  When a gravitational wave is detected by Advanced LIGO/Virgo, sophisticated
parameter estimation (PE) pipelines spring into action. These pipelines
leverage approximants to generate large numbers of theoretical gravitational
waveform predictions to characterize the detected signal. One of the most
accurate and physically comprehensive classes of approximants in wide use is
the "Spinning Effective One Body--Numerical Relativity" (SEOBNR) family.
Waveform generation with these approximants can be computationally expensive,
which has limited their usefulness in multiple data analysis contexts. In prior
work we improved the performance of the aligned-spin approximant SEOBNR version
2 (v2) by nearly 300x. In this work we focus on optimizing the full
eight-dimensional, precessing approximant SEOBNR version 3 (v3). While several
v2 optimizations were implemented during its development, v3 is far too slow
for use in state-of-the-art source characterization efforts for long-inspiral
detections. Completion of a PE run after such a detection could take centuries
to complete using v3. Here we develop and implement a host of optimizations for
v3, calling the optimized approximant v3_Opt. Our optimized approximant is
about 340x faster than v3, and generates waveforms that are numerically
indistinguishable.
