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NAME
looptool - graphically display loop timing data
SYNOPSIS
looptool [ -p path] [image-file] [timing-file]
loopreport [ -p path] [image-file] [timing-file]
DESCRIPTION
looptool and loopreport produce summaries of loop perfor-
mance. Compile your f77, f90 or C source files with -Zlp,
run the resulting executable and invoke either looptool or
loopreport. looptool is the graphical user interface.
loopreport is the command line interface, and it writes the
summary of loop performance to stdout.
OPTIONS
-p Search path first for loop timing files.
-x Disable usage tracking. Usage tracking is on by
default in early access releases. Usage tracking means
that when you use the tool, an email message is sent to
the developer.
USAGE
The first step is to instrument your program. Compile with
the switches -xO3 or -xO4, -xparallel, and -Zlp. If you do
not specify either -O3 or -O4, the driver adds -O3 to your
compile line. If you do not specify -parallel, the f77
driver adds -xdepend to your compile line.
The -Zlp switch takes an optional argument, n, which
instructs the compiler not to instrument loops with a nest-
ing level greater than n. By default, all loops are instru-
mented. If you specify -Zlp=2, then only the outer two
levels of loops are instrumented. This option is provided in
case the overhead of instrumenting all loops seems unaccept-
ably high.
The second step is to run the instrumented executable. The
instrumented executable silently creates a timing file when
it finishes running. The name of the timing file is
programname.looptimes by default. If you set the environ-
ment variable LVPATH, then the timing file is put in the
directory LVPATH and named pid.programname, where pid is the
process id, and programname is the name of your executable.
The third step is to run one of the postprocessors, looptool
or loopreport. If you invoke looptool without giving it the
name of a program, then by default the GUI prompts you with
a pop-up window for a program name. If you invoke looptool
or loopreport without specifying an executable, the default
file vgam is displayed.
Both looptool and loopreport read two files: the instru-
mented executable and its associated timing file. Typi-
cally, the timing file resides in the same directory as the
executable, and is named programname.looptimes. However, if
you use the command line option -p path then the directory
named path is searched first for timing files. Next, if
the environment variable LVPATH is set, the directory named
by LVPATH is searched. Finally, the current working direc-
tory is searched for timing files.
looptool represents loop timing data in bar charts. Click-
ing on a loop's representation with the first mouse button
brings up that loop's source code in an editor window. Loop
characteristics, such as which transformations were applied
to the loop, are shown as part of the source code display.
For example, some loop characteristics are
o loop's beginning source line number
o loop's nest level
o is loop parallel or serial?
o loop contains an MT-unsafe call
o compiler generated two versions of code for this
loop, parallel and serial
o a variable in the loop caused a data dependence
o loop is unprofitable to parallelize
o two or more loops were fused or interchanged
(and thus source line numbers may not match run-
time data exactly)
o loop was parallelized because the explicit
parallelization pragma was used
o loop has multiple exits, and therefore timing
data may be suspect
o loops contains I/O
o loop has backward flow of control
Check the manual for the version of Fortran or C you are
using to compile your program to make sure that the -Zlp
switch is recognized by the compiler.
ENVIRONMENT
LVPATH If the environment variable LVPATH contains a
value, then an instrumented executable will place
its loop timing data in that directory, in a file
named pid.programname. pid is the process id, and
programname is the value stored in argv[0], minus
any path prefixes. looptool and loopreport search
directories for timing files in this order: first,
a directory specified with -p on the command line;
second, a directory named by LVPATH; finally, the
current working directory.
LD_LIBRARY_PATH
If looptool cannot find the Motif library when it
starts up (libxm.so) then set this variable to
include a path with an appropriate Motif library
such as:
% setenv LD_LIBRARY_PATH /local-motif-path: $LD_LIBRARY_PATH
PARALLEL This variable should be set to the number of pro-
cessors on your machine, before you compile. For
example, if your machine has two processors:
% setenv PARALLEL 2
EXAMPLES
% f77 -xO4 -xparallel -Zlp prog.f -o foo (instrument foo)
% foo (run foo)
% looptool foo (run looptool)
% loopreport foo > foo.loopreport (create report)
FILES
programname Instrumented binary
liblv.a Library that contains loop timing
functions; an instrumented execut-
able links with liblv.a.
programname The text file that is silently
created by an instrumented execut-
able when it finishes running. It
contains the loop timing data.
loopreport Executable that prints a summary of
loop performance data to stdout.
looptool Executable that displays loop data
graphically.
SEE ALSO
f77(1)
cc(1)
Analyzing Program Performance With Sun WorkShop.
DIAGNOSTICS
The diagnostics produced by looptool and loopreport are
intended to be self-explanatory. Occasional messages may
be produced by system calls if a selected file cannot be
opened.
BUGS
The loop line numbers and nesting levels may be incorrect.
This information is derived by the compiler during its
optimization phase, and may not exactly match the source
line numbering and source nesting.
Loop times are measured as wallclock elapsed time. If a
loop is parallelized, it is credited with the elapsed time
for all of the instances of the loop. Thus, inner parallel-
ized loops may sometimes be credited with more elapsed run-
time than the outer loop that encompasses the parallelized
loop. This is not a bug - this is expected behavior! - but
it can be misleading.
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