
(FPCore (cosTheta c)
:precision binary32
(/
1.0
(+
(+ 1.0 c)
(*
(* (/ 1.0 (sqrt PI)) (/ (sqrt (- (- 1.0 cosTheta) cosTheta)) cosTheta))
(exp (* (- cosTheta) cosTheta))))))
float code(float cosTheta, float c) {
return 1.0f / ((1.0f + c) + (((1.0f / sqrtf(((float) M_PI))) * (sqrtf(((1.0f - cosTheta) - cosTheta)) / cosTheta)) * expf((-cosTheta * cosTheta))));
}
function code(cosTheta, c) return Float32(Float32(1.0) / Float32(Float32(Float32(1.0) + c) + Float32(Float32(Float32(Float32(1.0) / sqrt(Float32(pi))) * Float32(sqrt(Float32(Float32(Float32(1.0) - cosTheta) - cosTheta)) / cosTheta)) * exp(Float32(Float32(-cosTheta) * cosTheta))))) end
function tmp = code(cosTheta, c) tmp = single(1.0) / ((single(1.0) + c) + (((single(1.0) / sqrt(single(pi))) * (sqrt(((single(1.0) - cosTheta) - cosTheta)) / cosTheta)) * exp((-cosTheta * cosTheta)))); end
\begin{array}{l}
\\
\frac{1}{\left(1 + c\right) + \left(\frac{1}{\sqrt{\pi}} \cdot \frac{\sqrt{\left(1 - cosTheta\right) - cosTheta}}{cosTheta}\right) \cdot e^{\left(-cosTheta\right) \cdot cosTheta}}
\end{array}
Sampling outcomes in binary32 precision:
Herbie found 13 alternatives:
| Alternative | Accuracy | Speedup |
|---|
(FPCore (cosTheta c)
:precision binary32
(/
1.0
(+
(+ 1.0 c)
(*
(* (/ 1.0 (sqrt PI)) (/ (sqrt (- (- 1.0 cosTheta) cosTheta)) cosTheta))
(exp (* (- cosTheta) cosTheta))))))
float code(float cosTheta, float c) {
return 1.0f / ((1.0f + c) + (((1.0f / sqrtf(((float) M_PI))) * (sqrtf(((1.0f - cosTheta) - cosTheta)) / cosTheta)) * expf((-cosTheta * cosTheta))));
}
function code(cosTheta, c) return Float32(Float32(1.0) / Float32(Float32(Float32(1.0) + c) + Float32(Float32(Float32(Float32(1.0) / sqrt(Float32(pi))) * Float32(sqrt(Float32(Float32(Float32(1.0) - cosTheta) - cosTheta)) / cosTheta)) * exp(Float32(Float32(-cosTheta) * cosTheta))))) end
function tmp = code(cosTheta, c) tmp = single(1.0) / ((single(1.0) + c) + (((single(1.0) / sqrt(single(pi))) * (sqrt(((single(1.0) - cosTheta) - cosTheta)) / cosTheta)) * exp((-cosTheta * cosTheta)))); end
\begin{array}{l}
\\
\frac{1}{\left(1 + c\right) + \left(\frac{1}{\sqrt{\pi}} \cdot \frac{\sqrt{\left(1 - cosTheta\right) - cosTheta}}{cosTheta}\right) \cdot e^{\left(-cosTheta\right) \cdot cosTheta}}
\end{array}
(FPCore (cosTheta c)
:precision binary32
(/
1.0
(+
(+ 1.0 c)
(/
(exp (- (pow cosTheta 2.0)))
(* cosTheta (sqrt (/ PI (+ 1.0 (* cosTheta -2.0)))))))))
float code(float cosTheta, float c) {
return 1.0f / ((1.0f + c) + (expf(-powf(cosTheta, 2.0f)) / (cosTheta * sqrtf((((float) M_PI) / (1.0f + (cosTheta * -2.0f)))))));
}
function code(cosTheta, c) return Float32(Float32(1.0) / Float32(Float32(Float32(1.0) + c) + Float32(exp(Float32(-(cosTheta ^ Float32(2.0)))) / Float32(cosTheta * sqrt(Float32(Float32(pi) / Float32(Float32(1.0) + Float32(cosTheta * Float32(-2.0))))))))) end
