Falkner and Boettcher, Appendix B, 2

Percentage Accurate: 100.0% → 100.0%
Time: 5.8s
Alternatives: 7
Speedup: 1.0×

Specification

?
\[\begin{array}{l} \\ \left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - 3 \cdot \left(v \cdot v\right)}\right) \cdot \left(1 - v \cdot v\right) \end{array} \]
(FPCore (v)
 :precision binary64
 (* (* (/ (sqrt 2.0) 4.0) (sqrt (- 1.0 (* 3.0 (* v v))))) (- 1.0 (* v v))))
double code(double v) {
	return ((sqrt(2.0) / 4.0) * sqrt((1.0 - (3.0 * (v * v))))) * (1.0 - (v * v));
}
real(8) function code(v)
    real(8), intent (in) :: v
    code = ((sqrt(2.0d0) / 4.0d0) * sqrt((1.0d0 - (3.0d0 * (v * v))))) * (1.0d0 - (v * v))
end function
public static double code(double v) {
	return ((Math.sqrt(2.0) / 4.0) * Math.sqrt((1.0 - (3.0 * (v * v))))) * (1.0 - (v * v));
}
def code(v):
	return ((math.sqrt(2.0) / 4.0) * math.sqrt((1.0 - (3.0 * (v * v))))) * (1.0 - (v * v))
function code(v)
	return Float64(Float64(Float64(sqrt(2.0) / 4.0) * sqrt(Float64(1.0 - Float64(3.0 * Float64(v * v))))) * Float64(1.0 - Float64(v * v)))
end
function tmp = code(v)
	tmp = ((sqrt(2.0) / 4.0) * sqrt((1.0 - (3.0 * (v * v))))) * (1.0 - (v * v));
end
code[v_] := N[(N[(N[(N[Sqrt[2.0], $MachinePrecision] / 4.0), $MachinePrecision] * N[Sqrt[N[(1.0 - N[(3.0 * N[(v * v), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision] * N[(1.0 - N[(v * v), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
\left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - 3 \cdot \left(v \cdot v\right)}\right) \cdot \left(1 - v \cdot v\right)
\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: 100.0% accurate, 1.0× speedup?

\[\begin{array}{l} \\ \left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - 3 \cdot \left(v \cdot v\right)}\right) \cdot \left(1 - v \cdot v\right) \end{array} \]
(FPCore (v)
 :precision binary64
 (* (* (/ (sqrt 2.0) 4.0) (sqrt (- 1.0 (* 3.0 (* v v))))) (- 1.0 (* v v))))
double code(double v) {
	return ((sqrt(2.0) / 4.0) * sqrt((1.0 - (3.0 * (v * v))))) * (1.0 - (v * v));
}
real(8) function code(v)
    real(8), intent (in) :: v
    code = ((sqrt(2.0d0) / 4.0d0) * sqrt((1.0d0 - (3.0d0 * (v * v))))) * (1.0d0 - (v * v))
end function
public static double code(double v) {
	return ((Math.sqrt(2.0) / 4.0) * Math.sqrt((1.0 - (3.0 * (v * v))))) * (1.0 - (v * v));
}
def code(v):
	return ((math.sqrt(2.0) / 4.0) * math.sqrt((1.0 - (3.0 * (v * v))))) * (1.0 - (v * v))
function code(v)
	return Float64(Float64(Float64(sqrt(2.0) / 4.0) * sqrt(Float64(1.0 - Float64(3.0 * Float64(v * v))))) * Float64(1.0 - Float64(v * v)))
end
function tmp = code(v)
	tmp = ((sqrt(2.0) / 4.0) * sqrt((1.0 - (3.0 * (v * v))))) * (1.0 - (v * v));
end
code[v_] := N[(N[(N[(N[Sqrt[2.0], $MachinePrecision] / 4.0), $MachinePrecision] * N[Sqrt[N[(1.0 - N[(3.0 * N[(v * v), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision] * N[(1.0 - N[(v * v), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
\left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - 3 \cdot \left(v \cdot v\right)}\right) \cdot \left(1 - v \cdot v\right)
\end{array}

Alternative 1: 100.0% accurate, 0.7× speedup?

\[\begin{array}{l} \\ \sqrt{\mathsf{fma}\left(v, v \cdot -3, 1\right) \cdot \left(0.125 \cdot {\left(1 - v \cdot v\right)}^{2}\right)} \end{array} \]
(FPCore (v)
 :precision binary64
 (sqrt (* (fma v (* v -3.0) 1.0) (* 0.125 (pow (- 1.0 (* v v)) 2.0)))))
double code(double v) {
	return sqrt((fma(v, (v * -3.0), 1.0) * (0.125 * pow((1.0 - (v * v)), 2.0))));
}
function code(v)
	return sqrt(Float64(fma(v, Float64(v * -3.0), 1.0) * Float64(0.125 * (Float64(1.0 - Float64(v * v)) ^ 2.0))))
end
code[v_] := N[Sqrt[N[(N[(v * N[(v * -3.0), $MachinePrecision] + 1.0), $MachinePrecision] * N[(0.125 * N[Power[N[(1.0 - N[(v * v), $MachinePrecision]), $MachinePrecision], 2.0], $MachinePrecision]), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]
\begin{array}{l}

