\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 1.542338768776221979718923094404481642848 \cdot 10^{-162}:\\
\;\;\;\;\cos^{-1} \left({\left(\left(\cosh a\right) \bmod \left(a \cdot a\right)\right)}^{\left(2 \cdot \log \left(\sqrt[3]{e^{\mathsf{log1p}\left(a\right)}}\right) + \log \left(\sqrt[3]{e^{\mathsf{log1p}\left(a\right)}}\right)\right)}\right)\\
\mathbf{else}:\\
\;\;\;\;\cos^{-1} \left({\left(\log \left(e^{\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 r23360 = a;
double r23361 = cosh(r23360);
double r23362 = r23360 * r23360;
double r23363 = fmod(r23361, r23362);
double r23364 = log1p(r23360);
double r23365 = pow(r23363, r23364);
double r23366 = acos(r23365);
return r23366;
}
double f(double a) {
double r23367 = a;
double r23368 = 1.542338768776222e-162;
bool r23369 = r23367 <= r23368;
double r23370 = cosh(r23367);
double r23371 = r23367 * r23367;
double r23372 = fmod(r23370, r23371);
double r23373 = 2.0;
double r23374 = log1p(r23367);
double r23375 = exp(r23374);
double r23376 = cbrt(r23375);
double r23377 = log(r23376);
double r23378 = r23373 * r23377;
double r23379 = r23378 + r23377;
double r23380 = pow(r23372, r23379);
double r23381 = acos(r23380);
double r23382 = exp(r23372);
double r23383 = log(r23382);
double r23384 = pow(r23383, r23374);
double r23385 = acos(r23384);
double r23386 = r23369 ? r23381 : r23385;
return r23386;
}



Bits error versus a
if a < 1.542338768776222e-162Initial program 64.0
rmApplied add-log-exp61.3
rmApplied add-cube-cbrt61.3
Applied log-prod61.3
Simplified61.3
if 1.542338768776222e-162 < a Initial program 58.8
rmApplied add-log-exp56.9
Final simplification59.0
herbie shell --seed 2019325
(FPCore (a)
:name "Random Jason Timeout Test 012"
:precision binary64
(acos (pow (fmod (cosh a) (* a a)) (log1p a))))