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Subject: Re: [OMPI devel] MPI Message Communication over TCP/IP
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2009-04-17 08:13:30

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