  This paper presents, to the author's knowledge, the first graphics processing
unit (GPU) accelerated program that solves the evolution of interacting scalar
fields in an expanding universe. We present the implementation in NVIDIA's
Compute Unified Device Architecture (CUDA) and compare the performance to other
similar programs in chaotic inflation models. We report speedups between one
and two orders of magnitude depending on the used hardware and software while
achieving small errors in single precision. Simulations that used to last
roughly one day to compute can now be done in hours and this difference is
expected to increase in the future. The program has been written in the spirit
of LATTICEEASY and users of the aforementioned program should find it
relatively easy to start using CUDAEASY in lattice simulations. The program is
available at http://www.physics.utu.fi/theory/particlecosmology/cudaeasy/ under
the GNU General Public License.