\\
\sqrt{\mathsf{fma}\left(v, v \cdot -3, 1\right) \cdot \left(0.125 \cdot {\left(1 - v \cdot v\right)}^{2}\right)}
\end{array}
Derivation
  1. Initial program 100.0%

    \[\left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - 3 \cdot \left(v \cdot v\right)}\right) \cdot \left(1 - v \cdot v\right) \]
  2. Step-by-step derivation
    1. associate-*r*100.0%

      \[\leadsto \left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \color{blue}{\left(3 \cdot v\right) \cdot v}}\right) \cdot \left(1 - v \cdot v\right) \]
  3. Simplified100.0%

    \[\leadsto \color{blue}{\left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}\right) \cdot \left(1 - v \cdot v\right)} \]
  4. Step-by-step derivation
    1. add-sqr-sqrt98.4%

      \[\leadsto \color{blue}{\sqrt{\left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}\right) \cdot \left(1 - v \cdot v\right)} \cdot \sqrt{\left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}\right) \cdot \left(1 - v \cdot v\right)}} \]
    2. sqrt-unprod100.0%

      \[\leadsto \color{blue}{\sqrt{\left(\left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}\right) \cdot \left(1 - v \cdot v\right)\right) \cdot \left(\left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}\right) \cdot \left(1 - v \cdot v\right)\right)}} \]
    3. swap-sqr100.0%

      \[\leadsto \sqrt{\color{blue}{\left(\left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}\right) \cdot \left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}\right)\right) \cdot \left(\left(1 - v \cdot v\right) \cdot \left(1 - v \cdot v\right)\right)}} \]
  5. Applied egg-rr100.0%

    \[\leadsto \color{blue}{\sqrt{\left(\mathsf{fma}\left(v, v \cdot -3, 1\right) \cdot 0.125\right) \cdot {\left(1 - v \cdot v\right)}^{2}}} \]
  6. Step-by-step derivation
    1. associate-*l*100.0%

      \[\leadsto \sqrt{\color{blue}{\mathsf{fma}\left(v, v \cdot -3, 1\right) \cdot \left(0.125 \cdot {\left(1 - v \cdot v\right)}^{2}\right)}} \]
  7. Simplified100.0%

    \[\leadsto \color{blue}{\sqrt{\mathsf{fma}\left(v, v \cdot -3, 1\right) \cdot \left(0.125 \cdot {\left(1 - v \cdot v\right)}^{2}\right)}} \]
  8. Final simplification100.0%

    \[\leadsto \sqrt{\mathsf{fma}\left(v, v \cdot -3, 1\right) \cdot \left(0.125 \cdot {\left(1 - v \cdot v\right)}^{2}\right)} \]

Alternative 2: 100.0% accurate, 1.0× speedup?

\[\begin{array}{l} \\ \left(1 - v \cdot v\right) \cdot \sqrt{\mathsf{fma}\left(v, v \cdot -3, 1\right) \cdot 0.125} \end{array} \]
(FPCore (v)
 :precision binary64
 (* (- 1.0 (* v v)) (sqrt (* (fma v (* v -3.0) 1.0) 0.125))))
double code(double v) {
	return (1.0 - (v * v)) * sqrt((fma(v, (v * -3.0), 1.0) * 0.125));
}
function code(v)
	return Float64(Float64(1.0 - Float64(v * v)) * sqrt(Float64(fma(v, Float64(v * -3.0), 1.0) * 0.125)))
end
code[v_] := N[(N[(1.0 - N[(v * v), $MachinePrecision]), $MachinePrecision] * N[Sqrt[N[(N[(v * N[(v * -3.0), $MachinePrecision] + 1.0), $MachinePrecision] * 0.125), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
\left(1 - v \cdot v\right) \cdot \sqrt{\mathsf{fma}\left(v, v \cdot -3, 1\right) \cdot 0.125}
\end{array}
Derivation
  1. Initial program 100.0%

    \[\left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - 3 \cdot \left(v \cdot v\right)}\right) \cdot \left(1 - v \cdot v\right) \]
  2. Step-by-step derivation
    1. associate-*r*100.0%

      \[\leadsto \left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \color{blue}{\left(3 \cdot v\right) \cdot v}}\right) \cdot \left(1 - v \cdot v\right) \]
  3. Simplified100.0%

    \[\leadsto \color{blue}{\left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}\right) \cdot \left(1 - v \cdot v\right)} \]
  4. Step-by-step derivation
    1. add-sqr-sqrt98.4%

      \[\leadsto \color{blue}{\left(\sqrt{\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}} \cdot \sqrt{\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}}\right)} \cdot \left(1 - v \cdot v\right) \]
    2. sqrt-unprod100.0%

      \[\leadsto \color{blue}{\sqrt{\left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}\right) \cdot \left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}\right)}} \cdot \left(1 - v \cdot v\right) \]
    3. *-commutative100.0%

      \[\leadsto \sqrt{\color{blue}{\left(\sqrt{1 - \left(3 \cdot v\right) \cdot v} \cdot \frac{\sqrt{2}}{4}\right)} \cdot \left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}\right)} \cdot \left(1 - v \cdot v\right) \]
    4. *-commutative100.0%

