\log \left(N + 1\right) - \log N
\begin{array}{l}
\mathbf{if}\;N \le 9570.307657915993331698700785636901855469:\\
\;\;\;\;\log \left(\frac{N + 1}{N}\right)\\
\mathbf{else}:\\
\;\;\;\;\frac{\left(\frac{1}{{N}^{2}} \cdot \left({\left(\frac{0.3333333333333333148296162562473909929395}{N}\right)}^{3} - {0.5}^{3}\right)\right) \cdot N + \left(\frac{0.3333333333333333148296162562473909929395}{N} \cdot \frac{0.3333333333333333148296162562473909929395}{N} + \left(0.5 \cdot 0.5 + \frac{0.3333333333333333148296162562473909929395}{N} \cdot 0.5\right)\right) \cdot 1}{N \cdot \left(0.5 \cdot \left(0.5 + \frac{0.3333333333333333148296162562473909929395}{N}\right) + \frac{0.3333333333333333148296162562473909929395}{N} \cdot \frac{0.3333333333333333148296162562473909929395}{N}\right)}\\
\end{array}double f(double N) {
double r41333 = N;
double r41334 = 1.0;
double r41335 = r41333 + r41334;
double r41336 = log(r41335);
double r41337 = log(r41333);
double r41338 = r41336 - r41337;
return r41338;
}
double f(double N) {
double r41339 = N;
double r41340 = 9570.307657915993;
bool r41341 = r41339 <= r41340;
double r41342 = 1.0;
double r41343 = r41339 + r41342;
double r41344 = r41343 / r41339;
double r41345 = log(r41344);
double r41346 = 1.0;
double r41347 = 2.0;
double r41348 = pow(r41339, r41347);
double r41349 = r41346 / r41348;
double r41350 = 0.3333333333333333;
double r41351 = r41350 / r41339;
double r41352 = 3.0;
double r41353 = pow(r41351, r41352);
double r41354 = 0.5;
double r41355 = pow(r41354, r41352);
double r41356 = r41353 - r41355;
double r41357 = r41349 * r41356;
double r41358 = r41357 * r41339;
double r41359 = r41351 * r41351;
double r41360 = r41354 * r41354;
double r41361 = r41351 * r41354;
double r41362 = r41360 + r41361;
double r41363 = r41359 + r41362;
double r41364 = r41363 * r41342;
double r41365 = r41358 + r41364;
double r41366 = r41354 + r41351;
double r41367 = r41354 * r41366;
double r41368 = r41367 + r41359;
double r41369 = r41339 * r41368;
double r41370 = r41365 / r41369;
double r41371 = r41341 ? r41345 : r41370;
return r41371;
}



Bits error versus N
Results
if N < 9570.307657915993Initial program 0.1
rmApplied diff-log0.1
if 9570.307657915993 < N Initial program 59.4
Taylor expanded around inf 0.0
Simplified0.0
rmApplied flip3--0.0
Applied associate-*r/0.0
Applied frac-add0.0
Simplified0.0
Final simplification0.1
herbie shell --seed 2019353
(FPCore (N)
:name "2log (problem 3.3.6)"
:precision binary64
(- (log (+ N 1)) (log N)))