[petsc-users] [petsc-maint] petsc ksp solver hangs

[Zhang, Junchao]

Does it hang with  2 or 4 processes? Which PETSc version do you use (using the latest is easier for us to debug)?  Did you configure PETSc with --with-debugging=yes COPTFLAGS="-O0 -g"  CXXOPTFLAGS="-O0 -g"
After attaching gdb to one process, you can use bt  to see its stack trace.

--Junchao Zhang


On Sat, Sep 28, 2019 at 5:33 AM Michael Wick <michael.wick.1980 at gmail.com<mailto:michael.wick.1980 at gmail.com>> wrote:
I attached a debugger to my run. The code just hangs without throwing an error message, interestingly. I uses 72 processors. I turned on the ksp monitor. And I can see it hangs either at the beginning or the end of KSP iteration. I also uses valgrind to debug my code on my local machine, which does not detect any issue. I uses fgmres + fieldsplit, which is really a standard option.

Do you have any suggestions to do?

On Fri, Sep 27, 2019 at 8:17 PM Zhang, Junchao <jczhang at mcs.anl.gov<mailto:jczhang at mcs.anl.gov>> wrote:
How many MPI ranks did you use? If it is done on your desktop, you can just attach a debugger to a MPI process to see what is going on.

--Junchao Zhang


On Fri, Sep 27, 2019 at 4:24 PM Michael Wick via petsc-maint <petsc-maint at mcs.anl.gov<mailto:petsc-maint at mcs.anl.gov>> wrote:
Hi PETSc:

I have been experiencing a code stagnation at certain KSP iterations. This happens rather randomly, which means the code may stop at the middle of a KSP solve and hangs there.

I have used valgrind and detect nothing. I just wonder if you have any suggestions.

Thanks!!!
M
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