HairBSDF, Mp, lower

Percentage Accurate: 99.6% → 99.6%
Time: 4.4s
Alternatives: 4
Speedup: 1.0×

Specification

?
\[\left(\left(\left(\left(-1 \leq cosTheta\_i \land cosTheta\_i \leq 1\right) \land \left(-1 \leq cosTheta\_O \land cosTheta\_O \leq 1\right)\right) \land \left(-1 \leq sinTheta\_i \land sinTheta\_i \leq 1\right)\right) \land \left(-1 \leq sinTheta\_O \land sinTheta\_O \leq 1\right)\right) \land \left(-1.5707964 \leq v \land v \leq 0.1\right)\]
\[\begin{array}{l} \\ e^{\left(\left(\left(\frac{cosTheta\_i \cdot cosTheta\_O}{v} - \frac{sinTheta\_i \cdot sinTheta\_O}{v}\right) - \frac{1}{v}\right) + 0.6931\right) + \log \left(\frac{1}{2 \cdot v}\right)} \end{array} \]
(FPCore (cosTheta_i cosTheta_O sinTheta_i sinTheta_O v)
 :precision binary32
 (exp
  (+
   (+
    (-
     (- (/ (* cosTheta_i cosTheta_O) v) (/ (* sinTheta_i sinTheta_O) v))
     (/ 1.0 v))
    0.6931)
   (log (/ 1.0 (* 2.0 v))))))
float code(float cosTheta_i, float cosTheta_O, float sinTheta_i, float sinTheta_O, float v) {
	return expf(((((((cosTheta_i * cosTheta_O) / v) - ((sinTheta_i * sinTheta_O) / v)) - (1.0f / v)) + 0.6931f) + logf((1.0f / (2.0f * v)))));
}
real(4) function code(costheta_i, costheta_o, sintheta_i, sintheta_o, v)
    real(4), intent (in) :: costheta_i
    real(4), intent (in) :: costheta_o
    real(4), intent (in) :: sintheta_i
    real(4), intent (in) :: sintheta_o
    real(4), intent (in) :: v
    code = exp(((((((costheta_i * costheta_o) / v) - ((sintheta_i * sintheta_o) / v)) - (1.0e0 / v)) + 0.6931e0) + log((1.0e0 / (2.0e0 * v)))))
end function
function code(cosTheta_i, cosTheta_O, sinTheta_i, sinTheta_O, v)
	return exp(Float32(Float32(Float32(Float32(Float32(Float32(cosTheta_i * cosTheta_O) / v) - Float32(Float32(sinTheta_i * sinTheta_O) / v)) - Float32(Float32(1.0) / v)) + Float32(0.6931)) + log(Float32(Float32(1.0) / Float32(Float32(2.0) * v)))))
end
function tmp = code(cosTheta_i, cosTheta_O, sinTheta_i, sinTheta_O, v)
	tmp = exp(((((((cosTheta_i * cosTheta_O) / v) - ((sinTheta_i * sinTheta_O) / v)) - (single(1.0) / v)) + single(0.6931)) + log((single(1.0) / (single(2.0) * v)))));
end
\begin{array}{l}

\\
e^{\left(\left(\left(\frac{cosTheta\_i \cdot cosTheta\_O}{v} - \frac{sinTheta\_i \cdot sinTheta\_O}{v}\right) - \frac{1}{v}\right) + 0.6931\right) + \log \left(\frac{1}{2 \cdot v}\right)}
\end{array}

Sampling outcomes in binary32 precision:

Local Percentage Accuracy vs ?

The average percentage accuracy by input value. Horizontal axis shows value of an input variable; the variable is choosen in the title. Vertical axis is accuracy; higher is better. Red represent the original program, while blue represents Herbie's suggestion. These can be toggled with buttons below the plot. The line is an average while dots represent individual samples.

Accuracy vs Speed?

Herbie found 4 alternatives:

AlternativeAccuracySpeedup
The accuracy (vertical axis) and speed (horizontal axis) of each alternatives. Up and to the right is better. The red square shows the initial program, and each blue circle shows an alternative.The line shows the best available speed-accuracy tradeoffs.

