Tensorflow has a pow function.  This is the lite CPU implementation,
   part of an inline header file over 8k lines
   long: [1]https://github.com/tensorflow/tensorflow/blob/8c02285dc2664c2c
   74edbe7d2486f0845a4c499c/tensorflow/lite/kernels/internal/optimized/opt
   imized_ops.h#L6254 .  It automatically performs the integer
   optimization when its argument is an approximate integer.  The floating
   point implementation is labeled "slow".  The file is too big to easily
   review on my phone.
   Tensorflow has GPU implementations of all its ops, and a
   heavily-maintained tensor (numerical array) class.  Tensorflow's build
   system is bazel which has poor compatibility, but it just a pile of
   compilable sourcefiles.
   GPU is highly valued but a fast floating point pow approximation could
   be missing from tensorflow, unsure it's hard to look.

References

   1. https://github.com/tensorflow/tensorflow/blob/8c02285dc2664c2c74edbe7d2486f0845a4c499c/tensorflow/lite/kernels/internal/optimized/optimized_ops.h#L6254