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NOAA-SWPC / IPE

Ionosphere Plasmasphere Electrodynamics Model
GNU General Public License v3.0
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MPI barriers in IPE? #10

Open rmontuoro opened 5 years ago

rmontuoro commented 5 years ago

A few MPI barriers are used in the refactored IPE code.

We should discuss whether such barriers are required or could be eliminated since they affect runtime performance.

gmillward commented 5 years ago

Is this a problem with IPE running coupled to WAM? If it's just a performance issue then this would seem low-priority, unless the performance is terrible for some reason?

rmontuoro commented 5 years ago

It is a low-priority issue, indeed. However, it should be addressed before code delivery since MPI barriers do affect runtime performance and may mask code issues when run in parallel.

gmillward commented 5 years ago

Rafaelle - looking at the code, MPI_barrier is only used (during actual runtime) for writing out the IPE hdf5 'state' files. I think the barrier is in there because Joe had problems with the hdf5 files (ie, they were bogus/corrupted) when there was no barrier. I seem to recall Joe found a few bugs in hdf5 itself....but yeh, if it's a real performance issue then we can see what can be done.

twfang commented 4 years ago

Is it solved? should we close it?

rmontuoro commented 4 years ago

Active MPI barriers have been eliminated after introducing the updated HDF5 I/O layer in IPE.

One barrier still remain in the unused legacy subroutine Write_Electron_Density_to_HDF5 in IPE_Plasma_Class.F90. Can we delete this legacy subroutine, or should it be updated to use the HDF5 I/O later?

rmontuoro commented 4 years ago

Write_Electron_Density_to_HDF5() is not used in IPE and should be removed.