HP Fortran Programmer Guide HP-UX 11i v1, HP-UX 11i v2, and HP-UX 11i v3 (B3908-90032,December 2012)

prof
The profprofiler can also be used for profiling. Unlike the gprofprofiler, prof does not generate
the call graph profile. To use prof, do the following:
1. Compile the program with the +prof option. For example:
$ f90 -o prog +prof prog.f90
2. Run the program. This creates a file named mon.out in the current directory. For example:
$ prog$ ls mon.outmon.out
3. Run prof, giving the name of the program as an argument, as follows:
$ prof prog
profproduces a listing on standard output showing the time spent in each routine.
For more information about prof, see the prof((1))man page.
Using options to control optimization
HPFortranincludes a rich set of command-line options for controlling optimization. For most
applications, we recommend optimizing with -O, which enables the default level of optimization.
(For information about the default level of optimization, refer to Table on page149; look up +O2
in the first column.) You can raise or lower the level of optimization with the +Oopt-leveloption,
and you can use the +Ooptimizationoption to control the kinds of optimizations that are available
at each level.
The following sections describe how to use the +Oopt-leveland +Ooptimizationoptions. For
detailed descriptions of the optimization options, see the HPFortranProgrammer’s Reference.
Using +O to set optimization levels
HP Fortran provides four levels of optimization. Each higher level is a superset of the lower levels;
level 4 is the highest level and can result in a significant increase in program performance. Level
2 is the default level of optimization.
You invoke optimization by compiling with the +Oopt-leveloption, where opt-levelis an
integer in the range 0 - 4. The following command line invokes the optimizer at the highest level:
$ f90 +O4 file.f90
You can invoke level 2 (the default level) by specifying the -Ooption.
Table6-1 summarizes each level, giving the option that invokes that level, the advantages,
disadvantages, and recommended usages. For technical information about the specific optimizations
at each level, refer to the HP PA-RISC Compiler Optimization Technology White Paper. A PostScript
version of this document is available online in /opt/langtools/newconfig/white_papers/
optimize.ps.
NOTE: You can debug programs optimized up to level 2. To prepare an optimized program for
debugging, use the command line:
$ f90 -g +Oopt-level prog.f90
Table 27 Optimization levels
Recommended useDisadvantagesAdvantages
Optimizations
performedOption
During program development.Does very little
optimization.
Compiles fastest;
compatible with the
debugger option -g.
Constant folding and
partial evaluation of
test conditions.
+O0default
During program development.Compiles slower
than level 0.
Produces faster
programs than level 0;
Level 0
optimizations, plus
+O1
88 Performance and optimization