[petsc-users] Quite different behaviours of PETSc solver on different clusters

[Su,D.S. Danyang]

Dear PETSc users,

This is a question bother me for some time. I have the same code running on different clusters and both clusters have good speedup. However, I noticed some thing quite strange. On one cluster, the solver is quite stable in computing time while on another cluster, the solver is unstable in computing time. As shown in the figure below, the local calculation almost has no communication and the computing time in this part is quite stable. However, PETSc solver on Cluster B jumps quite a lot and the performance is not as good as Cluster A, even though the local calculation is a little better on Cluster B. There are some difference on hardware and PETSc configuration and optimization. Cluster A uses OpenMPI + GCC compiler and Cluster B uses MPICH + GCC compiler. The number of processors used is 128 on Cluster A and 120 on Cluster B. I also tested different number of processors but the problem is the same. Does anyone have any idea which part might cause this problem?

[cid:image001.png at 01D6ADEB.30817A80]

[cid:image002.png at 01D6ADEB.30817A80]

Thanks and regards,

Danyang

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