TotalView Users Guide - CI Wiki

Debugging OpenMP Applications
Viewing OpenMP THREADPRIVATE Common Blocks
The HP Alpha Tru64 UNIX OpenMP and SGI IRIX compilers implement
OpenMP THREADPRIVATE common blocks by using the thread local storage
system facility. This facility stores a variable declared in OpenMP
THREADPRIVATE common blocks at different memory locations in each
thread in an OpenMP process. This allows the variable to have different values
in each thread. In contrast, the IBM and Guide compilers use the
pthread key facility.
When you use SGI compilers, the compiler maps THREADPRIVATE variables
to the same virtual address. However, they have different physical
addresses.
To view a variable in an OpenMP THREADPRIVATE common block, or the
OpenMP THREADPRIVATE common block:
1 In the Threads Tab of the Process Window, select the thread that contains
the private copy of the variable or common block you want to view.
2 In the Stack Trace Pane of the Process Window, select the stack frame that
lets you access the OpenMP THREADPRIVATE common block variable. You
can select either the outlined routine or the original routine for an
OpenMP master thread. You must, however, select the outlined routine
for an OpenMP worker thread.
3 From the Process Window, dive on the variable name or common block
name, or select the View > Lookup Variable command. When prompted,
enter the name of the variable or common block. You may need to
append an underscore character (_) after the common block name.
CLI: dprint
TotalView opens a Variable Window that displays the value of the variable
or common block for the selected thread.
See “Displaying Variables” on page 283 for more information on displaying
variables.
4 To view OpenMP THREADPRIVATE common blocks or variables across all
threads, use the Variable Window’s Show across > Threads command. See
“Displaying a Variable in all Processes or Threads” on page 345.
The following figure shows Variable Windows displaying OpenMP
THREADPRIVATE common blocks. Because the Variable Window has the
same thread context as the Process Window from which it was created, the
title bar patterns for the same thread match. TotalView displays the values
of the common block across all threads when you use the View > Show
Across > Threads command. (See Figure 96 on page 137.)
136 Chapter 7: Setting Up Parallel Debugging Sessions