
(FPCore (s r) :precision binary32 (+ (/ (* 0.25 (exp (/ (- r) s))) (* (* (* 2.0 PI) s) r)) (/ (* 0.75 (exp (/ (- r) (* 3.0 s)))) (* (* (* 6.0 PI) s) r))))
float code(float s, float r) {
return ((0.25f * expf((-r / s))) / (((2.0f * ((float) M_PI)) * s) * r)) + ((0.75f * expf((-r / (3.0f * s)))) / (((6.0f * ((float) M_PI)) * s) * r));
}
function code(s, r) return Float32(Float32(Float32(Float32(0.25) * exp(Float32(Float32(-r) / s))) / Float32(Float32(Float32(Float32(2.0) * Float32(pi)) * s) * r)) + Float32(Float32(Float32(0.75) * exp(Float32(Float32(-r) / Float32(Float32(3.0) * s)))) / Float32(Float32(Float32(Float32(6.0) * Float32(pi)) * s) * r))) end
function tmp = code(s, r) tmp = ((single(0.25) * exp((-r / s))) / (((single(2.0) * single(pi)) * s) * r)) + ((single(0.75) * exp((-r / (single(3.0) * s)))) / (((single(6.0) * single(pi)) * s) * r)); end
\begin{array}{l}
\\
\frac{0.25 \cdot e^{\frac{-r}{s}}}{\left(\left(2 \cdot \pi\right) \cdot s\right) \cdot r} + \frac{0.75 \cdot e^{\frac{-r}{3 \cdot s}}}{\left(\left(6 \cdot \pi\right) \cdot s\right) \cdot r}
\end{array}
Sampling outcomes in binary32 precision:
Herbie found 15 alternatives:
| Alternative | Accuracy | Speedup |
|---|
(FPCore (s r) :precision binary32 (+ (/ (* 0.25 (exp (/ (- r) s))) (* (* (* 2.0 PI) s) r)) (/ (* 0.75 (exp (/ (- r) (* 3.0 s)))) (* (* (* 6.0 PI) s) r))))
float code(float s, float r) {
return ((0.25f * expf((-r / s))) / (((2.0f * ((float) M_PI)) * s) * r)) + ((0.75f * expf((-r / (3.0f * s)))) / (((6.0f * ((float) M_PI)) * s) * r));
}
function code(s, r) return Float32(Float32(Float32(Float32(0.25) * exp(Float32(Float32(-r) / s))) / Float32(Float32(Float32(Float32(2.0) * Float32(pi)) * s) * r)) + Float32(Float32(Float32(0.75) * exp(Float32(Float32(-r) / Float32(Float32(3.0) * s)))) / Float32(Float32(Float32(Float32(6.0) * Float32(pi)) * s) * r))) end
function tmp = code(s, r) tmp = ((single(0.25) * exp((-r / s))) / (((single(2.0) * single(pi)) * s) * r)) + ((single(0.75) * exp((-r / (single(3.0) * s)))) / (((single(6.0) * single(pi)) * s) * r)); end
\begin{array}{l}
\\
\frac{0.25 \cdot e^{\frac{-r}{s}}}{\left(\left(2 \cdot \pi\right) \cdot s\right) \cdot r} + \frac{0.75 \cdot e^{\frac{-r}{3 \cdot s}}}{\left(\left(6 \cdot \pi\right) \cdot s\right) \cdot r}
\end{array}
(FPCore (s r) :precision binary32 (+ (* (/ 0.125 (* s PI)) (/ (exp (/ r (- s))) r)) (* 0.75 (/ (exp (/ -0.3333333333333333 (/ s r))) (* r (* s (* PI 6.0)))))))
float code(float s, float r) {
return ((0.125f / (s * ((float) M_PI))) * (expf((r / -s)) / r)) + (0.75f * (expf((-0.3333333333333333f / (s / r))) / (r * (s * (((float) M_PI) * 6.0f)))));
}
function code(s, r) return Float32(Float32(Float32(Float32(0.125) / Float32(s * Float32(pi))) * Float32(exp(Float32(r / Float32(-s))) / r)) + Float32(Float32(0.75) * Float32(exp(Float32(Float32(-0.3333333333333333) / Float32(s / r))) / Float32(r * Float32(s * Float32(Float32(pi) * Float32(6.0))))))) end
function tmp = code(s, r) tmp = ((single(0.125) / (s * single(pi))) * (exp((r / -s)) / r)) + (single(0.75) * (exp((single(-0.3333333333333333) / (s / r))) / (r * (s * (single(pi) * single(6.0)))))); end
