MPIMSG(1)							   LAM COMMANDS 							 MPIMSG(1)

NAME

       mpimsg - Monitor MPI message buffers under LAM.

SYNOPSIS

       mpimsg [-gps] [-h] [-O] [-c seq] [-d seq] [-m seq] [-e #] [-B #] [nodes] [processes]

OPTIONS

       -gps	      Print process information in GPS format.

       -h	      Print useful information on this command.

       -O	      Multicomputer is homogeneous.  Do no data conversion.  See mpirun(1).

       -c seq	      Print a description of the communicator used in message seq.  See mpitask(1).

       -d seq	      Print a description of the datatype used in message seq.	See mpitask(1).

       -e nn	      Limit printing the contents of a message to # elements.

       -m seq	      Print the contents of message seq.  See "Message Contents".

       -B nn	      Change the limit on the number of messages reported.

       The -c, -d and -m options are mutually exclusive.

DESCRIPTION

       The mpimsg command displays information on buffered messages which were sent using the MPI library and are currently buffered on the speci-
       fied nodes and destined to the specified processes.  mpimsg typically only works when the "daemon" mode of communication is used; it cannot
       be used to monitor "client to client" (C2C) communications.

       With no processes or nodes explicitly specified on the command line, all MPI messages on all nodes are reported.

       % mpimsg

       SRC (G/L)   DEST (G/L)	TAG   COMM    COUNT   DATATYPE	 MSG
       0/0	   1/1		123   WORLD   64      INT	 n1,#0

       For each message mpimsg outputs the following information:

       SRC	      an  identification  of  the  source process - A `/' followed by the process's rank within the message's communicator is also
		      displayed.  See mpitask(1) for a discussion of process identification.

       DEST	      an identification of the destination process

       TAG	      the tag from the message envelope

       COMM	      the communicator identifier

       COUNT	      the number of data elements in the message

       DATATYPE       the element datatype

       MSG	      the message identifier - It is expressed in the form nnodeid,#seqnum, where nodeid is the physical location of the  buffered
		      message and seqnum is a sequence number assigned to the message by LAM.  These values are used to get further information on
		      the communicator, datatype or message contents.

       More detailed information on the message's communicator or datatype can be obtained with the -c or -d options.  The information is the same
       as obtained by mpitask(1) regarding processes.  Unlike mpitask(1), these options in mpimsg require a message identifier to isolate a single
       message.  Keep in mind that mpimsg invocations are snapshots of system status.  It is possible that a buffered message shown in a  call	of
       mpimsg may be received prior to a subsequent call to mpimsg made in order to display further information.  In this case nothing is printed.

   Message Contents
       If the -m option is given then the contents of the specified message are displayed.

       First  the destination process identification and the message identification is printed and then the message contents are printed in a for-
       mat somewhat similar to that produced by the UNIX utility od(1).  On the left hand side of each line the offset from the beginning  of  the
       data  buffer is printed in hexadecimal.	After that individual elements are printed according to their type as deduced from the type signa-
       ture.  Holes in the datatype and changes in basic type force newlines in the output so in effect all elements on the same  line	of  output
       are actually contiguous in the buffer and of the same basic type.

       The  amount  of	a message that is to be printed can be limited with the -e option.  The limit is specified in terms of a maximum number of
       elements of a basic datatype that are to be printed.  For example if a message consists of 100 structures with  each  structure	containing
       three  integers,  then a limit of 20 would result in the display of the first 20 integers in the message, as opposed to the first 20 struc-
       tures (or 60 integers).

       Buffered message data is by default stored in LAM representation and will be converted to local representation for display.  In the case of
       a  homogeneous  LAM and MPI processes run with the -O switch to mpirun(1) message data will be stored in the common local representation of
       the machines in the LAM.  In this case when using the -m option the -O switch can be given in order to prevent the data conversion for dis-
       play.

EXAMPLES

       mpimsg
	   Report all MPI messages.

       mpimsg n1 -m 8 -e 20
	   Print the first 20 elements of message #8 on node 1.

DIAGNOSTICS

       If no buffered messages are found, only the title line is displayed.  If the message specified by -c, -d or -m is no longer buffered, noth-
       ing is printed.

SEE ALSO

       bfctl(1), bfstate(1), libmpi(3), mpitask(1), sweep(1)

LAM 7.1.4							    July, 2007								 MPIMSG(1)