Migdal et al, Equation (64)

Average Accuracy: 99.1% → 99.3%

Time: 15.8s

Precision: binary64

Cost: 26240

Math

\[\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1\right) + \frac{\cos th}{\sqrt{2}} \cdot \left(a2 \cdot a2\right) \]

↓

\[\cos th \cdot \left(\mathsf{hypot}\left(a1, a2\right) \cdot \left(\mathsf{hypot}\left(a1, a2\right) \cdot {2}^{-0.5}\right)\right) \]

FPCore

(FPCore (a1 a2 th)
 :precision binary64
 (+
  (* (/ (cos th) (sqrt 2.0)) (* a1 a1))
  (* (/ (cos th) (sqrt 2.0)) (* a2 a2))))

↓

(FPCore (a1 a2 th)
 :precision binary64
 (* (cos th) (* (hypot a1 a2) (* (hypot a1 a2) (pow 2.0 -0.5)))))

C

double code(double a1, double a2, double th) {
	return ((cos(th) / sqrt(2.0)) * (a1 * a1)) + ((cos(th) / sqrt(2.0)) * (a2 * a2));
}

↓

double code(double a1, double a2, double th) {
	return cos(th) * (hypot(a1, a2) * (hypot(a1, a2) * pow(2.0, -0.5)));
}

Java

public static double code(double a1, double a2, double th) {
	return ((Math.cos(th) / Math.sqrt(2.0)) * (a1 * a1)) + ((Math.cos(th) / Math.sqrt(2.0)) * (a2 * a2));
}

↓

public static double code(double a1, double a2, double th) {
	return Math.cos(th) * (Math.hypot(a1, a2) * (Math.hypot(a1, a2) * Math.pow(2.0, -0.5)));
}

Python

def code(a1, a2, th):
	return ((math.cos(th) / math.sqrt(2.0)) * (a1 * a1)) + ((math.cos(th) / math.sqrt(2.0)) * (a2 * a2))

↓

def code(a1, a2, th):
	return math.cos(th) * (math.hypot(a1, a2) * (math.hypot(a1, a2) * math.pow(2.0, -0.5)))

Julia

function code(a1, a2, th)
	return Float64(Float64(Float64(cos(th) / sqrt(2.0)) * Float64(a1 * a1)) + Float64(Float64(cos(th) / sqrt(2.0)) * Float64(a2 * a2)))
end

↓

function code(a1, a2, th)
	return Float64(cos(th) * Float64(hypot(a1, a2) * Float64(hypot(a1, a2) * (2.0 ^ -0.5))))
end

MATLAB

function tmp = code(a1, a2, th)
	tmp = ((cos(th) / sqrt(2.0)) * (a1 * a1)) + ((cos(th) / sqrt(2.0)) * (a2 * a2));
end

↓

function tmp = code(a1, a2, th)
	tmp = cos(th) * (hypot(a1, a2) * (hypot(a1, a2) * (2.0 ^ -0.5)));
end

Wolfram

code[a1_, a2_, th_] := N[(N[(N[(N[Cos[th], $MachinePrecision] / N[Sqrt[2.0], $MachinePrecision]), $MachinePrecision] * N[(a1 * a1), $MachinePrecision]), $MachinePrecision] + N[(N[(N[Cos[th], $MachinePrecision] / N[Sqrt[2.0], $MachinePrecision]), $MachinePrecision] * N[(a2 * a2), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]

↓

code[a1_, a2_, th_] := N[(N[Cos[th], $MachinePrecision] * N[(N[Sqrt[a1 ^ 2 + a2 ^ 2], $MachinePrecision] * N[(N[Sqrt[a1 ^ 2 + a2 ^ 2], $MachinePrecision] * N[Power[2.0, -0.5], $MachinePrecision]), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]

Derivation

1. Initial program 99.1%

   \[\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1\right) + \frac{\cos th}{\sqrt{2}} \cdot \left(a2 \cdot a2\right) \]

2. Simplified 99.2%

   \[\leadsto \color{blue}{\cos th \cdot \frac{\mathsf{fma}\left(a1, a1, a2 \cdot a2\right)}{\sqrt{2}}} \]
   Proof

