math.sqrt on complex, imaginary part, im greater than 0 branch

Percentage Accurate: 41.1% → 89.8%
Time: 8.3s
Alternatives: 7
Speedup: 2.0×

Specification

?
\[im > 0\]
\[\begin{array}{l} \\ 0.5 \cdot \sqrt{2 \cdot \left(\sqrt{re \cdot re + im \cdot im} - re\right)} \end{array} \]
(FPCore (re im)
 :precision binary64
 (* 0.5 (sqrt (* 2.0 (- (sqrt (+ (* re re) (* im im))) re)))))
double code(double re, double im) {
	return 0.5 * sqrt((2.0 * (sqrt(((re * re) + (im * im))) - re)));
}

real(8) function code(re, im)
    real(8), intent (in) :: re
    real(8), intent (in) :: im
    code = 0.5d0 * sqrt((2.0d0 * (sqrt(((re * re) + (im * im))) - re)))
end function

public static double code(double re, double im) {
	return 0.5 * Math.sqrt((2.0 * (Math.sqrt(((re * re) + (im * im))) - re)));
}

def code(re, im):
	return 0.5 * math.sqrt((2.0 * (math.sqrt(((re * re) + (im * im))) - re)))

function code(re, im)
	return Float64(0.5 * sqrt(Float64(2.0 * Float64(sqrt(Float64(Float64(re * re) + Float64(im * im))) - re))))
end

function tmp = code(re, im)
	tmp = 0.5 * sqrt((2.0 * (sqrt(((re * re) + (im * im))) - re)));
end

code[re_, im_] := N[(0.5 * N[Sqrt[N[(2.0 * N[(N[Sqrt[N[(N[(re * re), $MachinePrecision] + N[(im * im), $MachinePrecision]), $MachinePrecision]], $MachinePrecision] - re), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]

\begin{array}{l}

\\
0.5 \cdot \sqrt{2 \cdot \left(\sqrt{re \cdot re + im \cdot im} - re\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: 41.1% accurate, 1.0× speedup?

\[\begin{array}{l} \\ 0.5 \cdot \sqrt{2 \cdot \left(\sqrt{re \cdot re + im \cdot im} - re\right)} \end{array} \]
(FPCore (re im)
 :precision binary64
 (* 0.5 (sqrt (* 2.0 (- (sqrt (+ (* re re) (* im im))) re)))))
double code(double re, double im) {
	return 0.5 * sqrt((2.0 * (sqrt(((re * re) + (im * im))) - re)));
}

real(8) function code(re, im)
    real(8), intent (in) :: re
    real(8), intent (in) :: im
    code = 0.5d0 * sqrt((2.0d0 * (sqrt(((re * re) + (im * im))) - re)))
end function

public static double code(double re, double im) {
	return 0.5 * Math.sqrt((2.0 * (Math.sqrt(((re * re) + (im * im))) - re)));
}

def code(re, im):
	return 0.5 * math.sqrt((2.0 * (math.sqrt(((re * re) + (im * im))) - re)))

function code(re, im)
	return Float64(0.5 * sqrt(Float64(2.0 * Float64(sqrt(Float64(Float64(re * re) + Float64(im * im))) - re))))
end

function tmp = code(re, im)
	tmp = 0.5 * sqrt((2.0 * (sqrt(((re * re) + (im * im))) - re)));
end

code[re_, im_] := N[(0.5 * N[Sqrt[N[(2.0 * N[(N[Sqrt[N[(N[(re * re), $MachinePrecision] + N[(im * im), $MachinePrecision]), $MachinePrecision]], $MachinePrecision] - re), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]

\begin{array}{l}

\\
0.5 \cdot \sqrt{2 \cdot \left(\sqrt{re \cdot re + im \cdot im} - re\right)}
\end{array}

Alternative 1: 89.8% accurate, 0.7× speedup?

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;\sqrt{re \cdot re + im \cdot im} - re \leq 0:\\ \;\;\;\;0.5 \cdot \left(im \cdot {re}^{-0.5}\right)\\ \mathbf{else}:\\ \;\;\;\;\sqrt{0.5 \cdot \left(\mathsf{hypot}\left(re, im\right) - re\right)}\\ \end{array} \end{array} \]
(FPCore (re im)
 :precision binary64
 (if (<= (- (sqrt (+ (* re re) (* im im))) re) 0.0)
   (* 0.5 (* im (pow re -0.5)))
   (sqrt (* 0.5 (- (hypot re im) re)))))
double code(double re, double im) {
	double tmp;
	if ((sqrt(((re * re) + (im * im))) - re) <= 0.0) {
		tmp = 0.5 * (im * pow(re, -0.5));
	} else {
		tmp = sqrt((0.5 * (hypot(re, im) - re)));
	}
	return tmp;
}

