  Neutrino oscillation experiments will be entering the precision era in the
next decade with the advent of high statistics experiments like DUNE, HK, and
JUNO. Correctly estimating the confidence intervals from data for the
oscillation parameters requires very large Monte Carlo data sets involving
calculating the oscillation probabilities in matter many, many times. In this
paper, we leverage past work to present a new, fast, precise technique for
calculating neutrino oscillation probabilities in matter optimized for
long-baseline neutrino oscillations in the Earth's crust including both
accelerator and reactor experiments. For ease of use by theorists and
experimentalists, we provide fast c++ and fortran codes.
