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Subsections

12.5 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 Sec.3.

12.5.0.1 How do I choose the number of processors/how do I setup my parallel calculation?

Please see above.

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

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 Sec.3 for more info.

12.5.0.3 Why is my parallel job crashing when reading input data / doing nothing?

If the same data work in serial execution, use code -inp input_file instead of code < input_file. Some MPI libraries do not properly handle input redirection.

12.5.0.4 The code stops with an error reading namelist xxxx

Most likely there is a misspelled variable in namelist xxxx. If there isn't any (have you looked carefully? really?? REALLY???), beware control characters like DOS control-M: they can confuse the namelist-reading code. If this happens to the first namelist to be read (usually "&CONTROL") in parallel execution, see above.


next up previous contents
Next: 12.6 Frequent errors during Up: 12 Frequently Asked Questions Previous: 12.4 Input data   Contents
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