      \[\leadsto \sqrt{\left(\sqrt{1 - \left(3 \cdot v\right) \cdot v} \cdot \frac{\sqrt{2}}{4}\right) \cdot \color{blue}{\left(\sqrt{1 - \left(3 \cdot v\right) \cdot v} \cdot \frac{\sqrt{2}}{4}\right)}} \cdot \left(1 - v \cdot v\right) \]
    5. swap-sqr100.0%

      \[\leadsto \sqrt{\color{blue}{\left(\sqrt{1 - \left(3 \cdot v\right) \cdot v} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}\right) \cdot \left(\frac{\sqrt{2}}{4} \cdot \frac{\sqrt{2}}{4}\right)}} \cdot \left(1 - v \cdot v\right) \]
    6. add-sqr-sqrt100.0%

      \[\leadsto \sqrt{\color{blue}{\left(1 - \left(3 \cdot v\right) \cdot v\right)} \cdot \left(\frac{\sqrt{2}}{4} \cdot \frac{\sqrt{2}}{4}\right)} \cdot \left(1 - v \cdot v\right) \]
    7. sub-neg100.0%

      \[\leadsto \sqrt{\color{blue}{\left(1 + \left(-\left(3 \cdot v\right) \cdot v\right)\right)} \cdot \left(\frac{\sqrt{2}}{4} \cdot \frac{\sqrt{2}}{4}\right)} \cdot \left(1 - v \cdot v\right) \]
    8. +-commutative100.0%

      \[\leadsto \sqrt{\color{blue}{\left(\left(-\left(3 \cdot v\right) \cdot v\right) + 1\right)} \cdot \left(\frac{\sqrt{2}}{4} \cdot \frac{\sqrt{2}}{4}\right)} \cdot \left(1 - v \cdot v\right) \]
    9. *-commutative100.0%

      \[\leadsto \sqrt{\left(\left(-\color{blue}{v \cdot \left(3 \cdot v\right)}\right) + 1\right) \cdot \left(\frac{\sqrt{2}}{4} \cdot \frac{\sqrt{2}}{4}\right)} \cdot \left(1 - v \cdot v\right) \]
    10. distribute-rgt-neg-in100.0%

      \[\leadsto \sqrt{\left(\color{blue}{v \cdot \left(-3 \cdot v\right)} + 1\right) \cdot \left(\frac{\sqrt{2}}{4} \cdot \frac{\sqrt{2}}{4}\right)} \cdot \left(1 - v \cdot v\right) \]
    11. fma-def100.0%

      \[\leadsto \sqrt{\color{blue}{\mathsf{fma}\left(v, -3 \cdot v, 1\right)} \cdot \left(\frac{\sqrt{2}}{4} \cdot \frac{\sqrt{2}}{4}\right)} \cdot \left(1 - v \cdot v\right) \]
    12. *-commutative100.0%

      \[\leadsto \sqrt{\mathsf{fma}\left(v, -\color{blue}{v \cdot 3}, 1\right) \cdot \left(\frac{\sqrt{2}}{4} \cdot \frac{\sqrt{2}}{4}\right)} \cdot \left(1 - v \cdot v\right) \]
    13. distribute-rgt-neg-in100.0%

      \[\leadsto \sqrt{\mathsf{fma}\left(v, \color{blue}{v \cdot \left(-3\right)}, 1\right) \cdot \left(\frac{\sqrt{2}}{4} \cdot \frac{\sqrt{2}}{4}\right)} \cdot \left(1 - v \cdot v\right) \]
    14. metadata-eval100.0%

      \[\leadsto \sqrt{\mathsf{fma}\left(v, v \cdot \color{blue}{-3}, 1\right) \cdot \left(\frac{\sqrt{2}}{4} \cdot \frac{\sqrt{2}}{4}\right)} \cdot \left(1 - v \cdot v\right) \]
  5. Applied egg-rr100.0%

    \[\leadsto \color{blue}{\sqrt{\mathsf{fma}\left(v, v \cdot -3, 1\right) \cdot 0.125}} \cdot \left(1 - v \cdot v\right) \]
  6. Final simplification100.0%

    \[\leadsto \left(1 - v \cdot v\right) \cdot \sqrt{\mathsf{fma}\left(v, v \cdot -3, 1\right) \cdot 0.125} \]

Alternative 3: 99.6% accurate, 1.0× speedup?

\[\begin{array}{l} \\ 0.25 \cdot \left(\sqrt{2} + \left(v \cdot v\right) \cdot \left(\sqrt{2} \cdot -2.5\right)\right) \end{array} \]
(FPCore (v)
 :precision binary64
 (* 0.25 (+ (sqrt 2.0) (* (* v v) (* (sqrt 2.0) -2.5)))))
double code(double v) {
	return 0.25 * (sqrt(2.0) + ((v * v) * (sqrt(2.0) * -2.5)));
}
real(8) function code(v)
    real(8), intent (in) :: v
    code = 0.25d0 * (sqrt(2.0d0) + ((v * v) * (sqrt(2.0d0) * (-2.5d0))))
end function
public static double code(double v) {
	return 0.25 * (Math.sqrt(2.0) + ((v * v) * (Math.sqrt(2.0) * -2.5)));
}
def code(v):
	return 0.25 * (math.sqrt(2.0) + ((v * v) * (math.sqrt(2.0) * -2.5)))
function code(v)
	return Float64(0.25 * Float64(sqrt(2.0) + Float64(Float64(v * v) * Float64(sqrt(2.0) * -2.5))))
end
function tmp = code(v)
	tmp = 0.25 * (sqrt(2.0) + ((v * v) * (sqrt(2.0) * -2.5)));
end
code[v_] := N[(0.25 * N[(N[Sqrt[2.0], $MachinePrecision] + N[(N[(v * v), $MachinePrecision] * N[(N[Sqrt[2.0], $MachinePrecision] * -2.5), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
0.25 \cdot \left(\sqrt{2} + \left(v \cdot v\right) \cdot \left(\sqrt{2} \cdot -2.5\right)\right)
\end{array}
Derivation
  1. Initial program 100.0%

