\cos^{-1} \left({\left(\left(\cosh a\right) \bmod \left(a \cdot a\right)\right)}^{\left(\mathsf{log1p}\left(a\right)\right)}\right)\begin{array}{l}
\mathbf{if}\;a \le 1.555092758736906 \cdot 10^{-162}:\\
\;\;\;\;\cos^{-1} \left({\left(\left(\cosh a\right) \bmod \left(a \cdot a\right)\right)}^{\left(\log \left(1 + a\right)\right)}\right)\\
\mathbf{else}:\\
\;\;\;\;\cos^{-1} \left({\left(\sqrt[3]{\left(\left(\cosh a\right) \bmod \left(a \cdot a\right)\right)}\right)}^{\left(\mathsf{log1p}\left(a\right)\right)} \cdot {\left(\log \left(e^{\sqrt[3]{\left(\left(\cosh a\right) \bmod \left(a \cdot a\right)\right)} \cdot \sqrt[3]{\left(\left(\cosh a\right) \bmod \left(a \cdot a\right)\right)}}\right)\right)}^{\left(\mathsf{log1p}\left(a\right)\right)}\right)\\
\end{array}double f(double a) {
double r5958 = a;
double r5959 = cosh(r5958);
double r5960 = r5958 * r5958;
double r5961 = fmod(r5959, r5960);
double r5962 = log1p(r5958);
double r5963 = pow(r5961, r5962);
double r5964 = acos(r5963);
return r5964;
}
double f(double a) {
double r5965 = a;
double r5966 = 1.555092758736906e-162;
bool r5967 = r5965 <= r5966;
double r5968 = cosh(r5965);
double r5969 = r5965 * r5965;
double r5970 = fmod(r5968, r5969);
double r5971 = 1.0;
double r5972 = r5971 + r5965;
double r5973 = log(r5972);
double r5974 = pow(r5970, r5973);
double r5975 = acos(r5974);
double r5976 = cbrt(r5970);
double r5977 = log1p(r5965);
double r5978 = pow(r5976, r5977);
double r5979 = r5976 * r5976;
double r5980 = exp(r5979);
double r5981 = log(r5980);
double r5982 = pow(r5981, r5977);
double r5983 = r5978 * r5982;
double r5984 = acos(r5983);
double r5985 = r5967 ? r5975 : r5984;
return r5985;
}



Bits error versus a
if a < 1.555092758736906e-162Initial program 64.0
rmApplied log1p-udef61.3
if 1.555092758736906e-162 < a Initial program 58.7
rmApplied add-log-exp56.9
rmApplied add-cube-cbrt56.9
Applied exp-prod56.9
Applied log-pow56.6
Applied unpow-prod-down56.6
Final simplification58.8
herbie shell --seed 2020065 +o rules:numerics
(FPCore (a)
:name "Random Jason Timeout Test 012"
:precision binary64
(acos (pow (fmod (cosh a) (* a a)) (log1p a))))