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<p class=MsoNormal><font size=2 face="Courier New"><span style='font-size:10.0pt;
font-family:"Courier New"'>You might try having a call like:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Courier New"><span style='font-size:10.0pt;
font-family:"Courier New"'>MPI_Recv( &sourceProcessRank, 1, MPI_INT, MPI_ANY_SOURCE,
0xFF, MPI_COMM_WORLD, &st );<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Courier New"><span style='font-size:10.0pt;
font-family:"Courier New"'>Inside a loop in your parent process (rank 0).
This is equivalent to saying “I’m waiting for somebody to talk to
me, and then asking them who they are.” Obviously the matching
MPI_Send sends the rank id of that child process. Then you can do your
record receiving inside the loop, since sourceProcessRank tells you what
process to receive from for each iteration. You can add a kind of “control”
receive before actually receiving the record, which may get a 0 or a 1 from the
child process indicating whether it has actually found a record and should
start receiving it, or if it is instead done with its search and won’t be
sending any more records. When you have received a “control”
code from each child node indicating it is finished, you exit the loop. You
can send a 1 from the child node if it’s done searching, and use that
value to just increment a counter which you check against the number of child
nodes as your loop condition. I use a solution like this in many
situations. It’s much simplier than requiring MPI thread support.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Courier New"><span style='font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Courier New"><span style='font-size:10.0pt;
font-family:"Courier New"'>Matt<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'> owner-mpich-discuss@mcs.anl.gov
[mailto:owner-mpich-discuss@mcs.anl.gov] <b><span style='font-weight:bold'>On
Behalf Of </span></b>Erich Peterson<br>
<b><span style='font-weight:bold'>Sent:</span></b> Tuesday, April 10, 2007
10:52 PM<br>
<b><span style='font-weight:bold'>To:</span></b> mpich-discuss@mcs.anl.gov<br>
<b><span style='font-weight:bold'>Subject:</span></b> [MPICH] Send and Recv
Guidance Needed</span></font><font size=3 face="Times New Roman"><span
style='font-size:12.0pt;font-family:"Times New Roman"'><o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=2 face=Calibri><span style='font-size:11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Calibri><span style='font-size:11.0pt'>Hi
all,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Calibri><span style='font-size:11.0pt'>
I am trying to come up with the best way to approach this. I am want to have
many processes access a file, each gathering records, using a specified
criteria (which is not important here). I want each process to send each record
(100 bytes long) it matches to process rank 0 as a string. Lastly, I want rank
0 to place all the records it receives into a vector of strings
(vector<string>).<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Calibri><span style='font-size:11.0pt'>
I thought of letting each process call MPI_Send() from each record it matches and
have process rank 0 call MPI_Recv, but, process rank 0 won’t know how
many times to call MPI_Recv to receive all the records.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Calibri><span style='font-size:11.0pt'>
<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Calibri><span style='font-size:11.0pt'>
Thanks,<o:p></o:p></span></font></p>
<p class=MsoNormal style='text-indent:.5in'><font size=2 face=Calibri><span
style='font-size:11.0pt'>Erich<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Calibri><span style='font-size:11.0pt'><o:p> </o:p></span></font></p>
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