[Trilinos-Users] ML hangs

[Jonas Thies]

Hi Ray,

I managed to produce a hang with a 3-level hierarchy where I use 
"symmetric Gauss-Seidel" (from Ifpack) on level 0, "do-nothing" on level 
1 and Amesos-KLU on level 3. I also got a hang with Aztec's ILUT 
smoother recently.
What they all have in common is that someone waits for a message never 
posted in the function

      Epetra_MpiDistributor::DoWaits

whereupon the rest gets stuck at whatever MPI call comes next, I guess.

regards,
Jonas

Ray Tuminaro wrote:
> Jonas,
>    Could you try switching to a symmetric Gauss-Seidel smoother to see 
> if things
> still hang?
> -Ray
> 
> 
> Jonas Thies wrote:
>> Hi,
>>
>> I have a rather technical problem with ML.
>> When running in parallel, from time to time the program
>> hangs during an ML preconditioned Aztec solve. I attached
>> a debugger and found the processes are MPI_Waiting in either of these
>> three functions:
>>
>> * Epetra_MpiDistributor::DoWaits
>>
>> * Epetra_MpiComm::SumAll
>>
>> * ML_Comm_CheapWait
>>
>> I'm using a full MGV cycle, my smoother is a non-overlapping
>> Ifpack_AdditiveSchwarz with custom ILU on each subdomain. I'm currently
>> using Trilinos 8.0.5 on 16 IBM Power6 cpu's, the compiler is IBM xlC_r
>> 9.0 with POE MPI.
>>
>> I guess that's pretty vague...
>> I'm not very good with totalview, maybe someone has some hints for me?
>> Or is it a known issue and I just have to update to a more recent
>> Trilinos version? Furthermore, I do not trust the machine and its
>> software :)
>>
>> Thanks,
>> Jonas
>>
>>
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>