Resent-Message-Id: <199911241558.JAA68522@XXXXXXXXXXX>Date: Wed, 24 Nov 1999 10:36:28 -0500
From: "Patrick H. Worley" <worleyph@XXXXXXXX>
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Organization: Oak Ridge National Laboratory
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Subject: problem with MPI_Get_count and MPI_Probe
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Resent-Date: Wed, 24 Nov 1999 10:00:26 -0600
Resent-From: Rusty Lusk <lusk@XXXXXXXXXXX>
Haven't since this is an errata or correction document  ....

1) MPI_Get_count(MPI_Status *status, MPI_Datatype datatype, int *count)

   Returns the number of entries received. (Again, we count entries, 
   each of type datatype, not bytes.) The datatype argument should 
   match the argument provided by the receive call that set the status 
   variable. ... 
  
   The datatype argument is passed to MPI_GET_COUNT so as to improve 
   performance. A message might be received without counting the number 
   of elements it contains, and the count value is often not needed.  
   Also, this allows the same function to be used after a call to
MPI_PROBE. 

2) int MPI_Probe(int source, int tag, MPI_Comm comm, MPI_Status *status)

   ...
   The call matches the same message that would have been received by a 
   call to MPI_RECV(..., source,tag, comm, status) executed at the same 
   point in the program, and returns in status the same value
   that would have been returned by MPI_RECV(). ...
   the content of the status object can be subsequently
   accessed as described in section Return status to find the 
   source, tag and length of the probed message. 

Problem: What datatype should be specified to MPI_Get_count when requesting
         the length of the message found by an MPI_Probe? There is no "matching"
         argument in MPI_Probe. Is it legal (by the standard) to specify
         MPI_BYTE?

Thanks.

Pat Worley