function tmp = code(cosTheta, c) tmp = single(1.0) / ((single(1.0) + c) + (exp(-(cosTheta ^ single(2.0))) / (cosTheta * sqrt((single(pi) / (single(1.0) + (cosTheta * single(-2.0)))))))); end
\begin{array}{l}
\\
\frac{1}{\left(1 + c\right) + \frac{e^{-{cosTheta}^{2}}}{cosTheta \cdot \sqrt{\frac{\pi}{1 + cosTheta \cdot -2}}}}
\end{array}
Initial program 97.9%
add-cube-cbrt97.9%
cbrt-unprod97.9%
inv-pow97.9%
inv-pow97.9%
pow-prod-down98.2%
add-sqr-sqrt98.2%
pow1/298.2%
pow-flip98.2%
metadata-eval98.2%
Applied egg-rr98.2%
unpow-198.2%
Simplified98.2%
*-commutative98.2%
associate--r+98.3%
cbrt-unprod97.8%
inv-pow97.8%
metadata-eval97.8%
pow-prod-up97.8%
add-cbrt-cube97.8%
metadata-eval97.8%
pow-flip97.8%
pow1/297.8%
div-inv98.5%
clear-num98.5%
associate--r+98.5%
Applied egg-rr98.5%
expm1-log1p-u98.5%
expm1-udef22.7%
Applied egg-rr22.7%
expm1-def98.5%
expm1-log1p98.5%
*-commutative98.5%
*-commutative98.5%
Simplified98.5%
Final simplification98.5%
(FPCore (cosTheta c)
:precision binary32
(/
1.0
(+
(+ 1.0 c)
(*
(/ 1.0 (* cosTheta (sqrt (/ PI (+ 1.0 (* cosTheta -2.0))))))
(exp (* cosTheta (- cosTheta)))))))
float code(float cosTheta, float c) {
return 1.0f / ((1.0f + c) + ((1.0f / (cosTheta * sqrtf((((float) M_PI) / (1.0f + (cosTheta * -2.0f)))))) * expf((cosTheta * -cosTheta))));
}
function code(cosTheta, c) return Float32(Float32(1.0) / Float32(Float32(Float32(1.0) + c) + Float32(Float32(Float32(1.0) / Float32(cosTheta * sqrt(Float32(Float32(pi) / Float32(Float32(1.0) + Float32(cosTheta * Float32(-2.0))))))) * exp(Float32(cosTheta * Float32(-cosTheta)))))) end
function tmp = code(cosTheta, c) tmp = single(1.0) / ((single(1.0) + c) + ((single(1.0) / (cosTheta * sqrt((single(pi) / (single(1.0) + (cosTheta * single(-2.0))))))) * exp((cosTheta * -cosTheta)))); end
\begin{array}{l}
\\
\frac{1}{\left(1 + c\right) + \frac{1}{cosTheta \cdot \sqrt{\frac{\pi}{1 + cosTheta \cdot -2}}} \cdot e^{cosTheta \cdot \left(-cosTheta\right)}}
\end{array}
Initial program 97.9%
add-cube-cbrt97.9%
cbrt-unprod97.9%
inv-pow97.9%
inv-pow97.9%
pow-prod-down98.2%
add-sqr-sqrt98.2%
pow1/298.2%
pow-flip98.2%
metadata-eval98.2%
Applied egg-rr98.2%
unpow-198.2%
Simplified98.2%
*-commutative98.2%
associate--r+98.3%
cbrt-unprod97.8%
inv-pow97.8%
metadata-eval97.8%
pow-prod-up97.8%
add-cbrt-cube97.8%
metadata-eval97.8%
pow-flip97.8%
pow1/297.8%
div-inv98.5%
clear-num98.5%
associate--r+98.5%
Applied egg-rr98.5%
associate-/r/98.5%
sqrt-undiv98.5%
cancel-sign-sub-inv98.5%
metadata-eval98.5%
Applied egg-rr98.5%
Final simplification98.5%
(FPCore (cosTheta c)
:precision binary32
(let* ((t_0 (sqrt (/ 1.0 PI))))
(/
1.0
(+ (+ 1.0 c) (+ (/ t_0 cosTheta) (* t_0 (+ (* cosTheta -1.5) -1.0)))))))
float code(float cosTheta, float c) {
float t_0 = sqrtf((1.0f / ((float) M_PI)));
return 1.0f / ((1.0f + c) + ((t_0 / cosTheta) + (t_0 * ((cosTheta * -1.5f) + -1.0f))));
}
