Eijkhout, Chow, and van de Geijn's "Introduction to High-Performance Scientific Computing, Chapter 2: Parallel Computer Architecture"
Read section 2.5 of Chapter 2 on pages 52-68. The reading covers two extreme approaches to parallel programming. First, parallelism is handled by the lower software and hardware layers. OpenMP is applicable in this first case. Secondly, parallelism is handled by the programmer. MPI is applicable in the second case.
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