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<p>I did not notice this until I was going over the Ballot 4 slides. I would prefer not to vote in the currently proposed wording<br>
<br>
The correction is for page 22, not 222<br>
<br>
I propose:<br>
<tt><br>
MPI 1.1, page 22, line 48 reads<br>
used after a call to MPI_PROBE. (End of rationale.)<br>
but should read<br>
used after a call to MPI_PROBE or MPI_IPROBE. </tt><br>
<tt> In this case the call to MPI_GET_COUNT should use the same</tt><br>
<tt> datatype as will be used in the MPI_RECV.<br>
(End of rationale.) <br>
<br>
(Advice to users.) </tt><br>
<tt> The buffer size required for the receive can be affected by </tt><br>
<tt> data conversions and by the stride of the receive </tt><br>
<tt> datatype. Calling MP_GET_COUNT with MPI_BYTE to calculate the</tt><br>
<tt> receive buffer size may not be portable unless the MPI_RECV </tt><br>
<tt> uses MPI_BYTE.<br>
(End of advice to users.)<br>
</tt><br>
<br>
Dick Treumann - MPI Team/TCEM <br>
IBM Systems & Technology Group<br>
Dept 0lva / MS P963 -- 2455 South Road -- Poughkeepsie, NY 12601<br>
Tele (845) 433-7846 Fax (845) 433-8363<br>
<br>
<img width="16" height="16" src="cid:1__=0ABBFE90DFE750128f9e8a93df938@us.ibm.com" border="0" alt="Inactive hide details for "Rolf Rabenseifner" <rabenseifner@hlrs.de>">"Rolf Rabenseifner" <rabenseifner@hlrs.de><br>
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<ul><b><font size="2">"Rolf Rabenseifner" <rabenseifner@hlrs.de></font></b><font size="2"> </font><br>
<font size="2">Sent by: mpi-21-bounces@cs.uiuc.edu</font>
<p><font size="2">01/18/2008 12:55 PM</font>
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<tr valign="top"><td width="168" bgcolor="#FFFFFF"><div align="center"><font size="2">Please respond to<br>
"Mailing list for discussion of MPI 2.1" <mpi-21@cs.uiuc.edu></font></div></td></tr>
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<div align="right"><font size="2">To</font></div></td><td width="100%"><img width="1" height="1" src="cid:3__=0ABBFE90DFE750128f9e8a93df938@us.ibm.com" border="0" alt=""><br>
<font size="2">mpi-21@cs.uiuc.edu</font></td></tr>
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<font size="2">mpi-21@mpi-forum.org</font></td></tr>
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<div align="right"><font size="2">Subject</font></div></td><td width="100%"><img width="1" height="1" src="cid:3__=0ABBFE90DFE750128f9e8a93df938@us.ibm.com" border="0" alt=""><br>
<font size="2">Re: [mpi-21] problem with MPI_Get_count and MPI_Probe</font></td></tr>
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<tt>This is a proposal for MPI 2.1, Ballot 4.<br>
<br>
This is a follow up to:<br>
Datatypes and MPI_PROBE <br>
in </tt><tt><a href="http://www.cs.uiuc.edu/homes/wgropp/projects/parallel/MPI/mpi-errata/index.html">http://www.cs.uiuc.edu/homes/wgropp/projects/parallel/MPI/mpi-errata/index.html</a></tt><tt><br>
with mail discussion in<br>
</tt><tt><a href="http://www.cs.uiuc.edu/homes/wgropp/projects/parallel/MPI/mpi-errata/discuss/probedatatype/">http://www.cs.uiuc.edu/homes/wgropp/projects/parallel/MPI/mpi-errata/discuss/probedatatype/</a></tt><tt><br>
<br>
<br>
Proposal for MPI 2.1, Ballot 4:<br>
-------------------------------<br>
MPI 1.1, page 222, line 48 reads<br>
used after a call to MPI_PROBE. (End of rationale.)<br>
but should read<br>
used after a call to MPI_PROBE or MPI_IPROBE. <br>
With a status returned from MPI_PROBE or MPI_IPROBE, the same<br>
dataypes are allowed as in a call to MPI_RECV to receive this message.<br>
(End of rationale.) <br>
<br>
Advice to users. To allocate the appropriate amount of memory as receive<br>
buffer, the same datatype as in the following receive call should be used<br>
to determine the needed space. In portable programs due to possible data <br>
conversions, it is not guaranteed that the count returned by MPI_GET_COUNT<br>
with datatype MPI_BYTE is the correct amount of needed memory space in <br>
the receive buffer (although MPI_BYTE is matching every datatype). <br>
(End of advice to users.)<br>
-------------------------------<br>
<br>
Reason for the first part: The current MPI-1.1 text says "The datatype argument<br>
should match the argument provided by the receive call that set the status <br>
variable." With MPI_PROBE, there isn't such a receive call.<br>
<br>
Reason for the advice to users: It helps to write portable code. <br>
Because malloc needs a byte count, users may write wrong programs <br>
by using MPI_BYTE.<br>
<br>
-------------------------------<br>
<br>
Discussion should be done through the new mailing list<br>
mpi-21@cs.uiuc.edu.<br>
<br>
I have sent out this mail with CC through the old general list<br>
mpi-21@mpi-forum.org<br>
<br>
Best regards<br>
Rolf<br>
<br>
<br>
<br>
Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner@hlrs.de<br>
High Performance Computing Center (HLRS) . phone ++49(0)711/685-65530<br>
University of Stuttgart . . . . . . . . .. fax ++49(0)711 / 685-65832<br>
Head of Dpmt Parallel Computing . . . www.hlrs.de/people/rabenseifner<br>
Nobelstr. 19, D-70550 Stuttgart, Germany . (Office: Allmandring 30)<br>
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