\begin{array}{l}
\\
\frac{0.125}{s \cdot \pi} \cdot \frac{e^{\frac{r}{-s}}}{r} + 0.75 \cdot \frac{e^{\frac{-0.3333333333333333}{\frac{s}{r}}}}{r \cdot \left(s \cdot \left(\pi \cdot 6\right)\right)}
\end{array}
Initial program 99.4%
times-frac99.4%
*-commutative99.4%
distribute-frac-neg99.4%
associate-/l*99.5%
*-commutative99.5%
*-commutative99.5%
associate-*l*99.4%
Simplified99.4%
Taylor expanded in s around 0 99.4%
*-commutative99.4%
associate-*r*99.5%
Simplified99.5%
Taylor expanded in r around 0 99.4%
associate-*r/99.5%
*-commutative99.5%
associate-*r/99.5%
Simplified99.5%
Taylor expanded in s around 0 99.5%
associate-*r/99.5%
associate-*l/99.4%
*-commutative99.4%
clear-num99.5%
un-div-inv99.5%
Applied egg-rr99.5%
Final simplification99.5%
(FPCore (s r) :precision binary32 (+ (* (/ 0.125 (* s PI)) (/ (exp (/ r (- s))) r)) (* 0.75 (/ (exp (* r (/ -0.3333333333333333 s))) (* r (* s (* PI 6.0)))))))
float code(float s, float r) {
return ((0.125f / (s * ((float) M_PI))) * (expf((r / -s)) / r)) + (0.75f * (expf((r * (-0.3333333333333333f / s))) / (r * (s * (((float) M_PI) * 6.0f)))));
}
function code(s, r) return Float32(Float32(Float32(Float32(0.125) / Float32(s * Float32(pi))) * Float32(exp(Float32(r / Float32(-s))) / r)) + Float32(Float32(0.75) * Float32(exp(Float32(r * Float32(Float32(-0.3333333333333333) / s))) / Float32(r * Float32(s * Float32(Float32(pi) * Float32(6.0))))))) end
function tmp = code(s, r) tmp = ((single(0.125) / (s * single(pi))) * (exp((r / -s)) / r)) + (single(0.75) * (exp((r * (single(-0.3333333333333333) / s))) / (r * (s * (single(pi) * single(6.0)))))); end
\begin{array}{l}
\\
\frac{0.125}{s \cdot \pi} \cdot \frac{e^{\frac{r}{-s}}}{r} + 0.75 \cdot \frac{e^{r \cdot \frac{-0.3333333333333333}{s}}}{r \cdot \left(s \cdot \left(\pi \cdot 6\right)\right)}
\end{array}
Initial program 99.4%
times-frac99.4%
*-commutative99.4%
distribute-frac-neg99.4%
associate-/l*99.5%
*-commutative99.5%
*-commutative99.5%
associate-*l*99.4%
Simplified99.4%
Taylor expanded in s around 0 99.4%
*-commutative99.4%
associate-*r*99.5%
Simplified99.5%
Taylor expanded in r around 0 99.4%
associate-*r/99.5%
*-commutative99.5%
associate-*r/99.5%
Simplified99.5%
Taylor expanded in s around 0 99.5%
Final simplification99.5%
(FPCore (s r) :precision binary32 (/ (+ (* 0.125 (/ (exp (/ r (- s))) (* PI r))) (* 0.125 (/ (exp (* (/ r s) -0.3333333333333333)) (* PI r)))) s))
float code(float s, float r) {
return ((0.125f * (expf((r / -s)) / (((float) M_PI) * r))) + (0.125f * (expf(((r / s) * -0.3333333333333333f)) / (((float) M_PI) * r)))) / s;
}
function code(s, r) return Float32(Float32(Float32(Float32(0.125) * Float32(exp(Float32(r / Float32(-s))) / Float32(Float32(pi) * r))) + Float32(Float32(0.125) * Float32(exp(Float32(Float32(r / s) * Float32(-0.3333333333333333))) / Float32(Float32(pi) * r)))) / s) end
function tmp = code(s, r) tmp = ((single(0.125) * (exp((r / -s)) / (single(pi) * r))) + (single(0.125) * (exp(((r / s) * single(-0.3333333333333333))) / (single(pi) * r)))) / s; end
