Migdal et al, Equation (64)

Percentage Accurate: 99.5% → 99.6%
Time: 9.3s
Alternatives: 7
Speedup: 2.0×

Specification

?
\[\begin{array}{l} \\ \begin{array}{l} t_1 := \frac{\cos th}{\sqrt{2}}\\ t\_1 \cdot \left(a1 \cdot a1\right) + t\_1 \cdot \left(a2 \cdot a2\right) \end{array} \end{array} \]
(FPCore (a1 a2 th)
 :precision binary64
 (let* ((t_1 (/ (cos th) (sqrt 2.0))))
   (+ (* t_1 (* a1 a1)) (* t_1 (* a2 a2)))))
double code(double a1, double a2, double th) {
	double t_1 = cos(th) / sqrt(2.0);
	return (t_1 * (a1 * a1)) + (t_1 * (a2 * a2));
}
real(8) function code(a1, a2, th)
    real(8), intent (in) :: a1
    real(8), intent (in) :: a2
    real(8), intent (in) :: th
    real(8) :: t_1
    t_1 = cos(th) / sqrt(2.0d0)
    code = (t_1 * (a1 * a1)) + (t_1 * (a2 * a2))
end function
public static double code(double a1, double a2, double th) {
	double t_1 = Math.cos(th) / Math.sqrt(2.0);
	return (t_1 * (a1 * a1)) + (t_1 * (a2 * a2));
}
def code(a1, a2, th):
	t_1 = math.cos(th) / math.sqrt(2.0)
	return (t_1 * (a1 * a1)) + (t_1 * (a2 * a2))
function code(a1, a2, th)
	t_1 = Float64(cos(th) / sqrt(2.0))
	return Float64(Float64(t_1 * Float64(a1 * a1)) + Float64(t_1 * Float64(a2 * a2)))
end
function tmp = code(a1, a2, th)
	t_1 = cos(th) / sqrt(2.0);
	tmp = (t_1 * (a1 * a1)) + (t_1 * (a2 * a2));
end
code[a1_, a2_, th_] := Block[{t$95$1 = N[(N[Cos[th], $MachinePrecision] / N[Sqrt[2.0], $MachinePrecision]), $MachinePrecision]}, N[(N[(t$95$1 * N[(a1 * a1), $MachinePrecision]), $MachinePrecision] + N[(t$95$1 * N[(a2 * a2), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]]
\begin{array}{l}

\\
\begin{array}{l}
t_1 := \frac{\cos th}{\sqrt{2}}\\
t\_1 \cdot \left(a1 \cdot a1\right) + t\_1 \cdot \left(a2 \cdot a2\right)
\end{array}
\end{array}

Sampling outcomes in binary64 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 7 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: 99.5% accurate, 1.0× speedup?

\[\begin{array}{l} \\ \begin{array}{l} t_1 := \frac{\cos th}{\sqrt{2}}\\ t\_1 \cdot \left(a1 \cdot a1\right) + t\_1 \cdot \left(a2 \cdot a2\right) \end{array} \end{array} \]
(FPCore (a1 a2 th)
 :precision binary64
 (let* ((t_1 (/ (cos th) (sqrt 2.0))))
   (+ (* t_1 (* a1 a1)) (* t_1 (* a2 a2)))))
double code(double a1, double a2, double th) {
	double t_1 = cos(th) / sqrt(2.0);
	return (t_1 * (a1 * a1)) + (t_1 * (a2 * a2));
}
real(8) function code(a1, a2, th)
    real(8), intent (in) :: a1
    real(8), intent (in) :: a2
    real(8), intent (in) :: th
    real(8) :: t_1
    t_1 = cos(th) / sqrt(2.0d0)
    code = (t_1 * (a1 * a1)) + (t_1 * (a2 * a2))
end function
public static double code(double a1, double a2, double th) {
	double t_1 = Math.cos(th) / Math.sqrt(2.0);
	return (t_1 * (a1 * a1)) + (t_1 * (a2 * a2));
}
def code(a1, a2, th):
	t_1 = math.cos(th) / math.sqrt(2.0)
	return (t_1 * (a1 * a1)) + (t_1 * (a2 * a2))
function code(a1, a2, th)
	t_1 = Float64(cos(th) / sqrt(2.0))
	return Float64(Float64(t_1 * Float64(a1 * a1)) + Float64(t_1 * Float64(a2 * a2)))
end
function tmp = code(a1, a2, th)
	t_1 = cos(th) / sqrt(2.0);
	tmp = (t_1 * (a1 * a1)) + (t_1 * (a2 * a2));
end
code[a1_, a2_, th_] := Block[{t$95$1 = N[(N[Cos[th], $MachinePrecision] / N[Sqrt[2.0], $MachinePrecision]), $MachinePrecision]}, N[(N[(t$95$1 * N[(a1 * a1), $MachinePrecision]), $MachinePrecision] + N[(t$95$1 * N[(a2 * a2), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]]
\begin{array}{l}