function code(cosTheta, c) t_0 = sqrt(Float32(Float32(1.0) / Float32(pi))) return Float32(Float32(1.0) / Float32(Float32(Float32(1.0) + c) + Float32(Float32(t_0 / cosTheta) + Float32(t_0 * Float32(Float32(cosTheta * Float32(-1.5)) + Float32(-1.0)))))) end
function tmp = code(cosTheta, c) t_0 = sqrt((single(1.0) / single(pi))); tmp = single(1.0) / ((single(1.0) + c) + ((t_0 / cosTheta) + (t_0 * ((cosTheta * single(-1.5)) + single(-1.0))))); end
\begin{array}{l}
\\
\begin{array}{l}
t_0 := \sqrt{\frac{1}{\pi}}\\
\frac{1}{\left(1 + c\right) + \left(\frac{t_0}{cosTheta} + t_0 \cdot \left(cosTheta \cdot -1.5 + -1\right)\right)}
\end{array}
\end{array}
Initial program 97.9%
add-cube-cbrt97.9%
cbrt-unprod97.9%
inv-pow97.9%
inv-pow97.9%
pow-prod-down98.2%
add-sqr-sqrt98.2%
pow1/298.2%
pow-flip98.2%
metadata-eval98.2%
Applied egg-rr98.2%
unpow-198.2%
Simplified98.2%
*-commutative98.2%
associate--r+98.3%
cbrt-unprod97.8%
inv-pow97.8%
metadata-eval97.8%
pow-prod-up97.8%
add-cbrt-cube97.8%
metadata-eval97.8%
pow-flip97.8%
pow1/297.8%
div-inv98.5%
clear-num98.5%
associate--r+98.5%
Applied egg-rr98.5%
expm1-log1p-u98.5%
expm1-udef22.7%
Applied egg-rr22.7%
expm1-def98.5%
expm1-log1p98.5%
*-commutative98.5%
*-commutative98.5%
Simplified98.5%
Taylor expanded in cosTheta around 0 96.2%
+-commutative96.2%
+-commutative96.2%
associate-+l+96.2%
associate-*l/96.2%
*-lft-identity96.2%
Simplified96.2%
Final simplification96.2%
(FPCore (cosTheta c)
:precision binary32
(/
1.0
(+
(+ 1.0 c)
(*
(exp (* cosTheta (- cosTheta)))
(/ 1.0 (/ (sqrt PI) (+ -1.0 (/ 1.0 cosTheta))))))))
float code(float cosTheta, float c) {
return 1.0f / ((1.0f + c) + (expf((cosTheta * -cosTheta)) * (1.0f / (sqrtf(((float) M_PI)) / (-1.0f + (1.0f / cosTheta))))));
}
function code(cosTheta, c) return Float32(Float32(1.0) / Float32(Float32(Float32(1.0) + c) + Float32(exp(Float32(cosTheta * Float32(-cosTheta))) * Float32(Float32(1.0) / Float32(sqrt(Float32(pi)) / Float32(Float32(-1.0) + Float32(Float32(1.0) / cosTheta))))))) end
function tmp = code(cosTheta, c) tmp = single(1.0) / ((single(1.0) + c) + (exp((cosTheta * -cosTheta)) * (single(1.0) / (sqrt(single(pi)) / (single(-1.0) + (single(1.0) / cosTheta)))))); end
\begin{array}{l}
\\
\frac{1}{\left(1 + c\right) + e^{cosTheta \cdot \left(-cosTheta\right)} \cdot \frac{1}{\frac{\sqrt{\pi}}{-1 + \frac{1}{cosTheta}}}}
\end{array}
Initial program 97.9%
add-cube-cbrt97.9%
cbrt-unprod97.9%
inv-pow97.9%
inv-pow97.9%
pow-prod-down98.2%
add-sqr-sqrt98.2%
pow1/298.2%
pow-flip98.2%
metadata-eval98.2%
Applied egg-rr98.2%
unpow-198.2%
Simplified98.2%
*-commutative98.2%
associate--r+98.3%
cbrt-unprod97.8%
inv-pow97.8%
metadata-eval97.8%
pow-prod-up97.8%
add-cbrt-cube97.8%
metadata-eval97.8%
pow-flip97.8%
pow1/297.8%
div-inv98.5%
clear-num98.5%
associate--r+98.5%
Applied egg-rr98.5%
Taylor expanded in cosTheta around 0 95.9%
Final simplification95.9%
(FPCore (cosTheta c)
:precision binary32
