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
timethis ($count, "code");
# Use Perl code in strings...
timethese($count, {
'Name1' => '...code1...',
'Name2' => '...code2...',
});
# ... or use subroutine references.
timethese($count, {
'Name1' => sub { ...code1... },
'Name2' => sub { ...code2... },
});
$t = timeit($count, '...other code...')
print "$count loops of other code took:",timestr($t),"\n";
The Benchmark module encapsulates a number of routines to help you figure out how long it takes to execute some code.
use Benchmark;
$t0 = new Benchmark;
# ... your code here ...
$t1 = new Benchmark;
$td = timediff($t1, $t0);
print "the code took:",timestr($td),"\n";
$Benchmark::Debug flag:
debug Benchmark 1;
$t = timeit(10, ' 5 ** $Global ');
debug Benchmark 0;
The following routines will be exported into your namespace if you use the Benchmark module:
Returns: a Benchmark object.
timestr() below.
The COUNT can be zero or negative: this means the minimum number of CPU seconds to run. A zero signifies the default of 3 seconds. For example to run at least for 10 seconds:
timethis(-10, $code)
or to run two pieces of code tests for at least 3 seconds:
timethese(0, { test1 => '...', test2 => '...'})
CPU seconds is, in UNIX terms, the user time plus the system time of the process itself, as opposed to the real (wallclock) time and the time spent by the child processes. Less than 0.1 seconds is not accepted (-0.01 as the count, for example, will cause a fatal runtime exception).
Note that the
CPU seconds is the minimum time:
CPU scheduling and other operating system factors may
complicate the attempt so that a little bit more time is spent. The
benchmark output will, however, also tell the number of $code runs/second, which should be a more interesting number than the actually
spent seconds.
Returns a Benchmark object.
timethis(COUNT, VALUE, KEY, STYLE)
The routines are called in string comparison order of KEY.
The
COUNT can be zero or negative, see
timethis().
timestr().
timediff().
STYLE can be any of 'all', 'noc', 'nop' or 'auto'. 'all' shows each of the 5 times available ('wallclock' time, user time, system time, user time of children, and system time of children). 'noc' shows all except the two children times. 'nop' shows only wallclock and the two children times. 'auto' (the default) will act as 'all' unless the children times are both zero, in which case it acts as 'noc'.
FORMAT is the printf(3)-style format specifier (without the leading '%') to use to print the times. It defaults to '5.2f'.
The following routines will be exported into your namespace if you specifically ask that they be imported:
The data is stored as a list of values from the time and times functions:
($real, $user, $system, $children_user, $children_system)
in seconds for the whole loop (not divided by the number of rounds).
The timing is done using
time(3) and
times(3).
Code is executed in the caller's package.
The time of the null loop (a loop with the same number of rounds but empty loop body) is subtracted from the time of the real loop.
The null loop times are cached, the key being the number of rounds. The caching can be controlled using calls like these:
clearcache($key);
clearallcache();
disablecache();
enablecache();
Benchmark inherits from no other class, except of course for Exporter.
Comparing eval'd strings with code references will give you inaccurate results: a code reference will show a slower execution time than the equivalent eval'd string.
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.
Jarkko Hietaniemi <jhi@iki.fi>, Tim Bunce <Tim.Bunce@ig.co.uk>
September 8th, 1994; by Tim Bunce.
March 28th, 1997; by Hugo van der Sanden: added support for code references and the already documented 'debug' method; revamped documentation.
April 04-07th, 1997: by Jarkko Hietaniemi, added the run-for-some-time functionality.
If rather than formatting bugs, you encounter substantive content errors in these documents, such as mistakes in the explanations or code, please use the perlbug utility included with the Perl distribution.