\begin{array}{l}
\\
\frac{0.125 \cdot \frac{e^{\frac{r}{-s}}}{\pi \cdot r} + 0.125 \cdot \frac{e^{\frac{r}{s} \cdot -0.3333333333333333}}{\pi \cdot r}}{s}
\end{array}
Initial program 99.4%
+-commutative99.4%
times-frac99.4%
fma-define99.5%
associate-*l*99.4%
associate-/r*99.4%
metadata-eval99.4%
*-commutative99.4%
neg-mul-199.4%
times-frac99.4%
metadata-eval99.4%
times-frac99.4%
Simplified99.4%
Taylor expanded in s around 0 99.4%
Final simplification99.4%
(FPCore (s r) :precision binary32 (* (/ 0.125 (* s PI)) (+ (/ (exp (/ r (- s))) r) (/ (exp (* (/ r s) -0.3333333333333333)) r))))
float code(float s, float r) {
return (0.125f / (s * ((float) M_PI))) * ((expf((r / -s)) / r) + (expf(((r / s) * -0.3333333333333333f)) / r));
}
function code(s, r) return Float32(Float32(Float32(0.125) / Float32(s * Float32(pi))) * Float32(Float32(exp(Float32(r / Float32(-s))) / r) + Float32(exp(Float32(Float32(r / s) * Float32(-0.3333333333333333))) / r))) end
function tmp = code(s, r) tmp = (single(0.125) / (s * single(pi))) * ((exp((r / -s)) / r) + (exp(((r / s) * single(-0.3333333333333333))) / r)); end
\begin{array}{l}
\\
\frac{0.125}{s \cdot \pi} \cdot \left(\frac{e^{\frac{r}{-s}}}{r} + \frac{e^{\frac{r}{s} \cdot -0.3333333333333333}}{r}\right)
\end{array}
Initial program 99.4%
Simplified99.2%
pow-exp99.3%
*-commutative99.3%
Applied egg-rr99.3%
Final simplification99.3%
(FPCore (s r) :precision binary32 (/ 0.25 (log1p (expm1 (* (* s PI) r)))))
float code(float s, float r) {
return 0.25f / log1pf(expm1f(((s * ((float) M_PI)) * r)));
}
function code(s, r) return Float32(Float32(0.25) / log1p(expm1(Float32(Float32(s * Float32(pi)) * r)))) end
\begin{array}{l}
\\
\frac{0.25}{\mathsf{log1p}\left(\mathsf{expm1}\left(\left(s \cdot \pi\right) \cdot r\right)\right)}
\end{array}
Initial program 99.4%
+-commutative99.4%
times-frac99.4%
fma-define99.5%
associate-*l*99.4%
associate-/r*99.4%
metadata-eval99.4%
*-commutative99.4%
neg-mul-199.4%
times-frac99.4%
metadata-eval99.4%
times-frac99.4%
Simplified99.4%
Taylor expanded in s around inf 7.5%
log1p-expm1-u9.2%
Applied egg-rr9.2%
Final simplification9.2%
(FPCore (s r) :precision binary32 (* (/ -0.125 r) (/ (+ -1.0 (/ -1.0 (exp (/ r s)))) (* s PI))))
float code(float s, float r) {
return (-0.125f / r) * ((-1.0f + (-1.0f / expf((r / s)))) / (s * ((float) M_PI)));
}
function code(s, r) return Float32(Float32(Float32(-0.125) / r) * Float32(Float32(Float32(-1.0) + Float32(Float32(-1.0) / exp(Float32(r / s)))) / Float32(s * Float32(pi)))) end
function tmp = code(s, r) tmp = (single(-0.125) / r) * ((single(-1.0) + (single(-1.0) / exp((r / s)))) / (s * single(pi))); end
\begin{array}{l}
\\
\frac{-0.125}{r} \cdot \frac{-1 + \frac{-1}{e^{\frac{r}{s}}}}{s \cdot \pi}
\end{array}
Initial program 99.4%
Simplified99.2%
Taylor expanded in r around 0 7.8%
Taylor expanded in r around -inf 7.8%
associate-*r/7.8%
times-frac7.8%
sub-neg7.8%
mul-1-neg7.8%
mul-1-neg7.8%
rec-exp7.8%
distribute-neg-frac7.8%