\\
\begin{array}{l}
t_1 := \frac{\cos th}{\sqrt{2}}\\
t\_1 \cdot \left(a1 \cdot a1\right) + t\_1 \cdot \left(a2 \cdot a2\right)
\end{array}
\end{array}

Alternative 1: 99.6% accurate, 2.0× speedup?

\[\begin{array}{l} \\ \left(\sqrt{0.5} \cdot \cos th\right) \cdot \left(a1 \cdot a1 + a2 \cdot a2\right) \end{array} \]
(FPCore (a1 a2 th)
 :precision binary64
 (* (* (sqrt 0.5) (cos th)) (+ (* a1 a1) (* a2 a2))))
double code(double a1, double a2, double th) {
	return (sqrt(0.5) * cos(th)) * ((a1 * a1) + (a2 * a2));
}
real(8) function code(a1, a2, th)
    real(8), intent (in) :: a1
    real(8), intent (in) :: a2
    real(8), intent (in) :: th
    code = (sqrt(0.5d0) * cos(th)) * ((a1 * a1) + (a2 * a2))
end function
public static double code(double a1, double a2, double th) {
	return (Math.sqrt(0.5) * Math.cos(th)) * ((a1 * a1) + (a2 * a2));
}
def code(a1, a2, th):
	return (math.sqrt(0.5) * math.cos(th)) * ((a1 * a1) + (a2 * a2))
function code(a1, a2, th)
	return Float64(Float64(sqrt(0.5) * cos(th)) * Float64(Float64(a1 * a1) + Float64(a2 * a2)))
end
function tmp = code(a1, a2, th)
	tmp = (sqrt(0.5) * cos(th)) * ((a1 * a1) + (a2 * a2));
end
code[a1_, a2_, th_] := N[(N[(N[Sqrt[0.5], $MachinePrecision] * N[Cos[th], $MachinePrecision]), $MachinePrecision] * N[(N[(a1 * a1), $MachinePrecision] + N[(a2 * a2), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
\left(\sqrt{0.5} \cdot \cos th\right) \cdot \left(a1 \cdot a1 + a2 \cdot a2\right)
\end{array}
Derivation
  1. Initial program 99.6%

    \[\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1\right) + \frac{\cos th}{\sqrt{2}} \cdot \left(a2 \cdot a2\right) \]
  2. Step-by-step derivation
    1. distribute-lft-out99.6%

      \[\leadsto \color{blue}{\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right)} \]
  3. Simplified99.6%

    \[\leadsto \color{blue}{\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right)} \]
  4. Add Preprocessing
  5. Step-by-step derivation
    1. clear-num99.5%

      \[\leadsto \color{blue}{\frac{1}{\frac{\sqrt{2}}{\cos th}}} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right) \]
    2. associate-/r/99.5%

      \[\leadsto \color{blue}{\left(\frac{1}{\sqrt{2}} \cdot \cos th\right)} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right) \]
    3. pow1/299.5%

      \[\leadsto \left(\frac{1}{\color{blue}{{2}^{0.5}}} \cdot \cos th\right) \cdot \left(a1 \cdot a1 + a2 \cdot a2\right) \]
    4. pow-flip99.7%

      \[\leadsto \left(\color{blue}{{2}^{\left(-0.5\right)}} \cdot \cos th\right) \cdot \left(a1 \cdot a1 + a2 \cdot a2\right) \]
    5. metadata-eval99.7%

      \[\leadsto \left({2}^{\color{blue}{-0.5}} \cdot \cos th\right) \cdot \left(a1 \cdot a1 + a2 \cdot a2\right) \]
  6. Applied egg-rr99.7%

    \[\leadsto \color{blue}{\left({2}^{-0.5} \cdot \cos th\right)} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right) \]
  7. Taylor expanded in th around inf 99.7%

