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Thank you Ken. Really appreciate this. From: Raffenetti, Ken <raffenet@ anl. gov> Date: Thursday, October 10, 2024 at 9: 55 AM To: Niyaz Murshed <Niyaz. Murshed@ arm. com>, discuss@ mpich. org <discuss@ mpich. org> Cc: nd <nd@ arm. com></div>
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<p class="MsoNormal"><span style="font-size:11.0pt">Thank you Ken.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Really appreciate this.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><b><span style="color:black">From:
</span></b><span style="color:black">Raffenetti, Ken <raffenet@anl.gov><br>
<b>Date: </b>Thursday, October 10, 2024 at 9:55</span><span style="font-family:"Arial",sans-serif;color:black"> </span><span style="color:black">AM<br>
<b>To: </b>Niyaz Murshed <Niyaz.Murshed@arm.com>, discuss@mpich.org <discuss@mpich.org><br>
<b>Cc: </b>nd <nd@arm.com><br>
<b>Subject: </b>Re: [mpich-discuss] MPI_Send over ibverbs<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt">This is the post of the recv for the acknowledgement message:
<a href="https://urldefense.us/v3/__https://github.com/pmodels/mpich/blob/824b5b37c8d2e413ead3474f098f7b252f45a3f8/src/mpid/ch4/netmod/ofi/ofi_send.h*L58-L89__;Iw!!G_uCfscf7eWS!fuDIIllrOktlZwT5jyixWqsApj3WQlbM5W6glp4A1-Ypom4MYicGMXutv8Opd164gH4pSGGdEAziyMcPbyM$">
https://github.com/pmodels/mpich/blob/824b5b37c8d2e413ead3474f098f7b252f45a3f8/src/mpid/ch4/netmod/ofi/ofi_send.h#L58-L89</a></span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt">This is where the ack message is sent:
<a href="https://urldefense.us/v3/__https://github.com/pmodels/mpich/blob/824b5b37c8d2e413ead3474f098f7b252f45a3f8/src/mpid/ch4/netmod/ofi/ofi_impl.h*L1084__;Iw!!G_uCfscf7eWS!fuDIIllrOktlZwT5jyixWqsApj3WQlbM5W6glp4A1-Ypom4MYicGMXutv8Opd164gH4pSGGdEAziuIzVU8Y$">
https://github.com/pmodels/mpich/blob/824b5b37c8d2e413ead3474f098f7b252f45a3f8/src/mpid/ch4/netmod/ofi/ofi_impl.h#L1084</a></span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Ken</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
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<b><span style="color:black">From: </span></b><span style="color:black">Niyaz Murshed <Niyaz.Murshed@arm.com><br>
<b>Date: </b>Tuesday, October 8, 2024 at 11:32</span><span style="font-family:"Arial",sans-serif;color:black"> </span><span style="color:black">AM<br>
<b>To: </b>Raffenetti, Ken <raffenet@anl.gov>, discuss@mpich.org <discuss@mpich.org><br>
<b>Cc: </b>nd <nd@arm.com><br>
<b>Subject: </b>Re: [mpich-discuss] MPI_Send over ibverbs</span><o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:1.0pt;color:white">Thank you Ken. Do you know where I can see the code of these acks ; message sequences. From: Raffenetti, Ken <raffenet@</span><span style="font-size:1.0pt;font-family:"Arial",sans-serif;color:white"> </span><span style="font-size:1.0pt;color:white">anl.</span><span style="font-size:1.0pt;font-family:"Arial",sans-serif;color:white"> </span><span style="font-size:1.0pt;color:white">gov>
Date: Tuesday, October 8, 2024 at 11:</span><span style="font-size:1.0pt;font-family:"Arial",sans-serif;color:white"> </span><span style="font-size:1.0pt;color:white">10 AM To: Niyaz Murshed <Niyaz.</span><span style="font-size:1.0pt;font-family:"Arial",sans-serif;color:white"> </span><span style="font-size:1.0pt;color:white">Murshed@</span><span style="font-size:1.0pt;font-family:"Arial",sans-serif;color:white"> </span><span style="font-size:1.0pt;color:white">arm.</span><span style="font-size:1.0pt;font-family:"Arial",sans-serif;color:white"> </span><span style="font-size:1.0pt;color:white">com>,
discuss@</span><span style="font-size:1.0pt;font-family:"Arial",sans-serif;color:white"> </span><span style="font-size:1.0pt;color:white">mpich.</span><span style="font-size:1.0pt;font-family:"Arial",sans-serif;color:white"> </span><span style="font-size:1.0pt;color:white">org</span><o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:11.0pt">Thank you Ken.</span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:11.0pt">Do you know where I can see the code of these acks ; message sequences.</span><o:p></o:p></p>
