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<P>
Benchmark - benchmark running times of code
<P>
timethis - run a chunk of code several times
<P>
timethese - run several chunks of code several times
<P>
timeit - run a chunk of code and see how long it goes
<P>
<HR>
<P>
<PRE> timethis ($count, "code");
</PRE>
<P>
<PRE> # Use Perl code in strings...
timethese($count, {
'Name1' => '...code1...',
'Name2' => '...code2...',
});
</PRE>
<P>
<PRE> # ... or use subroutine refe
<P>
The Benchmark module encapsulates a number of routines to help you figure
out how long it takes to execute some code.
<P>
<HR>
<H2><A NAME="Methods">Methods</A></H2>
<DL>
<DT><STRONG><A NAME="item_new">new</A></STRONG><P>
<DD>
Returns the current time. Example:
<P>
<PRE> use Benchmark;
$t0 = new Benchmark;
# ... your code here ...
$t1 = new Benchmark;
$td = timediff($t1, $t0);
print "the code took:",timestr($td),"\n";
</PRE>
<DT><STRONG><A NAME="item_debug">debug</A></STRONG><P>
<DD>
Enables or disable debugging by setting the <CODE>$Benchmark::Debug</CODE> flag:
<P>
<PRE> debug Benchmark 1;
$t = timeit(10, ' 5 ** $Global ');
debug Benchmark 0;
</PRE>
</DL>
<P>
<HR>
<H2><A NAME="Standard_Exports">Standard Exports</A></H2>
<P>
The following routines will be exported into your namespace if you use the
Benchmark module:
<DL>
<DT><STRONG><A NAME="item_timeit">timeit(COUNT, CODE)</A></STRONG><P>
<DD>
Arguments:
<FONT SIZE=-1>COUNT</FONT> is the number of times to run the loop, and
<FONT SIZE=-1>CODE</FONT> is the code to run.
<FONT SIZE=-1>CODE</FONT> may be either a code reference or a string to be eval'd; either way it will be run in the caller's package.
<P>
Returns: a Benchmark object.
<P><DT><STRONG><A NAME="item_timethis">timethis ( COUNT, CODE, [ TITLE, [ STYLE ]] )</A></STRONG><P>
<DD>
Time
<FONT SIZE=-1>COUNT</FONT> iterations of
<FONT SIZE=-1>CODE.</FONT>
<FONT SIZE=-1>CODE</FONT> may be a string to eval or a code reference; either way the
<FONT SIZE=-1>CODE</FONT> will run in the caller's package. Results will be printed to
<FONT SIZE=-1>STDOUT</FONT> as
<FONT SIZE=-1>TITLE</FONT> followed by the times.
<FONT SIZE=-1>TITLE</FONT> defaults to ``timethis
<FONT SIZE=-1>COUNT''</FONT> if none is provided.
<FONT SIZE=-1>STYLE</FONT> determines the format of the output, as described for
<CODE>timestr()</CODE> below.
<P>
The
<FONT SIZE=-1>COUNT</FONT> can be zero or negative: this means the <EM>minimum number of
CPU seconds</EM> to run.
<FONT SIZE=-1>A</FONT> zero signifies the default of 3 seconds. For example
to run at least for 10 seconds:
<P>
<PRE> timethis(-10, $code)
</PRE>
<P>
or to run two pieces of code tests for at least 3 seconds:
<P>
<PRE> timethese(0, { test1 => '...', test2 => '...'})
</PRE>
<P>
<FONT SIZE=-1>CPU</FONT> seconds is, in
<FONT SIZE=-1>UNIX</FONT> terms, the user time plus the system time of the process itself, as opposed to the real (wallclock) time and the time spent by the child processes. Less than 0.1 seconds is not accepted (-0.01 as the count, for example, will cause a fatal runtime exception).
<P>
Note that the
<FONT SIZE=-1>CPU</FONT> seconds is the <STRONG>minimum</STRONG> time:
<FONT SIZE=-1>CPU</FONT> scheduling and other operating system factors may
complicate the attempt so that a little bit more time is spent. The
benchmark output will, however, also tell the number of <CODE>$code</CODE> runs/second, which should be a more interesting number than the actually
spent seconds.
<P>
Returns a Benchmark object.
