\log \left(N + 1\right) - \log N
\begin{array}{l}
\mathbf{if}\;N \le 9516.15297930401:\\
\;\;\;\;\log \left(\frac{1 + N}{N}\right)\\
\mathbf{else}:\\
\;\;\;\;\frac{\frac{\frac{1}{3}}{N}}{N \cdot N} + \left(\frac{1}{N} - \frac{\frac{1}{2}}{N \cdot N}\right)\\
\end{array}double f(double N) {
double r1865089 = N;
double r1865090 = 1.0;
double r1865091 = r1865089 + r1865090;
double r1865092 = log(r1865091);
double r1865093 = log(r1865089);
double r1865094 = r1865092 - r1865093;
return r1865094;
}
double f(double N) {
double r1865095 = N;
double r1865096 = 9516.15297930401;
bool r1865097 = r1865095 <= r1865096;
double r1865098 = 1.0;
double r1865099 = r1865098 + r1865095;
double r1865100 = r1865099 / r1865095;
double r1865101 = log(r1865100);
double r1865102 = 0.3333333333333333;
double r1865103 = r1865102 / r1865095;
double r1865104 = r1865095 * r1865095;
double r1865105 = r1865103 / r1865104;
double r1865106 = r1865098 / r1865095;
double r1865107 = 0.5;
double r1865108 = r1865107 / r1865104;
double r1865109 = r1865106 - r1865108;
double r1865110 = r1865105 + r1865109;
double r1865111 = r1865097 ? r1865101 : r1865110;
return r1865111;
}



Bits error versus N
Results
if N < 9516.15297930401Initial program 0.1
rmApplied add-log-exp0.1
Simplified0.1
if 9516.15297930401 < N Initial program 59.4
Taylor expanded around -inf 0.0
Simplified0.0
Final simplification0.1
herbie shell --seed 2019141
(FPCore (N)
:name "2log (problem 3.3.6)"
(- (log (+ N 1)) (log N)))