metadata-eval7.8%
metadata-eval7.8%
Simplified7.8%
Final simplification7.8%
(FPCore (s r) :precision binary32 (* 0.125 (/ (+ (exp (/ r (- s))) 1.0) (* PI (* s r)))))
float code(float s, float r) {
return 0.125f * ((expf((r / -s)) + 1.0f) / (((float) M_PI) * (s * r)));
}
function code(s, r) return Float32(Float32(0.125) * Float32(Float32(exp(Float32(r / Float32(-s))) + Float32(1.0)) / Float32(Float32(pi) * Float32(s * r)))) end
function tmp = code(s, r) tmp = single(0.125) * ((exp((r / -s)) + single(1.0)) / (single(pi) * (s * r))); end
\begin{array}{l}
\\
0.125 \cdot \frac{e^{\frac{r}{-s}} + 1}{\pi \cdot \left(s \cdot r\right)}
\end{array}
Initial program 99.4%
Simplified99.2%
Taylor expanded in r around 0 7.8%
Taylor expanded in r around inf 7.8%
associate-*r/7.8%
neg-mul-17.8%
associate-*r*7.8%
*-commutative7.8%
*-commutative7.8%
Simplified7.8%
Final simplification7.8%
(FPCore (s r) :precision binary32 (* 0.125 (/ (+ (exp (/ r (- s))) 1.0) (* (* s PI) r))))
float code(float s, float r) {
return 0.125f * ((expf((r / -s)) + 1.0f) / ((s * ((float) M_PI)) * r));
}
function code(s, r) return Float32(Float32(0.125) * Float32(Float32(exp(Float32(r / Float32(-s))) + Float32(1.0)) / Float32(Float32(s * Float32(pi)) * r))) end
function tmp = code(s, r) tmp = single(0.125) * ((exp((r / -s)) + single(1.0)) / ((s * single(pi)) * r)); end
\begin{array}{l}
\\
0.125 \cdot \frac{e^{\frac{r}{-s}} + 1}{\left(s \cdot \pi\right) \cdot r}
\end{array}
Initial program 99.4%
Simplified99.2%
Taylor expanded in r around 0 7.8%
Taylor expanded in r around inf 7.8%
Final simplification7.8%
(FPCore (s r)
:precision binary32
(/
(+
(/
(-
(* 0.16666666666666666 (/ -1.0 PI))
(/ (+ (* -0.0625 (/ r PI)) (* (/ r PI) -0.006944444444444444)) s))
s)
(* 0.25 (/ 1.0 (* PI r))))
s))
float code(float s, float r) {
return ((((0.16666666666666666f * (-1.0f / ((float) M_PI))) - (((-0.0625f * (r / ((float) M_PI))) + ((r / ((float) M_PI)) * -0.006944444444444444f)) / s)) / s) + (0.25f * (1.0f / (((float) M_PI) * r)))) / s;
}
function code(s, r) return Float32(Float32(Float32(Float32(Float32(Float32(0.16666666666666666) * Float32(Float32(-1.0) / Float32(pi))) - Float32(Float32(Float32(Float32(-0.0625) * Float32(r / Float32(pi))) + Float32(Float32(r / Float32(pi)) * Float32(-0.006944444444444444))) / s)) / s) + Float32(Float32(0.25) * Float32(Float32(1.0) / Float32(Float32(pi) * r)))) / s) end
function tmp = code(s, r) tmp = ((((single(0.16666666666666666) * (single(-1.0) / single(pi))) - (((single(-0.0625) * (r / single(pi))) + ((r / single(pi)) * single(-0.006944444444444444))) / s)) / s) + (single(0.25) * (single(1.0) / (single(pi) * r)))) / s; end
\begin{array}{l}
\\
\frac{\frac{0.16666666666666666 \cdot \frac{-1}{\pi} - \frac{-0.0625 \cdot \frac{r}{\pi} + \frac{r}{\pi} \cdot -0.006944444444444444}{s}}{s} + 0.25 \cdot \frac{1}{\pi \cdot r}}{s}
\end{array}
Initial program 99.4%
+-commutative99.4%
times-frac99.4%
fma-define99.5%
associate-*l*99.4%
associate-/r*99.4%
metadata-eval99.4%
*-commutative99.4%
neg-mul-199.4%
times-frac99.4%
