  Iharm3D is an open-source C code for simulating black hole accretion systems
in arbitrary stationary spacetimes using ideal general-relativistic
magnetohydrodynamics (GRMHD). It is an implementation of the HARM ("High
Accuracy Relativistic Magnetohydrodynamics") algorithm outlined in Gammie et
al. (2003) with updates as outlined in McKinney & Gammie (2004) and Noble et
al. (2006). The code is most directly derived from Ryan et al. (2015) but with
radiative transfer portions removed. HARM is a conservative finite-volume
scheme for solving the equations of ideal GRMHD, a hyperbolic system of partial
differential equations, on a logically Cartesian mesh in arbitrary coordinates.