public static double code(double re, double im) {
	double tmp;
	if ((Math.sqrt(((re * re) + (im * im))) - re) <= 0.0) {
		tmp = 0.5 * (im * Math.pow(re, -0.5));
	} else {
		tmp = Math.sqrt((0.5 * (Math.hypot(re, im) - re)));
	}
	return tmp;
}

def code(re, im):
	tmp = 0
	if (math.sqrt(((re * re) + (im * im))) - re) <= 0.0:
		tmp = 0.5 * (im * math.pow(re, -0.5))
	else:
		tmp = math.sqrt((0.5 * (math.hypot(re, im) - re)))
	return tmp

function code(re, im)
	tmp = 0.0
	if (Float64(sqrt(Float64(Float64(re * re) + Float64(im * im))) - re) <= 0.0)
		tmp = Float64(0.5 * Float64(im * (re ^ -0.5)));
	else
		tmp = sqrt(Float64(0.5 * Float64(hypot(re, im) - re)));
	end
	return tmp
end

function tmp_2 = code(re, im)
	tmp = 0.0;
	if ((sqrt(((re * re) + (im * im))) - re) <= 0.0)
		tmp = 0.5 * (im * (re ^ -0.5));
	else
		tmp = sqrt((0.5 * (hypot(re, im) - re)));
	end
	tmp_2 = tmp;
end

code[re_, im_] := If[LessEqual[N[(N[Sqrt[N[(N[(re * re), $MachinePrecision] + N[(im * im), $MachinePrecision]), $MachinePrecision]], $MachinePrecision] - re), $MachinePrecision], 0.0], N[(0.5 * N[(im * N[Power[re, -0.5], $MachinePrecision]), $MachinePrecision]), $MachinePrecision], N[Sqrt[N[(0.5 * N[(N[Sqrt[re ^ 2 + im ^ 2], $MachinePrecision] - re), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]]

\begin{array}{l}

\\
\begin{array}{l}
\mathbf{if}\;\sqrt{re \cdot re + im \cdot im} - re \leq 0:\\
\;\;\;\;0.5 \cdot \left(im \cdot {re}^{-0.5}\right)\\

\mathbf{else}:\\
\;\;\;\;\sqrt{0.5 \cdot \left(\mathsf{hypot}\left(re, im\right) - re\right)}\\


\end{array}
\end{array}
Derivation
    &prev;&pcontext;&pcontext2;&ctx;
  1. Add Preprocessing

Alternative 2: 76.2% accurate, 1.8× speedup?

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;re \leq -1.35 \cdot 10^{+39}:\\ \;\;\;\;0.5 \cdot \sqrt{re \cdot -4}\\ \mathbf{elif}\;re \leq 3.8 \cdot 10^{-142}:\\ \;\;\;\;0.5 \cdot \sqrt{2 \cdot \left(im - re\right)}\\ \mathbf{elif}\;re \leq 1.05 \cdot 10^{-129}:\\ \;\;\;\;im \cdot \frac{0.5}{\sqrt{re}}\\ \mathbf{elif}\;re \leq 2.45 \cdot 10^{-26} \lor \neg \left(re \leq 5.6 \cdot 10^{+52}\right) \land re \leq 2.85 \cdot 10^{+85}:\\ \;\;\;\;0.5 \cdot \sqrt{im \cdot 2}\\ \mathbf{else}:\\ \;\;\;\;0.5 \cdot \left(im \cdot {re}^{-0.5}\right)\\ \end{array} \end{array} \]
(FPCore (re im)
 :precision binary64
 (if (<= re -1.35e+39)
   (* 0.5 (sqrt (* re -4.0)))
   (if (<= re 3.8e-142)
     (* 0.5 (sqrt (* 2.0 (- im re))))
     (if (<= re 1.05e-129)
       (* im (/ 0.5 (sqrt re)))
       (if (or (<= re 2.45e-26) (and (not (<= re 5.6e+52)) (<= re 2.85e+85)))
         (* 0.5 (sqrt (* im 2.0)))
         (* 0.5 (* im (pow re -0.5))))))))
double code(double re, double im) {
	double tmp;
	if (re <= -1.35e+39) {
		tmp = 0.5 * sqrt((re * -4.0));
	} else if (re <= 3.8e-142) {
		tmp = 0.5 * sqrt((2.0 * (im - re)));
	} else if (re <= 1.05e-129) {
		tmp = im * (0.5 / sqrt(re));
	} else if ((re <= 2.45e-26) || (!(re <= 5.6e+52) && (re <= 2.85e+85))) {
		tmp = 0.5 * sqrt((im * 2.0));
	} else {
		tmp = 0.5 * (im * pow(re, -0.5));
	}
	return tmp;
}

