HP Fortran Programmer Guide (766160-001, March 2014)

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 page 149; 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, see 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
90 Performance and optimization