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June 10, 2008, 08:29 |
Dear OpenFOAMers,
When I de
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#1 |
New Member
Andre
Join Date: Mar 2009
Posts: 19
Rep Power: 17 |
Dear OpenFOAMers,
When I decompose my mesh and run in parallel on 4 cores (with all decomposition techniques), I get a lot of the following warnings: simpleFoam(4449): unaligned access to 0x6000000001fbaf47, ip=0x2000000001ee7ad1 I can disable the warnings with: prctl --unaligned=silent mpirun -np 4 simpleFoam . <casename> -parallel However, the unaligned memory accesses could have a bad effect on the performance. I wonder if am the only one facing them, since I didn't find it else on the forum. The mesh I am using is in the order of 200 MB. I dont get these warnings with other meshes (e.g running pitzDaily on 4 cores) Regards, Andre |
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June 10, 2008, 13:48 |
Do you have processor patches
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#2 |
Senior Member
Mattijs Janssens
Join Date: Mar 2009
Posts: 1,419
Rep Power: 26 |
Do you have processor patches with odd (as in 'not even') sizes? Just check the output of decomposePar - see how many faces you have to neighbouring processors. Does this correlate to whether you get the warning or not?
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June 11, 2008, 05:10 |
Thank you for the always fast
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#3 |
New Member
Andre
Join Date: Mar 2009
Posts: 19
Rep Power: 17 |
Thank you for the always fast replies. Let me output the results of decomposePar tool for this mesh:
---------------------------------------------------- Nprocs : 1 Create time Time = 0 Create mesh Calculating distribution of cells Selecting decompositionMethod metis Finished decomposition in 34.416 s Calculating original mesh data Distributing cells to processors Distributing faces to processors Calculating processor boundary addressing Distributing points to processors Constructing processor meshes Processor 0 Number of cells = 1715464 Number of faces shared with processor 2 = 6885 Number of faces shared with processor 1 = 5946 Number of faces shared with processor 3 = 549 Number of processor patches = 3 Number of processor faces = 13380 Number of boundary faces = 82738 Processor 1 Number of cells = 1713283 Number of faces shared with processor 0 = 5946 Number of processor patches = 1 Number of processor faces = 5946 Number of boundary faces = 90936 Processor 2 Number of cells = 1714303 Number of faces shared with processor 0 = 6885 Number of faces shared with processor 3 = 6981 Number of processor patches = 2 Number of processor faces = 13866 Number of boundary faces = 83589 Processor 3 Number of cells = 1715374 Number of faces shared with processor 2 = 6981 Number of faces shared with processor 0 = 549 Number of processor patches = 2 Number of processor faces = 7530 Number of boundary faces = 85262 Number of processor faces = 20361 Max number of processor patches = 3 Max number of faces between processors = 13866 Processor 0: field transfer Processor 1: field transfer Processor 2: field transfer Processor 3: field transfer End. ---------------------------------------------------- This are the results for decomposing pitzDaily: ---------------------------------------------------- Nprocs : 1 Create time Time = 0 Create mesh Calculating distribution of cells Selecting decompositionMethod metis Finished decomposition in 0.032 s Calculating original mesh data Distributing cells to processors Distributing faces to processors Calculating processor boundary addressing Distributing points to processors Constructing processor meshes Processor 0 Number of cells = 3105 Number of faces shared with processor 1 = 90 Number of processor patches = 1 Number of processor faces = 90 Number of boundary faces = 6382 Processor 1 Number of cells = 3023 Number of faces shared with processor 2 = 68 Number of faces shared with processor 0 = 90 Number of processor patches = 2 Number of processor faces = 158 Number of boundary faces = 6142 Processor 2 Number of cells = 3035 Number of faces shared with processor 3 = 71 Number of faces shared with processor 1 = 68 Number of processor patches = 2 Number of processor faces = 139 Number of boundary faces = 6175 Processor 3 Number of cells = 3062 Number of faces shared with processor 2 = 71 Number of processor patches = 1 Number of processor faces = 71 Number of boundary faces = 6311 Number of processor faces = 229 Max number of processor patches = 2 Max number of faces between processors = 158 Processor 0: field transfer Processor 1: field transfer Processor 2: field transfer Processor 3: field transfer End. ---------------------------------------------------- Regards, Andre |
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June 16, 2008, 08:57 |
Hey Mattijs Janssens,
Can
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#4 |
New Member
Andre
Join Date: Mar 2009
Posts: 19
Rep Power: 17 |
Hey Mattijs Janssens,
Can I safely ignore the warnings, without getting a huge decrease in performance. Regards, Andre |
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June 23, 2008, 08:57 |
No idea. Still quite weird. Do
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#5 |
Senior Member
Mattijs Janssens
Join Date: Mar 2009
Posts: 1,419
Rep Power: 26 |
No idea. Still quite weird. Do you know where the message comes from? The only place I can think of where we interface with the system is inside mpi/Pstream/. During compilation check whether you get any pointer casting warnings.
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June 23, 2008, 10:37 |
I believe this issue is due to
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#6 |
Senior Member
Eugene de Villiers
Join Date: Mar 2009
Posts: 725
Rep Power: 21 |
I believe this issue is due to a bug/issue in your native SGI mpi. We encountered the same problem and it only occurs for one specific patch of RHEL 3 (I think Taroon 4) on the Altix.
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