530 lines
14 KiB
Perl
530 lines
14 KiB
Perl
package Benchmark;
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=head1 NAME
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Benchmark - benchmark running times of code
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timethis - run a chunk of code several times
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timethese - run several chunks of code several times
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timeit - run a chunk of code and see how long it goes
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=head1 SYNOPSIS
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timethis ($count, "code");
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# Use Perl code in strings...
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timethese($count, {
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'Name1' => '...code1...',
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'Name2' => '...code2...',
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});
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# ... or use subroutine references.
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timethese($count, {
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'Name1' => sub { ...code1... },
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'Name2' => sub { ...code2... },
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});
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$t = timeit($count, '...other code...')
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print "$count loops of other code took:",timestr($t),"\n";
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=head1 DESCRIPTION
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The Benchmark module encapsulates a number of routines to help you
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figure out how long it takes to execute some code.
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=head2 Methods
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=over 10
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=item new
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Returns the current time. Example:
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use Benchmark;
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$t0 = new Benchmark;
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# ... your code here ...
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$t1 = new Benchmark;
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$td = timediff($t1, $t0);
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print "the code took:",timestr($td),"\n";
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=item debug
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Enables or disable debugging by setting the C<$Benchmark::Debug> flag:
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debug Benchmark 1;
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$t = timeit(10, ' 5 ** $Global ');
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debug Benchmark 0;
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=back
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=head2 Standard Exports
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The following routines will be exported into your namespace
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if you use the Benchmark module:
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=over 10
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=item timeit(COUNT, CODE)
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Arguments: COUNT is the number of times to run the loop, and CODE is
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the code to run. CODE may be either a code reference or a string to
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be eval'd; either way it will be run in the caller's package.
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Returns: a Benchmark object.
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=item timethis ( COUNT, CODE, [ TITLE, [ STYLE ]] )
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Time COUNT iterations of CODE. CODE may be a string to eval or a
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code reference; either way the CODE will run in the caller's package.
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Results will be printed to STDOUT as TITLE followed by the times.
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TITLE defaults to "timethis COUNT" if none is provided. STYLE
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determines the format of the output, as described for timestr() below.
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The COUNT can be zero or negative: this means the I<minimum number of
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CPU seconds> to run. A zero signifies the default of 3 seconds. For
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example to run at least for 10 seconds:
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timethis(-10, $code)
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or to run two pieces of code tests for at least 3 seconds:
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timethese(0, { test1 => '...', test2 => '...'})
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CPU seconds is, in UNIX terms, the user time plus the system time of
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the process itself, as opposed to the real (wallclock) time and the
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time spent by the child processes. Less than 0.1 seconds is not
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accepted (-0.01 as the count, for example, will cause a fatal runtime
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exception).
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Note that the CPU seconds is the B<minimum> time: CPU scheduling and
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other operating system factors may complicate the attempt so that a
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little bit more time is spent. The benchmark output will, however,
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also tell the number of C<$code> runs/second, which should be a more
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interesting number than the actually spent seconds.
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Returns a Benchmark object.
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=item timethese ( COUNT, CODEHASHREF, [ STYLE ] )
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The CODEHASHREF is a reference to a hash containing names as keys
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and either a string to eval or a code reference for each value.
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For each (KEY, VALUE) pair in the CODEHASHREF, this routine will
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call
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timethis(COUNT, VALUE, KEY, STYLE)
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The routines are called in string comparison order of KEY.
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The COUNT can be zero or negative, see timethis().
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=item timediff ( T1, T2 )
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Returns the difference between two Benchmark times as a Benchmark
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object suitable for passing to timestr().
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=item timesum ( T1, T2 )
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Returns the sum of two Benchmark times as a Benchmark object suitable
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for passing to timestr().
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=item timestr ( TIMEDIFF, [ STYLE, [ FORMAT ] ] )
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Returns a string that formats the times in the TIMEDIFF object in
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the requested STYLE. TIMEDIFF is expected to be a Benchmark object
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similar to that returned by timediff().