    \[\left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - 3 \cdot \left(v \cdot v\right)}\right) \cdot \left(1 - v \cdot v\right) \]
  2. Step-by-step derivation
    1. associate-*r*100.0%

      \[\leadsto \left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \color{blue}{\left(3 \cdot v\right) \cdot v}}\right) \cdot \left(1 - v \cdot v\right) \]
  3. Simplified100.0%

    \[\leadsto \color{blue}{\left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}\right) \cdot \left(1 - v \cdot v\right)} \]
  4. Taylor expanded in v around 0 99.3%

    \[\leadsto \color{blue}{0.25 \cdot \sqrt{2} + 0.25 \cdot \left({v}^{2} \cdot \left(-1 \cdot \sqrt{2} + -1.5 \cdot \sqrt{2}\right)\right)} \]
  5. Step-by-step derivation
    1. distribute-lft-out99.3%

      \[\leadsto \color{blue}{0.25 \cdot \left(\sqrt{2} + {v}^{2} \cdot \left(-1 \cdot \sqrt{2} + -1.5 \cdot \sqrt{2}\right)\right)} \]
    2. unpow299.3%

      \[\leadsto 0.25 \cdot \left(\sqrt{2} + \color{blue}{\left(v \cdot v\right)} \cdot \left(-1 \cdot \sqrt{2} + -1.5 \cdot \sqrt{2}\right)\right) \]
    3. neg-mul-199.3%

      \[\leadsto 0.25 \cdot \left(\sqrt{2} + \left(v \cdot v\right) \cdot \left(\color{blue}{\left(-\sqrt{2}\right)} + -1.5 \cdot \sqrt{2}\right)\right) \]
    4. distribute-lft-in99.3%

      \[\leadsto 0.25 \cdot \left(\sqrt{2} + \color{blue}{\left(\left(v \cdot v\right) \cdot \left(-\sqrt{2}\right) + \left(v \cdot v\right) \cdot \left(-1.5 \cdot \sqrt{2}\right)\right)}\right) \]
    5. associate-+r+99.3%

      \[\leadsto 0.25 \cdot \color{blue}{\left(\left(\sqrt{2} + \left(v \cdot v\right) \cdot \left(-\sqrt{2}\right)\right) + \left(v \cdot v\right) \cdot \left(-1.5 \cdot \sqrt{2}\right)\right)} \]
    6. *-commutative99.3%

      \[\leadsto 0.25 \cdot \left(\left(\sqrt{2} + \left(v \cdot v\right) \cdot \left(-\sqrt{2}\right)\right) + \color{blue}{\left(-1.5 \cdot \sqrt{2}\right) \cdot \left(v \cdot v\right)}\right) \]
    7. *-commutative99.3%

      \[\leadsto 0.25 \cdot \left(\left(\sqrt{2} + \left(v \cdot v\right) \cdot \left(-\sqrt{2}\right)\right) + \color{blue}{\left(v \cdot v\right) \cdot \left(-1.5 \cdot \sqrt{2}\right)}\right) \]
    8. associate-+r+99.3%

      \[\leadsto 0.25 \cdot \color{blue}{\left(\sqrt{2} + \left(\left(v \cdot v\right) \cdot \left(-\sqrt{2}\right) + \left(v \cdot v\right) \cdot \left(-1.5 \cdot \sqrt{2}\right)\right)\right)} \]
    9. distribute-lft-in99.3%

      \[\leadsto 0.25 \cdot \left(\sqrt{2} + \color{blue}{\left(v \cdot v\right) \cdot \left(\left(-\sqrt{2}\right) + -1.5 \cdot \sqrt{2}\right)}\right) \]
    10. neg-mul-199.3%

      \[\leadsto 0.25 \cdot \left(\sqrt{2} + \left(v \cdot v\right) \cdot \left(\color{blue}{-1 \cdot \sqrt{2}} + -1.5 \cdot \sqrt{2}\right)\right) \]
  6. Simplified99.3%

    \[\leadsto \color{blue}{0.25 \cdot \left(\sqrt{2} + \left(\sqrt{2} \cdot -2.5\right) \cdot \left(v \cdot v\right)\right)} \]
  7. Final simplification99.3%

    \[\leadsto 0.25 \cdot \left(\sqrt{2} + \left(v \cdot v\right) \cdot \left(\sqrt{2} \cdot -2.5\right)\right) \]

Alternative 4: 99.5% accurate, 1.9× speedup?