Initial Program: 99.6% accurate, 1.0× speedup?

\[\begin{array}{l} \\ e^{\left(\left(\left(\frac{cosTheta\_i \cdot cosTheta\_O}{v} - \frac{sinTheta\_i \cdot sinTheta\_O}{v}\right) - \frac{1}{v}\right) + 0.6931\right) + \log \left(\frac{1}{2 \cdot v}\right)} \end{array} \]
(FPCore (cosTheta_i cosTheta_O sinTheta_i sinTheta_O v)
 :precision binary32
 (exp
  (+
   (+
    (-
     (- (/ (* cosTheta_i cosTheta_O) v) (/ (* sinTheta_i sinTheta_O) v))
     (/ 1.0 v))
    0.6931)
   (log (/ 1.0 (* 2.0 v))))))
float code(float cosTheta_i, float cosTheta_O, float sinTheta_i, float sinTheta_O, float v) {
	return expf(((((((cosTheta_i * cosTheta_O) / v) - ((sinTheta_i * sinTheta_O) / v)) - (1.0f / v)) + 0.6931f) + logf((1.0f / (2.0f * v)))));
}
real(4) function code(costheta_i, costheta_o, sintheta_i, sintheta_o, v)
    real(4), intent (in) :: costheta_i
    real(4), intent (in) :: costheta_o
    real(4), intent (in) :: sintheta_i
    real(4), intent (in) :: sintheta_o
    real(4), intent (in) :: v
    code = exp(((((((costheta_i * costheta_o) / v) - ((sintheta_i * sintheta_o) / v)) - (1.0e0 / v)) + 0.6931e0) + log((1.0e0 / (2.0e0 * v)))))
end function
function code(cosTheta_i, cosTheta_O, sinTheta_i, sinTheta_O, v)
	return exp(Float32(Float32(Float32(Float32(Float32(Float32(cosTheta_i * cosTheta_O) / v) - Float32(Float32(sinTheta_i * sinTheta_O) / v)) - Float32(Float32(1.0) / v)) + Float32(0.6931)) + log(Float32(Float32(1.0) / Float32(Float32(2.0) * v)))))
end
function tmp = code(cosTheta_i, cosTheta_O, sinTheta_i, sinTheta_O, v)
	tmp = exp(((((((cosTheta_i * cosTheta_O) / v) - ((sinTheta_i * sinTheta_O) / v)) - (single(1.0) / v)) + single(0.6931)) + log((single(1.0) / (single(2.0) * v)))));
end
\begin{array}{l}

\\
e^{\left(\left(\left(\frac{cosTheta\_i \cdot cosTheta\_O}{v} - \frac{sinTheta\_i \cdot sinTheta\_O}{v}\right) - \frac{1}{v}\right) + 0.6931\right) + \log \left(\frac{1}{2 \cdot v}\right)}
\end{array}

Alternative 1: 99.6% accurate, 1.0× speedup?