    \[\leadsto \color{blue}{\left(\cos th \cdot \sqrt{0.5}\right)} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right) \]
  8. Step-by-step derivation
    1. *-commutative99.7%

      \[\leadsto \color{blue}{\left(\sqrt{0.5} \cdot \cos th\right)} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right) \]
  9. Simplified99.7%

    \[\leadsto \color{blue}{\left(\sqrt{0.5} \cdot \cos th\right)} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right) \]
  10. Final simplification99.7%

    \[\leadsto \left(\sqrt{0.5} \cdot \cos th\right) \cdot \left(a1 \cdot a1 + a2 \cdot a2\right) \]
  11. Add Preprocessing

Alternative 2: 58.0% accurate, 2.0× speedup?

\[\begin{array}{l} \\ \cos th \cdot \left(a2 \cdot \left(a2 \cdot {2}^{-0.5}\right)\right) \end{array} \]
(FPCore (a1 a2 th)
 :precision binary64
 (* (cos th) (* a2 (* a2 (pow 2.0 -0.5)))))
double code(double a1, double a2, double th) {
	return cos(th) * (a2 * (a2 * pow(2.0, -0.5)));
}
real(8) function code(a1, a2, th)
    real(8), intent (in) :: a1
    real(8), intent (in) :: a2
    real(8), intent (in) :: th
    code = cos(th) * (a2 * (a2 * (2.0d0 ** (-0.5d0))))
end function
public static double code(double a1, double a2, double th) {
	return Math.cos(th) * (a2 * (a2 * Math.pow(2.0, -0.5)));
}
def code(a1, a2, th):
	return math.cos(th) * (a2 * (a2 * math.pow(2.0, -0.5)))
function code(a1, a2, th)
	return Float64(cos(th) * Float64(a2 * Float64(a2 * (2.0 ^ -0.5))))
end
function tmp = code(a1, a2, th)
	tmp = cos(th) * (a2 * (a2 * (2.0 ^ -0.5)));
end
code[a1_, a2_, th_] := N[(N[Cos[th], $MachinePrecision] * N[(a2 * N[(a2 * N[Power[2.0, -0.5], $MachinePrecision]), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
\cos th \cdot \left(a2 \cdot \left(a2 \cdot {2}^{-0.5}\right)\right)
\end{array}
Derivation
  1. Initial program 99.6%

    \[\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1\right) + \frac{\cos th}{\sqrt{2}} \cdot \left(a2 \cdot a2\right) \]
  2. Step-by-step derivation
    1. distribute-lft-out99.6%

      \[\leadsto \color{blue}{\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right)} \]
    2. cos-neg99.6%

      \[\leadsto \frac{\color{blue}{\cos \left(-th\right)}}{\sqrt{2}} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right) \]
    3. associate-*l/99.6%

      \[\leadsto \color{blue}{\frac{\cos \left(-th\right) \cdot \left(a1 \cdot a1 + a2 \cdot a2\right)}{\sqrt{2}}} \]
    4. associate-/l*99.6%

      \[\leadsto \color{blue}{\cos \left(-th\right) \cdot \frac{a1 \cdot a1 + a2 \cdot a2}{\sqrt{2}}} \]
    5. cos-neg99.6%

      \[\leadsto \color{blue}{\cos th} \cdot \frac{a1 \cdot a1 + a2 \cdot a2}{\sqrt{2}} \]
    6. +-commutative99.6%

      \[\leadsto \cos th \cdot \frac{\color{blue}{a2 \cdot a2 + a1 \cdot a1}}{\sqrt{2}} \]
    7. fma-define99.6%

      \[\leadsto \cos th \cdot \frac{\color{blue}{\mathsf{fma}\left(a2, a2, a1 \cdot a1\right)}}{\sqrt{2}} \]
  3. Simplified99.6%

    \[\leadsto \color{blue}{\cos th \cdot \frac{\mathsf{fma}\left(a2, a2, a1 \cdot a1\right)}{\sqrt{2}}} \]
  4. Add Preprocessing
  5. Taylor expanded in a2 around inf 62.8%

    \[\leadsto \cos th \cdot \color{blue}{\frac{{a2}^{2}}{\sqrt{2}}} \]
  6. Step-by-step derivation
    1. pow243.6%