real(8) function code(re, im)
    real(8), intent (in) :: re
    real(8), intent (in) :: im
    real(8) :: tmp
    if (re <= (-1.35d+39)) then
        tmp = 0.5d0 * sqrt((re * (-4.0d0)))
    else if (re <= 3.8d-142) then
        tmp = 0.5d0 * sqrt((2.0d0 * (im - re)))
    else if (re <= 1.05d-129) then
        tmp = im * (0.5d0 / sqrt(re))
    else if ((re <= 2.45d-26) .or. (.not. (re <= 5.6d+52)) .and. (re <= 2.85d+85)) then
        tmp = 0.5d0 * sqrt((im * 2.0d0))
    else
        tmp = 0.5d0 * (im * (re ** (-0.5d0)))
    end if
    code = tmp
end function

public static double code(double re, double im) {
	double tmp;
	if (re <= -1.35e+39) {
		tmp = 0.5 * Math.sqrt((re * -4.0));
	} else if (re <= 3.8e-142) {
		tmp = 0.5 * Math.sqrt((2.0 * (im - re)));
	} else if (re <= 1.05e-129) {
		tmp = im * (0.5 / Math.sqrt(re));
	} else if ((re <= 2.45e-26) || (!(re <= 5.6e+52) && (re <= 2.85e+85))) {
		tmp = 0.5 * Math.sqrt((im * 2.0));
	} else {
		tmp = 0.5 * (im * Math.pow(re, -0.5));
	}
	return tmp;
}

def code(re, im):
	tmp = 0
	if re <= -1.35e+39:
		tmp = 0.5 * math.sqrt((re * -4.0))
	elif re <= 3.8e-142:
		tmp = 0.5 * math.sqrt((2.0 * (im - re)))
	elif re <= 1.05e-129:
		tmp = im * (0.5 / math.sqrt(re))
	elif (re <= 2.45e-26) or (not (re <= 5.6e+52) and (re <= 2.85e+85)):
		tmp = 0.5 * math.sqrt((im * 2.0))
	else:
		tmp = 0.5 * (im * math.pow(re, -0.5))
	return tmp

function code(re, im)
	tmp = 0.0
	if (re <= -1.35e+39)
		tmp = Float64(0.5 * sqrt(Float64(re * -4.0)));
	elseif (re <= 3.8e-142)
		tmp = Float64(0.5 * sqrt(Float64(2.0 * Float64(im - re))));
	elseif (re <= 1.05e-129)
		tmp = Float64(im * Float64(0.5 / sqrt(re)));
	elseif ((re <= 2.45e-26) || (!(re <= 5.6e+52) && (re <= 2.85e+85)))
		tmp = Float64(0.5 * sqrt(Float64(im * 2.0)));
	else
		tmp = Float64(0.5 * Float64(im * (re ^ -0.5)));
	end
	return tmp
end

function tmp_2 = code(re, im)
	tmp = 0.0;
	if (re <= -1.35e+39)
		tmp = 0.5 * sqrt((re * -4.0));
	elseif (re <= 3.8e-142)
		tmp = 0.5 * sqrt((2.0 * (im - re)));
	elseif (re <= 1.05e-129)
		tmp = im * (0.5 / sqrt(re));
	elseif ((re <= 2.45e-26) || (~((re <= 5.6e+52)) && (re <= 2.85e+85)))
		tmp = 0.5 * sqrt((im * 2.0));
	else
		tmp = 0.5 * (im * (re ^ -0.5));
	end
	tmp_2 = tmp;
end

code[re_, im_] := If[LessEqual[re, -1.35e+39], N[(0.5 * N[Sqrt[N[(re * -4.0), $MachinePrecision]], $MachinePrecision]), $MachinePrecision], If[LessEqual[re, 3.8e-142], N[(0.5 * N[Sqrt[N[(2.0 * N[(im - re), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision], If[LessEqual[re, 1.05e-129], N[(im * N[(0.5 / N[Sqrt[re], $MachinePrecision]), $MachinePrecision]), $MachinePrecision], If[Or[LessEqual[re, 2.45e-26], And[N[Not[LessEqual[re, 5.6e+52]], $MachinePrecision], LessEqual[re, 2.85e+85]]], N[(0.5 * N[Sqrt[N[(im * 2.0), $MachinePrecision]], $MachinePrecision]), $MachinePrecision], N[(0.5 * N[(im * N[Power[re, -0.5], $MachinePrecision]), $MachinePrecision]), $MachinePrecision]]]]]

\begin{array}{l}

\\
\begin{array}{l}
\mathbf{if}\;re \leq -1.35 \cdot 10^{+39}:\\
\;\;\;\;0.5 \cdot \sqrt{re \cdot -4}\\