\[\begin{array}{l} \\ e^{\left(\left(\left(\frac{cosTheta\_i \cdot cosTheta\_O}{v} - \frac{sinTheta\_i \cdot sinTheta\_O}{v}\right) - \frac{1}{v}\right) + 0.6931\right) + \log \left(\frac{1}{2 \cdot v}\right)} \end{array} \]
(FPCore (cosTheta_i cosTheta_O sinTheta_i sinTheta_O v)
 :precision binary32
 (exp
  (+
   (+
    (-
     (- (/ (* cosTheta_i cosTheta_O) v) (/ (* sinTheta_i sinTheta_O) v))
     (/ 1.0 v))
    0.6931)
   (log (/ 1.0 (* 2.0 v))))))
float code(float cosTheta_i, float cosTheta_O, float sinTheta_i, float sinTheta_O, float v) {
	return expf(((((((cosTheta_i * cosTheta_O) / v) - ((sinTheta_i * sinTheta_O) / v)) - (1.0f / v)) + 0.6931f) + logf((1.0f / (2.0f * v)))));
}
real(4) function code(costheta_i, costheta_o, sintheta_i, sintheta_o, v)
    real(4), intent (in) :: costheta_i
    real(4), intent (in) :: costheta_o
    real(4), intent (in) :: sintheta_i
    real(4), intent (in) :: sintheta_o
    real(4), intent (in) :: v
    code = exp(((((((costheta_i * costheta_o) / v) - ((sintheta_i * sintheta_o) / v)) - (1.0e0 / v)) + 0.6931e0) + log((1.0e0 / (2.0e0 * v)))))
end function
function code(cosTheta_i, cosTheta_O, sinTheta_i, sinTheta_O, v)
	return exp(Float32(Float32(Float32(Float32(Float32(Float32(cosTheta_i * cosTheta_O) / v) - Float32(Float32(sinTheta_i * sinTheta_O) / v)) - Float32(Float32(1.0) / v)) + Float32(0.6931)) + log(Float32(Float32(1.0) / Float32(Float32(2.0) * v)))))
end
function tmp = code(cosTheta_i, cosTheta_O, sinTheta_i, sinTheta_O, v)
	tmp = exp(((((((cosTheta_i * cosTheta_O) / v) - ((sinTheta_i * sinTheta_O) / v)) - (single(1.0) / v)) + single(0.6931)) + log((single(1.0) / (single(2.0) * v)))));
end
\begin{array}{l}

\\
e^{\left(\left(\left(\frac{cosTheta\_i \cdot cosTheta\_O}{v} - \frac{sinTheta\_i \cdot sinTheta\_O}{v}\right) - \frac{1}{v}\right) + 0.6931\right) + \log \left(\frac{1}{2 \cdot v}\right)}
\end{array}
Derivation
  1. Initial program 99.6%

    \[e^{\left(\left(\left(\frac{cosTheta\_i \cdot cosTheta\_O}{v} - \frac{sinTheta\_i \cdot sinTheta\_O}{v}\right) - \frac{1}{v}\right) + 0.6931\right) + \log \left(\frac{1}{2 \cdot v}\right)} \]
  2. Add Preprocessing
  3. Add Preprocessing

Alternative 2: 97.7% accurate, 7.6× speedup?

\[\begin{array}{l} \\ \begin{array}{l} t_0 := \frac{sinTheta\_i \cdot sinTheta\_O}{v}\\ t\_0 - t\_0 \end{array} \end{array} \]
(FPCore (cosTheta_i cosTheta_O sinTheta_i sinTheta_O v)
 :precision binary32
 (let* ((t_0 (/ (* sinTheta_i sinTheta_O) v))) (- t_0 t_0)))
float code(float cosTheta_i, float cosTheta_O, float sinTheta_i, float sinTheta_O, float v) {
	float t_0 = (sinTheta_i * sinTheta_O) / v;
	return t_0 - t_0;
}
real(4) function code(costheta_i, costheta_o, sintheta_i, sintheta_o, v)
    real(4), intent (in) :: costheta_i
    real(4), intent (in) :: costheta_o
    real(4), intent (in) :: sintheta_i
    real(4), intent (in) :: sintheta_o
    real(4), intent (in) :: v
    real(4) :: t_0
    t_0 = (sintheta_i * sintheta_o) / v
    code = t_0 - t_0
end function
function code(cosTheta_i, cosTheta_O, sinTheta_i, sinTheta_O, v)
	t_0 = Float32(Float32(sinTheta_i * sinTheta_O) / v)
	return Float32(t_0 - t_0)
end
function tmp = code(cosTheta_i, cosTheta_O, sinTheta_i, sinTheta_O, v)
	t_0 = (sinTheta_i * sinTheta_O) / v;
	tmp = t_0 - t_0;
end
\begin{array}{l}

