wj - \frac{wj \cdot e^{wj} - x}{e^{wj} + wj \cdot e^{wj}}\begin{array}{l}
\mathbf{if}\;x \le 6.814864601083122 \cdot 10^{-38}:\\
\;\;\;\;x + \left(wj \cdot wj - \left(wj + wj\right) \cdot x\right)\\
\mathbf{else}:\\
\;\;\;\;\left(wj - e^{wj} \cdot \frac{wj \cdot e^{wj} - x}{\left(e^{wj} - wj \cdot e^{wj}\right) \cdot \left(wj \cdot e^{wj} + e^{wj}\right)}\right) - \left(-\frac{wj \cdot e^{wj} - x}{\left(e^{wj} - wj \cdot e^{wj}\right) \cdot \left(wj \cdot e^{wj} + e^{wj}\right)}\right) \cdot \left(wj \cdot e^{wj}\right)\\
\end{array}double f(double wj, double x) {
double r9318539 = wj;
double r9318540 = exp(r9318539);
double r9318541 = r9318539 * r9318540;
double r9318542 = x;
double r9318543 = r9318541 - r9318542;
double r9318544 = r9318540 + r9318541;
double r9318545 = r9318543 / r9318544;
double r9318546 = r9318539 - r9318545;
return r9318546;
}
double f(double wj, double x) {
double r9318547 = x;
double r9318548 = 6.814864601083122e-38;
bool r9318549 = r9318547 <= r9318548;
double r9318550 = wj;
double r9318551 = r9318550 * r9318550;
double r9318552 = r9318550 + r9318550;
double r9318553 = r9318552 * r9318547;
double r9318554 = r9318551 - r9318553;
double r9318555 = r9318547 + r9318554;
double r9318556 = exp(r9318550);
double r9318557 = r9318550 * r9318556;
double r9318558 = r9318557 - r9318547;
double r9318559 = r9318556 - r9318557;
double r9318560 = r9318557 + r9318556;
double r9318561 = r9318559 * r9318560;
double r9318562 = r9318558 / r9318561;
double r9318563 = r9318556 * r9318562;
double r9318564 = r9318550 - r9318563;
double r9318565 = -r9318562;
double r9318566 = r9318565 * r9318557;
double r9318567 = r9318564 - r9318566;
double r9318568 = r9318549 ? r9318555 : r9318567;
return r9318568;
}




Bits error versus wj




Bits error versus x
Results
| Original | 13.7 |
|---|---|
| Target | 13.0 |
| Herbie | 1.8 |
if x < 6.814864601083122e-38Initial program 18.7
Taylor expanded around 0 2.2
Simplified2.2
if 6.814864601083122e-38 < x Initial program 0.7
rmApplied flip-+0.8
Applied associate-/r/0.8
Simplified0.8
rmApplied sub-neg0.8
Applied distribute-lft-in0.8
Applied associate--r+0.8
Final simplification1.8
herbie shell --seed 2019146
(FPCore (wj x)
:name "Jmat.Real.lambertw, newton loop step"
:herbie-target
(- wj (- (/ wj (+ wj 1)) (/ x (+ (exp wj) (* wj (exp wj))))))
(- wj (/ (- (* wj (exp wj)) x) (+ (exp wj) (* wj (exp wj))))))