\mathbf{elif}\;re \leq 3.8 \cdot 10^{-142}:\\
\;\;\;\;0.5 \cdot \sqrt{2 \cdot \left(im - re\right)}\\

\mathbf{elif}\;re \leq 1.05 \cdot 10^{-129}:\\
\;\;\;\;im \cdot \frac{0.5}{\sqrt{re}}\\

\mathbf{elif}\;re \leq 2.45 \cdot 10^{-26} \lor \neg \left(re \leq 5.6 \cdot 10^{+52}\right) \land re \leq 2.85 \cdot 10^{+85}:\\
\;\;\;\;0.5 \cdot \sqrt{im \cdot 2}\\

\mathbf{else}:\\
\;\;\;\;0.5 \cdot \left(im \cdot {re}^{-0.5}\right)\\


\end{array}
\end{array}
Derivation
    &prev;&pcontext;&pcontext2;&ctx;
  1. Add Preprocessing

Alternative 3: 75.8% accurate, 1.9× speedup?

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;re \leq -4.1 \cdot 10^{+37}:\\ \;\;\;\;0.5 \cdot \sqrt{re \cdot -4}\\ \mathbf{elif}\;re \leq 2.05 \cdot 10^{-25} \lor \neg \left(re \leq 5.6 \cdot 10^{+52}\right) \land re \leq 2.5 \cdot 10^{+85}:\\ \;\;\;\;0.5 \cdot \sqrt{im \cdot 2}\\ \mathbf{else}:\\ \;\;\;\;0.5 \cdot \left(im \cdot {re}^{-0.5}\right)\\ \end{array} \end{array} \]
(FPCore (re im)
 :precision binary64
 (if (<= re -4.1e+37)
   (* 0.5 (sqrt (* re -4.0)))
   (if (or (<= re 2.05e-25) (and (not (<= re 5.6e+52)) (<= re 2.5e+85)))
     (* 0.5 (sqrt (* im 2.0)))
     (* 0.5 (* im (pow re -0.5))))))
double code(double re, double im) {
	double tmp;
	if (re <= -4.1e+37) {
		tmp = 0.5 * sqrt((re * -4.0));
	} else if ((re <= 2.05e-25) || (!(re <= 5.6e+52) && (re <= 2.5e+85))) {
		tmp = 0.5 * sqrt((im * 2.0));
	} else {
		tmp = 0.5 * (im * pow(re, -0.5));
	}
	return tmp;
}

real(8) function code(re, im)
    real(8), intent (in) :: re
    real(8), intent (in) :: im
    real(8) :: tmp
    if (re <= (-4.1d+37)) then
        tmp = 0.5d0 * sqrt((re * (-4.0d0)))
    else if ((re <= 2.05d-25) .or. (.not. (re <= 5.6d+52)) .and. (re <= 2.5d+85)) then
        tmp = 0.5d0 * sqrt((im * 2.0d0))
    else
        tmp = 0.5d0 * (im * (re ** (-0.5d0)))
    end if
    code = tmp
end function

public static double code(double re, double im) {
	double tmp;
	if (re <= -4.1e+37) {
		tmp = 0.5 * Math.sqrt((re * -4.0));
	} else if ((re <= 2.05e-25) || (!(re <= 5.6e+52) && (re <= 2.5e+85))) {
		tmp = 0.5 * Math.sqrt((im * 2.0));
	} else {
		tmp = 0.5 * (im * Math.pow(re, -0.5));
	}
	return tmp;
}

def code(re, im):
	tmp = 0
	if re <= -4.1e+37:
		tmp = 0.5 * math.sqrt((re * -4.0))
	elif (re <= 2.05e-25) or (not (re <= 5.6e+52) and (re <= 2.5e+85)):
		tmp = 0.5 * math.sqrt((im * 2.0))
	else:
		tmp = 0.5 * (im * math.pow(re, -0.5))
	return tmp

function code(re, im)
	tmp = 0.0
	if (re <= -4.1e+37)
		tmp = Float64(0.5 * sqrt(Float64(re * -4.0)));
	elseif ((re <= 2.05e-25) || (!(re <= 5.6e+52) && (re <= 2.5e+85)))
		tmp = Float64(0.5 * sqrt(Float64(im * 2.0)));
	else
		tmp = Float64(0.5 * Float64(im * (re ^ -0.5)));
	end
	return tmp
end