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STYLE can be any of 'all', 'noc', 'nop' or 'auto'. 'all' shows each
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of the 5 times available ('wallclock' time, user time, system time,
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user time of children, and system time of children). 'noc' shows all
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except the two children times. 'nop' shows only wallclock and the
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two children times. 'auto' (the default) will act as 'all' unless
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the children times are both zero, in which case it acts as 'noc'.
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FORMAT is the L<printf(3)>-style format specifier (without the
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leading '%') to use to print the times. It defaults to '5.2f'.
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=back
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=head2 Optional Exports
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The following routines will be exported into your namespace
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if you specifically ask that they be imported:
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=over 10
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=item clearcache ( COUNT )
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Clear the cached time for COUNT rounds of the null loop.
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=item clearallcache ( )
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Clear all cached times.
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=item disablecache ( )
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Disable caching of timings for the null loop. This will force Benchmark
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to recalculate these timings for each new piece of code timed.
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=item enablecache ( )
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Enable caching of timings for the null loop. The time taken for COUNT
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rounds of the null loop will be calculated only once for each
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different COUNT used.
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=back
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=head1 NOTES
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The data is stored as a list of values from the time and times
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functions:
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($real, $user, $system, $children_user, $children_system)
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in seconds for the whole loop (not divided by the number of rounds).
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The timing is done using time(3) and times(3).
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Code is executed in the caller's package.
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The time of the null loop (a loop with the same
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number of rounds but empty loop body) is subtracted
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from the time of the real loop.
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The null loop times are cached, the key being the
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number of rounds. The caching can be controlled using
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calls like these:
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clearcache($key);
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clearallcache();
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disablecache();
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enablecache();
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=head1 INHERITANCE
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Benchmark inherits from no other class, except of course
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for Exporter.
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=head1 CAVEATS
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Comparing eval'd strings with code references will give you
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inaccurate results: a code reference will show a slower
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execution time than the equivalent eval'd string.
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The real time timing is done using time(2) and
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the granularity is therefore only one second.
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Short tests may produce negative figures because perl
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can appear to take longer to execute the empty loop
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than a short test; try:
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timethis(100,'1');
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The system time of the null loop might be slightly
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more than the system time of the loop with the actual
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code and therefore the difference might end up being E<lt> 0.
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=head1 AUTHORS
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Jarkko Hietaniemi <F<jhi@iki.fi>>, Tim Bunce <F<Tim.Bunce@ig.co.uk>>
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=head1 MODIFICATION HISTORY
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September 8th, 1994; by Tim Bunce.
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March 28th, 1997; by Hugo van der Sanden: added support for code
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references and the already documented 'debug' method; revamped
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documentation.
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April 04-07th, 1997: by Jarkko Hietaniemi, added the run-for-some-time
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functionality.
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=cut
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# evaluate something in a clean lexical environment
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sub _doeval { eval shift }
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#
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# put any lexicals at file scope AFTER here
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#
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use Carp;
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use Exporter;
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@ISA=(Exporter);
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@EXPORT=qw(timeit timethis timethese timediff timestr);
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@EXPORT_OK=qw(clearcache clearallcache disablecache enablecache);
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&init;
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sub init {
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$debug = 0;
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$min_count = 4;
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$min_cpu = 0.4;
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$defaultfmt = '5.2f';
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$defaultstyle = 'auto';
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# The cache can cause a slight loss of sys time accuracy. If a
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# user does many tests (>10) with *very* large counts (>10000)
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# or works on a very slow machine the cache may be useful.
