[petsc-users] Question about using Hypre with OpenMP under Petsc

[frank]

Hi Barry,

Thank you for your prompt reply.
Which executable lib should I use ldd to check?

Thank you,
Frank.

On 05/26/2015 02:41 PM, Barry Smith wrote:
>> On May 26, 2015, at 4:18 PM, frank <hengjiew at uci.edu> wrote:
>>
>> Hi
>>
>> I am trying to use multigrid to solve a large sparse linear system. I use Hypre boomeramg as the preconditioner. The code calling KSPSolve is paralleled by MPI.
>>
>> I want to set Hypre to use OpenMP. Here is what I did:
>> * I downloaded and compiled Hypre through Petsc
>> * I recompiled the Hypre with " --with-opemp ".
>     Ok, you need to make sure that PETSc is linking against the OpenMP compiled version of hypre libraries. Use ldd on linux or otool -L on Mac.
>
>> * I set "-pc_type hypre" and "-pc_type_type boomeramg" for Petsc.
>>
>> My question:
>> ? In this way, would Hypre use OpenMP to parallel the execution when KSPSolve is called ?
>> ? If this does not work, is there another way I can set Hypre to use OpenMP under Petsc ?
>> ? Is there a way I can know explicitly whether Hypre is using OpenMP under Petsc or not ?
>     Your question really has little to do with PETSc and more to do with hypre. You need to look through the hypre documentation and find out how you control the number of OpenMP threads that hypre uses (likely it is some environmental variables).  Then run varying this number of threads and see what happens, if you use more threads does it go faster?  It is best to make this test with just a single MPI process and 1,2,4, 8 OpenMP threads.
>
>    Barry
>
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>     
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>> Thank you so much
>> Frank
>>
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