\sqrt{\frac{e^{2 \cdot x} - 1}{e^{x} - 1}}\begin{array}{l}
\mathbf{if}\;x \le -4.284857974241761 \cdot 10^{-11}:\\
\;\;\;\;\sqrt{\frac{e^{2 \cdot x} - 1}{\mathsf{fma}\left(-1, 1, e^{x + x}\right)} \cdot \frac{{\left(e^{x}\right)}^{3} + {1}^{3}}{\mathsf{fma}\left(1, 1 - e^{x}, e^{2 \cdot x}\right)}}\\
\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 r13584 = 2.0;
double r13585 = x;
double r13586 = r13584 * r13585;
double r13587 = exp(r13586);
double r13588 = 1.0;
double r13589 = r13587 - r13588;
double r13590 = exp(r13585);
double r13591 = r13590 - r13588;
double r13592 = r13589 / r13591;
double r13593 = sqrt(r13592);
return r13593;
}
double f(double x) {
double r13594 = x;
double r13595 = -4.2848579742417606e-11;
bool r13596 = r13594 <= r13595;
double r13597 = 2.0;
double r13598 = r13597 * r13594;
double r13599 = exp(r13598);
double r13600 = 1.0;
double r13601 = r13599 - r13600;
double r13602 = -r13600;
double r13603 = r13594 + r13594;
double r13604 = exp(r13603);
double r13605 = fma(r13602, r13600, r13604);
double r13606 = r13601 / r13605;
double r13607 = exp(r13594);
double r13608 = 3.0;
double r13609 = pow(r13607, r13608);
double r13610 = pow(r13600, r13608);
double r13611 = r13609 + r13610;
double r13612 = r13600 - r13607;
double r13613 = 2.0;
double r13614 = r13613 * r13594;
double r13615 = exp(r13614);
double r13616 = fma(r13600, r13612, r13615);
double r13617 = r13611 / r13616;
double r13618 = r13606 * r13617;
double r13619 = sqrt(r13618);
double r13620 = 0.5;
double r13621 = pow(r13594, r13613);
double r13622 = fma(r13600, r13594, r13597);
double r13623 = fma(r13620, r13621, r13622);
double r13624 = sqrt(r13623);
double r13625 = r13596 ? r13619 : r13624;
return r13625;
}



Bits error versus x
if x < -4.2848579742417606e-11Initial program 0.4
rmApplied flip--0.2
Applied associate-/r/0.2
Simplified0.0
rmApplied flip3-+0.0
Simplified0.0
if -4.2848579742417606e-11 < x Initial program 34.7
Taylor expanded around 0 7.6
Simplified7.6
Final simplification0.9
herbie shell --seed 2020100 +o rules:numerics
(FPCore (x)
:name "sqrtexp (problem 3.4.4)"
:precision binary64
(sqrt (/ (- (exp (* 2 x)) 1) (- (exp x) 1))))