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April 6, 2014, 04:39 |
Question about SU2 convergence
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#1 |
New Member
zhen yi
Join Date: Mar 2014
Posts: 16
Rep Power: 12 |
Hello guys,
In fact, I have a big problem with SU2 now. It’s about metis and convergence. When I use mpirun to run SU2 with different -np numbers, the speedup curve is not an increasing function. For example, when -np = 42 the TestCase runs for thousands Iters with the residual around -4. But when I run SU2 with -np=84 the Testcase exited succeed for 570 Iters, the residual around -1. Why? Does the SU2’s kernel algorithms have different convergence speed with different metis diced? Or may be I got the wrong way? Thank you |
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April 8, 2014, 03:47 |
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#2 |
Super Moderator
Thomas D. Economon
Join Date: Jan 2013
Location: Stanford, CA
Posts: 271
Rep Power: 14 |
Hi,
While the values of the residuals may not be equivalent iteration-by-iteration for implicit, parallel calculations, the residuals should report identical values for every iteration if you choose an explicit method. Unfortunately, it is difficult to identify some problem/mesh-dependent issues. Just to test your installation without any aggressive settings that may be causing issues, you might turn off multigrid (MGLEVEL= 0), switch to explicit time integration (TIME_DISCRE_FLOW= EULER_EXPLICIT), and turn the CFL number down (perhaps CFL= 0.5). Try running several iterations, say 10, on various numbers of processors. If you are still seeing odd behavior and the residuals don't match with each iteration, I recommend that you check your configure options & rebuild the code. Hope this helps, Tom |
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April 8, 2014, 04:02 |
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#3 | |
New Member
zhen yi
Join Date: Mar 2014
Posts: 16
Rep Power: 12 |
Quote:
Thank you |
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Tags |
convergence, metis, mpi, su2 |
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