function tmp_2 = code(re, im)
	tmp = 0.0;
	if (re <= -4.1e+37)
		tmp = 0.5 * sqrt((re * -4.0));
	elseif ((re <= 2.05e-25) || (~((re <= 5.6e+52)) && (re <= 2.5e+85)))
		tmp = 0.5 * sqrt((im * 2.0));
	else
		tmp = 0.5 * (im * (re ^ -0.5));
	end
	tmp_2 = tmp;
end

code[re_, im_] := If[LessEqual[re, -4.1e+37], N[(0.5 * N[Sqrt[N[(re * -4.0), $MachinePrecision]], $MachinePrecision]), $MachinePrecision], If[Or[LessEqual[re, 2.05e-25], And[N[Not[LessEqual[re, 5.6e+52]], $MachinePrecision], LessEqual[re, 2.5e+85]]], N[(0.5 * N[Sqrt[N[(im * 2.0), $MachinePrecision]], $MachinePrecision]), $MachinePrecision], N[(0.5 * N[(im * N[Power[re, -0.5], $MachinePrecision]), $MachinePrecision]), $MachinePrecision]]]

\begin{array}{l}

\\
\begin{array}{l}
\mathbf{if}\;re \leq -4.1 \cdot 10^{+37}:\\
\;\;\;\;0.5 \cdot \sqrt{re \cdot -4}\\

\mathbf{elif}\;re \leq 2.05 \cdot 10^{-25} \lor \neg \left(re \leq 5.6 \cdot 10^{+52}\right) \land re \leq 2.5 \cdot 10^{+85}:\\
\;\;\;\;0.5 \cdot \sqrt{im \cdot 2}\\

\mathbf{else}:\\
\;\;\;\;0.5 \cdot \left(im \cdot {re}^{-0.5}\right)\\


\end{array}
\end{array}
Derivation
    &prev;&pcontext;&pcontext2;&ctx;
  1. Add Preprocessing

Alternative 4: 75.7% accurate, 1.9× speedup?

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;re \leq -2.8 \cdot 10^{+37}:\\ \;\;\;\;0.5 \cdot \sqrt{re \cdot -4}\\ \mathbf{elif}\;re \leq 4.7 \cdot 10^{-24} \lor \neg \left(re \leq 4.4 \cdot 10^{+52}\right) \land re \leq 2.5 \cdot 10^{+85}:\\ \;\;\;\;0.5 \cdot \sqrt{im \cdot 2}\\ \mathbf{else}:\\ \;\;\;\;im \cdot \frac{0.5}{\sqrt{re}}\\ \end{array} \end{array} \]
(FPCore (re im)
 :precision binary64
 (if (<= re -2.8e+37)
   (* 0.5 (sqrt (* re -4.0)))
   (if (or (<= re 4.7e-24) (and (not (<= re 4.4e+52)) (<= re 2.5e+85)))
     (* 0.5 (sqrt (* im 2.0)))
     (* im (/ 0.5 (sqrt re))))))
double code(double re, double im) {
	double tmp;
	if (re <= -2.8e+37) {
		tmp = 0.5 * sqrt((re * -4.0));
	} else if ((re <= 4.7e-24) || (!(re <= 4.4e+52) && (re <= 2.5e+85))) {
		tmp = 0.5 * sqrt((im * 2.0));
	} else {
		tmp = im * (0.5 / sqrt(re));
	}
	return tmp;
}

real(8) function code(re, im)
    real(8), intent (in) :: re
    real(8), intent (in) :: im
    real(8) :: tmp
    if (re <= (-2.8d+37)) then
        tmp = 0.5d0 * sqrt((re * (-4.0d0)))
    else if ((re <= 4.7d-24) .or. (.not. (re <= 4.4d+52)) .and. (re <= 2.5d+85)) then
        tmp = 0.5d0 * sqrt((im * 2.0d0))
    else
        tmp = im * (0.5d0 / sqrt(re))
    end if
    code = tmp
end function

public static double code(double re, double im) {
	double tmp;
	if (re <= -2.8e+37) {
		tmp = 0.5 * Math.sqrt((re * -4.0));
	} else if ((re <= 4.7e-24) || (!(re <= 4.4e+52) && (re <= 2.5e+85))) {
		tmp = 0.5 * Math.sqrt((im * 2.0));
	} else {
		tmp = im * (0.5 / Math.sqrt(re));
	}
	return tmp;
}

