mpimsg - Online in the Cloud

PROGRAM:

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 specified 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 format 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 signature. 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 structures (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 display.

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, nothing is printed.

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