Steve Lantz (original author), Brandon Barker
Cornell Center for Advanced Computing

Revisions: 2/2024, 1/2023, 11/2020, 1/2014, 6/2011 (original)

Hybrid programming is a coding strategy to create programs that make the best use of multi-node HPC systems. HPC cluster architectures are necessarily characterized by NUMA: Non-Uniform Memory Access. In multi-node systems, global memory is distributed across all the nodes, but shared within nodes (though divided among sockets within a node).

  • A multithreaded programming strategy is effective and efficient for shared memory, but a program that relies only on shared memory can only use the resources of a single node.
  • A message passing strategy permits processes on different nodes to communicate with one another but cannot take advantage of the efficiency of shared memory.

A hybrid strategy combines multithreading within nodes and message passing between nodes.


After you complete this workshop, you should be able to:

  • Explain how HPC cluster hardware configuration relates to shared memory and distributed memory
  • Compare programming strategies for shared and distributed memory
  • Distinguish between using OpenMP vs. MPI when writing parallel programs
  • Discuss reasons to use or not use hybrid programming
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