Hello Tim,<br><br>Thanks for providing the details. I was going through the code of MPI_Send and I found a function pointer being invoked mca_pml.send of struct mca_pml_base_module_t. I am trying to figureout when are these PML function pointers get initialized to call internal BTL functions. I am trying to know how MPI program communicate over TPC/IP for message passing in a distributed setup and would appreciate if you can provide more details or any report that you would like to share.<br>
<br>Regards<br>Pranav Jadhav<br><br><div class="gmail_quote">On Thu, Apr 16, 2009 at 11:38 AM, Timothy Hayes <span dir="ltr">&lt;<a href="mailto:hayesti@tcd.ie">hayesti@tcd.ie</a>&gt;</span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div>From what I understand MPI_Send will hit 3 seprate layers of code before reaching the socket file descriptors you&#39;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 &#39;ob1&#39; 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&#39;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 ;-)</div>


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<div>If you&#39;re interested, I&#39;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.</div>


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<div>Tim</div>
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<div class="gmail_quote">2009/4/16 pranav jadhav <span dir="ltr">&lt;<a href="mailto:pranavjadhav@gmail.com" target="_blank">pranavjadhav@gmail.com</a>&gt;</span><br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0px 0px 0px 0.8ex; padding-left: 1ex;"><div><div></div><div class="h5">
<div class="gmail_quote">
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<div><br></div>Hi All,<br><br>I am new to MPI library. I downloaded and started using OpenMPI library to build MPI programs. I wanted to know how does MPI program communicates over the network. I am trying to trace the flow of MPI_Send and MPI_Bcast APIS to find the actual send/recv calls being used for sending the packets over the network. I was trying to look into the code , I found some tcp related socket connections in code base in &quot;ompi/mca/btl/tcp/&quot; but I am not able to figureout how does MPI_Send works. Please if anyone knows how MPI_Send and MPI_Recv APIs works for communicating over network,please let me know. <br>

<br>Thankyou,<br clear="all">
<div><br></div>
<div>Regards,</div>
<div>Pranav Jadhav</div></div>
<div>Stony Brook University</div>
<div><br></div>
<div> </div></div><br></div></div>_______________________________________________<br>devel mailing list<br><a href="mailto:devel@open-mpi.org" target="_blank">devel@open-mpi.org</a><br><a href="http://www.open-mpi.org/mailman/listinfo.cgi/devel" target="_blank">http://www.open-mpi.org/mailman/listinfo.cgi/devel</a><br>

</blockquote></div><br>
<br>_______________________________________________<br>
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<a href="http://www.open-mpi.org/mailman/listinfo.cgi/devel" target="_blank">http://www.open-mpi.org/mailman/listinfo.cgi/devel</a><br></blockquote></div><br><br clear="all"><br>-- <br>Pranav Jadhav<br>Graduate Student<br>
Computer Science Department<br>Stony Brook University<br>NY-11790.<br><br>