\\
\begin{array}{l}
t_0 := \frac{sinTheta\_i \cdot sinTheta\_O}{v}\\
t\_0 - t\_0
\end{array}
\end{array}
Derivation
  1. Initial program 99.6%

    \[e^{\left(\left(\left(\frac{cosTheta\_i \cdot cosTheta\_O}{v} - \frac{sinTheta\_i \cdot sinTheta\_O}{v}\right) - \frac{1}{v}\right) + 0.6931\right) + \log \left(\frac{1}{2 \cdot v}\right)} \]
  2. Add Preprocessing
  3. Taylor expanded in cosTheta_i around 0

    \[\leadsto \color{blue}{e^{\left(\frac{6931}{10000} + \log \left(\frac{\frac{1}{2}}{v}\right)\right) - \left(\frac{1}{v} + \frac{sinTheta\_O \cdot sinTheta\_i}{v}\right)} + cosTheta\_i \cdot \left(\frac{1}{2} \cdot \frac{{cosTheta\_O}^{2} \cdot \left(cosTheta\_i \cdot e^{\left(\frac{6931}{10000} + \log \left(\frac{\frac{1}{2}}{v}\right)\right) - \left(\frac{1}{v} + \frac{sinTheta\_O \cdot sinTheta\_i}{v}\right)}\right)}{{v}^{2}} + \frac{cosTheta\_O \cdot e^{\left(\frac{6931}{10000} + \log \left(\frac{\frac{1}{2}}{v}\right)\right) - \left(\frac{1}{v} + \frac{sinTheta\_O \cdot sinTheta\_i}{v}\right)}}{v}\right)} \]
  4. Applied rewrites4.5%

    \[\leadsto \color{blue}{\left(\left(\frac{cosTheta\_i \cdot cosTheta\_O}{v} - \frac{sinTheta\_i \cdot sinTheta\_O}{v}\right) - \frac{1}{v}\right) + 0.6931} \]
  5. Taylor expanded in cosTheta_i around 0

    \[\leadsto \color{blue}{e^{\left(\frac{6931}{10000} + \log \left(\frac{\frac{1}{2}}{v}\right)\right) - \left(\frac{1}{v} + \frac{sinTheta\_O \cdot sinTheta\_i}{v}\right)} + cosTheta\_i \cdot \left(cosTheta\_i \cdot \left(\frac{1}{6} \cdot \frac{{cosTheta\_O}^{3} \cdot \left(cosTheta\_i \cdot e^{\left(\frac{6931}{10000} + \log \left(\frac{\frac{1}{2}}{v}\right)\right) - \left(\frac{1}{v} + \frac{sinTheta\_O \cdot sinTheta\_i}{v}\right)}\right)}{{v}^{3}} + \frac{1}{2} \cdot \frac{{cosTheta\_O}^{2} \cdot e^{\left(\frac{6931}{10000} + \log \left(\frac{\frac{1}{2}}{v}\right)\right) - \left(\frac{1}{v} + \frac{sinTheta\_O \cdot sinTheta\_i}{v}\right)}}{{v}^{2}}\right) + \frac{cosTheta\_O \cdot e^{\left(\frac{6931}{10000} + \log \left(\frac{\frac{1}{2}}{v}\right)\right) - \left(\frac{1}{v} + \frac{sinTheta\_O \cdot sinTheta\_i}{v}\right)}}{v}\right)} \]
  6. Applied rewrites17.5%

    \[\leadsto \color{blue}{\frac{cosTheta\_i \cdot cosTheta\_O}{v} - \frac{sinTheta\_i \cdot sinTheta\_O}{v}} \]
  7. Taylor expanded in cosTheta_i around 0

    \[\leadsto \frac{cosTheta\_O \cdot cosTheta\_i}{v} - \frac{\color{blue}{sinTheta\_i \cdot sinTheta\_O}}{v} \]
  8. Applied rewrites21.1%

    \[\leadsto cosTheta\_i \cdot cosTheta\_O - \frac{\color{blue}{sinTheta\_i \cdot sinTheta\_O}}{v} \]
  9. Taylor expanded in cosTheta_i around 0

    \[\leadsto \frac{cosTheta\_O \cdot cosTheta\_i}{v} - \frac{\color{blue}{sinTheta\_i \cdot sinTheta\_O}}{v} \]
  10. Applied rewrites96.5%

    \[\leadsto \frac{sinTheta\_i \cdot sinTheta\_O}{v} - \frac{\color{blue}{sinTheta\_i \cdot sinTheta\_O}}{v} \]
  11. Add Preprocessing

Alternative 3: 68.3% accurate, 9.7× speedup?

