0.5 \cdot \sqrt{2 \cdot \left(\sqrt{re \cdot re + im \cdot im} - re\right)}\begin{array}{l}
\mathbf{if}\;re \le 1.666629672552327473847126428691428249131 \cdot 10^{65}:\\
\;\;\;\;0.5 \cdot \sqrt{2 \cdot \left(\left(\mathsf{hypot}\left(re, im\right) - re\right) + 0\right)}\\
\mathbf{else}:\\
\;\;\;\;0.5 \cdot \sqrt{2 \cdot \frac{{im}^{2} + 0}{re + \mathsf{hypot}\left(re, im\right)}}\\
\end{array}double f(double re, double im) {
double r32261 = 0.5;
double r32262 = 2.0;
double r32263 = re;
double r32264 = r32263 * r32263;
double r32265 = im;
double r32266 = r32265 * r32265;
double r32267 = r32264 + r32266;
double r32268 = sqrt(r32267);
double r32269 = r32268 - r32263;
double r32270 = r32262 * r32269;
double r32271 = sqrt(r32270);
double r32272 = r32261 * r32271;
return r32272;
}
double f(double re, double im) {
double r32273 = re;
double r32274 = 1.6666296725523275e+65;
bool r32275 = r32273 <= r32274;
double r32276 = 0.5;
double r32277 = 2.0;
double r32278 = im;
double r32279 = hypot(r32273, r32278);
double r32280 = r32279 - r32273;
double r32281 = 0.0;
double r32282 = r32280 + r32281;
double r32283 = r32277 * r32282;
double r32284 = sqrt(r32283);
double r32285 = r32276 * r32284;
double r32286 = 2.0;
double r32287 = pow(r32278, r32286);
double r32288 = r32287 + r32281;
double r32289 = r32273 + r32279;
double r32290 = r32288 / r32289;
double r32291 = r32277 * r32290;
double r32292 = sqrt(r32291);
double r32293 = r32276 * r32292;
double r32294 = r32275 ? r32285 : r32293;
return r32294;
}



Bits error versus re



Bits error versus im
Results
if re < 1.6666296725523275e+65Initial program 33.5
rmApplied add-cube-cbrt33.8
Applied add-sqr-sqrt33.8
Applied sqrt-prod33.9
Applied prod-diff33.9
Simplified7.3
Simplified7.1
if 1.6666296725523275e+65 < re Initial program 59.6
rmApplied flip--59.6
Simplified44.0
Simplified31.7
Final simplification12.1
herbie shell --seed 2019353 +o rules:numerics
(FPCore (re im)
:name "math.sqrt on complex, imaginary part, im greater than 0 branch"
:precision binary64
(* 0.5 (sqrt (* 2 (- (sqrt (+ (* re re) (* im im))) re)))))