(/
1.0
(+
(+ 1.0 c)
(*
(exp (* cosTheta (- cosTheta)))
(/ (/ (- 1.0 cosTheta) cosTheta) (sqrt PI))))))
float code(float cosTheta, float c) {
return 1.0f / ((1.0f + c) + (expf((cosTheta * -cosTheta)) * (((1.0f - cosTheta) / cosTheta) / sqrtf(((float) M_PI)))));
}
function code(cosTheta, c) return Float32(Float32(1.0) / Float32(Float32(Float32(1.0) + c) + Float32(exp(Float32(cosTheta * Float32(-cosTheta))) * Float32(Float32(Float32(Float32(1.0) - cosTheta) / cosTheta) / sqrt(Float32(pi)))))) end
function tmp = code(cosTheta, c) tmp = single(1.0) / ((single(1.0) + c) + (exp((cosTheta * -cosTheta)) * (((single(1.0) - cosTheta) / cosTheta) / sqrt(single(pi))))); end
\begin{array}{l}
\\
\frac{1}{\left(1 + c\right) + e^{cosTheta \cdot \left(-cosTheta\right)} \cdot \frac{\frac{1 - cosTheta}{cosTheta}}{\sqrt{\pi}}}
\end{array}
Initial program 97.9%
associate-*l/98.5%
*-un-lft-identity98.5%
associate--l-98.5%
Applied egg-rr98.5%
Taylor expanded in cosTheta around 0 95.8%
neg-mul-195.8%
sub-neg95.8%
Simplified95.8%
Final simplification95.8%
(FPCore (cosTheta c) :precision binary32 (/ 1.0 (+ 1.0 (fma (+ -1.0 (+ (/ 1.0 cosTheta) (* cosTheta -0.5))) (sqrt (/ 1.0 PI)) c))))
float code(float cosTheta, float c) {
return 1.0f / (1.0f + fmaf((-1.0f + ((1.0f / cosTheta) + (cosTheta * -0.5f))), sqrtf((1.0f / ((float) M_PI))), c));
}
function code(cosTheta, c) return Float32(Float32(1.0) / Float32(Float32(1.0) + fma(Float32(Float32(-1.0) + Float32(Float32(Float32(1.0) / cosTheta) + Float32(cosTheta * Float32(-0.5)))), sqrt(Float32(Float32(1.0) / Float32(pi))), c))) end
\begin{array}{l}
\\
\frac{1}{1 + \mathsf{fma}\left(-1 + \left(\frac{1}{cosTheta} + cosTheta \cdot -0.5\right), \sqrt{\frac{1}{\pi}}, c\right)}
\end{array}
Initial program 97.9%
associate-+l+97.9%
+-commutative97.9%
*-commutative97.9%
associate-*l*97.8%
fma-def97.8%
Simplified97.9%
Taylor expanded in cosTheta around 0 96.2%
Taylor expanded in cosTheta around 0 95.2%
Final simplification95.2%
(FPCore (cosTheta c) :precision binary32 (/ 1.0 (+ 1.0 (+ c (- (/ -1.0 (* cosTheta (- (sqrt PI)))) (sqrt (/ 1.0 PI)))))))
float code(float cosTheta, float c) {
return 1.0f / (1.0f + (c + ((-1.0f / (cosTheta * -sqrtf(((float) M_PI)))) - sqrtf((1.0f / ((float) M_PI))))));
}
function code(cosTheta, c) return Float32(Float32(1.0) / Float32(Float32(1.0) + Float32(c + Float32(Float32(Float32(-1.0) / Float32(cosTheta * Float32(-sqrt(Float32(pi))))) - sqrt(Float32(Float32(1.0) / Float32(pi))))))) end
function tmp = code(cosTheta, c) tmp = single(1.0) / (single(1.0) + (c + ((single(-1.0) / (cosTheta * -sqrt(single(pi)))) - sqrt((single(1.0) / single(pi)))))); end
\begin{array}{l}
\\
\frac{1}{1 + \left(c + \left(\frac{-1}{cosTheta \cdot \left(-\sqrt{\pi}\right)} - \sqrt{\frac{1}{\pi}}\right)\right)}
\end{array}
Initial program 97.9%
associate-+l+97.9%
+-commutative97.9%
*-commutative97.9%
