NAME

NAME
Benchmark::Forking - About the forking benchmarks distribution

MOTIVATION
The standard Benchmark module can sometimes report inaccurate or
misleading results, in part because it doesn't isolate its test cases
from one another. This means that the order that cases are run in can
influence the results, because side effects, either obvious or obscure,
can accumulate and affect later tests.

Data in global variables is an obvious source of side effects; in the
below example, the grep takes longer as more items are pushed onto the
array, so the test functions that run later will be reported by
Benchmark as being slower, despite their code being identical:

cmpthese( 1000, {
"test_1" => sub { push @global, scalar grep 1, @global },
"test_2" => sub { push @global, scalar grep 1, @global },
"test_3" => sub { push @global, scalar grep 1, @global },
} );

More cryptic sources of side effects can include cache priming,
idiosyncrasies of the underlying Perl implementation, or the state of
the operating system and environment. For example, if the code to be
benchmarked require a lot of in-process RAM, earlier tests may be slowed
down by having to allocate the memory the first time, or later tests may
be slowed down by having to pick through the heap looking for free
space. These effects are difficult to predict and can be laborious to
identify and compensate for.

This module provides a solution to most aspects of this problem. Once
you use Benchmark::Forking, the example benchmark above will report the
correct conclusion that the three identical tests run at approximately
the same speed.

VERSION
This is version 1.00 of Benchmark::Forking.

Changes

2010−02−01: Updated documentation.

2004−09−05: Expanded documentation and packaged for distribution.

2004−09−03: First version written.

INSTALLATION
This module should work with any version of Perl 5, without platform
dependencies or additional modules beyond the core distribution.

You should be able to install this module using the CPAN shell
interface:

perl −MCPAN −e 'install Benchmark::Forking'

Alternately, you may retrieve this package from CPAN
("http://search.cpan.org/~evo/") and follow the normal procedure to
unpack and install it, using the commands shown below or their local
equivalents on your system:

tar xzf Benchmark−Forking−*.tar.gz
cd Benchmark−Forking−*
perl Makefile.PL
make test && sudo make install

SUPPORT
Once installed, this module’s documentation is available as a manual
page via "perldoc Benchmark::Forking" or on CPAN sites such as
"http://search.cpan.org/dist/Benchmark−Forking".

If you have questions or feedback about this module, please feel free
to contact the author at the below address. Although there is no formal
support program, I do attempt to answer email promptly.

Bug reports that contain a failing test case are greatly appreciated,
and suggested patches will be promptly considered for inclusion in
future releases.

To report bugs via the CPAN web tracking system, go to
"http://rt.cpan.org/NoAuth/Bugs.html?Dist=Benchmark−Forking" or send
mail to "Dist=Benchmark−Forking#rt.cpan.org", replacing "#" with "@".

If you’ve found this module useful or have feedback about your
experience with it, consider sharing your opinion with other Perl users
by posting your comment to CPAN’s ratings system
("http://cpanratings.perl.org/rate/?distribution=Benchmark−Forking").

For more general discussion, you may wish to post a message on
PerlMonks ("http://perlmonks.org/?node=Seekers%20of%20Perl%20Wisdom")
or on the comp.lang.perl.misc newsgroup
("http://groups.google.com/group/comp.lang.perl.misc/topics").

AUTHOR
Developed by Matthew Simon Cavalletto. You may contact the author
directly at "[email protected]" or "[email protected]".

Inspired by a discussion with Jim Keenan in the Perl Monks community.

My thanks also to other members of the Perl Monks community for
feedback on this module, including graff, tachyon, Aristotle,
pbeckingham, and others. http://perlmonks.org/?node_id=388481

LICENSE
Copyright 2010, 2004 Matthew Simon Cavalletto.

You may use, modify, and distribute this software under the same terms
as Perl.

See http://dev.perl.org/licenses/ for more information.