\[\begin{array}{l} \\ \left(1 - v \cdot v\right) \cdot \left(\sqrt{2} \cdot \left(0.25 + \left(v \cdot v\right) \cdot -0.375\right)\right) \end{array} \]
(FPCore (v)
 :precision binary64
 (* (- 1.0 (* v v)) (* (sqrt 2.0) (+ 0.25 (* (* v v) -0.375)))))
double code(double v) {
	return (1.0 - (v * v)) * (sqrt(2.0) * (0.25 + ((v * v) * -0.375)));
}
real(8) function code(v)
    real(8), intent (in) :: v
    code = (1.0d0 - (v * v)) * (sqrt(2.0d0) * (0.25d0 + ((v * v) * (-0.375d0))))
end function
public static double code(double v) {
	return (1.0 - (v * v)) * (Math.sqrt(2.0) * (0.25 + ((v * v) * -0.375)));
}
def code(v):
	return (1.0 - (v * v)) * (math.sqrt(2.0) * (0.25 + ((v * v) * -0.375)))
function code(v)
	return Float64(Float64(1.0 - Float64(v * v)) * Float64(sqrt(2.0) * Float64(0.25 + Float64(Float64(v * v) * -0.375))))
end
function tmp = code(v)
	tmp = (1.0 - (v * v)) * (sqrt(2.0) * (0.25 + ((v * v) * -0.375)));
end
code[v_] := N[(N[(1.0 - N[(v * v), $MachinePrecision]), $MachinePrecision] * N[(N[Sqrt[2.0], $MachinePrecision] * N[(0.25 + N[(N[(v * v), $MachinePrecision] * -0.375), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
\left(1 - v \cdot v\right) \cdot \left(\sqrt{2} \cdot \left(0.25 + \left(v \cdot v\right) \cdot -0.375\right)\right)
\end{array}
Derivation
  1. Initial program 100.0%

    \[\left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - 3 \cdot \left(v \cdot v\right)}\right) \cdot \left(1 - v \cdot v\right) \]
  2. Step-by-step derivation
    1. associate-*r*100.0%

      \[\leadsto \left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \color{blue}{\left(3 \cdot v\right) \cdot v}}\right) \cdot \left(1 - v \cdot v\right) \]
  3. Simplified100.0%

    \[\leadsto \color{blue}{\left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}\right) \cdot \left(1 - v \cdot v\right)} \]
  4. Taylor expanded in v around 0 99.3%

    \[\leadsto \color{blue}{\left(0.25 \cdot \sqrt{2} + -0.375 \cdot \left(\sqrt{2} \cdot {v}^{2}\right)\right)} \cdot \left(1 - v \cdot v\right) \]
  5. Step-by-step derivation
    1. *-commutative99.3%

      \[\leadsto \left(\color{blue}{\sqrt{2} \cdot 0.25} + -0.375 \cdot \left(\sqrt{2} \cdot {v}^{2}\right)\right) \cdot \left(1 - v \cdot v\right) \]
    2. *-commutative99.3%

      \[\leadsto \left(\sqrt{2} \cdot 0.25 + \color{blue}{\left(\sqrt{2} \cdot {v}^{2}\right) \cdot -0.375}\right) \cdot \left(1 - v \cdot v\right) \]
    3. unpow299.3%

      \[\leadsto \left(\sqrt{2} \cdot 0.25 + \left(\sqrt{2} \cdot \color{blue}{\left(v \cdot v\right)}\right) \cdot -0.375\right) \cdot \left(1 - v \cdot v\right) \]
    4. associate-*l*99.3%

      \[\leadsto \left(\sqrt{2} \cdot 0.25 + \color{blue}{\sqrt{2} \cdot \left(\left(v \cdot v\right) \cdot -0.375\right)}\right) \cdot \left(1 - v \cdot v\right) \]
    5. distribute-lft-out99.3%

      \[\leadsto \color{blue}{\left(\sqrt{2} \cdot \left(0.25 + \left(v \cdot v\right) \cdot -0.375\right)\right)} \cdot \left(1 - v \cdot v\right) \]
  6. Simplified99.3%

    \[\leadsto \color{blue}{\left(\sqrt{2} \cdot \left(0.25 + \left(v \cdot v\right) \cdot -0.375\right)\right)} \cdot \left(1 - v \cdot v\right) \]
  7. Final simplification99.3%

    \[\leadsto \left(1 - v \cdot v\right) \cdot \left(\sqrt{2} \cdot \left(0.25 + \left(v \cdot v\right) \cdot -0.375\right)\right) \]

Alternative 5: 99.0% accurate, 2.0× speedup?

\[\begin{array}{l} \\ \left(1 - v \cdot v\right) \cdot \left(0.25 \cdot \sqrt{2}\right) \end{array} \]
(FPCore (v) :precision binary64 (* (- 1.0 (* v v)) (* 0.25 (sqrt 2.0))))
double code(double v) {
	return (1.0 - (v * v)) * (0.25 * sqrt(2.0));
}
real(8) function code(v)
    real(8), intent (in) :: v
    code = (1.0d0 - (v * v)) * (0.25d0 * sqrt(2.0d0))
end function
public static double code(double v) {
	return (1.0 - (v * v)) * (0.25 * Math.sqrt(2.0));
}
def code(v):
	return (1.0 - (v * v)) * (0.25 * math.sqrt(2.0))
function code(v)
	return Float64(Float64(1.0 - Float64(v * v)) * Float64(0.25 * sqrt(2.0)))
end
function tmp = code(v)
	tmp = (1.0 - (v * v)) * (0.25 * sqrt(2.0));
end
code[v_] := N[(N[(1.0 - N[(v * v), $MachinePrecision]), $MachinePrecision] * N[(0.25 * N[Sqrt[2.0], $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
\left(1 - v \cdot v\right) \cdot \left(0.25 \cdot \sqrt{2}\right)
\end{array}
Derivation
  1. Initial program 100.0%