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;sinTheta\_i \cdot sinTheta\_O \leq -9.99994610111476 \cdot 10^{-41}:\\ \;\;\;\;cosTheta\_i \cdot cosTheta\_O\\ \mathbf{elif}\;sinTheta\_i \cdot sinTheta\_O \leq 2.0038568039844884 \cdot 10^{-43}:\\ \;\;\;\;sinTheta\_i \cdot sinTheta\_O\\ \mathbf{else}:\\ \;\;\;\;cosTheta\_i \cdot cosTheta\_O\\ \end{array} \end{array} \]
(FPCore (cosTheta_i cosTheta_O sinTheta_i sinTheta_O v)
 :precision binary32
 (if (<= (* sinTheta_i sinTheta_O) -9.99994610111476e-41)
   (* cosTheta_i cosTheta_O)
   (if (<= (* sinTheta_i sinTheta_O) 2.0038568039844884e-43)
     (* sinTheta_i sinTheta_O)
     (* cosTheta_i cosTheta_O))))
float code(float cosTheta_i, float cosTheta_O, float sinTheta_i, float sinTheta_O, float v) {
	float tmp;
	if ((sinTheta_i * sinTheta_O) <= -9.99994610111476e-41f) {
		tmp = cosTheta_i * cosTheta_O;
	} else if ((sinTheta_i * sinTheta_O) <= 2.0038568039844884e-43f) {
		tmp = sinTheta_i * sinTheta_O;
	} else {
		tmp = cosTheta_i * cosTheta_O;
	}
	return tmp;
}
real(4) function code(costheta_i, costheta_o, sintheta_i, sintheta_o, v)
    real(4), intent (in) :: costheta_i
    real(4), intent (in) :: costheta_o
    real(4), intent (in) :: sintheta_i
    real(4), intent (in) :: sintheta_o
    real(4), intent (in) :: v
    real(4) :: tmp
    if ((sintheta_i * sintheta_o) <= (-9.99994610111476e-41)) then
        tmp = costheta_i * costheta_o
    else if ((sintheta_i * sintheta_o) <= 2.0038568039844884e-43) then
        tmp = sintheta_i * sintheta_o
    else
        tmp = costheta_i * costheta_o
    end if
    code = tmp
end function
function code(cosTheta_i, cosTheta_O, sinTheta_i, sinTheta_O, v)
	tmp = Float32(0.0)
	if (Float32(sinTheta_i * sinTheta_O) <= Float32(-9.99994610111476e-41))
		tmp = Float32(cosTheta_i * cosTheta_O);
	elseif (Float32(sinTheta_i * sinTheta_O) <= Float32(2.0038568039844884e-43))
		tmp = Float32(sinTheta_i * sinTheta_O);
	else
		tmp = Float32(cosTheta_i * cosTheta_O);
	end
	return tmp
end
function tmp_2 = code(cosTheta_i, cosTheta_O, sinTheta_i, sinTheta_O, v)
	tmp = single(0.0);
	if ((sinTheta_i * sinTheta_O) <= single(-9.99994610111476e-41))
		tmp = cosTheta_i * cosTheta_O;
	elseif ((sinTheta_i * sinTheta_O) <= single(2.0038568039844884e-43))
		tmp = sinTheta_i * sinTheta_O;
	else
		tmp = cosTheta_i * cosTheta_O;
	end
	tmp_2 = tmp;
end
\begin{array}{l}

\\
\begin{array}{l}
\mathbf{if}\;sinTheta\_i \cdot sinTheta\_O \leq -9.99994610111476 \cdot 10^{-41}:\\
\;\;\;\;cosTheta\_i \cdot cosTheta\_O\\

\mathbf{elif}\;sinTheta\_i \cdot sinTheta\_O \leq 2.0038568039844884 \cdot 10^{-43}:\\
\;\;\;\;sinTheta\_i \cdot sinTheta\_O\\

