(FPCore (x s) :precision binary32 (/ (exp (/ x (- s))) (* s 4.0)))
float code(float x, float s) {
return expf((x / -s)) / (s * 4.0f);
}
real(4) function code(x, s)
real(4), intent (in) :: x
real(4), intent (in) :: s
code = exp((x / -s)) / (s * 4.0e0)
end function
function code(x, s) return Float32(exp(Float32(x / Float32(-s))) / Float32(s * Float32(4.0))) end
function tmp = code(x, s) tmp = exp((x / -s)) / (s * single(4.0)); end
\begin{array}{l}
\\
\frac{e^{\frac{x}{-s}}}{s \cdot 4}
\end{array}
Initial program 99.7%
*-commutative99.7%
fabs-neg99.7%
+-commutative99.7%
fabs-neg99.7%
distribute-lft-in99.7%
*-rgt-identity99.7%
+-commutative99.7%
Simplified99.7%
Taylor expanded in s around 0 99.7%
rec-exp99.7%
mul-1-neg99.7%
unpow299.7%
associate-*r/99.7%
mul-1-neg99.7%
Simplified99.7%
distribute-frac-neg99.7%
exp-neg99.6%
add-sqr-sqrt52.6%
fabs-sqr52.6%
add-sqr-sqrt95.8%
add-sqr-sqrt52.6%
sqrt-unprod99.6%
add-sqr-sqrt52.6%
fabs-sqr52.6%
add-sqr-sqrt54.2%
add-sqr-sqrt52.6%
fabs-sqr52.6%
add-sqr-sqrt99.6%
sqr-neg99.6%
distribute-frac-neg99.6%
distribute-frac-neg99.6%
sqrt-unprod-0.0%
add-sqr-sqrt93.9%
Applied egg-rr95.8%
rec-exp95.8%
mul-1-neg95.8%
associate-*r/95.8%
mul-1-neg95.8%
Simplified95.8%
distribute-frac-neg99.7%
exp-neg99.6%
add-sqr-sqrt52.6%
fabs-sqr52.6%
add-sqr-sqrt95.8%
add-sqr-sqrt52.6%
sqrt-unprod99.6%
add-sqr-sqrt52.6%
fabs-sqr52.6%
add-sqr-sqrt54.2%
add-sqr-sqrt52.6%
fabs-sqr52.6%
add-sqr-sqrt99.6%
sqr-neg99.6%
distribute-frac-neg99.6%
distribute-frac-neg99.6%
sqrt-unprod-0.0%
add-sqr-sqrt93.9%
Applied egg-rr66.9%
rec-exp95.8%
mul-1-neg95.8%
associate-*r/95.8%
mul-1-neg95.8%
Simplified67.0%
Taylor expanded in x around 0 63.2%
Final simplification63.2%
(FPCore (x s) :precision binary32 (/ (+ 1.0 (/ x s)) (+ (* s 4.0) (* x (+ 4.0 (* (/ x s) 3.0))))))
float code(float x, float s) {
return (1.0f + (x / s)) / ((s * 4.0f) + (x * (4.0f + ((x / s) * 3.0f))));
}
real(4) function code(x, s)
real(4), intent (in) :: x
real(4), intent (in) :: s
code = (1.0e0 + (x / s)) / ((s * 4.0e0) + (x * (4.0e0 + ((x / s) * 3.0e0))))
end function
function code(x, s) return Float32(Float32(Float32(1.0) + Float32(x / s)) / Float32(Float32(s * Float32(4.0)) + Float32(x * Float32(Float32(4.0) + Float32(Float32(x / s) * Float32(3.0)))))) end
function tmp = code(x, s) tmp = (single(1.0) + (x / s)) / ((s * single(4.0)) + (x * (single(4.0) + ((x / s) * single(3.0))))); end
\begin{array}{l}
\\
\frac{1 + \frac{x}{s}}{s \cdot 4 + x \cdot \left(4 + \frac{x}{s} \cdot 3\right)}
\end{array}
Initial program 99.7%
fabs-neg99.7%
distribute-frac-neg99.7%
distribute-frac-neg299.7%
fabs-neg99.7%
*-commutative99.7%
fabs-neg99.7%
+-commutative99.7%
fabs-neg99.7%
Simplified99.7%
Applied egg-rr60.3%
*-lft-identity60.3%
associate-/r*60.6%
Simplified60.6%
Taylor expanded in x around 0 57.8%
Taylor expanded in x around 0 40.1%
Final simplification40.1%
(FPCore (x s) :precision binary32 (/ 0.25 s))
float code(float x, float s) {
return 0.25f / s;
}
real(4) function code(x, s)
real(4), intent (in) :: x
real(4), intent (in) :: s
code = 0.25e0 / s
end function
function code(x, s) return Float32(Float32(0.25) / s) end
function tmp = code(x, s) tmp = single(0.25) / s; end
\begin{array}{l}
\\
\frac{0.25}{s}
\end{array}
Initial program 99.7%
fabs-neg99.7%
distribute-frac-neg99.7%
distribute-frac-neg299.7%
fabs-neg99.7%
*-commutative99.7%
fabs-neg99.7%
+-commutative99.7%
fabs-neg99.7%
Simplified99.7%
Taylor expanded in s around inf 28.1%
(FPCore (x s) :precision binary32 1.0)
float code(float x, float s) {
return 1.0f;
}
real(4) function code(x, s)
real(4), intent (in) :: x
real(4), intent (in) :: s
code = 1.0e0
end function
function code(x, s) return Float32(1.0) end
function tmp = code(x, s) tmp = single(1.0); end
\begin{array}{l}
\\
1
\end{array}
Initial program 99.7%
fabs-neg99.7%
distribute-frac-neg99.7%
distribute-frac-neg299.7%
fabs-neg99.7%
*-commutative99.7%
fabs-neg99.7%
+-commutative99.7%
fabs-neg99.7%
Simplified99.7%
add-exp-log97.6%
log-div97.6%
add-log-exp97.6%
add-sqr-sqrt-0.0%
add-sqr-sqrt-0.0%
fabs-sqr-0.0%
add-sqr-sqrt-0.0%
sqrt-unprod53.4%
sqr-neg53.4%
sqrt-unprod58.2%
add-sqr-sqrt58.2%
*-commutative58.2%
Applied egg-rr81.4%
Taylor expanded in x around inf 37.2%
Taylor expanded in x around 0 6.6%
Taylor expanded in x around 0 8.5%
herbie shell --seed 2024083
(FPCore (x s)
:name "Logistic distribution"
:precision binary32
:pre (and (<= 0.0 s) (<= s 1.0651631))
(/ (exp (/ (- (fabs x)) s)) (* (* s (+ 1.0 (exp (/ (- (fabs x)) s)))) (+ 1.0 (exp (/ (- (fabs x)) s))))))