    \[\left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - 3 \cdot \left(v \cdot v\right)}\right) \cdot \left(1 - v \cdot v\right) \]
  2. Step-by-step derivation
    1. associate-*r*100.0%

      \[\leadsto \left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \color{blue}{\left(3 \cdot v\right) \cdot v}}\right) \cdot \left(1 - v \cdot v\right) \]
  3. Simplified100.0%

    \[\leadsto \color{blue}{\left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}\right) \cdot \left(1 - v \cdot v\right)} \]
  4. Step-by-step derivation
    1. *-commutative100.0%

      \[\leadsto \color{blue}{\left(1 - v \cdot v\right) \cdot \left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}\right)} \]
    2. associate-*l/100.0%

      \[\leadsto \left(1 - v \cdot v\right) \cdot \color{blue}{\frac{\sqrt{2} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}}{4}} \]
    3. associate-*r/100.0%

      \[\leadsto \color{blue}{\frac{\left(1 - v \cdot v\right) \cdot \left(\sqrt{2} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}\right)}{4}} \]
    4. sqrt-unprod100.0%

      \[\leadsto \frac{\left(1 - v \cdot v\right) \cdot \color{blue}{\sqrt{2 \cdot \left(1 - \left(3 \cdot v\right) \cdot v\right)}}}{4} \]
    5. sub-neg100.0%

      \[\leadsto \frac{\left(1 - v \cdot v\right) \cdot \sqrt{2 \cdot \color{blue}{\left(1 + \left(-\left(3 \cdot v\right) \cdot v\right)\right)}}}{4} \]
    6. +-commutative100.0%

      \[\leadsto \frac{\left(1 - v \cdot v\right) \cdot \sqrt{2 \cdot \color{blue}{\left(\left(-\left(3 \cdot v\right) \cdot v\right) + 1\right)}}}{4} \]
    7. *-commutative100.0%

      \[\leadsto \frac{\left(1 - v \cdot v\right) \cdot \sqrt{2 \cdot \left(\left(-\color{blue}{v \cdot \left(3 \cdot v\right)}\right) + 1\right)}}{4} \]
    8. distribute-rgt-neg-in100.0%

      \[\leadsto \frac{\left(1 - v \cdot v\right) \cdot \sqrt{2 \cdot \left(\color{blue}{v \cdot \left(-3 \cdot v\right)} + 1\right)}}{4} \]
    9. fma-def100.0%

      \[\leadsto \frac{\left(1 - v \cdot v\right) \cdot \sqrt{2 \cdot \color{blue}{\mathsf{fma}\left(v, -3 \cdot v, 1\right)}}}{4} \]
    10. *-commutative100.0%

      \[\leadsto \frac{\left(1 - v \cdot v\right) \cdot \sqrt{2 \cdot \mathsf{fma}\left(v, -\color{blue}{v \cdot 3}, 1\right)}}{4} \]
    11. distribute-rgt-neg-in100.0%

      \[\leadsto \frac{\left(1 - v \cdot v\right) \cdot \sqrt{2 \cdot \mathsf{fma}\left(v, \color{blue}{v \cdot \left(-3\right)}, 1\right)}}{4} \]
    12. metadata-eval100.0%

      \[\leadsto \frac{\left(1 - v \cdot v\right) \cdot \sqrt{2 \cdot \mathsf{fma}\left(v, v \cdot \color{blue}{-3}, 1\right)}}{4} \]
  5. Applied egg-rr100.0%

    \[\leadsto \color{blue}{\frac{\left(1 - v \cdot v\right) \cdot \sqrt{2 \cdot \mathsf{fma}\left(v, v \cdot -3, 1\right)}}{4}} \]
  6. Step-by-step derivation
    1. *-commutative100.0%

      \[\leadsto \frac{\color{blue}{\sqrt{2 \cdot \mathsf{fma}\left(v, v \cdot -3, 1\right)} \cdot \left(1 - v \cdot v\right)}}{4} \]
    2. associate-/l*100.0%

      \[\leadsto \color{blue}{\frac{\sqrt{2 \cdot \mathsf{fma}\left(v, v \cdot -3, 1\right)}}{\frac{4}{1 - v \cdot v}}} \]
  7. Simplified100.0%

    \[\leadsto \color{blue}{\frac{\sqrt{2 \cdot \mathsf{fma}\left(v, v \cdot -3, 1\right)}}{\frac{4}{1 - v \cdot v}}} \]
  8. Taylor expanded in v around 0 98.7%

    \[\leadsto \frac{\color{blue}{\sqrt{2}}}{\frac{4}{1 - v \cdot v}} \]
  9. Step-by-step derivation
    1. associate-/r/98.7%

      \[\leadsto \color{blue}{\frac{\sqrt{2}}{4} \cdot \left(1 - v \cdot v\right)} \]
    2. *-commutative98.7%

