[petsc-users] HYPRE BOOMERAMG no output

[Hao Zhang]

CFD is 3D with problem size 150 X 20 X 400 for X, Y and Z direction. : If
I'm using less total number of processors conducting parallel simulation,
the code runs but at late simulating time, my matrix will have 0 max and
min singular value out of nowhere, which confuses me deeply. when I double
the total number of processors, my simulations halt at late simulating
time. I have petsc running options on but no more output no error message.
It's been 12 hours. very weird.

to sum up, 3 problems are:
(1) max(min) singular value  of matrix is 0s starting at late time out of
nowhere with or without BOOMERAMG
(2) different number of processors BOOMERAMG behaves very differently
(3) petsc part halt for unknown reason without crashing or any information

On Tue, Dec 12, 2017 at 9:09 PM, Hao Zhang <hbcbh1999 at gmail.com> wrote:

> Thanks. Barry.
>
>
>
> On Tue, Dec 12, 2017 at 2:03 PM, Smith, Barry F. <bsmith at mcs.anl.gov>
> wrote:
>
>>
>>
>> > On Dec 12, 2017, at 12:04 PM, Hao Zhang <hbcbh1999 at gmail.com> wrote:
>> >
>> > hi,
>> >
>> > before I introduce HYPRE with BOOMERAMG to my CFD code, I will have
>> output with good convergence rate. with BOOMERAMG, the same code will take
>> longer time to run and there's a good chance that no output will be
>> produced whatsoever.
>>
>>   Are you running with -ksp_monitor -ksp_view_pre -ksp_converged_reason ?
>>
>>   If you are using -ksp_monitor and getting no output it could be that
>> hypre is taking a very long time to form the AMG preconditioner, but I
>> won't expect to see this unless the problem is very very big.
>>
>>    You can always run with -start_in_debugger and then type cont in the
>> debugger wait a couple minutes and then use control C in the debugger and
>> type where to determine what it is doing at the time (you can email the
>> output to petsc-maint at mcs.anl.gov).
>>
>>    Boomeramg is not good for all classes of matrices, it is fine for
>> elliptic/parabolic generally but if you hand it something that is
>> hyperbolically dominated it will not work well.
>>
>>    Barry
>>
>> >
>> > what happened? thanks!
>> >
>> > --
>> > Hao Zhang
>> > Dept. of Applid Mathematics and Statistics,
>> > Stony Brook University,
>> > Stony Brook, New York, 11790
>>
>>
>
>
> --
> Hao Zhang
> Dept. of Applid Mathematics and Statistics,
> Stony Brook University,
> Stony Brook, New York, 11790
>



-- 
Hao Zhang
Dept. of Applid Mathematics and Statistics,
Stony Brook University,
Stony Brook, New York, 11790
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