Benchmark::Timer(3pm)					User Contributed Perl Documentation				     Benchmark::Timer(3pm)

NAME

       Benchmark::Timer - Benchmarking with statistical confidence

SYNOPSIS

	 # Non-statistical usage
	 use Benchmark::Timer;
	 $t = Benchmark::Timer->new(skip => 1);

	 for(1 .. 1000) {
	     $t->start('tag');
	     &long_running_operation();
	     $t->stop('tag');
	 }
	 print $t->report;

	 # --------------------------------------------------------------------

	 # Statistical usage
	 use Benchmark::Timer;
	 $t = Benchmark::Timer->new(skip => 1, confidence => 97.5, error => 2);

	 while($t->need_more_samples('tag')) {
	     $t->start('tag');
	     &long_running_operation();
	     $t->stop('tag');
	 }
	 print $t->report;

DESCRIPTION

       The Benchmark::Timer class allows you to time portions of code conveniently, as well as benchmark code by allowing timings of repeated
       trials. It is perfect for when you need more precise information about the running time of portions of your code than the Benchmark module
       will give you, but don't want to go all out and profile your code.

       The methodology is simple; create a Benchmark::Timer object, and wrap portions of code that you want to benchmark with "start()" and
       "stop()" method calls.  You can supply a tag to those methods if you plan to time multiple portions of code.  If you provide error and
       confidence values, you can also use "need_more_samples()" to determine, statistically, whether you need to collect more data.

       After you have run your code, you can obtain information about the running time by calling the "results()" method, or get a descriptive
       benchmark report by calling "report()".	If you run your code over multiple trials, the average time is reported.  This is wonderful for
       benchmarking time-critical portions of code in a rigorous way. You can also optionally choose to skip any number of initial trials to cut
       down on initial case irregularities.

METHODS

       In all of the following methods, $tag refers to the user-supplied name of the code being timed. Unless otherwise specified, $tag defaults
       to the tag of the last call to "start()", or "_default" if "start()" was not previously called with a tag.

       $t = Benchmark::Timer->new( [options] );
	   Constructor for the Benchmark::Timer object; returns a reference to a timer object. Takes the following named arguments:

	   skip
	       The number of trials (if any) to skip before recording timing information.

	   minimum
	       The minimum number of trials to run.

	   error
	       A percentage between 0 and 100 which indicates how much error you are willing to tolerate in the average time measured by the
	       benchmark.  For example, a value of 1 means that you want the reported average time to be within 1% of the real average time.
	       "need_more_samples()" will use this value to determine when it is okay to stop collecting data.

	       If you specify an error you must also specify a confidence.

	   confidence
	       A percentage between 0 and 100 which indicates how confident you want to be in the error measured by the benchmark. For example, a
	       value of 97.5 means that you want to be 97.5% confident that the real average time is within the error margin you have specified.
	       "need_more_samples()" will use this value to compute the estimated error for the collected data, so that it can determine when it
	       is okay to stop.

	       If you specify a confidence you must also specify an error.

       $t->reset;
	   Reset the timer object to the pristine state it started in.	Erase all memory of tags and any previously accumulated timings.  Returns
	   a reference to the timer object. It takes the same arguments the constructor takes.

       $t->start($tag);
	   Record the current time so that when "stop()" is called, we can calculate an elapsed time.

       $t->stop($tag);
	   Record timing information. If $tag is supplied, it must correspond to one given to a previously called "start()" call. It returns the
	   elapsed time in milliseconds.  "stop()" croaks if the timer gets out of sync (e.g. the number of "start()"s does not match the number
	   of "stop()"s.)

       $t->need_more_samples($tag);
	   Compute the estimated error in the average of the data collected thus far, and return true if that error exceeds the user-specified
	   error. If a $tag is supplied, it must correspond to one given to a previously called "start()" call.

	   This routine assumes that the data are normally distributed.

       $t->report($tag);
	   Returns a string containing a simple report on the collected timings for $tag.  This report contains the number of trials run, the
	   total time taken, and, if more than one trial was run, the average time needed to run one trial and error information.  "report()" will
	   complain (via a warning) if a tag is still active.

       $t->reports;
	   In a scalar context, returns a string containing a simple report on the collected timings for all tags. The report is a concatenation
	   of the individual tag reports, in the original tag order. In an list context, returns a hash keyed by tag and containing reports for
	   each tag. The return value is actually an array, so that the original tag order is preserved if you assign to an array instead of a
	   hash. "reports()" will complain (via a warning) if a tag is still active.

       $t->result($tag);
	   Return the time it took for $tag to elapse, or the mean time it took for $tag to elapse once, if $tag was used to time code more than
	   once. "result()" will complain (via a warning) if a tag is still active.

       $t->results;
	   Returns the timing data as a hash keyed on tags where each value is the time it took to run that code, or the average time it took, if
	   that code ran more than once. In scalar context it returns a reference to that hash. The return value is actually an array, so that the
	   original tag order is preserved if you assign to an array instead of a hash.

       $t->data($tag), $t->data;
	   These methods are useful if you want to recover the full internal timing data to roll your own reports.

	   If called with a $tag, returns the raw timing data for that $tag as an array (or a reference to an array if called in scalar context).
	   This is useful for feeding to something like the Statistics::Descriptive package.

	   If called with no arguments, returns the raw timing data as a hash keyed on tags, where the values of the hash are lists of timings for
	   that code. In scalar context, it returns a reference to that hash. As with "results()", the data is internally represented as an array
	   so you can recover the original tag order by assigning to an array instead of a hash.

BUGS

       Benchmarking is an inherently futile activity, fraught with uncertainty not dissimilar to that experienced in quantum mechanics. But things
       are a little better if you apply statistics.

LICENSE

       This code is distributed under the GNU General Public License (GPL). See the file LICENSE in the distribution,
       http://www.opensource.org/gpl-license.html, and http://www.opensource.org/.

AUTHOR

       The original code (written before April 20, 2001) was written by Andrew Ho <andrew@zeuscat.com>, and is copyright (c) 2000-2001 Andrew Ho.
       Versions up to 0.5 are distributed under the same terms as Perl.

       Maintenance of this module is now being done by David Coppit <david@coppit.org>.

SEE ALSO

       Benchmark, Time::HiRes, Time::Stopwatch, Statistics::Descriptive

perl v5.10.1							    2009-12-03						     Benchmark::Timer(3pm)