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Re: [charm] [ppl] MPI_Allgather


Chronological Thread 
  • From: "Kale, Laxmikant V" <kale AT illinois.edu>
  • To: Shad Kirmani <sxk5292 AT cse.psu.edu>, "Venkataraman, Ramprasad" <ramv AT illinois.edu>
  • Cc: "charm AT cs.uiuc.edu" <charm AT cs.uiuc.edu>
  • Subject: Re: [charm] [ppl] MPI_Allgather
  • Date: Thu, 1 Mar 2012 17:47:00 +0000
  • Accept-language: en-US
  • List-archive: <http://lists.cs.uiuc.edu/pipermail/charm>
  • List-id: CHARM parallel programming system <charm.cs.uiuc.edu>

We often tend to do this things on demand :-)
Actually, right now we are engaged in re-doing collectives with sections (sort of like communicators). So this is a timely request. I will see if we can get a quick implementation for you.

Since the best algorithms are different depending on the message and distributions, can you say: 

. Whats the size of contribution form each core?
. Is it same or very different for different processors? (min, max, average, ..)
. How many nodes and cores are you targeting for now?

Sanjay

-- 
Laxmikant (Sanjay) Kale         http://charm.cs.uiuc.edu
Professor, Computer Science     kale AT illinois.edu
201 N. Goodwin Avenue           Ph:  (217) 244-0094
Urbana, IL  61801-2302          FAX: (217) 265-6582

On 2/29/12 12:03 AM, "Shad Kirmani" <sxk5292 AT cse.psu.edu> wrote:

I want to do MPI_Allgather on group. Having an allgather would have helped a lot. 

Thanks,
Shad

On Tue, Feb 28, 2012 at 4:29 PM, Ramprasad Venkataraman <ramv AT illinois.edu> wrote:
There is not yet a direct way to achieve an allgather in charm.

An immediate mechanism to achieve something like this would be to
perform a reduction using a CkReduction::set or a CkReduction::concat
reducer. The result of the reduction (gather) can then be broadcast to
all the contributing entities.However, data element ordering within
the result is not guaranteed and has to be achieved manually.

What charm entity do you want to do this on: group, chare array, section?

Ram


On Tue, Feb 28, 2012 at 15:12, Shad Kirmani <sxk5292 AT cse.psu.edu> wrote:
> Hello,
>
> I want to do an MPI_Allgather in charm code. Can anybody please help me with
> this?
>
> Thanks,
> Shad
>
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--
Ramprasad Venkataraman
Parallel Programming Lab
Univ. of Illinois

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