      \[\leadsto \frac{\color{blue}{a2 \cdot a2}}{\sqrt{2}} \]
    2. div-inv43.6%

      \[\leadsto \color{blue}{\left(a2 \cdot a2\right) \cdot \frac{1}{\sqrt{2}}} \]
    3. associate-*l*43.6%

      \[\leadsto \color{blue}{a2 \cdot \left(a2 \cdot \frac{1}{\sqrt{2}}\right)} \]
    4. pow1/243.6%

      \[\leadsto a2 \cdot \left(a2 \cdot \frac{1}{\color{blue}{{2}^{0.5}}}\right) \]
    5. pow-flip43.6%

      \[\leadsto a2 \cdot \left(a2 \cdot \color{blue}{{2}^{\left(-0.5\right)}}\right) \]
    6. metadata-eval43.6%

      \[\leadsto a2 \cdot \left(a2 \cdot {2}^{\color{blue}{-0.5}}\right) \]
  7. Applied egg-rr62.8%

    \[\leadsto \cos th \cdot \color{blue}{\left(a2 \cdot \left(a2 \cdot {2}^{-0.5}\right)\right)} \]
  8. Final simplification62.8%

    \[\leadsto \cos th \cdot \left(a2 \cdot \left(a2 \cdot {2}^{-0.5}\right)\right) \]
  9. Add Preprocessing

Alternative 3: 58.0% accurate, 2.0× speedup?

\[\begin{array}{l} \\ \cos th \cdot \left(a2 \cdot \frac{a2}{\sqrt{2}}\right) \end{array} \]
(FPCore (a1 a2 th) :precision binary64 (* (cos th) (* a2 (/ a2 (sqrt 2.0)))))
double code(double a1, double a2, double th) {
	return cos(th) * (a2 * (a2 / sqrt(2.0)));
}
real(8) function code(a1, a2, th)
    real(8), intent (in) :: a1
    real(8), intent (in) :: a2
    real(8), intent (in) :: th
    code = cos(th) * (a2 * (a2 / sqrt(2.0d0)))
end function
public static double code(double a1, double a2, double th) {
	return Math.cos(th) * (a2 * (a2 / Math.sqrt(2.0)));
}
def code(a1, a2, th):
	return math.cos(th) * (a2 * (a2 / math.sqrt(2.0)))
function code(a1, a2, th)
	return Float64(cos(th) * Float64(a2 * Float64(a2 / sqrt(2.0))))
end
function tmp = code(a1, a2, th)
	tmp = cos(th) * (a2 * (a2 / sqrt(2.0)));
end
code[a1_, a2_, th_] := N[(N[Cos[th], $MachinePrecision] * N[(a2 * N[(a2 / N[Sqrt[2.0], $MachinePrecision]), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
\cos th \cdot \left(a2 \cdot \frac{a2}{\sqrt{2}}\right)
\end{array}
Derivation
  1. Initial program 99.6%

    \[\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1\right) + \frac{\cos th}{\sqrt{2}} \cdot \left(a2 \cdot a2\right) \]
  2. Step-by-step derivation
    1. distribute-lft-out99.6%

      \[\leadsto \color{blue}{\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right)} \]
    2. cos-neg99.6%

      \[\leadsto \frac{\color{blue}{\cos \left(-th\right)}}{\sqrt{2}} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right) \]
    3. associate-*l/99.6%

      \[\leadsto \color{blue}{\frac{\cos \left(-th\right) \cdot \left(a1 \cdot a1 + a2 \cdot a2\right)}{\sqrt{2}}} \]
    4. associate-/l*99.6%

      \[\leadsto \color{blue}{\cos \left(-th\right) \cdot \frac{a1 \cdot a1 + a2 \cdot a2}{\sqrt{2}}} \]
    5. cos-neg99.6%

      \[\leadsto \color{blue}{\cos th} \cdot \frac{a1 \cdot a1 + a2 \cdot a2}{\sqrt{2}} \]
    6. +-commutative99.6%

      \[\leadsto \cos th \cdot \frac{\color{blue}{a2 \cdot a2 + a1 \cdot a1}}{\sqrt{2}} \]
    7. fma-define99.6%

      \[\leadsto \cos th \cdot \frac{\color{blue}{\mathsf{fma}\left(a2, a2, a1 \cdot a1\right)}}{\sqrt{2}} \]
  3. Simplified99.6%

