Brian is totally correct; we just don't have the time to help everyone
debug their MPI codes. But your point is valid as well -- where does
one go to get practical knowledge about MPI?
I should mention that the tutorial Brian cited is actually quite
excellent -- I'd strongly advise looking into it.
But having a community MPI site would be a Good Thing exactly for the
reasons you cited. Some LAM users brought this up a month or three
ago. We started some off-list conversations about it and then I
dropped the ball and never carried through. Mea culpa.
I'll re-start those conversations and see what we come up with.
On Mar 13, 2005, at 8:49 PM, karla b wrote:
> Hi Brian, many thanks for the response
>
>> So what exactly is the problem you are seeing? We (the LAM
>> developers)
>> unfortunately can not provide general debugging assistance - there are
>> too many users and not nearly enough developers. That being said,
>> we're more than willing to answer specific questions you might have
>> about MPI and specifically about the LAM implementation.
>
> I completely understand what you are saying here, however I would
> point out that for new users there seem to be very few places to go to
> receive help when attempting to scale the learning curve of parallel
> programming. Although this problem was posted here, suggestions came
> originally from a subscriber to the list, it simply raises the issue
> of where else is there a central repository of working know how and
> experience? experts exchange for example list only 79 mpi related
> queries.
>
> Most searches on the internet seem to point to academic style lecture
> notes/publications or very high end applications, the nature of which
> can often be very specific or just difficult to comprehend for
> newcommers to parallel programming. As I'm sure was the case with
> everyone subscribed, we all had to learn somewhere and of course by
> attemping solutions and having mistakes pointed out usually leads to
> far better learning than trying to decipher existing code and tailor
> it, so that said, thanks again for pointing out the errors, is there
> anywhere else then that I can go so that I don't keep annoying the LAM
> developers but may get in touch with people who may point out newbie
> (silly) mistakes ??? ; )
>
> Many thanks,
> k
>
>> I do see a couple of problems with your code that seem to indicate a
>> misunderstanding of the MPI send/recv interfaces. You might want to
>> find a good resource on using MPI and work through the examples. One
>> I
>> would suggest is the NCSA's Introduction to MPI:
>>
>> http://webct.ncsa.uiuc.edu:8900/public/MPI/
>>
>> In particular, in the client you have an MPI_Waitany at the top of a
>> while(1) loop, but only post a non-blocking operation outside of the
>> while() loop. This might work the first time through the loop, but
>> after that, you might not have any requests that can be progressed to
>> completion. You also don't call any Test or Wait functions for the
>> non-blocking communication used in the master, so the communication
>> may
>> never complete there.
>>
>>
>> Hope this helps,
>>
>> Brian
>>
>> --
>> Brian Barrett
>> LAM/MPI developer and all around nice guy
>> Have an LAM/MPI day: http://www.lam-mpi.org/
>>
>>
> _______________________________________________
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>
--
{+} Jeff Squyres
{+} jsquyres_at_[hidden]
{+} http://www.lam-mpi.org/
|
