  In response to LIGO's observation of GW170104, we performed a series of full
numerical simulations of binary black holes, each designed to replicate likely
realizations of its dynamics and radiation. These simulations have been
performed at multiple resolutions and with two independent techniques to solve
Einstein's equations. For the nonprecessing and precessing simulations, we
demonstrate the two techniques agree mode by mode, at a precision substantially
in excess of statistical uncertainties in current LIGO's observations.
Conversely, we demonstrate our full numerical solutions contain information
which is not accurately captured with the approximate phenomenological models
commonly used to infer compact binary parameters. To quantify the impact of
these differences on parameter inference for GW170104 specifically, we compare
the predictions of our simulations and these approximate models to LIGO's
observations of GW170104.