    \[\leadsto \color{blue}{\cos th \cdot \frac{\mathsf{fma}\left(a2, a2, a1 \cdot a1\right)}{\sqrt{2}}} \]
  4. Add Preprocessing
  5. Taylor expanded in a2 around inf 62.8%

    \[\leadsto \cos th \cdot \color{blue}{\frac{{a2}^{2}}{\sqrt{2}}} \]
  6. Step-by-step derivation
    1. pow243.6%

      \[\leadsto \frac{\color{blue}{a2 \cdot a2}}{\sqrt{2}} \]
    2. associate-/l*43.6%

      \[\leadsto \color{blue}{a2 \cdot \frac{a2}{\sqrt{2}}} \]
  7. Applied egg-rr62.8%

    \[\leadsto \cos th \cdot \color{blue}{\left(a2 \cdot \frac{a2}{\sqrt{2}}\right)} \]
  8. Final simplification62.8%

    \[\leadsto \cos th \cdot \left(a2 \cdot \frac{a2}{\sqrt{2}}\right) \]
  9. Add Preprocessing

Alternative 4: 66.4% accurate, 3.8× speedup?

\[\begin{array}{l} \\ \sqrt{0.5} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right) \end{array} \]
(FPCore (a1 a2 th) :precision binary64 (* (sqrt 0.5) (+ (* a1 a1) (* a2 a2))))
double code(double a1, double a2, double th) {
	return sqrt(0.5) * ((a1 * a1) + (a2 * a2));
}
real(8) function code(a1, a2, th)
    real(8), intent (in) :: a1
    real(8), intent (in) :: a2
    real(8), intent (in) :: th
    code = sqrt(0.5d0) * ((a1 * a1) + (a2 * a2))
end function
public static double code(double a1, double a2, double th) {
	return Math.sqrt(0.5) * ((a1 * a1) + (a2 * a2));
}
def code(a1, a2, th):
	return math.sqrt(0.5) * ((a1 * a1) + (a2 * a2))
function code(a1, a2, th)
	return Float64(sqrt(0.5) * Float64(Float64(a1 * a1) + Float64(a2 * a2)))
end
function tmp = code(a1, a2, th)
	tmp = sqrt(0.5) * ((a1 * a1) + (a2 * a2));
end
code[a1_, a2_, th_] := N[(N[Sqrt[0.5], $MachinePrecision] * N[(N[(a1 * a1), $MachinePrecision] + N[(a2 * a2), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
\sqrt{0.5} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right)
\end{array}
Derivation
  1. Initial program 99.6%

    \[\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1\right) + \frac{\cos th}{\sqrt{2}} \cdot \left(a2 \cdot a2\right) \]
  2. Step-by-step derivation
    1. distribute-lft-out99.6%

      \[\leadsto \color{blue}{\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right)} \]
  3. Simplified99.6%

    \[\leadsto \color{blue}{\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right)} \]
  4. Add Preprocessing
  5. Step-by-step derivation
    1. clear-num99.5%

      \[\leadsto \color{blue}{\frac{1}{\frac{\sqrt{2}}{\cos th}}} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right) \]
    2. associate-/r/99.5%

      \[\leadsto \color{blue}{\left(\frac{1}{\sqrt{2}} \cdot \cos th\right)} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right) \]
    3. pow1/299.5%

      \[\leadsto \left(\frac{1}{\color{blue}{{2}^{0.5}}} \cdot \cos th\right) \cdot \left(a1 \cdot a1 + a2 \cdot a2\right) \]
    4. pow-flip99.7%

      \[\leadsto \left(\color{blue}{{2}^{\left(-0.5\right)}} \cdot \cos th\right) \cdot \left(a1 \cdot a1 + a2 \cdot a2\right) \]
    5. metadata-eval99.7%

      \[\leadsto \left({2}^{\color{blue}{-0.5}} \cdot \cos th\right) \cdot \left(a1 \cdot a1 + a2 \cdot a2\right) \]
  6. Applied egg-rr99.7%

    \[\leadsto \color{blue}{\left({2}^{-0.5} \cdot \cos th\right)} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right) \]
  7. Taylor expanded in th around 0 65.2%

    \[\leadsto \color{blue}{\sqrt{0.5}} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right) \]
  8. Final simplification65.2%

    \[\leadsto \sqrt{0.5} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right) \]
  9. Add Preprocessing

