  We describe the implementation and testing of a smoothed particle
hydrodynamics (SPH) code that solves the equations of radiation hydrodynamics
in the flux-limited diffusion (FLD) approximation. The SPH equations of
radiation hydrodynamics for an explicit integration scheme are derived and
tested. We also discuss the implementation of an implicit numerical scheme for
solving the radiation equations that allows the system to be evolved using
timesteps much longer than the explicit radiation timestep. The code is tested
on a variety of one-dimensional radiation hydrodynamics problems including
radiation propagating in an optically thin medium, optically thick and thin
shocks, subcritical and supercritical radiating shocks, and a radiation
dominated shock. Many of the tests were also performed by Turner and Stone
(2001) to test their implementation of a FLD module for the ZEUS-2D code. The
SPH code performs at least as well as the ZEUS-2D code in these tests.
