The most computationally demanding part of Lattice QCD simulations is solving quark propagators. Quark propagators are typically obtained with a linear equation solver utilizing HPC machines. The CCS QCD Benchmark is a benchmark program solving the Wilson-Clover quark propagator, and is developed at the Center for Computational Sciences (CCS), University of Tsukuba. We optimized the benchmark program for a Intel XeonPhi (Knights Corner, KNC) system named COMA (PACS-IX) at CCS Tsukuba under the Intel Parallel Computing Center program. A single precision BiCGStab solver with the overlapped Restricted Additive Schwarz (RAS) preconditioner was implemented using SIMD intrinsics, OpenMP and MPI in the offload mode. With the reverse-offloading technique, we could reduce the communication and offloading overheads. We observed a performance of $sim 200$ GFlops sustained for the Wilson-Clover hopping matrix multiplication on the lattice sizes larger than $24^3times 32$ on a sinlge card of the COMA system. A good weak scaling perofmace was observed on the local lattice sizes larger than $24^3times 32$.
Download