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Subject: Re: [OMPI devel] matching code rewrite in OB1
From: Brian W. Barrett (brbarret_at_[hidden])
Date: 2007-12-12 16:10:10


On Wed, 12 Dec 2007, Gleb Natapov wrote:

> On Wed, Dec 12, 2007 at 03:46:10PM -0500, Richard Graham wrote:
>> This is better than nothing, but really not very helpful for looking at the
>> specific issues that can arise with this, unless these systems have several
>> parallel networks, with tests that will generate a lot of parallel network
>> traffic, and be able to self check for out-of-order received - i.e. this
>> needs to be encoded into the payload for verification purposes. There are
>> some out-of-order scenarios that need to be generated and checked. I think
>> that George may have a system that will be good for this sort of testing.
>>
> I am running various test with multiple networks right now. I use
> several IB BTLs and TCP BTL simultaneously. I see many reordered
> messages and all tests were OK till now, but they don't encode
> message sequence in a payload as far as I know. I'll change one of
> them to do so.

Other than Rich's comment that we need sequence numbers, why add them? We
haven't had them for non-matching packets for the last 3 years in Open MPI
(ie, forever), and I can't see why we would need them. Yes, we need
sequence numbers for match headers to make sure MPI ordering is correct.
But for the rest of the payload, there's no need with OMPI's datatype
engine. It's just more payload for no gain.

Brian