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<b><span style="color:black">From: </span></b><span style="color:black">Raffenetti, Ken <raffenet@anl.gov><br>
<b>Date: </b>Tuesday, October 8, 2024 at 11:10</span><span style="font-family:"Arial",sans-serif;color:black"> </span><span style="color:black">AM<br>
<b>To: </b>Niyaz Murshed <Niyaz.Murshed@arm.com>, discuss@mpich.org <discuss@mpich.org><br>
<b>Cc: </b>nd <nd@arm.com><br>
<b>Subject: </b>Re: [mpich-discuss] MPI_Send over ibverbs</span><o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:11.0pt">It’s in MPI scope. To my knowledge, that level of acknowledgement is not exposed from the verbs API.</span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:11.0pt">Ken</span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
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<b><span style="color:black">From: </span></b><span style="color:black">Niyaz Murshed <Niyaz.Murshed@arm.com><br>
<b>Date: </b>Tuesday, October 8, 2024 at 11:08</span><span style="font-family:"Arial",sans-serif;color:black"> </span><span style="color:black">AM<br>
<b>To: </b>Raffenetti, Ken <raffenet@anl.gov>, discuss@mpich.org <discuss@mpich.org><br>
<b>Cc: </b>nd <nd@arm.com><br>
<b>Subject: </b>Re: [mpich-discuss] MPI_Send over ibverbs</span><o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:1.0in"><span style="font-size:1.0pt;color:white">Are you talking about the ack of RC connection? Or is it MPI’s scope? From: Raffenetti, Ken <raffenet@</span><span style="font-size:1.0pt;font-family:"Arial",sans-serif;color:white"> </span><span style="font-size:1.0pt;color:white">anl.</span><span style="font-size:1.0pt;font-family:"Arial",sans-serif;color:white"> </span><span style="font-size:1.0pt;color:white">gov>
Date: Tuesday, October 8, 2024 at 11:</span><span style="font-size:1.0pt;font-family:"Arial",sans-serif;color:white"> </span><span style="font-size:1.0pt;color:white">05 AM To: discuss@</span><span style="font-size:1.0pt;font-family:"Arial",sans-serif;color:white"> </span><span style="font-size:1.0pt;color:white">mpich.</span><span style="font-size:1.0pt;font-family:"Arial",sans-serif;color:white"> </span><span style="font-size:1.0pt;color:white">org
<discuss@</span><span style="font-size:1.0pt;font-family:"Arial",sans-serif;color:white"> </span><span style="font-size:1.0pt;color:white">mpich.</span><span style="font-size:1.0pt;font-family:"Arial",sans-serif;color:white"> </span><span style="font-size:1.0pt;color:white">org>
Cc: Niyaz Murshed <Niyaz.</span><span style="font-size:1.0pt;font-family:"Arial",sans-serif;color:white"> </span><span style="font-size:1.0pt;color:white">Murshed@</span><span style="font-size:1.0pt;font-family:"Arial",sans-serif;color:white"> </span><span style="font-size:1.0pt;color:white">arm.</span><span style="font-size:1.0pt;font-family:"Arial",sans-serif;color:white"> </span><span style="font-size:1.0pt;color:white">com>,</span><o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:1.0in"><span style="font-size:11.0pt">Are you talking about the ack of RC connection? Or is it MPI’s scope?</span><o:p></o:p></p>
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<b><span style="color:black">From: </span></b><span style="color:black">Raffenetti, Ken <raffenet@anl.gov><br>
<b>Date: </b>Tuesday, October 8, 2024 at 11:05</span><span style="font-family:"Arial",sans-serif;color:black"> </span><span style="color:black">AM<br>
<b>To: </b>discuss@mpich.org <discuss@mpich.org><br>
<b>Cc: </b>Niyaz Murshed <Niyaz.Murshed@arm.com>, nd <nd@arm.com><br>
<b>Subject: </b>Re: [mpich-discuss] MPI_Send over ibverbs</span><o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:1.0in"><span style="font-size:11.0pt">An internal acknowledgement message is sent from the receiver to the sender indicating that a particular synchronous send operation was matched.</span><o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:1.0in"><span style="font-size:11.0pt">Ken</span><o:p></o:p></p>