associate-*l*97.8%
fma-def97.8%
Simplified97.9%
Taylor expanded in cosTheta around 0 95.0%
pow1/295.0%
inv-pow95.0%
pow-pow95.0%
metadata-eval95.0%
add-cbrt-cube95.0%
pow-prod-up95.0%
metadata-eval95.0%
inv-pow95.0%
cbrt-unprod95.2%
*-commutative95.2%
pow1/395.2%
pow-pow95.2%
metadata-eval95.2%
cbrt-div95.2%
metadata-eval95.2%
Applied egg-rr95.2%
associate-*r/95.2%
*-rgt-identity95.2%
Simplified95.2%
inv-pow95.2%
clear-num95.2%
pow1/395.2%
pow-div95.0%
metadata-eval95.0%
pow1/295.0%
inv-pow95.0%
unpow-prod-down95.5%
inv-pow95.5%
frac-2neg95.5%
metadata-eval95.5%
Applied egg-rr95.5%
distribute-rgt-neg-in95.5%
Simplified95.5%
Final simplification95.5%
(FPCore (cosTheta c) :precision binary32 (/ 1.0 (+ 1.0 (fma (pow PI -0.5) (+ -1.0 (/ 1.0 cosTheta)) c))))
float code(float cosTheta, float c) {
return 1.0f / (1.0f + fmaf(powf(((float) M_PI), -0.5f), (-1.0f + (1.0f / cosTheta)), c));
}
function code(cosTheta, c) return Float32(Float32(1.0) / Float32(Float32(1.0) + fma((Float32(pi) ^ Float32(-0.5)), Float32(Float32(-1.0) + Float32(Float32(1.0) / cosTheta)), c))) end
\begin{array}{l}
\\
\frac{1}{1 + \mathsf{fma}\left({\pi}^{-0.5}, -1 + \frac{1}{cosTheta}, c\right)}
\end{array}
Initial program 97.9%
associate-+l+97.9%
+-commutative97.9%
*-commutative97.9%
associate-*l*97.8%
fma-def97.8%
Simplified97.9%
Taylor expanded in cosTheta around 0 95.0%
expm1-log1p-u95.0%
expm1-udef20.3%
Applied egg-rr20.3%
expm1-def95.0%
expm1-log1p95.0%
+-commutative95.0%
Simplified95.0%
Final simplification95.0%
(FPCore (cosTheta c) :precision binary32 (/ 1.0 (+ 1.0 (+ c (* (pow PI -0.5) (+ -1.0 (/ 1.0 cosTheta)))))))
float code(float cosTheta, float c) {
return 1.0f / (1.0f + (c + (powf(((float) M_PI), -0.5f) * (-1.0f + (1.0f / cosTheta)))));
}
function code(cosTheta, c) return Float32(Float32(1.0) / Float32(Float32(1.0) + Float32(c + Float32((Float32(pi) ^ Float32(-0.5)) * Float32(Float32(-1.0) + Float32(Float32(1.0) / cosTheta)))))) end
function tmp = code(cosTheta, c) tmp = single(1.0) / (single(1.0) + (c + ((single(pi) ^ single(-0.5)) * (single(-1.0) + (single(1.0) / cosTheta))))); end
\begin{array}{l}
\\
\frac{1}{1 + \left(c + {\pi}^{-0.5} \cdot \left(-1 + \frac{1}{cosTheta}\right)\right)}
\end{array}
Initial program 97.9%
associate-+l+97.9%
+-commutative97.9%
*-commutative97.9%
associate-*l*97.8%
fma-def97.8%
Simplified97.9%
Taylor expanded in cosTheta around 0 95.0%
expm1-log1p-u87.7%
expm1-udef87.7%
distribute-rgt-out87.7%
pow1/287.7%
inv-pow87.7%
pow-pow87.7%
metadata-eval87.7%
Applied egg-rr87.7%
expm1-def87.7%
expm1-log1p95.0%
+-commutative95.0%
Simplified95.0%
Final simplification95.0%
(FPCore (cosTheta c) :precision binary32 (/ 1.0 (+ 1.0 (* (sqrt (/ 1.0 PI)) (+ -1.0 (/ 1.0 cosTheta))))))
float code(float cosTheta, float c) {
return 1.0f / (1.0f + (sqrtf((1.0f / ((float) M_PI))) * (-1.0f + (1.0f / cosTheta))));
}
