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4.1 Running on parallel machines

Parallel execution is strongly system- and installation-dependent. Typically one has to specify:

  1. a launcher program (not always needed), such as poe, mpirun, mpiexec, with the appropriate options (if any);
  2. the number of processors, typically as an option to the launcher program, but in some cases to be specified after the name of the program to be executed;
  3. the program to be executed, with the proper path if needed: for instance, ./neb.x, or $HOME/bin/neb.x, or whatever applies;
  4. other PWscf-specific parallelization options, to be read and interpreted by the running code;
  5. the number of ``images'' used by NEB.
Items 1) and 2) are machine- and installation-dependent, and may be different for interactive and batch execution. Note that large parallel machines are often configured so as to disallow interactive execution: if in doubt, ask your system administrator. Item 3) also depend on your specific configuration (shell, execution path, etc). Item 4) is optional but may be important: see the following section for the meaning of the various options.

For illustration, here is how to run neb.x on 16 processors partitioned into 4 images (4 processors each), for a path containing at least 4 points.

IBM SP machines, batch:

   neb.x -nimages 4 -inp input


next up previous contents
Next: 4.2 Parallelization levels Up: 4 Parallelism Previous: 4 Parallelism   Contents
Layla Martin-Samos Colomer 2012-05-10