\sqrt{\frac{e^{2 \cdot x} - 1}{e^{x} - 1}}\begin{array}{l}
\mathbf{if}\;x \le -5.69778124812825276 \cdot 10^{-17}:\\
\;\;\;\;\sqrt{\frac{\mathsf{expm1}\left(\mathsf{log1p}\left(\mathsf{fma}\left(\sqrt{e^{2 \cdot x}}, \sqrt{e^{2 \cdot x}}, -1\right)\right)\right)}{e^{x} - 1}}\\
\mathbf{else}:\\
\;\;\;\;\sqrt{\mathsf{fma}\left(0.5, {x}^{2}, \mathsf{fma}\left(1, x, 2\right)\right)}\\
\end{array}double f(double x) {
double r25474 = 2.0;
double r25475 = x;
double r25476 = r25474 * r25475;
double r25477 = exp(r25476);
double r25478 = 1.0;
double r25479 = r25477 - r25478;
double r25480 = exp(r25475);
double r25481 = r25480 - r25478;
double r25482 = r25479 / r25481;
double r25483 = sqrt(r25482);
return r25483;
}
double f(double x) {
double r25484 = x;
double r25485 = -5.697781248128253e-17;
bool r25486 = r25484 <= r25485;
double r25487 = 2.0;
double r25488 = r25487 * r25484;
double r25489 = exp(r25488);
double r25490 = sqrt(r25489);
double r25491 = 1.0;
double r25492 = -r25491;
double r25493 = fma(r25490, r25490, r25492);
double r25494 = log1p(r25493);
double r25495 = expm1(r25494);
double r25496 = exp(r25484);
double r25497 = r25496 - r25491;
double r25498 = r25495 / r25497;
double r25499 = sqrt(r25498);
double r25500 = 0.5;
double r25501 = 2.0;
double r25502 = pow(r25484, r25501);
double r25503 = fma(r25491, r25484, r25487);
double r25504 = fma(r25500, r25502, r25503);
double r25505 = sqrt(r25504);
double r25506 = r25486 ? r25499 : r25505;
return r25506;
}



Bits error versus x
if x < -5.697781248128253e-17Initial program 1.0
rmApplied add-sqr-sqrt0.8
Applied fma-neg0.3
rmApplied expm1-log1p-u0.3
if -5.697781248128253e-17 < x Initial program 37.1
Taylor expanded around 0 9.3
Simplified9.3
Final simplification1.3
herbie shell --seed 2020034 +o rules:numerics
(FPCore (x)
:name "sqrtexp (problem 3.4.4)"
:precision binary64
(sqrt (/ (- (exp (* 2 x)) 1) (- (exp x) 1))))