function code(cosTheta, c) return Float32(Float32(1.0) / Float32(Float32(1.0) + Float32(sqrt(Float32(Float32(1.0) / Float32(pi))) * Float32(Float32(-1.0) + Float32(Float32(1.0) / cosTheta))))) end
function tmp = code(cosTheta, c) tmp = single(1.0) / (single(1.0) + (sqrt((single(1.0) / single(pi))) * (single(-1.0) + (single(1.0) / cosTheta)))); end
\begin{array}{l}
\\
\frac{1}{1 + \sqrt{\frac{1}{\pi}} \cdot \left(-1 + \frac{1}{cosTheta}\right)}
\end{array}
Initial program 97.9%
associate-+l+97.9%
+-commutative97.9%
*-commutative97.9%
associate-*l*97.8%
fma-def97.8%
Simplified97.9%
Taylor expanded in cosTheta around 0 95.0%
Taylor expanded in c around 0 94.8%
distribute-rgt-out94.8%
+-commutative94.8%
Simplified94.8%
Final simplification94.8%
(FPCore (cosTheta c) :precision binary32 (* cosTheta (sqrt PI)))
float code(float cosTheta, float c) {
return cosTheta * sqrtf(((float) M_PI));
}
function code(cosTheta, c) return Float32(cosTheta * sqrt(Float32(pi))) end
function tmp = code(cosTheta, c) tmp = cosTheta * sqrt(single(pi)); end
\begin{array}{l}
\\
cosTheta \cdot \sqrt{\pi}
\end{array}
Initial program 97.9%
associate-+l+97.9%
+-commutative97.9%
*-commutative97.9%
associate-*l*97.8%
fma-def97.8%
Simplified97.9%
Taylor expanded in cosTheta around 0 92.8%
Final simplification92.8%
(FPCore (cosTheta c) :precision binary32 (- 1.0 c))
float code(float cosTheta, float c) {
return 1.0f - c;
}
real(4) function code(costheta, c)
real(4), intent (in) :: costheta
real(4), intent (in) :: c
code = 1.0e0 - c
end function
function code(cosTheta, c) return Float32(Float32(1.0) - c) end
function tmp = code(cosTheta, c) tmp = single(1.0) - c; end
\begin{array}{l}
\\
1 - c
\end{array}
Initial program 97.9%
associate-+l+97.9%
+-commutative97.9%
*-commutative97.9%
associate-*l*97.8%
fma-def97.8%
Simplified97.9%
Taylor expanded in cosTheta around inf 10.9%
Taylor expanded in c around 0 10.9%
mul-1-neg10.9%
unsub-neg10.9%
Simplified10.9%
Final simplification10.9%
(FPCore (cosTheta c) :precision binary32 1.0)
float code(float cosTheta, float c) {
return 1.0f;
}
real(4) function code(costheta, c)
real(4), intent (in) :: costheta
real(4), intent (in) :: c
code = 1.0e0
end function
function code(cosTheta, c) return Float32(1.0) end
function tmp = code(cosTheta, c) tmp = single(1.0); end
\begin{array}{l}
\\
1
\end{array}
Initial program 97.9%
associate-+l+97.9%
+-commutative97.9%
*-commutative97.9%
associate-*l*97.8%
fma-def97.8%
Simplified97.9%
Taylor expanded in cosTheta around inf 10.9%
Taylor expanded in c around 0 10.9%
Final simplification10.9%
herbie shell --seed 2024021
(FPCore (cosTheta c)
:name "Beckmann Sample, normalization factor"
:precision binary32
:pre (and (and (< 0.0 cosTheta) (< cosTheta 0.9999)) (and (< -1.0 c) (< c 1.0)))
(/ 1.0 (+ (+ 1.0 c) (* (* (/ 1.0 (sqrt PI)) (/ (sqrt (- (- 1.0 cosTheta) cosTheta)) cosTheta)) (exp (* (- cosTheta) cosTheta))))))