TotalView Users Guide - CI Wiki

Debugging Parallel Applications Tips
Figure 92: Stop Before Going
Parallel Question Box
Figure 93: File > Preferences:
Parallel Page
Many applications place values that indicate the rank in a variable so that
the program can refer to them as they are needed. If you do this, you can
display the variable in a Variable Window and then select the Tools > Attach
Subset (Array of Ranks) command to display this dialog box.
You can use the Group > Attach Subset command at any time, but you
would probably use it immediately before TotalView launches processes.
Unless you have set preferences otherwise, TotalView stops and asks if you
want it to stop your processes. When selected, the Halt control group
check box also tells TotalView to stop a process just before it begins executing.
(See Figure 92.)
If you click Yes, when the job stops the starter process should be at a “magic breakpoint.”
These are set by TotalView behind the scene, and usually not visible. The other
processes may or may not be at a “magic breakpoint.”
The commands on the Parallel Page in the File > Preferences Dialog Box let
you control what TotalView does when your program goes parallel. (See
Figure 93.)
126 Chapter 6: Setting Up MPI Debugging Sessions