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<b><span style="color:black">From: </span></b><span style="color:black">Niyaz Murshed via discuss <discuss@mpich.org><br>
<b>Date: </b>Tuesday, October 8, 2024 at 10:49</span><span style="font-family:"Arial",sans-serif;color:black"> </span><span style="color:black">AM<br>
<b>To: </b>discuss@mpich.org <discuss@mpich.org><br>
<b>Cc: </b>Niyaz Murshed <Niyaz.Murshed@arm.com>, nd <nd@arm.com><br>
<b>Subject: </b>Re: [mpich-discuss] MPI_Send over ibverbs</span><o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:1.5in"><span style="font-size:1.0pt;color:white">Thank you for the reply Joachim. ‘MPI_Ssend has the requirement to return after the message was matched at the receiver’ – From the above statement, how do the sender know
that the receiver called a matching receive? I am asking from the point</span><o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:1.5in"><span style="font-size:11.0pt">Thank you for the reply Joachim.</span><o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:1.5in"><span style="font-size:11.0pt">‘MPI_Ssend has the requirement to return after the message was matched at <br>
the receiver’ –</span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:1.5in"><span style="font-size:11.0pt">From the above statement, how do the sender know that the receiver called a matching receive?</span><o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:1.5in"><span style="font-size:11.0pt">I am asking from the point of view of MPI_Send over RDMA.</span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:1.5in"><span style="font-size:11.0pt">In case of RDMA, internally it will call rdma_send which does not know when a matching rdma_recv was called on destination. How do the sender knows when rdma_recv was called?</span><o:p></o:p></p>
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<b><span style="color:black">From: </span></b><span style="color:black">Joachim Jenke via discuss <discuss@mpich.org><br>
<b>Date: </b>Tuesday, October 8, 2024 at 9:42</span><span style="font-family:"Arial",sans-serif;color:black"> </span><span style="color:black">AM<br>
<b>To: </b>discuss@mpich.org <discuss@mpich.org><br>
<b>Cc: </b>Joachim Jenke <jenke@itc.rwth-aachen.de><br>
<b>Subject: </b>Re: [mpich-discuss] MPI_Send over ibverbs</span><o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:1.5in"><span style="font-size:11.0pt">Hi,<br>
<br>
none of the MPI send calls has a requirement to return after the message <br>
was received. MPI_Send can return as soon as the caller can write to <br>
buffer without impact to the data being transferred. This might be after <br>
the data is put to the network, or the MPI library copied the data to an <br>
internal buffer.<br>
<br>
MPI_Ssend has the requirement to return after the message was matched at <br>
the receiver, which implies that the matching Receive was called. But it <br>
still does not require that the message was received at this point.<br>
<br>
Best<br>
Joachim<br>
<br>
Am 08.10.24 um 04:55 schrieb Niyaz Murshed via discuss:<br>
> Hi,<br>
> <br>
> Is there a way to check the implementation of MPI_Send?<br>
> <br>
> As I understand there is an implicit barrier which allows MPI_Send to <br>
> return only after the buffer is received by the destination.<br>
> <br>
> How is this communication done? How does the destination notify the <br>
> sender that buffer is received?<br>
> <br>
> How is this implemented when using rocev2 ?<br>
> <br>
> Regards,<br>
> <br>
> Niyaz<br>
> <br>
> <br>
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<br>
-- <br>
Dr. rer. nat. Joachim Jenke<br>
<br>
IT Center<br>
Group: High Performance Computing<br>
Division: Computational Science and Engineering<br>
RWTH Aachen University<br>
Seffenter Weg 23<br>
D 52074 Aachen (Germany)<br>
Tel: +49 241 80- 24765<br>
Fax: +49 241 80-624765<br>
jenke@itc.rwth-aachen.de<br>
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