   [Start] 99.1	\[ \frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1\right) + \frac{\cos th}{\sqrt{2}} \cdot \left(a2 \cdot a2\right) \]
   distribute-lft-out [=>] 99.1	\[ \color{blue}{\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1 + a2 \cdot a2\right)} \]
   associate-*l/ [=>] 99.2	\[ \color{blue}{\frac{\cos th \cdot \left(a1 \cdot a1 + a2 \cdot a2\right)}{\sqrt{2}}} \]
   associate-*r/ [<=] 99.2	\[ \color{blue}{\cos th \cdot \frac{a1 \cdot a1 + a2 \cdot a2}{\sqrt{2}}} \]
   fma-def [=>] 99.2	\[ \cos th \cdot \frac{\color{blue}{\mathsf{fma}\left(a1, a1, a2 \cdot a2\right)}}{\sqrt{2}} \]

3. Applied egg-rr 99.3%

   \[\leadsto \cos th \cdot \color{blue}{\left(\mathsf{hypot}\left(a1, a2\right) \cdot \left(\mathsf{hypot}\left(a1, a2\right) \cdot {2}^{-0.5}\right)\right)} \]
   Proof

   [Start] 99.2	\[ \cos th \cdot \frac{\mathsf{fma}\left(a1, a1, a2 \cdot a2\right)}{\sqrt{2}} \]
   div-inv [=>] 99.1	\[ \cos th \cdot \color{blue}{\left(\mathsf{fma}\left(a1, a1, a2 \cdot a2\right) \cdot \frac{1}{\sqrt{2}}\right)} \]
   add-sqr-sqrt [=>] 99.1	\[ \cos th \cdot \left(\color{blue}{\left(\sqrt{\mathsf{fma}\left(a1, a1, a2 \cdot a2\right)} \cdot \sqrt{\mathsf{fma}\left(a1, a1, a2 \cdot a2\right)}\right)} \cdot \frac{1}{\sqrt{2}}\right) \]
   associate-*l* [=>] 99.1	\[ \cos th \cdot \color{blue}{\left(\sqrt{\mathsf{fma}\left(a1, a1, a2 \cdot a2\right)} \cdot \left(\sqrt{\mathsf{fma}\left(a1, a1, a2 \cdot a2\right)} \cdot \frac{1}{\sqrt{2}}\right)\right)} \]
   fma-udef [=>] 99.1	\[ \cos th \cdot \left(\sqrt{\color{blue}{a1 \cdot a1 + a2 \cdot a2}} \cdot \left(\sqrt{\mathsf{fma}\left(a1, a1, a2 \cdot a2\right)} \cdot \frac{1}{\sqrt{2}}\right)\right) \]
   hypot-def [=>] 99.1	\[ \cos th \cdot \left(\color{blue}{\mathsf{hypot}\left(a1, a2\right)} \cdot \left(\sqrt{\mathsf{fma}\left(a1, a1, a2 \cdot a2\right)} \cdot \frac{1}{\sqrt{2}}\right)\right) \]
   fma-udef [=>] 99.1	\[ \cos th \cdot \left(\mathsf{hypot}\left(a1, a2\right) \cdot \left(\sqrt{\color{blue}{a1 \cdot a1 + a2 \cdot a2}} \cdot \frac{1}{\sqrt{2}}\right)\right) \]
   hypot-def [=>] 99.2	\[ \cos th \cdot \left(\mathsf{hypot}\left(a1, a2\right) \cdot \left(\color{blue}{\mathsf{hypot}\left(a1, a2\right)} \cdot \frac{1}{\sqrt{2}}\right)\right) \]
   pow1/2 [=>] 99.2	\[ \cos th \cdot \left(\mathsf{hypot}\left(a1, a2\right) \cdot \left(\mathsf{hypot}\left(a1, a2\right) \cdot \frac{1}{\color{blue}{{2}^{0.5}}}\right)\right) \]
   pow-flip [=>] 99.3	\[ \cos th \cdot \left(\mathsf{hypot}\left(a1, a2\right) \cdot \left(\mathsf{hypot}\left(a1, a2\right) \cdot \color{blue}{{2}^{\left(-0.5\right)}}\right)\right) \]
   metadata-eval [=>] 99.3	\[ \cos th \cdot \left(\mathsf{hypot}\left(a1, a2\right) \cdot \left(\mathsf{hypot}\left(a1, a2\right) \cdot {2}^{\color{blue}{-0.5}}\right)\right) \]

