Working Group Report: Lattice Field Theory

This is the report of the Computing Frontierworking group on Lattice Field Theoryprepared for the proceedings of the 2013 Community Summer Study ("Snowmass"). We present the future computing needs and plans of the U.S. lattice gauge theorycommunity and argue that continued support of the U.S. (and worldwide) lattice-QCDeffort is essential to fully capitalize on the enormous investment in the high-energy physics experimental program. We first summarize the dramatic progress of numerical lattice-QCDsimulations in the past decade, with some emphasis on calculations carried out under the auspices of the U.S. Lattice-QCDCollaboration, and describe a broad program of lattice-QCDcalculations that will be relevant for future experiments at the intensity and energy frontiers. We then present details of the computational hardwareand software resources needed to undertake these calculations.