- https://stackoverflow.com/questions/6475373/optimizations-for-pow-with-const-non-integer-exponent

- https://martin.ankerl.com/2007/10/04/optimized-pow-approximation-for-java-and-c-c/

I think it was the second answer to the stackoverflow link that contained a pow() implementation that could be made arbitrarily accurate and took just a few instructions to execute.

Integer optimizations for pow():

- https://gist.github.com/orlp/3551590

- https://github.com/ampl/gsl/blob/master/sys/pow_int.c

I'm not yet finding a library that contains these from google.  The optimizations are almost a decade old.