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Speaker: Amrita Mathuriya, Intel
Orbital representations that are based on B-splines are widely used in quantum Monte Carlo (QMC) simulations of solids, which historically take as much as 50 percent of the total runtime. Random access to a large four-dimensional array make it challenging to efficiently use caches and wide vector units in modern CPUs. So, we present node-level optimizations of B-spline evaluations on multicore and manycore shared memory processors.
To increase single instruction multiple data (SIMD) efficiency and bandwidth utilization, we first apply data layout transformation from an array of structures (AoS) to a structure of arrays (SoA). Then, by blocking SoA objects, we optimize cache reuse and get sustained throughput for a range of problem sizes. We implement efficient nested threading in B-spline orbital evaluation kernels, paving the way towards enabling strong scaling of QMC simulations, resulting with performance enhancements. Finally, we employ roofline performance analysis to model the impacts of our optimizations.