      \[\leadsto \color{blue}{\left(1 - v \cdot v\right) \cdot \frac{\sqrt{2}}{4}} \]
    3. div-inv98.7%

      \[\leadsto \left(1 - v \cdot v\right) \cdot \color{blue}{\left(\sqrt{2} \cdot \frac{1}{4}\right)} \]
    4. metadata-eval98.7%

      \[\leadsto \left(1 - v \cdot v\right) \cdot \left(\sqrt{2} \cdot \color{blue}{0.25}\right) \]
  10. Applied egg-rr98.7%

    \[\leadsto \color{blue}{\left(1 - v \cdot v\right) \cdot \left(\sqrt{2} \cdot 0.25\right)} \]
  11. Final simplification98.7%

    \[\leadsto \left(1 - v \cdot v\right) \cdot \left(0.25 \cdot \sqrt{2}\right) \]

Alternative 6: 99.0% accurate, 2.0× speedup?

\[\begin{array}{l} \\ \frac{\sqrt{2}}{\frac{4}{1 - v \cdot v}} \end{array} \]
(FPCore (v) :precision binary64 (/ (sqrt 2.0) (/ 4.0 (- 1.0 (* v v)))))
double code(double v) {
	return sqrt(2.0) / (4.0 / (1.0 - (v * v)));
}
real(8) function code(v)
    real(8), intent (in) :: v
    code = sqrt(2.0d0) / (4.0d0 / (1.0d0 - (v * v)))
end function
public static double code(double v) {
	return Math.sqrt(2.0) / (4.0 / (1.0 - (v * v)));
}
def code(v):
	return math.sqrt(2.0) / (4.0 / (1.0 - (v * v)))
function code(v)
	return Float64(sqrt(2.0) / Float64(4.0 / Float64(1.0 - Float64(v * v))))
end
function tmp = code(v)
	tmp = sqrt(2.0) / (4.0 / (1.0 - (v * v)));
end
code[v_] := N[(N[Sqrt[2.0], $MachinePrecision] / N[(4.0 / N[(1.0 - N[(v * v), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
\frac{\sqrt{2}}{\frac{4}{1 - v \cdot v}}
\end{array}
Derivation
  1. Initial program 100.0%

    \[\left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - 3 \cdot \left(v \cdot v\right)}\right) \cdot \left(1 - v \cdot v\right) \]
  2. Step-by-step derivation
    1. associate-*r*100.0%

      \[\leadsto \left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \color{blue}{\left(3 \cdot v\right) \cdot v}}\right) \cdot \left(1 - v \cdot v\right) \]
  3. Simplified100.0%

    \[\leadsto \color{blue}{\left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}\right) \cdot \left(1 - v \cdot v\right)} \]
  4. Step-by-step derivation
    1. *-commutative100.0%

      \[\leadsto \color{blue}{\left(1 - v \cdot v\right) \cdot \left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}\right)} \]
    2. associate-*l/100.0%

      \[\leadsto \left(1 - v \cdot v\right) \cdot \color{blue}{\frac{\sqrt{2} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}}{4}} \]
    3. associate-*r/100.0%

      \[\leadsto \color{blue}{\frac{\left(1 - v \cdot v\right) \cdot \left(\sqrt{2} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}\right)}{4}} \]
    4. sqrt-unprod100.0%

      \[\leadsto \frac{\left(1 - v \cdot v\right) \cdot \color{blue}{\sqrt{2 \cdot \left(1 - \left(3 \cdot v\right) \cdot v\right)}}}{4} \]
    5. sub-neg100.0%

      \[\leadsto \frac{\left(1 - v \cdot v\right) \cdot \sqrt{2 \cdot \color{blue}{\left(1 + \left(-\left(3 \cdot v\right) \cdot v\right)\right)}}}{4} \]
    6. +-commutative100.0%

      \[\leadsto \frac{\left(1 - v \cdot v\right) \cdot \sqrt{2 \cdot \color{blue}{\left(\left(-\left(3 \cdot v\right) \cdot v\right) + 1\right)}}}{4} \]
    7. *-commutative100.0%

      \[\leadsto \frac{\left(1 - v \cdot v\right) \cdot \sqrt{2 \cdot \left(\left(-\color{blue}{v \cdot \left(3 \cdot v\right)}\right) + 1\right)}}{4} \]
    8. distribute-rgt-neg-in100.0%

      \[\leadsto \frac{\left(1 - v \cdot v\right) \cdot \sqrt{2 \cdot \left(\color{blue}{v \cdot \left(-3 \cdot v\right)} + 1\right)}}{4} \]
    9. fma-def100.0%

      \[\leadsto \frac{\left(1 - v \cdot v\right) \cdot \sqrt{2 \cdot \color{blue}{\mathsf{fma}\left(v, -3 \cdot v, 1\right)}}}{4} \]
    10. *-commutative100.0%

      \[\leadsto \frac{\left(1 - v \cdot v\right) \cdot \sqrt{2 \cdot \mathsf{fma}\left(v, -\color{blue}{v \cdot 3}, 1\right)}}{4} \]
    11. distribute-rgt-neg-in100.0%

      \[\leadsto \frac{\left(1 - v \cdot v\right) \cdot \sqrt{2 \cdot \mathsf{fma}\left(v, \color{blue}{v \cdot \left(-3\right)}, 1\right)}}{4} \]
    12. metadata-eval100.0%

