Benchmark(3) Benchmark(3)
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 ($count, "code");
# Use Perl code in strings...
timethese($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";
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, $t0);
print "the code took:",timestr($td),"\n";
debug Enables or disable debugging by setting the $Benchmark::Debug
flag:
debug Benchmark 1;
$t = timeit(10, ' 5 ** $Global ');
debug Benchmark 0;
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Benchmark(3) Benchmark(3)
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 times to run the loop, and
CODE is the code to run. CODE may be either a code reference
or a string to be eval'd; either way it will be run in the
caller's package.
Returns: a Benchmark object.
timethis ( COUNT, CODE, [ TITLE, [ STYLE ]] )
Time COUNT iterations of CODE. CODE may be a string to eval or
a code reference; either way the CODE will run in the caller's
package. Results will be printed to STDOUT as TITLE followed
by the times. TITLE defaults to "timethis COUNT" if none is
provided. STYLE determines the format of the output, as
described for timestr() below.
timethese ( COUNT, CODEHASHREF, [ STYLE ] )
The CODEHASHREF is a reference to a hash containing names as
keys and either a string to eval or a code reference for each
value. For each (KEY, VALUE) pair in the CODEHASHREF, this
routine will call
timethis(COUNT, VALUE, KEY, STYLE)
timediff ( T1, T2 )
Returns the difference between two Benchmark times as a
Benchmark object suitable for passing to timestr().
timestr ( TIMEDIFF, [ STYLE, [ FORMAT ]] )
Returns a string that formats the times in the TIMEDIFF object
in the requested STYLE. TIMEDIFF is expected to be a Benchmark
object similar to that returned by 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 the printf(3) manpage-style format specifier
(without the leading '%') to use to print the times. It
defaults to '5.2f'.
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Benchmark(3) Benchmark(3)
Optional Exports
The following routines will be exported into your namespace if you
specifically ask that they be imported:
clearcache ( COUNT )
Clear the cached time for COUNT rounds of the null loop.
clearallcache ( )
Clear all cached times.
disablecache ( )
Disable caching of timings for the null loop. This will force
Benchmark to recalculate these timings for each new piece of
code timed.
enablecache ( )
Enable caching of timings for the null loop. The time taken for
COUNT rounds of the null loop will be calculated only once for
each different COUNT used.
NOTES
The data is stored as a list of values from the time and times functions:
($real, $user, $system, $children_user, $children_system)
in seconds for the whole loop (not divided by the number of rounds).
The timing is done using time(3) and times(3).
Code is executed in the caller's package.
The time of the null loop (a loop with the same number of rounds but
empty loop body) is subtracted from the time of the real loop.
The null loop times are cached, the key being the number of rounds. The
caching can be controlled using calls like these:
clearcache($key);
clearallcache();
disablecache();
enablecache();
INHERITANCE
Benchmark inherits from no other class, except of course for Exporter.
CAVEATS
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.
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Benchmark(3) Benchmark(3)
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.
AUTHORS
Jarkko Hietaniemi <jhi@iki.fi>, Tim Bunce <Tim.Bunce@ig.co.uk>
MODIFICATION HISTORY
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.
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