[petsc-users] MatAssemblyBegin freezes during MPI communication
袁煕
yuanxi at advancesoft.jp
Thu Jan 18 01:46:47 CST 2024
Dear PETSc Experts,
My FEM program works well generally, but in some specific cases with
multiple CPUs are used, it freezes when calling MatAssemblyBegin where
PMPI_Allreduce is called (see attached file).
After some investigation, I found that it is most probably due to
・ MatSetValue is not called from all CPUs before MatAssemblyBegin
For example, when 4 CPUs are used, if there are elements in CPU 0,1,2 but
no elements in CPU 3, then all CPUs other than CPU 3 would call
MatSetValue function. I want to know
1. If my conjecture could be right? And If so
2. Are there any convenient means to avoid this problem?
Thanks,
Xi YUAN, PhD Solid Mechanics
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