Alternative 5: 39.1% accurate, 4.0× speedup?

\[\begin{array}{l} \\ a1 \cdot \frac{a1}{\sqrt{2}} \end{array} \]
(FPCore (a1 a2 th) :precision binary64 (* a1 (/ a1 (sqrt 2.0))))
double code(double a1, double a2, double th) {
	return a1 * (a1 / sqrt(2.0));
}
real(8) function code(a1, a2, th)
    real(8), intent (in) :: a1
    real(8), intent (in) :: a2
    real(8), intent (in) :: th
    code = a1 * (a1 / sqrt(2.0d0))
end function
public static double code(double a1, double a2, double th) {
	return a1 * (a1 / Math.sqrt(2.0));
}
def code(a1, a2, th):
	return a1 * (a1 / math.sqrt(2.0))
function code(a1, a2, th)
	return Float64(a1 * Float64(a1 / sqrt(2.0)))
end
function tmp = code(a1, a2, th)
	tmp = a1 * (a1 / sqrt(2.0));
end
code[a1_, a2_, th_] := N[(a1 * N[(a1 / N[Sqrt[2.0], $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
a1 \cdot \frac{a1}{\sqrt{2}}
\end{array}
Derivation
  1. Initial program 99.6%

    \[\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1\right) + \frac{\cos th}{\sqrt{2}} \cdot \left(a2 \cdot a2\right) \]
  2. Step-by-step derivation
    1. distribute-lft-out99.6%

      \[\leadsto \color{blue}{\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right)} \]
  3. Simplified99.6%

    \[\leadsto \color{blue}{\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right)} \]
  4. Add Preprocessing
  5. Taylor expanded in th around 0 65.2%

    \[\leadsto \frac{\color{blue}{1}}{\sqrt{2}} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right) \]
  6. Taylor expanded in a1 around inf 36.3%

    \[\leadsto \color{blue}{\frac{{a1}^{2}}{\sqrt{2}}} \]
  7. Step-by-step derivation
    1. unpow236.3%

      \[\leadsto \frac{\color{blue}{a1 \cdot a1}}{\sqrt{2}} \]
    2. associate-/l*36.3%

      \[\leadsto \color{blue}{a1 \cdot \frac{a1}{\sqrt{2}}} \]
  8. Applied egg-rr36.3%

    \[\leadsto \color{blue}{a1 \cdot \frac{a1}{\sqrt{2}}} \]
  9. Final simplification36.3%

    \[\leadsto a1 \cdot \frac{a1}{\sqrt{2}} \]
  10. Add Preprocessing

Alternative 6: 40.3% accurate, 4.0× speedup?

\[\begin{array}{l} \\ a2 \cdot \frac{a2}{\sqrt{2}} \end{array} \]
(FPCore (a1 a2 th) :precision binary64 (* a2 (/ a2 (sqrt 2.0))))
double code(double a1, double a2, double th) {
	return a2 * (a2 / sqrt(2.0));
}
real(8) function code(a1, a2, th)
    real(8), intent (in) :: a1
    real(8), intent (in) :: a2
    real(8), intent (in) :: th
    code = a2 * (a2 / sqrt(2.0d0))
end function
public static double code(double a1, double a2, double th) {
	return a2 * (a2 / Math.sqrt(2.0));
}
def code(a1, a2, th):
	return a2 * (a2 / math.sqrt(2.0))
function code(a1, a2, th)
	return Float64(a2 * Float64(a2 / sqrt(2.0)))
end
function tmp = code(a1, a2, th)
	tmp = a2 * (a2 / sqrt(2.0));
end
code[a1_, a2_, th_] := N[(a2 * N[(a2 / N[Sqrt[2.0], $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
a2 \cdot \frac{a2}{\sqrt{2}}
\end{array}
Derivation
  1. Initial program 99.6%

    \[\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1\right) + \frac{\cos th}{\sqrt{2}} \cdot \left(a2 \cdot a2\right) \]
  2. Step-by-step derivation
    1. distribute-lft-out99.6%

      \[\leadsto \color{blue}{\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right)} \]
  3. Simplified99.6%

    \[\leadsto \color{blue}{\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right)} \]
  4. Add Preprocessing
  5. Taylor expanded in th around 0 65.2%

    \[\leadsto \frac{\color{blue}{1}}{\sqrt{2}} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right) \]
  6. Taylor expanded in a1 around 0 43.6%