<P><DT><STRONG><A NAME="item_timethese">timethese ( COUNT, CODEHASHREF, [ STYLE ] )</A></STRONG><P>
<DD>
The
<FONT SIZE=-1>CODEHASHREF</FONT> 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
<FONT SIZE=-1>(KEY,</FONT>
<FONT SIZE=-1>VALUE)</FONT> pair in the
<FONT SIZE=-1>CODEHASHREF,</FONT> this routine will call
<P>
<PRE> timethis(COUNT, VALUE, KEY, STYLE)
</PRE>
<P>
The routines are called in string comparison order of
<FONT SIZE=-1>KEY.</FONT>
<P>
The
<FONT SIZE=-1>COUNT</FONT> can be zero or negative, see
<CODE>timethis().</CODE>
<P><DT><STRONG><A NAME="item_timediff">timediff ( T1, T2 )</A></STRONG><P>
<DD>
Returns the difference between two Benchmark times as a Benchmark object suitable for passing to
<CODE>timestr().</CODE>
<P><DT><STRONG><A NAME="item_timestr">timestr ( TIMEDIFF, [ STYLE, [ FORMAT ] ] )</A></STRONG><P>
<DD>
Returns a string that formats the times in the
<FONT SIZE=-1>TIMEDIFF</FONT> object in the requested
<FONT SIZE=-1>STYLE.</FONT>
<FONT SIZE=-1>TIMEDIFF</FONT> is expected to be a Benchmark object similar to that returned by
<CODE>timediff().</CODE>
<P>
<FONT SIZE=-1>STYLE</FONT> 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'.
<P>
<FONT SIZE=-1>FORMAT</FONT> is the <EM>printf(3)</EM>-style format specifier (without the leading '%') to use to print the
times. It defaults to '5.2f'.
</DL>
<P>
<HR>
<H2><A NAME="Optional_Exports">Optional Exports</A></H2>
<P>
The following routines will be exported into your namespace if you
specifically ask that they be imported:
<DL>
<DT><STRONG><A NAME="item_clearcache">clearcache ( COUNT )</A></STRONG><P>
<DD>
Clear the cached time for
<FONT SIZE=-1>COUNT</FONT> rounds of the null loop.
<P><DT><STRONG><A NAME="item_clearallcache">clearallcache ( )</A></STRONG><P>
<DD>
Clear all cached times.
<P><DT><STRONG><A NAME="item_disablecache">disablecache ( )</A></STRONG><P>
<DD>
Disable caching of timings for the null loop. This will force Benchmark to
recalculate these timings for each new piece of code timed.
<P><DT><STRONG><A NAME="item_enablecache">enablecache ( )</A></STRONG><P>
<DD>
Enable caching of timings for the null loop. The time taken for
<FONT SIZE=-1>COUNT</FONT> rounds of the null loop will be calculated only once for each different
<FONT SIZE=-1>COUNT</FONT> used.
</DL>
<P>
<HR>
<H1><A NAME="NOTES">NOTES</A></H1>
<P>
The data is stored as a list of values from the time and times functions:
<P>
<PRE> ($real, $user, $system, $children_user, $children_system)
</PRE>
<P>
in seconds for the whole loop (not divided by the number of rounds).
<P>
The timing is done using
<CODE>time(3)</CODE> and
<CODE>times(3).</CODE>
<P>
Code is executed in the caller's package.
<P>
The time of the null loop (a loop with the same number of rounds but empty
loop body) is subtracted from the time of the real loop.
<P>
The null loop times are cached, the key being the number of rounds. The
caching can be controlled using calls like these:
<P>
<PRE> clearcache($key);
clearallcache();
</PRE>
<P>
<PRE> disablecache();
enablecache();
</PRE>
<P>
<HR>
<H1><A NAME="INHERITANCE">INHERITANCE</A></H1>
<P>
Benchmark inherits from no other class, except of course for Exporter.
<P>
<HR>
<H1><A NAME="CAVEATS">CAVEATS</A></H1>
<P>
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.
<P>
The real time timing is done using
<CODE>time(2)</CODE> and the granularity
is therefore only one second.
<P>
Short tests may produce negative figures because perl can appear to take
longer to execute the empty loop than a short test; try:
<P>
<PRE> timethis(100,'1');
</PRE>
<P>
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.
<P>
<HR>
<H1><A NAME="AUTHORS">AUTHORS</A></H1>
<P>
Jarkko Hietaniemi <<EM>jhi@iki.fi</EM>>, Tim Bunce <<EM>Tim.Bunce@ig.co.uk</EM>>
<P>
<HR>
<H1><A NAME="MODIFICATION_HISTORY">MODIFICATION HISTORY</A></H1>
<P>
September 8th, 1994; by Tim Bunce.
<P>
March 28th, 1997; by Hugo van der Sanden: added support for code references
and the already documented 'debug' method; revamped documentation.
<P>
April 04-07th, 1997: by Jarkko Hietaniemi, added the run-for-some-time
functionality.
<HR>