4. Final simplification 99.3%

   \[\leadsto \cos th \cdot \left(\mathsf{hypot}\left(a1, a2\right) \cdot \left(\mathsf{hypot}\left(a1, a2\right) \cdot {2}^{-0.5}\right)\right) \]

Alternatives

Alternative 1
Accuracy	99.2%
Cost	13568

\[\left(\cos th \cdot {2}^{-0.5}\right) \cdot \left(a1 \cdot a1 + a2 \cdot a2\right) \]

Alternative 2
Accuracy	76.4%
Cost	13513

\[\begin{array}{l} \mathbf{if}\;th \leq -5.8 \cdot 10^{+26} \lor \neg \left(th \leq 7.6 \cdot 10^{-6}\right):\\ \;\;\;\;\cos th \cdot \left(\left(a1 \cdot a1\right) \cdot \sqrt{0.5}\right)\\ \mathbf{else}:\\ \;\;\;\;\frac{a1 \cdot a1 + a2 \cdot a2}{\sqrt{2}} \cdot \left(1 + -0.5 \cdot \left(th \cdot th\right)\right)\\ \end{array} \]

Alternative 3
Accuracy	99.2%
Cost	13504

\[\cos th \cdot \frac{a1 \cdot a1 + a2 \cdot a2}{\sqrt{2}} \]

Alternative 4
Accuracy	68.0%
Cost	13380

\[\begin{array}{l} \mathbf{if}\;a1 \leq -2.2 \cdot 10^{-131}:\\ \;\;\;\;\cos th \cdot \left(\left(a1 \cdot a1\right) \cdot \sqrt{0.5}\right)\\ \mathbf{else}:\\ \;\;\;\;\cos th \cdot \frac{a2}{\frac{\sqrt{2}}{a2}}\\ \end{array} \]

Alternative 5
Accuracy	67.9%
Cost	13380

\[\begin{array}{l} \mathbf{if}\;a1 \leq -2.2 \cdot 10^{-131}:\\ \;\;\;\;\cos th \cdot \left(\left(a1 \cdot a1\right) \cdot \sqrt{0.5}\right)\\ \mathbf{else}:\\ \;\;\;\;\sqrt{0.5} \cdot \left(\cos th \cdot \left(a2 \cdot a2\right)\right)\\ \end{array} \]

Alternative 6
Accuracy	67.9%
Cost	13380

\[\begin{array}{l} \mathbf{if}\;a1 \leq -2.2 \cdot 10^{-131}:\\ \;\;\;\;\cos th \cdot \left(\left(a1 \cdot a1\right) \cdot \sqrt{0.5}\right)\\ \mathbf{else}:\\ \;\;\;\;\left(a2 \cdot a2\right) \cdot \left(\cos th \cdot \sqrt{0.5}\right)\\ \end{array} \]

Alternative 7
Accuracy	42.7%
Cost	6980

\[\begin{array}{l} \mathbf{if}\;a1 \leq -2.6 \cdot 10^{-133}:\\ \;\;\;\;\frac{1}{\frac{\sqrt{2}}{a1 \cdot a1}}\\ \mathbf{else}:\\ \;\;\;\;\left(a2 \cdot a2\right) \cdot \sqrt{0.5}\\ \end{array} \]

Alternative 8
Accuracy	59.7%
Cost	6976

\[\left(a1 \cdot a1 + a2 \cdot a2\right) \cdot \sqrt{0.5} \]

Alternative 9
Accuracy	42.8%
Cost	6852

\[\begin{array}{l} \mathbf{if}\;a1 \leq -2.5 \cdot 10^{-133}:\\ \;\;\;\;a1 \cdot \left(a1 \cdot \sqrt{0.5}\right)\\ \mathbf{else}:\\ \;\;\;\;\left(a2 \cdot a2\right) \cdot \sqrt{0.5}\\ \end{array} \]

Alternative 10
Accuracy	36.8%
Cost	6720

\[a1 \cdot \left(a1 \cdot \sqrt{0.5}\right) \]

Reproduce

herbie shell --seed 2023146 
(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))))