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MPI comunication wrong after use of gather/scatter |
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October 5, 2011, 05:09 |
MPI comunication wrong after use of gather/scatter
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#1 |
Member
matteo lombardi
Join Date: Apr 2009
Posts: 67
Rep Power: 16 |
Hello,
I have implemented my own version of a mesh motion solver that, when run in parallel, it needs to exchange data with other partitions. To do so I have used the gather/scatter and IPStream/OPStream functions available in OF. The new library seems to work fine. The problem is that now when i run my code in parallel the fluid solver doesn't work anymore! The residual of U and P solver are very high and looking at the solution (see attached image) it seems like there is no more comunications between processors since there is a very high unphysical boundary layer where the different partitions touch each other. The cube shoew in the picture has been decomposed in 3 subdomain with simple (1 1 3) scheme. The correct result should be a small value everywhere but on the top (cavity problem, initial time step). Any idea how can I have managed to mess up with the MPI comunications in the linear solvers? I haven't touched them at all and my own library I have used only OF MPI functions (i.e. gather/scatter/PStream). Thanks, Matteo |
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October 10, 2011, 13:19 |
Gather/scatter is not the problem... mesh.update() is the trigger..
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#2 |
Member
matteo lombardi
Join Date: Apr 2009
Posts: 67
Rep Power: 16 |
After some more analysis, I have discovered that the problem is not linked at all to gather/scatter...
In fact I have no problem If I use my mesh motion solver as long as i don' t call for mesh.update(). mesh.update() call for my own version of curPoints() anbd solve(). Even If i set solve() to do nothing and curPoitns() just to give back the current mesh points without modifiyng them, I still have the problem described above in parallel.. How can this be possible? What else is called in mesh.update that could create such a strange behaviour? Thanks again, Matteo |
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