[petsc-users] MatAssemblyEnd taking too long

[Junchao Zhang]

See if you could reproduce the problem on another machine, e.g., a Linux
workstation with MPICH?

--Junchao Zhang


On Wed, Aug 19, 2020 at 7:32 PM Manav Bhatia <bhatiamanav at gmail.com> wrote:

> Hi,
>
>    I have an application that uses the KSP solver and I am looking at the
> performance with increasing system size. I am currently running on MacBook
> Pro with 32 GB memory and Petsc obtained from GitHub (commit
> df0e43005dbe6ff47eff22a32b336a6c37d02c3a).
>
>    The application runs fine till about 2e6 DoFs using gamg without any
> problems.
>
>    However, when I try a larger system size, in this case with 5.4e6 DoFs,
> the application hangs for an hour and I have to kill the MPI processes.
>
>    I tried to use Xcode Instruments to profile the 8 MPI processes and I
> have attached a screenshot of the recorded results from each process. All
> processes are stuck inside MatAssemblyEnd, but at different function calls.
>
>    I am not sure how to debug this issue, and would greatly appreciate any
> guidance.
>
>    For reference, I am calling PETSc with the following options:
>   -ksp_type gmres -pc_type gamg -mat_block_size 3 -mg_levels_ksp_max_it 4
> -ksp_monitor -ksp_converged_reason
>
> Regards,
> Manav
>
>
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