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High Performance Parallelism Pearls Volume Two by James Reinders, Jim Jeffers

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Chapter 18

Exploiting Multilevel Parallelism in Quantum Simulations

Jeongnim Kim; Lawrence Meadows    Intel Corporation, USA

Abstract

Exploiting multilevel parallelism deserves consideration even if rejected in the past. OpenMP nesting is turned off by default by most implementations, and is generally consider unsafe by typical users due to concerns of oversubscription and the resulting poor application performance. Proper considerations of how to express and use nested parallelism can have a profound impact on performance. This chapter segments this challenge into two parts: nesting of OpenMP within an MPI program, and then use of nesting within OpenMP itself. This logical decomposition provides the understanding necessary to make proper ...

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