\mathbf{else}:\\
\;\;\;\;cosTheta\_i \cdot cosTheta\_O\\


\end{array}
\end{array}
Derivation
  1. Split input into 2 regimes
  2. if (*.f32 sinTheta_i sinTheta_O) < -9.99995e-41 or 2.00386e-43 < (*.f32 sinTheta_i sinTheta_O)

    1. Initial program 99.5%

      \[e^{\left(\left(\left(\frac{cosTheta\_i \cdot cosTheta\_O}{v} - \frac{sinTheta\_i \cdot sinTheta\_O}{v}\right) - \frac{1}{v}\right) + 0.6931\right) + \log \left(\frac{1}{2 \cdot v}\right)} \]
    2. Add Preprocessing
    3. Taylor expanded in cosTheta_i around 0

      \[\leadsto \color{blue}{e^{\left(\frac{6931}{10000} + \log \left(\frac{\frac{1}{2}}{v}\right)\right) - \left(\frac{1}{v} + \frac{sinTheta\_O \cdot sinTheta\_i}{v}\right)} + cosTheta\_i \cdot \left(cosTheta\_i \cdot \left(\frac{1}{6} \cdot \frac{{cosTheta\_O}^{3} \cdot \left(cosTheta\_i \cdot e^{\left(\frac{6931}{10000} + \log \left(\frac{\frac{1}{2}}{v}\right)\right) - \left(\frac{1}{v} + \frac{sinTheta\_O \cdot sinTheta\_i}{v}\right)}\right)}{{v}^{3}} + \frac{1}{2} \cdot \frac{{cosTheta\_O}^{2} \cdot e^{\left(\frac{6931}{10000} + \log \left(\frac{\frac{1}{2}}{v}\right)\right) - \left(\frac{1}{v} + \frac{sinTheta\_O \cdot sinTheta\_i}{v}\right)}}{{v}^{2}}\right) + \frac{cosTheta\_O \cdot e^{\left(\frac{6931}{10000} + \log \left(\frac{\frac{1}{2}}{v}\right)\right) - \left(\frac{1}{v} + \frac{sinTheta\_O \cdot sinTheta\_i}{v}\right)}}{v}\right)} \]
    4. Applied rewrites4.5%

      \[\leadsto \color{blue}{\left(\frac{cosTheta\_i \cdot cosTheta\_O}{v} - \frac{sinTheta\_i \cdot sinTheta\_O}{v}\right) - \frac{1}{v}} \]
    5. Taylor expanded in cosTheta_i around 0

      \[\leadsto \frac{cosTheta\_O \cdot cosTheta\_i}{v} - \color{blue}{\left(\frac{1}{v} + \frac{sinTheta\_O \cdot sinTheta\_i}{v}\right)} \]
    6. Applied rewrites39.0%

      \[\leadsto \frac{cosTheta\_i \cdot cosTheta\_O}{\color{blue}{v}} \]
    7. Taylor expanded in cosTheta_i around 0

      \[\leadsto \frac{cosTheta\_O \cdot cosTheta\_i}{v} \]
    8. Applied rewrites50.9%

      \[\leadsto cosTheta\_i \cdot cosTheta\_O \]

    if -9.99995e-41 < (*.f32 sinTheta_i sinTheta_O) < 2.00386e-43

    1. Initial program 99.7%

      \[e^{\left(\left(\left(\frac{cosTheta\_i \cdot cosTheta\_O}{v} - \frac{sinTheta\_i \cdot sinTheta\_O}{v}\right) - \frac{1}{v}\right) + 0.6931\right) + \log \left(\frac{1}{2 \cdot v}\right)} \]
    2. Add Preprocessing
    3. Taylor expanded in cosTheta_i around 0