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&disablecache;
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&clearallcache;
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}
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sub debug { $debug = ($_[1] != 0); }
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sub clearcache { delete $cache{$_[0]}; }
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sub clearallcache { %cache = (); }
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sub enablecache { $cache = 1; }
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sub disablecache { $cache = 0; }
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# --- Functions to process the 'time' data type
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sub new { my @t = (time, times, @_ == 2 ? $_[1] : 0);
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print "new=@t\n" if $debug;
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bless \@t; }
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sub cpu_p { my($r,$pu,$ps,$cu,$cs) = @{$_[0]}; $pu+$ps ; }
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sub cpu_c { my($r,$pu,$ps,$cu,$cs) = @{$_[0]}; $cu+$cs ; }
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sub cpu_a { my($r,$pu,$ps,$cu,$cs) = @{$_[0]}; $pu+$ps+$cu+$cs ; }
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sub real { my($r,$pu,$ps,$cu,$cs) = @{$_[0]}; $r ; }
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sub timediff {
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my($a, $b) = @_;
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my @r;
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for (my $i=0; $i < @$a; ++$i) {
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push(@r, $a->[$i] - $b->[$i]);
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}
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bless \@r;
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}
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sub timesum {
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my($a, $b) = @_;
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my @r;
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for (my $i=0; $i < @$a; ++$i) {
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push(@r, $a->[$i] + $b->[$i]);
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}
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bless \@r;
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}
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sub timestr {
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my($tr, $style, $f) = @_;
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my @t = @$tr;
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warn "bad time value (@t)" unless @t==6;
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my($r, $pu, $ps, $cu, $cs, $n) = @t;
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my($pt, $ct, $t) = ($tr->cpu_p, $tr->cpu_c, $tr->cpu_a);
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$f = $defaultfmt unless defined $f;
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# format a time in the required style, other formats may be added here
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$style ||= $defaultstyle;
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$style = ($ct>0) ? 'all' : 'noc' if $style eq 'auto';
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my $s = "@t $style"; # default for unknown style
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$s=sprintf("%2d wallclock secs (%$f usr %$f sys + %$f cusr %$f csys = %$f CPU)",
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@t,$t) if $style eq 'all';
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$s=sprintf("%2d wallclock secs (%$f usr + %$f sys = %$f CPU)",
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$r,$pu,$ps,$pt) if $style eq 'noc';
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$s=sprintf("%2d wallclock secs (%$f cusr + %$f csys = %$f CPU)",
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$r,$cu,$cs,$ct) if $style eq 'nop';
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$s .= sprintf(" @ %$f/s (n=$n)", $n / ( $pu + $ps )) if $n;
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$s;
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}
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sub timedebug {
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my($msg, $t) = @_;
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print STDERR "$msg",timestr($t),"\n" if $debug;
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}
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# --- Functions implementing low-level support for timing loops
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sub runloop {
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my($n, $c) = @_;
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$n+=0; # force numeric now, so garbage won't creep into the eval
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croak "negative loopcount $n" if $n<0;
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confess "Usage: runloop(number, [string | coderef])" unless defined $c;
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my($t0, $t1, $td); # before, after, difference
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# find package of caller so we can execute code there
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my($curpack) = caller(0);
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my($i, $pack)= 0;
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while (($pack) = caller(++$i)) {
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last if $pack ne $curpack;
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}
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my ($subcode, $subref);
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if (ref $c eq 'CODE') {
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$subcode = "sub { for (1 .. $n) { local \$_; package $pack; &\$c; } }";
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$subref = eval $subcode;
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}
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else {
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$subcode = "sub { for (1 .. $n) { local \$_; package $pack; $c;} }";
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$subref = _doeval($subcode);
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}
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croak "runloop unable to compile '$c': $@\ncode: $subcode\n" if $@;
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print STDERR "runloop $n '$subcode'\n" if $debug;
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$t0 = Benchmark->new(0);
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&$subref;
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$t1 = Benchmark->new($n);
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$td = &timediff($t1, $t0);
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timedebug("runloop:",$td);
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$td;
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}
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sub timeit {
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my($n, $code) = @_;
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my($wn, $wc, $wd);
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printf STDERR "timeit $n $code\n" if $debug;
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if ($cache && exists $cache{$n}) {
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$wn = $cache{$n};
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} else {
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$wn = &runloop($n, '');
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$cache{$n} = $wn;
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}
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$wc = &runloop($n, $code);
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$wd = timediff($wc, $wn);
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timedebug("timeit: ",$wc);
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timedebug(" - ",$wn);
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timedebug(" = ",$wd);
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$wd;
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}
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my $default_for = 3;
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my $min_for = 0.1;
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sub runfor {
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my ($code, $tmax) = @_;
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if ( not defined $tmax or $tmax == 0 ) {
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$tmax = $default_for;
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} elsif ( $tmax < 0 ) {
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$tmax = -$tmax;
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}
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die "runfor(..., $tmax): timelimit cannot be less than $min_for.\n"
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if $tmax < $min_for;
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my ($n, $td, $tc, $ntot, $rtot, $utot, $stot, $cutot, $cstot );
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# First find the minimum $n that gives a non-zero timing.
