  We describe a C++ program that we have written and made available for
calculating the evolution of interacting scalar fields in an expanding
universe. The program is particularly useful for the study of reheating and
thermalization after inflation. The program and its full documentation are
available on the Web at http://physics.stanford.edu/gfelder/latticeeasy/ . In
this paper we provide a brief overview of what the program does and what it is
useful for.
