Report of the Snowmass T7 working group on high performance computing

The T7 Working Group on High Performance Computing (HPC) had more than 30 participants. During the three weeks at Snowmass there were about 30 presentations. This working group also had joint sessions with a number of other working groups, including E1 (Neutrino Factories and Muon Colliders), M1 (Muon Based Systems), M6 (High Intensity Proton Sources), T4 (Particle sources), T5 (Beam dynamics), and T8 (Advanced Accelerators). The topics that were discussed fall naturally into three areas: (1) HPC requirements for next-generation accelerator design, (2) state-of-the-art in HPC simulation of accelerator systems, and (3) applied mathematics and computer science activities related to the development of HPC tools that will be of use to the accelerator community (as well as other communities). This document summarizes the material mentioned above and includes recommendations for future HPC activities in the accelerator community. The relationship of those activities to the HENP/SciDAC project on 21st century accelerator simulation is also discussed