metadata-eval99.4%
times-frac99.4%
Simplified99.4%
Taylor expanded in s around -inf 7.6%
Final simplification7.6%
(FPCore (s r)
:precision binary32
(/
(+
(/
(- (/ -0.16666666666666666 PI) (* (/ r PI) (/ -0.06944444444444445 s)))
s)
(/ (/ 0.25 r) PI))
s))
float code(float s, float r) {
return ((((-0.16666666666666666f / ((float) M_PI)) - ((r / ((float) M_PI)) * (-0.06944444444444445f / s))) / s) + ((0.25f / r) / ((float) M_PI))) / s;
}
function code(s, r) return Float32(Float32(Float32(Float32(Float32(Float32(-0.16666666666666666) / Float32(pi)) - Float32(Float32(r / Float32(pi)) * Float32(Float32(-0.06944444444444445) / s))) / s) + Float32(Float32(Float32(0.25) / r) / Float32(pi))) / s) end
function tmp = code(s, r) tmp = ((((single(-0.16666666666666666) / single(pi)) - ((r / single(pi)) * (single(-0.06944444444444445) / s))) / s) + ((single(0.25) / r) / single(pi))) / s; end
\begin{array}{l}
\\
\frac{\frac{\frac{-0.16666666666666666}{\pi} - \frac{r}{\pi} \cdot \frac{-0.06944444444444445}{s}}{s} + \frac{\frac{0.25}{r}}{\pi}}{s}
\end{array}
Initial program 99.4%
+-commutative99.4%
times-frac99.4%
fma-define99.5%
associate-*l*99.4%
associate-/r*99.4%
metadata-eval99.4%
*-commutative99.4%
neg-mul-199.4%
times-frac99.4%
metadata-eval99.4%
times-frac99.4%
Simplified99.4%
Taylor expanded in s around -inf 7.6%
associate-*r/7.6%
Simplified7.6%
Final simplification7.6%
(FPCore (s r)
:precision binary32
(/
(-
(/ 0.25 (* PI r))
(/
(+ (/ (* (/ r PI) -0.06944444444444445) s) (/ 0.16666666666666666 PI))
s))
s))
float code(float s, float r) {
return ((0.25f / (((float) M_PI) * r)) - (((((r / ((float) M_PI)) * -0.06944444444444445f) / s) + (0.16666666666666666f / ((float) M_PI))) / s)) / s;
}
function code(s, r) return Float32(Float32(Float32(Float32(0.25) / Float32(Float32(pi) * r)) - Float32(Float32(Float32(Float32(Float32(r / Float32(pi)) * Float32(-0.06944444444444445)) / s) + Float32(Float32(0.16666666666666666) / Float32(pi))) / s)) / s) end
function tmp = code(s, r) tmp = ((single(0.25) / (single(pi) * r)) - (((((r / single(pi)) * single(-0.06944444444444445)) / s) + (single(0.16666666666666666) / single(pi))) / s)) / s; end
\begin{array}{l}
\\
\frac{\frac{0.25}{\pi \cdot r} - \frac{\frac{\frac{r}{\pi} \cdot -0.06944444444444445}{s} + \frac{0.16666666666666666}{\pi}}{s}}{s}
\end{array}
Initial program 99.4%
+-commutative99.4%
times-frac99.4%
fma-define99.5%
associate-*l*99.4%
associate-/r*99.4%
metadata-eval99.4%
*-commutative99.4%
neg-mul-199.4%
times-frac99.4%
metadata-eval99.4%
times-frac99.4%
Simplified99.4%
Taylor expanded in s around -inf 7.6%
mul-1-neg7.6%
Simplified7.6%
Final simplification7.6%
(FPCore (s r) :precision binary32 (/ 0.25 (* (* s PI) r)))
float code(float s, float r) {
return 0.25f / ((s * ((float) M_PI)) * r);
}
function code(s, r) return Float32(Float32(0.25) / Float32(Float32(s * Float32(pi)) * r)) end
function tmp = code(s, r) tmp = single(0.25) / ((s * single(pi)) * r); end
\begin{array}{l}
\\
\frac{0.25}{\left(s \cdot \pi\right) \cdot r}
\end{array}
Initial program 99.4%
