Hi Ralph,
Thanks for the response. And Yes, this give me a good starting point Thanks.
Leo.P
________________________________
From: Ralph Castain <r...@open-mpi.org>
To: Open MPI Developers <de...@open-mpi.org>
Sent: Thursday, 18 June, 2009 9:26:46 PM
Subject: Re: [OMPI devel] some question about OMPI communication infrastructure
Hi Leo
The MPI communications is contained in the ompi/mca/btl code area. The BTL's
(Bit Transport Layer) actually moves the message data. Each BTL is responsible
for opening its own connections - ORTE has nothing to do with it, except to
transport out-of-band (OOB) messages to support creating the connection if that
specific BTL requires it.
If you are interested in TCP communications, you will find all of that code in
ompi/mca/btl/tcp. It can be confusing down there, so expect to spend a little
time trying to understand it. I believe Jeff has some documentation on the OMPI
web site about it (perhaps a video?).
The source/destination is embedded in the message, again done by each BTL since
the receiver must be a BTL of the same type. Again, this has nothing to do with
ORTE - it is purely up to the BTL. MPI communications are also coordinated by
the PML, which is responsible for matching messages with posted receives. You
might need to look at the ompi/mca/pml/ob1 code to understand how that works.
Hope that gives you a starting point
Ralph
On Jun 18, 2009, at 7:57 AM, Leo P. wrote:
Hi Everyone,
I wanted to ask some questions about things I am having trouble understanding.
1. As far as my understanding of MPI_INIT function, I assumed MPI_INIT
typically procedure resources required including the sockets. But now as I
understand from the documentation that openMPI only allocated socket when the
process has to send a message to a peer. If some one could let me where exactly
in the code this is happening I would appreciate a lot. I guess this is
happening in ORTE layer so I am spending time looking at it. But if some one
could let me in which function this is happening it will help me a lot.
2. Also I think most of the MPI implementation embed source and
destination address with the communication protocol. Am I right to assume
openMPI does the same thing. Is this also happening in the ORTE layer.
Is there a documentation about this openMPI site? if there can someone please
let me know the location of it.
Sincerely,
Leo.P
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