def code(re, im):
	tmp = 0
	if re <= -2.8e+37:
		tmp = 0.5 * math.sqrt((re * -4.0))
	elif (re <= 4.7e-24) or (not (re <= 4.4e+52) and (re <= 2.5e+85)):
		tmp = 0.5 * math.sqrt((im * 2.0))
	else:
		tmp = im * (0.5 / math.sqrt(re))
	return tmp

function code(re, im)
	tmp = 0.0
	if (re <= -2.8e+37)
		tmp = Float64(0.5 * sqrt(Float64(re * -4.0)));
	elseif ((re <= 4.7e-24) || (!(re <= 4.4e+52) && (re <= 2.5e+85)))
		tmp = Float64(0.5 * sqrt(Float64(im * 2.0)));
	else
		tmp = Float64(im * Float64(0.5 / sqrt(re)));
	end
	return tmp
end

function tmp_2 = code(re, im)
	tmp = 0.0;
	if (re <= -2.8e+37)
		tmp = 0.5 * sqrt((re * -4.0));
	elseif ((re <= 4.7e-24) || (~((re <= 4.4e+52)) && (re <= 2.5e+85)))
		tmp = 0.5 * sqrt((im * 2.0));
	else
		tmp = im * (0.5 / sqrt(re));
	end
	tmp_2 = tmp;
end

code[re_, im_] := If[LessEqual[re, -2.8e+37], N[(0.5 * N[Sqrt[N[(re * -4.0), $MachinePrecision]], $MachinePrecision]), $MachinePrecision], If[Or[LessEqual[re, 4.7e-24], And[N[Not[LessEqual[re, 4.4e+52]], $MachinePrecision], LessEqual[re, 2.5e+85]]], N[(0.5 * N[Sqrt[N[(im * 2.0), $MachinePrecision]], $MachinePrecision]), $MachinePrecision], N[(im * N[(0.5 / N[Sqrt[re], $MachinePrecision]), $MachinePrecision]), $MachinePrecision]]]

\begin{array}{l}

\\
\begin{array}{l}
\mathbf{if}\;re \leq -2.8 \cdot 10^{+37}:\\
\;\;\;\;0.5 \cdot \sqrt{re \cdot -4}\\

\mathbf{elif}\;re \leq 4.7 \cdot 10^{-24} \lor \neg \left(re \leq 4.4 \cdot 10^{+52}\right) \land re \leq 2.5 \cdot 10^{+85}:\\
\;\;\;\;0.5 \cdot \sqrt{im \cdot 2}\\

\mathbf{else}:\\
\;\;\;\;im \cdot \frac{0.5}{\sqrt{re}}\\


\end{array}
\end{array}
Derivation
    &prev;&pcontext;&pcontext2;&ctx;
  1. Add Preprocessing

Alternative 5: 75.7% accurate, 1.9× speedup?

\[\begin{array}{l} \\ \begin{array}{l} t_0 := 0.5 \cdot \sqrt{im \cdot 2}\\ \mathbf{if}\;re \leq -3.1 \cdot 10^{+37}:\\ \;\;\;\;0.5 \cdot \sqrt{re \cdot -4}\\ \mathbf{elif}\;re \leq 4.5 \cdot 10^{-24}:\\ \;\;\;\;t_0\\ \mathbf{elif}\;re \leq 5.5 \cdot 10^{+52}:\\ \;\;\;\;im \cdot \frac{0.5}{\sqrt{re}}\\ \mathbf{elif}\;re \leq 2.5 \cdot 10^{+85}:\\ \;\;\;\;t_0\\ \mathbf{else}:\\ \;\;\;\;\frac{im \cdot 0.5}{\sqrt{re}}\\ \end{array} \end{array} \]
(FPCore (re im)
 :precision binary64
 (let* ((t_0 (* 0.5 (sqrt (* im 2.0)))))
   (if (<= re -3.1e+37)
     (* 0.5 (sqrt (* re -4.0)))
     (if (<= re 4.5e-24)
       t_0
       (if (<= re 5.5e+52)
         (* im (/ 0.5 (sqrt re)))
         (if (<= re 2.5e+85) t_0 (/ (* im 0.5) (sqrt re))))))))
double code(double re, double im) {
	double t_0 = 0.5 * sqrt((im * 2.0));
	double tmp;
	if (re <= -3.1e+37) {
		tmp = 0.5 * sqrt((re * -4.0));
	} else if (re <= 4.5e-24) {
		tmp = t_0;
	} else if (re <= 5.5e+52) {
		tmp = im * (0.5 / sqrt(re));
	} else if (re <= 2.5e+85) {
		tmp = t_0;
	} else {
		tmp = (im * 0.5) / sqrt(re);
	}
	return tmp;
}

