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<p class="MsoNormal"><span style="font-family:"Lucida Grande",sans-serif">To help narrow down the problem, can you try your code with some other MPI implementation on any system? If it works, can you send us a small test program that reproduces the problem?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Lucida Grande",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Lucida Grande",sans-serif">Rajeev<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Lucida Grande",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Lucida Grande",sans-serif"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:12.0pt;color:black">From: </span></b><span style="font-size:12.0pt;color:black">"Mccall, Kurt E. (MSFC-EV41) via discuss" <discuss@mpich.org><br>
<b>Reply-To: </b>"discuss@mpich.org" <discuss@mpich.org><br>
<b>Date: </b>Wednesday, June 14, 2023 at 4:13 PM<br>
<b>To: </b>"discuss@mpich.org" <discuss@mpich.org><br>
<b>Cc: </b>"Mccall, Kurt E. (MSFC-EV41)" <kurt.e.mccall@nasa.gov><br>
<b>Subject: </b>[mpich-discuss] Duplicate reception of messages<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">My code seems to be receiving particular messages more than once -- I can tell from the unique variables they contain.<o:p></o:p></p>
<p class="MsoNormal">I have verified that each unique variable is being sent exactly once. The sender simply calls MPI_ISend to send a single
<o:p></o:p></p>
<p class="MsoNormal">message containing an array of variables.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The receiver pseudo-code is as follows. Have I made a mistake in my use of MPI_Iprobe?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">MPI_Status status;<o:p></o:p></p>
<p class="MsoNormal">int flag;<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">// loop in case there was more than one message queued up due to asynchrony between<o:p></o:p></p>
<p class="MsoNormal">// sender and receiver. Most of the time, there is only one message.
<o:p></o:p></p>
<p class="MsoNormal">do {<o:p></o:p></p>
<p class="MsoNormal"> flag = false;<o:p></o:p></p>
<p class="MsoNormal"> MPI_Iprobe (sender_rank, tag, intercom, &flag, &status);<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"> if (flag)<o:p></o:p></p>
<p class="MsoNormal"> {<o:p></o:p></p>
<p class="MsoNormal"> int len;<o:p></o:p></p>
<p class="MsoNormal"> MPI_Get_count (&status, data_type, &len);<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"> MPI_Recv (buffer, len, data_type, sender_rank, tag, intercom, MPI_STATUS_IGNORE);<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"> // at this point, sometimes I see duplicate variable values in the buffer, in different
<o:p></o:p></p>
<p class="MsoNormal"> // calls to MPI_Recv. That is, s supposedly unique variable appears in two different
<o:p></o:p></p>
<p class="MsoNormal"> // message.<o:p></o:p></p>
<p class="MsoNormal"> }<o:p></o:p></p>
<p class="MsoNormal">} while(flag);<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks for your help. Here is my build information:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">MPICH Version: 4.0.1<o:p></o:p></p>
<p class="MsoNormal">MPICH Release date: Tue Feb 22 16:37:51 CST 2022<o:p></o:p></p>
<p class="MsoNormal">MPICH Device: ch3:nemesis<o:p></o:p></p>
<p class="MsoNormal">MPICH configure: --prefix=/opt/mpich --with-device=ch3:nemesis --with-slurm --disable-fortran -enable-debuginfo --enable-g=debug<o:p></o:p></p>
<p class="MsoNormal">MPICH CC: gcc -g -O2<o:p></o:p></p>
<p class="MsoNormal">MPICH CXX: g++ -g -O2<o:p></o:p></p>
<p class="MsoNormal">MPICH F77: -g<o:p></o:p></p>
<p class="MsoNormal">MPICH FC: -g<o:p></o:p></p>
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