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my $nmin;
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for ($n = 1, $tc = 0; $tc <= 0; $n *= 2 ) {
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$td = timeit($n, $code);
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$tc = $td->[1] + $td->[2];
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}
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$nmin = $n;
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my $ttot = 0;
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my $tpra = 0.05 * $tmax; # Target/time practice.
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# Double $n until we have think we have practiced enough.
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for ( $n = 1; $ttot < $tpra; $n *= 2 ) {
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$td = timeit($n, $code);
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$tc = $td->cpu_p;
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$ntot += $n;
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$rtot += $td->[0];
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$utot += $td->[1];
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$stot += $td->[2];
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$ttot = $utot + $stot;
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$cutot += $td->[3];
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$cstot += $td->[4];
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}
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my $r;
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# Then iterate towards the $tmax.
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while ( $ttot < $tmax ) {
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$r = $tmax / $ttot - 1; # Linear approximation.
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$n = int( $r * $n );
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$n = $nmin if $n < $nmin;
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$td = timeit($n, $code);
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$ntot += $n;
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$rtot += $td->[0];
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$utot += $td->[1];
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$stot += $td->[2];
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$ttot = $utot + $stot;
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$cutot += $td->[3];
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$cstot += $td->[4];
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}
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return bless [ $rtot, $utot, $stot, $cutot, $cstot, $ntot ];
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}
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# --- Functions implementing high-level time-then-print utilities
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sub n_to_for {
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my $n = shift;
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return $n == 0 ? $default_for : $n < 0 ? -$n : undef;
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}
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sub timethis{
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my($n, $code, $title, $style) = @_;
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my($t, $for, $forn);
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if ( $n > 0 ) {
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croak "non-integer loopcount $n, stopped" if int($n)<$n;
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$t = timeit($n, $code);
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$title = "timethis $n" unless defined $title;
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} else {
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$fort = n_to_for( $n );
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$t = runfor($code, $fort);
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$title = "timethis for $fort" unless defined $title;
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$forn = $t->[-1];
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}
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local $| = 1;
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$style = "" unless defined $style;
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printf("%10s: ", $title);
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print timestr($t, $style, $defaultfmt),"\n";
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$n = $forn if defined $forn;
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# A conservative warning to spot very silly tests.
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# Don't assume that your benchmark is ok simply because
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# you don't get this warning!
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print " (warning: too few iterations for a reliable count)\n"
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if $n < $min_count
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|| ($t->real < 1 && $n < 1000)
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|| $t->cpu_a < $min_cpu;
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$t;
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}
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sub timethese{
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my($n, $alt, $style) = @_;
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die "usage: timethese(count, { 'Name1'=>'code1', ... }\n"
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unless ref $alt eq HASH;
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my @names = sort keys %$alt;
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$style = "" unless defined $style;
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print "Benchmark: ";
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if ( $n > 0 ) {
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croak "non-integer loopcount $n, stopped" if int($n)<$n;
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print "timing $n iterations of";
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} else {
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print "running";
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}
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print " ", join(', ',@names);
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unless ( $n > 0 ) {
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my $for = n_to_for( $n );
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print ", each for at least $for CPU seconds";
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}
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print "...\n";
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# we could save the results in an array and produce a summary here
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# sum, min, max, avg etc etc
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foreach my $name (@names) {
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timethis ($n, $alt -> {$name}, $name, $style);
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}
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}
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1;
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