real(8) function code(re, im)
    real(8), intent (in) :: re
    real(8), intent (in) :: im
    real(8) :: t_0
    real(8) :: tmp
    t_0 = 0.5d0 * sqrt((im * 2.0d0))
    if (re <= (-3.1d+37)) then
        tmp = 0.5d0 * sqrt((re * (-4.0d0)))
    else if (re <= 4.5d-24) then
        tmp = t_0
    else if (re <= 5.5d+52) then
        tmp = im * (0.5d0 / sqrt(re))
    else if (re <= 2.5d+85) then
        tmp = t_0
    else
        tmp = (im * 0.5d0) / sqrt(re)
    end if
    code = tmp
end function

public static double code(double re, double im) {
	double t_0 = 0.5 * Math.sqrt((im * 2.0));
	double tmp;
	if (re <= -3.1e+37) {
		tmp = 0.5 * Math.sqrt((re * -4.0));
	} else if (re <= 4.5e-24) {
		tmp = t_0;
	} else if (re <= 5.5e+52) {
		tmp = im * (0.5 / Math.sqrt(re));
	} else if (re <= 2.5e+85) {
		tmp = t_0;
	} else {
		tmp = (im * 0.5) / Math.sqrt(re);
	}
	return tmp;
}

def code(re, im):
	t_0 = 0.5 * math.sqrt((im * 2.0))
	tmp = 0
	if re <= -3.1e+37:
		tmp = 0.5 * math.sqrt((re * -4.0))
	elif re <= 4.5e-24:
		tmp = t_0
	elif re <= 5.5e+52:
		tmp = im * (0.5 / math.sqrt(re))
	elif re <= 2.5e+85:
		tmp = t_0
	else:
		tmp = (im * 0.5) / math.sqrt(re)
	return tmp

function code(re, im)
	t_0 = Float64(0.5 * sqrt(Float64(im * 2.0)))
	tmp = 0.0
	if (re <= -3.1e+37)
		tmp = Float64(0.5 * sqrt(Float64(re * -4.0)));
	elseif (re <= 4.5e-24)
		tmp = t_0;
	elseif (re <= 5.5e+52)
		tmp = Float64(im * Float64(0.5 / sqrt(re)));
	elseif (re <= 2.5e+85)
		tmp = t_0;
	else
		tmp = Float64(Float64(im * 0.5) / sqrt(re));
	end
	return tmp
end

function tmp_2 = code(re, im)
	t_0 = 0.5 * sqrt((im * 2.0));
	tmp = 0.0;
	if (re <= -3.1e+37)
		tmp = 0.5 * sqrt((re * -4.0));
	elseif (re <= 4.5e-24)
		tmp = t_0;
	elseif (re <= 5.5e+52)
		tmp = im * (0.5 / sqrt(re));
	elseif (re <= 2.5e+85)
		tmp = t_0;
	else
		tmp = (im * 0.5) / sqrt(re);
	end
	tmp_2 = tmp;
end

code[re_, im_] := Block[{t$95$0 = N[(0.5 * N[Sqrt[N[(im * 2.0), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]}, If[LessEqual[re, -3.1e+37], N[(0.5 * N[Sqrt[N[(re * -4.0), $MachinePrecision]], $MachinePrecision]), $MachinePrecision], If[LessEqual[re, 4.5e-24], t$95$0, If[LessEqual[re, 5.5e+52], N[(im * N[(0.5 / N[Sqrt[re], $MachinePrecision]), $MachinePrecision]), $MachinePrecision], If[LessEqual[re, 2.5e+85], t$95$0, N[(N[(im * 0.5), $MachinePrecision] / N[Sqrt[re], $MachinePrecision]), $MachinePrecision]]]]]]

\begin{array}{l}

\\
\begin{array}{l}
t_0 := 0.5 \cdot \sqrt{im \cdot 2}\\
\mathbf{if}\;re \leq -3.1 \cdot 10^{+37}:\\
\;\;\;\;0.5 \cdot \sqrt{re \cdot -4}\\

\mathbf{elif}\;re \leq 4.5 \cdot 10^{-24}:\\
\;\;\;\;t_0\\

\mathbf{elif}\;re \leq 5.5 \cdot 10^{+52}:\\
\;\;\;\;im \cdot \frac{0.5}{\sqrt{re}}\\

\mathbf{elif}\;re \leq 2.5 \cdot 10^{+85}:\\
\;\;\;\;t_0\\

\mathbf{else}:\\
\;\;\;\;\frac{im \cdot 0.5}{\sqrt{re}}\\


\end{array}
\end{array}
Derivation
    &prev;&pcontext;&pcontext2;&ctx;
  1. Add Preprocessing

