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Subject: Re: [OMPI users] OpenMP + OMPI
From: Brock Palen (brockp_at_[hidden])
Date: 2008-01-12 22:29:23


Thanks

Brock Palen
Center for Advanced Computing
brockp_at_[hidden]
(734)936-1985

On Jan 12, 2008, at 10:20 PM, George Bosilca wrote:

> Both cases should work just fine. In fact as long as there is only
> one execution flow using MPI functions, the user will not face any
> problems.
>
> In a non-threaded build, there is no real progress outside the MPI
> calls. Here by real progress I understand MPI request progress,
> something that is visible from the user level (such as request
> completion).
>
> If a blocking send is used, and the length of the data is under the
> eager limit, the message will stay in the network until the
> receiver access some MPI function. However, in this case the sender
> is free to continue its execution. In the case where the length
> exceed the eager size, the sender will be blocked until the
> corresponding receive is posted (and then the rendez-vous protocol
> completed and data transmitted).
>
> george.
>
> On Jan 12, 2008, at 9:16 PM, Brock Palen wrote:
>
>> Hey guys,
>> I know that threading is very immature (or broken) in the 1.2
>> series, But what happens if a user wants to use a threaded BLAS
>> (GOTO) library with their MPI code and never has OpenMP/pthreads
>> parallel regions with MPI calls? Would this work?
>>
>> What about using OpenMP in their code but again all MPI calls happen
>> outside parallel regions. How would a process who is behind in
>> execution handle a incoming message when it has not yet hit outside
>> the threaded region ware the MPI_Recv() is called? Would the library
>> just hold on to it (if below the eager limit) and wait until someone
>> calls the Recv that matches the message?
>>
>>
>> Brock Palen
>> Center for Advanced Computing
>> brockp_at_[hidden]
>> (734)936-1985
>>
>>
>> _______________________________________________
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>
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