TotalView Users Guide - CI Wiki

Displaying the Message Queue
play its Tools > Message Queue Window, which has detailed information
about the messages. If TotalView has not attached to a process, it displays
this information in a grey box.
You can use the Message Queue Graph Window in many ways, including the
following:
� Pending messages often indicate that a process can’t keep up with the
amount of work it is expected to perform. These messages indicate
places where you may be able to improve your program’s efficiency.
� Unexpected messages can indicate that something is wrong with your
program because the receiving process doesn’t know how to process the
message. The red lines indicate unexpected messages.
� After a while, the shape of the graph tends to tell you something about
how your program is executing. If something doesn’t look right, you
might want to determine why.
� You can change the shape of the graph by dragging nodes or arrows. This
is often useful when you’re comparing sets of nodes and their messages
with one another. Ordinarily, TotalView doesn’t remember the places to
which you have dragged the nodes and arrows. This means that if you select
the Update button after you arrange the graph, your changes are
lost. However, if you select Keep nodes as positioned from with the
Options dialog box, updating the window does not change node positioning.
Displaying the Message Queue
The Tools > Message Queue Window displays your MPI program’s message
queue state textually. This can be useful when you need to find out why a
deadlock occurred.
The MPI versions for which we display the message queue are described in
our platforms guide. This document is contained within the online help and
is also available on our web site at http://www.totalviewtech.com/Documentation/
For more information, see:
� “About the Message Queue Display” on page 109
� “Using Message Operations” on page 110
About the Message Queue Display
After an MPI process returns from the call to MPI_Init(), you can display the
internal state of the MPI library by selecting the Tools > Message Queue
command. (See Figure 89 on page 110.)
This window displays the state of the process’s MPI communicators. If
user-visible communicators are implemented as two internal communica-
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