Difference between revisions of "MPI"

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(Tips & Tricks)
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* Attach to process(es) from [[GDB]]
 
* Attach to process(es) from [[GDB]]
 
** MPICH-1 runs a background process for each application process: 0, 0b, 1, 1b, ..., therefore, attach to the first ones.
 
** MPICH-1 runs a background process for each application process: 0, 0b, 1, 1b, ..., therefore, attach to the first ones.
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== Profiling ==
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[http://www.bsc.es/plantillaA.php?cat_id=488 Paraver] by Barcelona Supercomputing Center is a "a flexible performance visualization and analysis tool"

Revision as of 20:53, 17 November 2011

Documentation

Implementations

Manual installation

Install in separate subfolder $HOME/SUBDIR, because you may need some MPI implementations (see Libraries)

Tips & Tricks

  • For safe consecutive communications create new context, for example:
int communication_operation(MPI_Comm comm) {
MPI_Comm newcomm;
MPI_Comm_dup(comm, &newcomm);
... // work with newcomm
MPI_Comm_free(&newcomm);
}

Mind the overhead of MPI_Comm_dup and MPI_Comm_free.

  • If you are having trouble with the multi-homed nature of the HCL Cluster, check here

Debugging

  • Add the following code:
int rank;
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
if (!rank)
  getc(stdin);
MPI_Barrier(MPI_COMM_WORLD);
  • Compile your code with -g option
  • Run parallel application
  • Attach to process(es) from GDB
    • MPICH-1 runs a background process for each application process: 0, 0b, 1, 1b, ..., therefore, attach to the first ones.

Profiling

Paraver by Barcelona Supercomputing Center is a "a flexible performance visualization and analysis tool"