Alternative 6: 63.3% accurate, 2.0× speedup?

\[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;re \leq -1.7 \cdot 10^{+38}:\\ \;\;\;\;0.5 \cdot \sqrt{re \cdot -4}\\ \mathbf{else}:\\ \;\;\;\;0.5 \cdot \sqrt{im \cdot 2}\\ \end{array} \end{array} \]
(FPCore (re im)
 :precision binary64
 (if (<= re -1.7e+38) (* 0.5 (sqrt (* re -4.0))) (* 0.5 (sqrt (* im 2.0)))))
double code(double re, double im) {
	double tmp;
	if (re <= -1.7e+38) {
		tmp = 0.5 * sqrt((re * -4.0));
	} else {
		tmp = 0.5 * sqrt((im * 2.0));
	}
	return tmp;
}

real(8) function code(re, im)
    real(8), intent (in) :: re
    real(8), intent (in) :: im
    real(8) :: tmp
    if (re <= (-1.7d+38)) then
        tmp = 0.5d0 * sqrt((re * (-4.0d0)))
    else
        tmp = 0.5d0 * sqrt((im * 2.0d0))
    end if
    code = tmp
end function

public static double code(double re, double im) {
	double tmp;
	if (re <= -1.7e+38) {
		tmp = 0.5 * Math.sqrt((re * -4.0));
	} else {
		tmp = 0.5 * Math.sqrt((im * 2.0));
	}
	return tmp;
}

def code(re, im):
	tmp = 0
	if re <= -1.7e+38:
		tmp = 0.5 * math.sqrt((re * -4.0))
	else:
		tmp = 0.5 * math.sqrt((im * 2.0))
	return tmp

function code(re, im)
	tmp = 0.0
	if (re <= -1.7e+38)
		tmp = Float64(0.5 * sqrt(Float64(re * -4.0)));
	else
		tmp = Float64(0.5 * sqrt(Float64(im * 2.0)));
	end
	return tmp
end

function tmp_2 = code(re, im)
	tmp = 0.0;
	if (re <= -1.7e+38)
		tmp = 0.5 * sqrt((re * -4.0));
	else
		tmp = 0.5 * sqrt((im * 2.0));
	end
	tmp_2 = tmp;
end

code[re_, im_] := If[LessEqual[re, -1.7e+38], N[(0.5 * N[Sqrt[N[(re * -4.0), $MachinePrecision]], $MachinePrecision]), $MachinePrecision], N[(0.5 * N[Sqrt[N[(im * 2.0), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]]

\begin{array}{l}

\\
\begin{array}{l}
\mathbf{if}\;re \leq -1.7 \cdot 10^{+38}:\\
\;\;\;\;0.5 \cdot \sqrt{re \cdot -4}\\

\mathbf{else}:\\
\;\;\;\;0.5 \cdot \sqrt{im \cdot 2}\\


\end{array}
\end{array}
Derivation
    &prev;&pcontext;&pcontext2;&ctx;
  1. Add Preprocessing

Alternative 7: 51.5% accurate, 2.0× speedup?

\[\begin{array}{l} \\ 0.5 \cdot \sqrt{im \cdot 2} \end{array} \]
(FPCore (re im) :precision binary64 (* 0.5 (sqrt (* im 2.0))))
double code(double re, double im) {
	return 0.5 * sqrt((im * 2.0));
}

real(8) function code(re, im)
    real(8), intent (in) :: re
    real(8), intent (in) :: im
    code = 0.5d0 * sqrt((im * 2.0d0))
end function

public static double code(double re, double im) {
	return 0.5 * Math.sqrt((im * 2.0));
}

def code(re, im):
	return 0.5 * math.sqrt((im * 2.0))

function code(re, im)
	return Float64(0.5 * sqrt(Float64(im * 2.0)))
end

function tmp = code(re, im)
	tmp = 0.5 * sqrt((im * 2.0));
end

code[re_, im_] := N[(0.5 * N[Sqrt[N[(im * 2.0), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]

\begin{array}{l}

\\
0.5 \cdot \sqrt{im \cdot 2}
\end{array}
Derivation
    &prev;&pcontext;&pcontext2;&ctx;
  1. Add Preprocessing

Reproduce

?
herbie shell --seed 2023340 
(FPCore (re im)
  :name "math.sqrt on complex, imaginary part, im greater than 0 branch"
  :precision binary64
  :pre (> im 0.0)
  (* 0.5 (sqrt (* 2.0 (- (sqrt (+ (* re re) (* im im))) re)))))