      \[\leadsto \color{blue}{e^{\left(\frac{6931}{10000} + \log \left(\frac{\frac{1}{2}}{v}\right)\right) - \left(\frac{1}{v} + \frac{sinTheta\_O \cdot sinTheta\_i}{v}\right)} + cosTheta\_i \cdot \left(\frac{1}{2} \cdot \frac{{cosTheta\_O}^{2} \cdot \left(cosTheta\_i \cdot e^{\left(\frac{6931}{10000} + \log \left(\frac{\frac{1}{2}}{v}\right)\right) - \left(\frac{1}{v} + \frac{sinTheta\_O \cdot sinTheta\_i}{v}\right)}\right)}{{v}^{2}} + \frac{cosTheta\_O \cdot e^{\left(\frac{6931}{10000} + \log \left(\frac{\frac{1}{2}}{v}\right)\right) - \left(\frac{1}{v} + \frac{sinTheta\_O \cdot sinTheta\_i}{v}\right)}}{v}\right)} \]
    4. Applied rewrites4.6%

      \[\leadsto \color{blue}{\left(\left(\frac{cosTheta\_i \cdot cosTheta\_O}{v} - \frac{sinTheta\_i \cdot sinTheta\_O}{v}\right) - \frac{1}{v}\right) + 0.6931} \]
    5. Taylor expanded in cosTheta_i around 0

      \[\leadsto \color{blue}{e^{\left(\frac{6931}{10000} + \log \left(\frac{\frac{1}{2}}{v}\right)\right) - \left(\frac{1}{v} + \frac{sinTheta\_O \cdot sinTheta\_i}{v}\right)} + cosTheta\_i \cdot \left(cosTheta\_i \cdot \left(\frac{1}{6} \cdot \frac{{cosTheta\_O}^{3} \cdot \left(cosTheta\_i \cdot e^{\left(\frac{6931}{10000} + \log \left(\frac{\frac{1}{2}}{v}\right)\right) - \left(\frac{1}{v} + \frac{sinTheta\_O \cdot sinTheta\_i}{v}\right)}\right)}{{v}^{3}} + \frac{1}{2} \cdot \frac{{cosTheta\_O}^{2} \cdot e^{\left(\frac{6931}{10000} + \log \left(\frac{\frac{1}{2}}{v}\right)\right) - \left(\frac{1}{v} + \frac{sinTheta\_O \cdot sinTheta\_i}{v}\right)}}{{v}^{2}}\right) + \frac{cosTheta\_O \cdot e^{\left(\frac{6931}{10000} + \log \left(\frac{\frac{1}{2}}{v}\right)\right) - \left(\frac{1}{v} + \frac{sinTheta\_O \cdot sinTheta\_i}{v}\right)}}{v}\right)} \]
    6. Applied rewrites30.2%

      \[\leadsto \color{blue}{\frac{cosTheta\_i \cdot cosTheta\_O}{v} - \frac{sinTheta\_i \cdot sinTheta\_O}{v}} \]
    7. Taylor expanded in cosTheta_i around 0

      \[\leadsto -1 \cdot \color{blue}{\frac{sinTheta\_O \cdot sinTheta\_i}{v}} \]
    8. Applied rewrites93.4%

      \[\leadsto sinTheta\_i \cdot \color{blue}{sinTheta\_O} \]
  3. Recombined 2 regimes into one program.
  4. Add Preprocessing

Alternative 4: 49.9% accurate, 45.3× speedup?

\[\begin{array}{l} \\ cosTheta\_i \cdot cosTheta\_O \end{array} \]
(FPCore (cosTheta_i cosTheta_O sinTheta_i sinTheta_O v)
 :precision binary32
 (* cosTheta_i cosTheta_O))
float code(float cosTheta_i, float cosTheta_O, float sinTheta_i, float sinTheta_O, float v) {
	return cosTheta_i * cosTheta_O;
}
real(4) function code(costheta_i, costheta_o, sintheta_i, sintheta_o, v)
    real(4), intent (in) :: costheta_i
    real(4), intent (in) :: costheta_o
    real(4), intent (in) :: sintheta_i
    real(4), intent (in) :: sintheta_o
    real(4), intent (in) :: v
    code = costheta_i * costheta_o
end function
function code(cosTheta_i, cosTheta_O, sinTheta_i, sinTheta_O, v)
	return Float32(cosTheta_i * cosTheta_O)
end
function tmp = code(cosTheta_i, cosTheta_O, sinTheta_i, sinTheta_O, v)
	tmp = cosTheta_i * cosTheta_O;
end
\begin{array}{l}

