wj - \frac{wj \cdot e^{wj} - x}{e^{wj} + wj \cdot e^{wj}}\begin{array}{l}
\mathbf{if}\;wj \le 5.3258678519809691 \cdot 10^{-17}:\\
\;\;\;\;\left(x + {wj}^{2}\right) - 2 \cdot \left(wj \cdot x\right)\\
\mathbf{else}:\\
\;\;\;\;\frac{wj \cdot \left(\frac{\frac{x}{wj + 1}}{e^{wj}} \cdot \frac{\frac{x}{wj + 1}}{e^{wj}} - wj \cdot wj\right) + \left(1 \cdot \left(\frac{\frac{x}{wj + 1}}{e^{wj}} \cdot \frac{\frac{x}{wj + 1}}{e^{wj}} - wj \cdot wj\right) - \left(\frac{\frac{x}{wj + 1}}{e^{wj}} - wj\right) \cdot wj\right)}{\left(\frac{\frac{x}{wj + 1}}{e^{wj}} - wj\right) \cdot \left(wj + 1\right)}\\
\end{array}double f(double wj, double x) {
double r391143 = wj;
double r391144 = exp(r391143);
double r391145 = r391143 * r391144;
double r391146 = x;
double r391147 = r391145 - r391146;
double r391148 = r391144 + r391145;
double r391149 = r391147 / r391148;
double r391150 = r391143 - r391149;
return r391150;
}
double f(double wj, double x) {
double r391151 = wj;
double r391152 = 5.325867851980969e-17;
bool r391153 = r391151 <= r391152;
double r391154 = x;
double r391155 = 2.0;
double r391156 = pow(r391151, r391155);
double r391157 = r391154 + r391156;
double r391158 = r391151 * r391154;
double r391159 = r391155 * r391158;
double r391160 = r391157 - r391159;
double r391161 = 1.0;
double r391162 = r391151 + r391161;
double r391163 = r391154 / r391162;
double r391164 = exp(r391151);
double r391165 = r391163 / r391164;
double r391166 = r391165 * r391165;
double r391167 = r391151 * r391151;
double r391168 = r391166 - r391167;
double r391169 = r391151 * r391168;
double r391170 = r391161 * r391168;
double r391171 = r391165 - r391151;
double r391172 = r391171 * r391151;
double r391173 = r391170 - r391172;
double r391174 = r391169 + r391173;
double r391175 = r391171 * r391162;
double r391176 = r391174 / r391175;
double r391177 = r391153 ? r391160 : r391176;
return r391177;
}




Bits error versus wj




Bits error versus x
Results
| Original | 13.7 |
|---|---|
| Target | 13.1 |
| Herbie | 1.2 |
if wj < 5.325867851980969e-17Initial program 13.3
Simplified13.3
Taylor expanded around 0 0.8
if 5.325867851980969e-17 < wj Initial program 24.5
Simplified7.3
rmApplied flip-+16.8
Applied frac-sub17.0
rmApplied distribute-rgt-in16.8
Applied associate--l+10.7
Final simplification1.2
herbie shell --seed 2020049
(FPCore (wj x)
:name "Jmat.Real.lambertw, newton loop step"
:precision binary64
:herbie-target
(- wj (- (/ wj (+ wj 1)) (/ x (+ (exp wj) (* wj (exp wj))))))
(- wj (/ (- (* wj (exp wj)) x) (+ (exp wj) (* wj (exp wj))))))