+-commutative99.4%
times-frac99.4%
fma-define99.5%
associate-*l*99.4%
associate-/r*99.4%
metadata-eval99.4%
*-commutative99.4%
neg-mul-199.4%
times-frac99.4%
metadata-eval99.4%
times-frac99.4%
Simplified99.4%
Taylor expanded in s around inf 7.5%
Final simplification7.5%
(FPCore (s r) :precision binary32 (/ 0.25 (* PI (* s r))))
float code(float s, float r) {
return 0.25f / (((float) M_PI) * (s * r));
}
function code(s, r) return Float32(Float32(0.25) / Float32(Float32(pi) * Float32(s * r))) end
function tmp = code(s, r) tmp = single(0.25) / (single(pi) * (s * r)); end
\begin{array}{l}
\\
\frac{0.25}{\pi \cdot \left(s \cdot r\right)}
\end{array}
Initial program 99.4%
+-commutative99.4%
times-frac99.4%
fma-define99.5%
associate-*l*99.4%
associate-/r*99.4%
metadata-eval99.4%
*-commutative99.4%
neg-mul-199.4%
times-frac99.4%
metadata-eval99.4%
times-frac99.4%
Simplified99.4%
Taylor expanded in s around inf 7.5%
associate-/r*7.5%
*-un-lft-identity7.5%
*-commutative7.5%
times-frac7.5%
Applied egg-rr7.5%
*-commutative7.5%
associate-/l/7.5%
frac-times7.5%
metadata-eval7.5%
Applied egg-rr7.5%
Final simplification7.5%
(FPCore (s r) :precision binary32 (/ 0.25 (* s (* PI r))))
float code(float s, float r) {
return 0.25f / (s * (((float) M_PI) * r));
}
function code(s, r) return Float32(Float32(0.25) / Float32(s * Float32(Float32(pi) * r))) end
function tmp = code(s, r) tmp = single(0.25) / (s * (single(pi) * r)); end
\begin{array}{l}
\\
\frac{0.25}{s \cdot \left(\pi \cdot r\right)}
\end{array}
Initial program 99.4%
+-commutative99.4%
times-frac99.4%
fma-define99.5%
associate-*l*99.4%
associate-/r*99.4%
metadata-eval99.4%
*-commutative99.4%
neg-mul-199.4%
times-frac99.4%
metadata-eval99.4%
times-frac99.4%
Simplified99.4%
Taylor expanded in s around inf 7.5%
associate-/r*7.5%
*-un-lft-identity7.5%
*-commutative7.5%
times-frac7.5%
Applied egg-rr7.5%
*-commutative7.5%
div-inv7.5%
div-inv7.5%
associate-/l*7.5%
times-frac7.5%
div-inv7.5%
associate-/l/7.5%
*-commutative7.5%
Applied egg-rr7.5%
Final simplification7.5%
(FPCore (s r) :precision binary32 (/ (/ 0.25 r) (* s PI)))
float code(float s, float r) {
return (0.25f / r) / (s * ((float) M_PI));
}
function code(s, r) return Float32(Float32(Float32(0.25) / r) / Float32(s * Float32(pi))) end
function tmp = code(s, r) tmp = (single(0.25) / r) / (s * single(pi)); end
\begin{array}{l}
\\
\frac{\frac{0.25}{r}}{s \cdot \pi}
\end{array}
Initial program 99.4%
+-commutative99.4%
times-frac99.4%
fma-define99.5%
associate-*l*99.4%
associate-/r*99.4%
metadata-eval99.4%
*-commutative99.4%
neg-mul-199.4%
times-frac99.4%
metadata-eval99.4%
times-frac99.4%
Simplified99.4%
Taylor expanded in s around inf 7.5%
associate-/r*7.5%
Simplified7.5%
Final simplification7.5%
herbie shell --seed 2024069
(FPCore (s r)
:name "Disney BSSRDF, PDF of scattering profile"
:precision binary32
:pre (and (and (<= 0.0 s) (<= s 256.0)) (and (< 1e-6 r) (< r 1000000.0)))
(+ (/ (* 0.25 (exp (/ (- r) s))) (* (* (* 2.0 PI) s) r)) (/ (* 0.75 (exp (/ (- r) (* 3.0 s)))) (* (* (* 6.0 PI) s) r))))