      \[\leadsto \frac{\left(1 - v \cdot v\right) \cdot \sqrt{2 \cdot \mathsf{fma}\left(v, v \cdot \color{blue}{-3}, 1\right)}}{4} \]
  5. Applied egg-rr100.0%

    \[\leadsto \color{blue}{\frac{\left(1 - v \cdot v\right) \cdot \sqrt{2 \cdot \mathsf{fma}\left(v, v \cdot -3, 1\right)}}{4}} \]
  6. Step-by-step derivation
    1. *-commutative100.0%

      \[\leadsto \frac{\color{blue}{\sqrt{2 \cdot \mathsf{fma}\left(v, v \cdot -3, 1\right)} \cdot \left(1 - v \cdot v\right)}}{4} \]
    2. associate-/l*100.0%

      \[\leadsto \color{blue}{\frac{\sqrt{2 \cdot \mathsf{fma}\left(v, v \cdot -3, 1\right)}}{\frac{4}{1 - v \cdot v}}} \]
  7. Simplified100.0%

    \[\leadsto \color{blue}{\frac{\sqrt{2 \cdot \mathsf{fma}\left(v, v \cdot -3, 1\right)}}{\frac{4}{1 - v \cdot v}}} \]
  8. Taylor expanded in v around 0 98.7%

    \[\leadsto \frac{\color{blue}{\sqrt{2}}}{\frac{4}{1 - v \cdot v}} \]
  9. Final simplification98.7%

    \[\leadsto \frac{\sqrt{2}}{\frac{4}{1 - v \cdot v}} \]

Alternative 7: 98.9% accurate, 2.1× speedup?

\[\begin{array}{l} \\ \sqrt{0.125} \end{array} \]
(FPCore (v) :precision binary64 (sqrt 0.125))
double code(double v) {
	return sqrt(0.125);
}
real(8) function code(v)
    real(8), intent (in) :: v
    code = sqrt(0.125d0)
end function
public static double code(double v) {
	return Math.sqrt(0.125);
}
def code(v):
	return math.sqrt(0.125)
function code(v)
	return sqrt(0.125)
end
function tmp = code(v)
	tmp = sqrt(0.125);
end
code[v_] := N[Sqrt[0.125], $MachinePrecision]
\begin{array}{l}

\\
\sqrt{0.125}
\end{array}
Derivation
  1. Initial program 100.0%

    \[\left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - 3 \cdot \left(v \cdot v\right)}\right) \cdot \left(1 - v \cdot v\right) \]
  2. Step-by-step derivation
    1. associate-*r*100.0%

      \[\leadsto \left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \color{blue}{\left(3 \cdot v\right) \cdot v}}\right) \cdot \left(1 - v \cdot v\right) \]
  3. Simplified100.0%

    \[\leadsto \color{blue}{\left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}\right) \cdot \left(1 - v \cdot v\right)} \]
  4. Step-by-step derivation
    1. add-sqr-sqrt98.4%

      \[\leadsto \color{blue}{\sqrt{\left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}\right) \cdot \left(1 - v \cdot v\right)} \cdot \sqrt{\left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}\right) \cdot \left(1 - v \cdot v\right)}} \]
    2. sqrt-unprod100.0%

      \[\leadsto \color{blue}{\sqrt{\left(\left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}\right) \cdot \left(1 - v \cdot v\right)\right) \cdot \left(\left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}\right) \cdot \left(1 - v \cdot v\right)\right)}} \]
    3. swap-sqr100.0%

      \[\leadsto \sqrt{\color{blue}{\left(\left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}\right) \cdot \left(\frac{\sqrt{2}}{4} \cdot \sqrt{1 - \left(3 \cdot v\right) \cdot v}\right)\right) \cdot \left(\left(1 - v \cdot v\right) \cdot \left(1 - v \cdot v\right)\right)}} \]
  5. Applied egg-rr100.0%

    \[\leadsto \color{blue}{\sqrt{\left(\mathsf{fma}\left(v, v \cdot -3, 1\right) \cdot 0.125\right) \cdot {\left(1 - v \cdot v\right)}^{2}}} \]
  6. Step-by-step derivation
    1. associate-*l*100.0%

      \[\leadsto \sqrt{\color{blue}{\mathsf{fma}\left(v, v \cdot -3, 1\right) \cdot \left(0.125 \cdot {\left(1 - v \cdot v\right)}^{2}\right)}} \]
  7. Simplified100.0%

    \[\leadsto \color{blue}{\sqrt{\mathsf{fma}\left(v, v \cdot -3, 1\right) \cdot \left(0.125 \cdot {\left(1 - v \cdot v\right)}^{2}\right)}} \]
  8. Taylor expanded in v around 0 98.7%

    \[\leadsto \sqrt{\color{blue}{0.125}} \]
  9. Final simplification98.7%

    \[\leadsto \sqrt{0.125} \]

Reproduce

?
herbie shell --seed 2023279 
(FPCore (v)
  :name "Falkner and Boettcher, Appendix B, 2"
  :precision binary64
  (* (* (/ (sqrt 2.0) 4.0) (sqrt (- 1.0 (* 3.0 (* v v))))) (- 1.0 (* v v))))