\\
cosTheta\_i \cdot cosTheta\_O
\end{array}
Derivation
  1. Initial program 99.6%

    \[e^{\left(\left(\left(\frac{cosTheta\_i \cdot cosTheta\_O}{v} - \frac{sinTheta\_i \cdot sinTheta\_O}{v}\right) - \frac{1}{v}\right) + 0.6931\right) + \log \left(\frac{1}{2 \cdot v}\right)} \]
  2. Add Preprocessing
  3. Taylor expanded in cosTheta_i around 0

    \[\leadsto \color{blue}{e^{\left(\frac{6931}{10000} + \log \left(\frac{\frac{1}{2}}{v}\right)\right) - \left(\frac{1}{v} + \frac{sinTheta\_O \cdot sinTheta\_i}{v}\right)} + cosTheta\_i \cdot \left(cosTheta\_i \cdot \left(\frac{1}{6} \cdot \frac{{cosTheta\_O}^{3} \cdot \left(cosTheta\_i \cdot e^{\left(\frac{6931}{10000} + \log \left(\frac{\frac{1}{2}}{v}\right)\right) - \left(\frac{1}{v} + \frac{sinTheta\_O \cdot sinTheta\_i}{v}\right)}\right)}{{v}^{3}} + \frac{1}{2} \cdot \frac{{cosTheta\_O}^{2} \cdot e^{\left(\frac{6931}{10000} + \log \left(\frac{\frac{1}{2}}{v}\right)\right) - \left(\frac{1}{v} + \frac{sinTheta\_O \cdot sinTheta\_i}{v}\right)}}{{v}^{2}}\right) + \frac{cosTheta\_O \cdot e^{\left(\frac{6931}{10000} + \log \left(\frac{\frac{1}{2}}{v}\right)\right) - \left(\frac{1}{v} + \frac{sinTheta\_O \cdot sinTheta\_i}{v}\right)}}{v}\right)} \]
  4. Applied rewrites4.5%

    \[\leadsto \color{blue}{\left(\frac{cosTheta\_i \cdot cosTheta\_O}{v} - \frac{sinTheta\_i \cdot sinTheta\_O}{v}\right) - \frac{1}{v}} \]
  5. Taylor expanded in cosTheta_i around 0

    \[\leadsto \frac{cosTheta\_O \cdot cosTheta\_i}{v} - \color{blue}{\left(\frac{1}{v} + \frac{sinTheta\_O \cdot sinTheta\_i}{v}\right)} \]
  6. Applied rewrites36.9%

    \[\leadsto \frac{cosTheta\_i \cdot cosTheta\_O}{\color{blue}{v}} \]
  7. Taylor expanded in cosTheta_i around 0

    \[\leadsto \frac{cosTheta\_O \cdot cosTheta\_i}{v} \]
  8. Applied rewrites48.3%

    \[\leadsto cosTheta\_i \cdot cosTheta\_O \]
  9. Add Preprocessing

Reproduce

?
herbie shell --seed 2024321 
(FPCore (cosTheta_i cosTheta_O sinTheta_i sinTheta_O v)
  :name "HairBSDF, Mp, lower"
  :precision binary32
  :pre (and (and (and (and (and (<= -1.0 cosTheta_i) (<= cosTheta_i 1.0)) (and (<= -1.0 cosTheta_O) (<= cosTheta_O 1.0))) (and (<= -1.0 sinTheta_i) (<= sinTheta_i 1.0))) (and (<= -1.0 sinTheta_O) (<= sinTheta_O 1.0))) (and (<= -1.5707964 v) (<= v 0.1)))
  (exp (+ (+ (- (- (/ (* cosTheta_i cosTheta_O) v) (/ (* sinTheta_i sinTheta_O) v)) (/ 1.0 v)) 0.6931) (log (/ 1.0 (* 2.0 v))))))