[mpich-discuss] IBM BG/Q collectives

[Jeff Hammond]

That sounds about right.  Some of the names for the BGQ-specific optimized
collectives are pretty elaborate.  SCATTER_MPICH Is tame by comparison :-)

I can't remember if the names are listed in the redbook, but you can always
grep the source code.

Jeff

On Thu, Nov 19, 2015 at 8:24 PM, Jen B <jenbna at gmail.com> wrote:

> Thank you for your answers and helpful suggestions, Rob and Jeff!
>
> I have my last question I hope someone could help me clarify. So I get
> algorithm names for MPI collectives. Is there any convention for them? I
> did not find this information in the redbook. For example, for some of the
> algorithm names I get "SCATTER_MPICH", so I think this means that if the
> algorithm name ends with "_MPICH" then this is using the algorithm from
> MPICH, not the ones optimized for BG/Q. Is this correct?
>
> Thank you!
> Jen
>
>
> On Thu, Nov 19, 2015 at 5:49 PM, Jeff Hammond <jeff.science at gmail.com>
> wrote:
>
>> As Rob said, you will find lots of info in the redbook.  You can set all
>> sorts of debug options to print out the algorithm(s) used on every call, or
>> prescribe them explicitly (not recommended).
>>
>> Jeff
>>
>> On Thu, Nov 19, 2015 at 8:38 AM, Jen B <jenbna at gmail.com> wrote:
>>
>>> Thank you for your quick response, Jeff!
>>>
>>> I was wondering the values for "short" and "large" message sizes,
>>> they've been used throughout the paper but not mentioned explicitly. Do you
>>> happen to know if these values are explicitly mentioned somewhere?
>>>
>>> Also, if I get the last algorithm name used for the MPI collective
>>> routine, is there a way I can for sure tell which algorithm is being used?
>>> For example, is there any name formatting convention that is used.
>>>
>>> Sorry for so many questions. Any help with any of these questions will
>>> be greatly appreciated!
>>>
>>> Thank you!
>>> Jen
>>>
>>>
>>> On Wed, Nov 18, 2015 at 6:06 PM, Jeff Hammond <jeff.science at gmail.com>
>>> wrote:
>>>
>>>> A binary tree is the implementation of last resort.
>>>>
>>>> See these papers for details of the MPI collective implementations on
>>>> Blue Gene:
>>>> - http://dx.doi.org/10.1177/1094342014552086
>>>> - http://dx.doi.org/10.1109/HOTI.2009.12
>>>> (this is not an inclusive list)
>>>>
>>>> http://lists.mpich.org/pipermail/discuss/2015-March/003754.html has
>>>> some related info.
>>>>
>>>> Jeff
>>>>
>>>> On Wed, Nov 18, 2015 at 12:53 PM, Jen B <jenbna at gmail.com> wrote:
>>>>
>>>>> Hello,
>>>>>
>>>>> I have a couple of questions about BG/Q collectives and would
>>>>> appreciate any help.
>>>>> I was wondering if Do IBM BG/Q MPI collectives use binomial tree?
>>>>> Once I find the name of the algorithm used by the MPI collective
>>>>> routine using MPIX_Get_last_algorithm_name, is there a quick reference or
>>>>> guide to check how it is implemented?
>>>>>
>>>>> Thanks!
>>>>> Jen
>>>>>
>>>>>
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>>>>
>>>>
>>>>
>>>> --
>>>> Jeff Hammond
>>>> jeff.science at gmail.com
>>>> http://jeffhammond.github.io/
>>>>
>>>> _______________________________________________
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>>>
>>>
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>>
>>
>>
>> --
>> Jeff Hammond
>> jeff.science at gmail.com
>> http://jeffhammond.github.io/
>>
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>
>
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-- 
Jeff Hammond
jeff.science at gmail.com
http://jeffhammond.github.io/
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