Use --mca to pass the options directly through the mpirun.
George.
On Wed, Jul 1, 2015 at 9:14 AM, Saliya Ekanayake <esal...@gmail.com> wrote:
> Thank you George. This is very informative.
>
> Is it possible to pass the option in runtime rather setting up in the
> config file?
>
> Thank you
> Saliya
>
> On Tue, Jun 30, 2015 at 7:20 PM, George Bosilca <bosi...@icl.utk.edu>
> wrote:
>
>> Saliya,
>>
>> On Tue, Jun 30, 2015 at 10:50 AM, Saliya Ekanayake <esal...@gmail.com>
>> wrote:
>>
>>> Hi,
>>>
>>> I am experiencing some bottleneck with allgatherv routine in one of our
>>> programs and wonder how it works internally. Could you please share some
>>> details on this?
>>>
>>
>> Open MPI has a tunable approach to all the collective algorithms. In case
>> you have the tuned collective enabled (--mca coll tuned,inter,self,basic as
>> an example) you do have access to the pipelined ring version you made
>> reference to. However, in addition to that particular version you also have
>> access to other, sometimes faster, algorithms such as Bruck.
>>
>> Do a quick "ompi_info --param coll tuned -l 9" to see all the tuned
>> collective options. You can alter the selection of a particular AllgatherV
>> algorithm in Open MPI by adding the 2 following lines in yout
>> ${HOME}/.openmpi/mca-params.conf file.
>> coll_tuned_use_dynamic_rules = 1
>> coll_tuned_allgatherv_algorithm = 3
>> With the above 2 lines I force the Bruck algorithm (which has ID 3 in the
>> output of ompi_info) for all allgathev collectives.
>>
>> You can benchmark the MPI_Allgatherv for your particular case and then
>> force the selection of the right algorithm.
>>
>> George.
>>
>>
>>
>>
>>>
>>> I found this [1] paper from Gropp discussing an efficient
>>> implementation. Is this similar to what we get in OpenMPI?
>>>
>>>
>>>
>>> [1]
>>> http://www.researchgate.net/profile/William_Gropp/publication/221597354_A_Simple_Pipelined_Algorithm_for_Large_Irregular_All-gather_Problems/links/00b49525d291830c67000000.pdf
>>>
>>>
>>>
>>> Thank you,
>>> Saliya
>>> --
>>> Saliya Ekanayake
>>> Ph.D. Candidate | Research Assistant
>>> School of Informatics and Computing | Digital Science Center
>>> Indiana University, Bloomington
>>> Cell 812-391-4914
>>> http://saliya.org
>>>
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>>>
>>
>>
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>>
>
>
>
> --
> Saliya Ekanayake
> Ph.D. Candidate | Research Assistant
> School of Informatics and Computing | Digital Science Center
> Indiana University, Bloomington
> Cell 812-391-4914
> http://saliya.org
>
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