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Subject: Re: [OMPI devel] MPI Message Communication over TCP/IP
From: Timothy Hayes (hayesti_at_[hidden])
Date: 2009-04-25 10:05:41

I uploaded it to

I'm not sure if it's any good or even if it's 100% accurate; but if someone
gets any use out of it, that would be good.

2009/4/17 Jeff Squyres <jsquyres_at_[hidden]>

> On Apr 16, 2009, at 11:38 AM, Timothy Hayes wrote:
> From what I understand MPI_Send will hit 3 separate layers of code before
>> reaching the socket file descriptors you've found. The PML (Point to Point
>> Messaging Layer) is a layer that bridges the MPI semantics from the
>> underlying point to point communications. The standard PML implementation is
>> called 'ob1' which is what indirectly calls the code you found. MPI_Send
>> should go through pml_isend() or pml_send() which will request a BTL (Byte
>> Transfer Layer) modules from the BML (BTL Management Layer) and invoke the
>> BTL's btl_prepare_src() or btl_alloc() functions before calling the
>> btl_send(). It becomes clearer when you step through it all with a debugger
>> though ;-)
>> If you're interested, I've recently implemented a BTL component of my own
>> and am now writing up a report on the process. It will be ready next week,
>> so if you think it might be useful, just let me know.
> Ooohh... that would be positively yummy! We can even host/link to that on
> :-)
> --
> Jeff Squyres
> Cisco Systems
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