Average Error: 0.5 → 0.3
Time: 12.0s
Precision: binary64
\[\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1\right) + \frac{\cos th}{\sqrt{2}} \cdot \left(a2 \cdot a2\right)\]
↓
\[\cos th \cdot \left(\sqrt{a2 \cdot a2 + a1 \cdot a1} \cdot \sqrt{\frac{a2 \cdot a2 + a1 \cdot a1}{2}}\right)\]
\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(\sqrt{a2 \cdot a2 + a1 \cdot a1} \cdot \sqrt{\frac{a2 \cdot a2 + a1 \cdot a1}{2}}\right)
(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)
  (* (sqrt (+ (* a2 a2) (* a1 a1))) (sqrt (/ (+ (* a2 a2) (* a1 a1)) 2.0)))))
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) * (sqrt((a2 * a2) + (a1 * a1)) * sqrt(((a2 * a2) + (a1 * a1)) / 2.0));
}

Error

Bits error versus a1

Bits error versus a2

Bits error versus th

Try it out

Your Program's Arguments

Results

Enter valid numbers for all inputs

Derivation

  1. Initial program 0.5

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

  2. Simplified0.4

    \[\leadsto \color{blue}{\cos th \cdot \frac{a1 \cdot a1 + a2 \cdot a2}{\sqrt{2}}}\]
  3. Using strategy rm

  4. Applied *-un-lft-identity_binary64_4190.4

    \[\leadsto \cos th \cdot \frac{a1 \cdot a1 + a2 \cdot a2}{\sqrt{\color{blue}{1 \cdot 2}}}\]

  5. Applied sqrt-prod_binary64_4350.4

    \[\leadsto \cos th \cdot \frac{a1 \cdot a1 + a2 \cdot a2}{\color{blue}{\sqrt{1} \cdot \sqrt{2}}}\]

  6. Applied add-sqr-sqrt_binary64_4410.5

    \[\leadsto \cos th \cdot \frac{\color{blue}{\sqrt{a1 \cdot a1 + a2 \cdot a2} \cdot \sqrt{a1 \cdot a1 + a2 \cdot a2}}}{\sqrt{1} \cdot \sqrt{2}}\]

  7. Applied times-frac_binary64_4250.4

    \[\leadsto \cos th \cdot \color{blue}{\left(\frac{\sqrt{a1 \cdot a1 + a2 \cdot a2}}{\sqrt{1}} \cdot \frac{\sqrt{a1 \cdot a1 + a2 \cdot a2}}{\sqrt{2}}\right)}\]

  8. Simplified0.4

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

  9. Simplified0.4

    \[\leadsto \cos th \cdot \left(\sqrt{a2 \cdot a2 + a1 \cdot a1} \cdot \color{blue}{\frac{\sqrt{a2 \cdot a2 + a1 \cdot a1}}{\sqrt{2}}}\right)\]
  10. Using strategy rm

  11. Applied sqrt-undiv_binary64_4400.3

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

  12. Final simplification0.3

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

Reproduce

herbie shell --seed 2021019 
(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))))