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8.4 Parallel execution

Effective usage of parallelism requires some basic knowledge on how parallel machines work and how parallelism is implemented in QUANTUM ESPRESSO. If you have no experience and no clear ideas (or not idea at all), consider reading the section of the User Guide explaining some basic parallelism for QUANTUM ESPRESSO.

8.4.0.1 ''Why is my parallel job running in such a lousy way?''

'''A:''' A frequent reason for lousy parallel performances is a conflict between MPI parallelization (implemented in QUANTUM ESPRESSO) and the autoparallelizing feature of MKL libraries. Set the environment variable OPEN_MP_THREADS to 1. See the section dedicated to this problem in the User Guide.



Paolo Giannozzi 2009-10-01