    \[\leadsto \color{blue}{\frac{{a2}^{2}}{\sqrt{2}}} \]
  7. Step-by-step derivation
    1. pow243.6%

      \[\leadsto \frac{\color{blue}{a2 \cdot a2}}{\sqrt{2}} \]
    2. associate-/l*43.6%

      \[\leadsto \color{blue}{a2 \cdot \frac{a2}{\sqrt{2}}} \]
  8. Applied egg-rr43.6%

    \[\leadsto \color{blue}{a2 \cdot \frac{a2}{\sqrt{2}}} \]
  9. Final simplification43.6%

    \[\leadsto a2 \cdot \frac{a2}{\sqrt{2}} \]
  10. Add Preprocessing

Alternative 7: 40.3% accurate, 4.0× speedup?

\[\begin{array}{l} \\ a2 \cdot \left(\sqrt{0.5} \cdot a2\right) \end{array} \]
(FPCore (a1 a2 th) :precision binary64 (* a2 (* (sqrt 0.5) a2)))
double code(double a1, double a2, double th) {
	return a2 * (sqrt(0.5) * a2);
}
real(8) function code(a1, a2, th)
    real(8), intent (in) :: a1
    real(8), intent (in) :: a2
    real(8), intent (in) :: th
    code = a2 * (sqrt(0.5d0) * a2)
end function
public static double code(double a1, double a2, double th) {
	return a2 * (Math.sqrt(0.5) * a2);
}
def code(a1, a2, th):
	return a2 * (math.sqrt(0.5) * a2)
function code(a1, a2, th)
	return Float64(a2 * Float64(sqrt(0.5) * a2))
end
function tmp = code(a1, a2, th)
	tmp = a2 * (sqrt(0.5) * a2);
end
code[a1_, a2_, th_] := N[(a2 * N[(N[Sqrt[0.5], $MachinePrecision] * a2), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
a2 \cdot \left(\sqrt{0.5} \cdot a2\right)
\end{array}
Derivation
  1. Initial program 99.6%

    \[\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1\right) + \frac{\cos th}{\sqrt{2}} \cdot \left(a2 \cdot a2\right) \]
  2. Step-by-step derivation
    1. distribute-lft-out99.6%

      \[\leadsto \color{blue}{\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right)} \]
  3. Simplified99.6%

    \[\leadsto \color{blue}{\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right)} \]
  4. Add Preprocessing
  5. Taylor expanded in th around 0 65.2%

    \[\leadsto \frac{\color{blue}{1}}{\sqrt{2}} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right) \]
  6. Taylor expanded in a1 around 0 43.6%

    \[\leadsto \color{blue}{\frac{{a2}^{2}}{\sqrt{2}}} \]
  7. Step-by-step derivation
    1. pow243.6%

      \[\leadsto \frac{\color{blue}{a2 \cdot a2}}{\sqrt{2}} \]
    2. div-inv43.6%

      \[\leadsto \color{blue}{\left(a2 \cdot a2\right) \cdot \frac{1}{\sqrt{2}}} \]
    3. associate-*l*43.6%

      \[\leadsto \color{blue}{a2 \cdot \left(a2 \cdot \frac{1}{\sqrt{2}}\right)} \]
    4. pow1/243.6%

      \[\leadsto a2 \cdot \left(a2 \cdot \frac{1}{\color{blue}{{2}^{0.5}}}\right) \]
    5. pow-flip43.6%

      \[\leadsto a2 \cdot \left(a2 \cdot \color{blue}{{2}^{\left(-0.5\right)}}\right) \]
    6. metadata-eval43.6%

      \[\leadsto a2 \cdot \left(a2 \cdot {2}^{\color{blue}{-0.5}}\right) \]
  8. Applied egg-rr43.6%

    \[\leadsto \color{blue}{a2 \cdot \left(a2 \cdot {2}^{-0.5}\right)} \]
  9. Step-by-step derivation
    1. associate-*r*43.6%

      \[\leadsto \color{blue}{\left(a2 \cdot a2\right) \cdot {2}^{-0.5}} \]
    2. metadata-eval43.6%

      \[\leadsto \left(a2 \cdot a2\right) \cdot {2}^{\color{blue}{\left(2 \cdot -0.25\right)}} \]
    3. pow-sqr43.6%

