Ilya Zakharevich

NAME

Benchmark - benchmark running times of code

timethis - run a chunk of code several times

timethese - run several chunks of code several times

timeit - run a chunk of code and see how long it goes

SYNOPSIS

    timethis ($count, "code");

    timethese($count, {
        'Name1' => '...code1...',
        'Name2' => '...code2...',
    });

    $t = timeit($count, '...other code...')
    print "$count loops of other code took:",timestr($t),"\n";

DESCRIPTION

The Benchmark module encapsulates a number of routines to help you figure out how long it takes to execute some code.

Methods

new

Returns the current time. Example:

    use Benchmark;
    $t0 = new Benchmark;
    # ... your code here ...
    $t1 = new Benchmark;
    $td = timediff($t1, $t0);
    print "the code took:",timestr($dt),"\n";
debug

Enables or disable debugging by setting the $Benchmark::Debug flag:

    debug Benchmark 1; 
    $t = timeit(10, ' 5 ** $Global ');
    debug Benchmark 0; 

Standard Exports

The following routines will be exported into your namespace if you use the Benchmark module:

timeit(COUNT, CODE)

Arguments: COUNT is the number of time to run the loop, and the second is the code to run. CODE may be a string containing the code, a reference to the function to run, or a reference to a hash containing keys which are names and values which are more CODE specs.

Side-effects: prints out noise to standard out.

Returns: a Benchmark object.

timethis
timethese
timediff
timestr

Optional Exports

The following routines will be exported into your namespace if you specifically ask that they be imported:

    clearcache

    clearallcache

    disablecache

    enablecache

NOTES

The data is stored as a list of values from the time and times functions:

      ($real, $user, $system, $children_user, $children_system)

in seconds for the whole loop (not divided by the number of rounds).

The timing is done using time(3) and times(3).

Code is executed in the caller's package.

Enable debugging by:

    $Benchmark::debug = 1;

The time of the null loop (a loop with the same number of rounds but empty loop body) is subtracted from the time of the real loop.

The null loop times are cached, the key being the number of rounds. The caching can be controlled using calls like these:

    clearcache($key); 
    clearallcache();

    disablecache(); 
    enablecache();

INHERITANCE

Benchmark inherits from no other class, except of course for Exporter.

CAVEATS

The real time timing is done using time(2) and the granularity is therefore only one second.

Short tests may produce negative figures because perl can appear to take longer to execute the empty loop than a short test; try:

    timethis(100,'1');

The system time of the null loop might be slightly more than the system time of the loop with the actual code and therefore the difference might end up being < 0.

More documentation is needed :-( especially for styles and formats.

AUTHORS

Jarkko Hietaniemi <Jarkko.Hietaniemi@hut.fi>, Tim Bunce <Tim.Bunce@ig.co.uk>

MODIFICATION HISTORY

September 8th, 1994; by Tim Bunce.