[mvapich-discuss] one-sided passive communications

[Jim Dinan]

Hi Maria,

Enabling MPICH_ASYNC_PROGRESS does not require you to make any changes 
to your application.  So, you shouldn't need to replace MPI_Init with 
MPI_Init_thread.

  ~Jim.

On 12/11/12 7:09 AM, "María J. Martín" wrote:
> Hi Sreeram,
>
> One more question. Is it necessary to substitute MPI_init by
>   MPI_Init_thread with  required = MPI_THREAD_MULTIPLE  in order to make
> use of the helper threads?
>
> Thanks,
>
> María
>
>
>
> El 05/12/2012, a las 17:10, sreeram potluri escribió:
>
>> Hi Maria,
>>
>> Truly passive one-sided communication is currently supported at the
>> intra-node level (with LiMIC and shared memory-based windows), but not
>> at the inter-node level. Please refer to the following sections of our
>> user guide for further information on the intra-node designs
>>
>> LiMIC:
>> http://mvapich.cse.ohio-state.edu/support/user_guide_mvapich2-1.9a2.html#x1-540006.5
>> Shared Memory Based Windows:
>> http://mvapich.cse.ohio-state.edu/support/user_guide_mvapich2-1.9a2.html#x1-550006.6
>>
>> But, you can enable asynchronous progress for inter-node communication
>> by using helper threads. This can be done using the runtime parameters:
>>
>> MPICH_ASYNC_PROGRESS=1 MV2_ENABLE_AFFINITY=0
>>
>> However, as this involves a helper thread per process, you might see a
>> negative impact on performance when running MPI jobs in fully
>> subscribed mode, due to contention for cores. Do let us know if you
>> have further questions.
>>
>> As a side note, we suggest that you move to our latest standard
>> release MVAPICH2 1.8.1 as it has several features and bug fixes
>> compared to 1.7.
>>
>> Best
>> Sreeram Potluri
>>
>> On Wed, Dec 5, 2012 at 7:15 AM, "María J. Martín"
>> <maria.martin.santamaria at udc.es
>> <mailto:maria.martin.santamaria at udc.es>> wrote:
>>
>>     Hello,
>>
>>     We are using MVAPICH2.1-7 to run an asynchronous algorithm using
>>     one-sided passive communications on an Infiniband cluster. We
>>     observe that some unlocks take a long time to progress. If extra
>>     mpi calls are inserted, the times spent in some unlock calls
>>     decrease. It seems that the target of the remote operation
>>     should enter the MPI library to progress the unlock calls.
>>     However, we had understood from this article
>>     http://nowlab.cse.ohio-state.edu/publications/conf-papers/2008/santhana-ipdps08.pdf that
>>     this requirement was avoided through the use of RDMA data
>>     transfers. We have executed with the MV2_USE_RDMA_ONE_SIDED
>>     parameter set to 1 and to 0 but none difference was observed in
>>     the execution times. Any clarification about the behavior of
>>     passive one-sided communications would be welcome.
>>
>>     Thanks,
>>
>>     María
>>
>>     ---------------------------------------------
>>     María J. Martín
>>     Computer Architecture Group
>>     University of A Coruña
>>     Spain
>>
>>
>>
>>     _______________________________________________
>>     mvapich-discuss mailing list
>>     mvapich-discuss at cse.ohio-state.edu
>>     <mailto:mvapich-discuss at cse.ohio-state.edu>
>>     http://mail.cse.ohio-state.edu/mailman/listinfo/mvapich-discuss
>>
>>
>
>
>
> _______________________________________________
> mvapich-discuss mailing list
> mvapich-discuss at cse.ohio-state.edu
> http://mail.cse.ohio-state.edu/mailman/listinfo/mvapich-discuss
>