      \[\leadsto \left(a2 \cdot a2\right) \cdot \color{blue}{\left({2}^{-0.25} \cdot {2}^{-0.25}\right)} \]
    4. swap-sqr43.6%

      \[\leadsto \color{blue}{\left(a2 \cdot {2}^{-0.25}\right) \cdot \left(a2 \cdot {2}^{-0.25}\right)} \]
    5. unpow243.6%

      \[\leadsto \color{blue}{{\left(a2 \cdot {2}^{-0.25}\right)}^{2}} \]
  10. Simplified43.6%

    \[\leadsto \color{blue}{{\left(a2 \cdot {2}^{-0.25}\right)}^{2}} \]
  11. Step-by-step derivation
    1. unpow-prod-down43.6%

      \[\leadsto \color{blue}{{a2}^{2} \cdot {\left({2}^{-0.25}\right)}^{2}} \]
    2. pow-pow43.6%

      \[\leadsto {a2}^{2} \cdot \color{blue}{{2}^{\left(-0.25 \cdot 2\right)}} \]
    3. metadata-eval43.6%

      \[\leadsto {a2}^{2} \cdot {2}^{\color{blue}{-0.5}} \]
    4. metadata-eval43.6%

      \[\leadsto {a2}^{2} \cdot {2}^{\color{blue}{\left(-0.5\right)}} \]
    5. pow-flip43.6%

      \[\leadsto {a2}^{2} \cdot \color{blue}{\frac{1}{{2}^{0.5}}} \]
    6. pow1/243.6%

      \[\leadsto {a2}^{2} \cdot \frac{1}{\color{blue}{\sqrt{2}}} \]
    7. div-inv43.6%

      \[\leadsto \color{blue}{\frac{{a2}^{2}}{\sqrt{2}}} \]
    8. unpow243.6%

      \[\leadsto \frac{\color{blue}{a2 \cdot a2}}{\sqrt{2}} \]
    9. associate-*l/43.6%

      \[\leadsto \color{blue}{\frac{a2}{\sqrt{2}} \cdot a2} \]
    10. div-inv43.6%

      \[\leadsto \color{blue}{\left(a2 \cdot \frac{1}{\sqrt{2}}\right)} \cdot a2 \]
    11. pow1/243.6%

      \[\leadsto \left(a2 \cdot \frac{1}{\color{blue}{{2}^{0.5}}}\right) \cdot a2 \]
    12. pow-flip43.6%

      \[\leadsto \left(a2 \cdot \color{blue}{{2}^{\left(-0.5\right)}}\right) \cdot a2 \]
    13. metadata-eval43.6%

      \[\leadsto \left(a2 \cdot {2}^{\color{blue}{-0.5}}\right) \cdot a2 \]
    14. add-sqr-sqrt43.5%

      \[\leadsto \left(a2 \cdot \color{blue}{\left(\sqrt{{2}^{-0.5}} \cdot \sqrt{{2}^{-0.5}}\right)}\right) \cdot a2 \]
    15. sqrt-unprod43.6%

      \[\leadsto \left(a2 \cdot \color{blue}{\sqrt{{2}^{-0.5} \cdot {2}^{-0.5}}}\right) \cdot a2 \]
    16. pow-prod-up43.6%

      \[\leadsto \left(a2 \cdot \sqrt{\color{blue}{{2}^{\left(-0.5 + -0.5\right)}}}\right) \cdot a2 \]
    17. metadata-eval43.6%

      \[\leadsto \left(a2 \cdot \sqrt{{2}^{\color{blue}{-1}}}\right) \cdot a2 \]
    18. metadata-eval43.6%

      \[\leadsto \left(a2 \cdot \sqrt{\color{blue}{0.5}}\right) \cdot a2 \]
  12. Applied egg-rr43.6%

    \[\leadsto \color{blue}{\left(a2 \cdot \sqrt{0.5}\right) \cdot a2} \]
  13. Final simplification43.6%

    \[\leadsto a2 \cdot \left(\sqrt{0.5} \cdot a2\right) \]
  14. Add Preprocessing

Reproduce

?
herbie shell --seed 2024073 
(FPCore (a1 a2 th)
  :name "Migdal et al, Equation (64)"
  :precision binary64
  (+ (* (/ (cos th) (sqrt 2.0)) (* a1 a1)) (* (/ (cos th) (sqrt 2.0)) (* a2 a2))))