Andrew Ho > Benchmark-Timer > Benchmark::Timer



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Benchmark::Timer - Perl code benchmarking tool


    use Benchmark::Timer;
    $t = Benchmark::Timer->new(skip => 1);

    for(0 .. 1000) {


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 supply a unique tag, or event name, to those methods. This allows one Benchmark::Timer object to benchmark many pieces of code.

When you have run your code (one time or over multiple trials), you can obtain information about the running time by calling the results() method or print 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.


$t = Benchmark::Timer->new( [options] );

Constructor for the Benchmark::Timer object; returns a reference to a timer object. Takes named arguments, of which right now there is only one, skip, which is the number of trials (if any) to skip before recording timing information.


Reset the timer object to the pristine state it started in. Erase all memory of events and any previously accumulated timings. Returns a reference to the timer object. It takes the same arguments the constructor takes.


Record the current time so that when stop() is called, we can calculate an elapsed time. Supply a $tag which is simply a string that is the descriptive name of the event you are timing. If you do not supply a $tag, the last event tag is used; if there is none, a "_default" tag is used instead.


Record timing information. The optional $tag is the event for which you are timing, and defaults to the $tag supplied to the last start() call. If a $tag is supplied, it must correspond to one given to a previously called start() call. It returns the elapsed time in milliseconds. stop() throws an exception if the timer gets out of sync (e.g. the number of start()s does not match the number of stop()s.


Print a simple report on the collected timings to STDERR. This report prints 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. It prints the events out in the order they were start()ed.


Return the time it took for $event to elapse, or the mean time it took for $event to elapse once, if $event happened more than once. result() will complain (via a warning) if an event is still active.


Returns the timing data as a hash keyed on event tags where each value is the time it took to run that event, or the are the average time it took, if that event 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 event order is preserved.

$t->data($event), $t->data;

These methods are useful if you want to recover the full internal timing data to roll your own reports.

If called with an $event, returns the raw timing data for that $event 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 event tags, where the values of the hash are lists of timings for that event. 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 event order by assigning to an array instead of a hash.


Benchmarking is an inherently futile activity, fraught with uncertainty not dissimilar to that experienced in quantum mechanics.


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


Andrew Ho <>


Copyright(c) 2000-2001 Andrew Ho.

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

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