=head1 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
+Benchmark - benchmark running times of Perl code
=head1 SYNOPSIS
'Name2' => sub { ...code2... },
});
+ # cmpthese can be used both ways as well
+ cmpthese($count, {
+ 'Name1' => '...code1...',
+ 'Name2' => '...code2...',
+ });
+
+ cmpthese($count, {
+ 'Name1' => sub { ...code1... },
+ 'Name2' => sub { ...code2... },
+ });
+
+ # ...or in two stages
+ $results = timethese($count,
+ {
+ 'Name1' => sub { ...code1... },
+ 'Name2' => sub { ...code2... },
+ },
+ 'none'
+ );
+ cmpthese( $results ) ;
+
$t = timeit($count, '...other code...')
print "$count loops of other code took:",timestr($t),"\n";
+ $t = countit($time, '...other code...')
+ $count = $t->iters ;
+ print "$count loops of other code took:",timestr($t),"\n";
+
=head1 DESCRIPTION
The Benchmark module encapsulates a number of routines to help you
figure out how long it takes to execute some code.
+timethis - run a chunk of code several times
+
+timethese - run several chunks of code several times
+
+cmpthese - print results of timethese as a comparison chart
+
+timeit - run a chunk of code and see how long it goes
+
+countit - see how many times a chunk of code runs in a given time
+
+
=head2 Methods
=over 10
$t = timeit(10, ' 5 ** $Global ');
debug Benchmark 0;
+=item iters
+
+Returns the number of iterations.
+
=back
=head2 Standard Exports
The COUNT can be zero or negative, see timethis().
+Returns a hash of Benchmark objects, keyed by name.
+
=item timediff ( T1, T2 )
Returns the difference between two Benchmark times as a Benchmark
object suitable for passing to timestr().
-=item timesum ( T1, T2 )
-
-Returns the sum of two Benchmark times as a Benchmark object suitable
-for passing to timestr().
-
=item 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,
+STYLE can be any of 'all', 'none', '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'.
+'none' prevents output.
FORMAT is the L<printf(3)>-style format specifier (without the
leading '%') to use to print the times. It defaults to '5.2f'.
Clear all cached times.
+=item cmpthese ( COUT, CODEHASHREF, [ STYLE ] )
+
+=item cmpthese ( RESULTSHASHREF )
+
+Optionally calls timethese(), then outputs comparison chart. This
+chart is sorted from slowest to fastest, and shows the percent
+speed difference between each pair of tests. Can also be passed
+the data structure that timethese() returns:
+
+ $results = timethese( .... );
+ cmpthese( $results );
+
+Returns the data structure returned by timethese() (or passed in).
+
+=item countit(TIME, CODE)
+
+Arguments: TIME is the minimum length of time to run CODE for, and CODE is
+the code to run. CODE may be either a code reference or a string to
+be eval'd; either way it will be run in the caller's package.
+
+TIME is I<not> negative. countit() will run the loop many times to
+calculate the speed of CODE before running it for TIME. The actual
+time run for will usually be greater than TIME due to system clock
+resolution, so it's best to look at the number of iterations divided
+by the times that you are concerned with, not just the iterations.
+
+Returns: a Benchmark object.
+
=item disablecache ( )
Disable caching of timings for the null loop. This will force Benchmark
rounds of the null loop will be calculated only once for each
different COUNT used.
+=item timesum ( T1, T2 )
+
+Returns the sum of two Benchmark times as a Benchmark object suitable
+for passing to timestr().
+
=back
=head1 NOTES
The data is stored as a list of values from the time and times
functions:
- ($real, $user, $system, $children_user, $children_system)
+ ($real, $user, $system, $children_user, $children_system, $iters)
in seconds for the whole loop (not divided by the number of rounds).
number of rounds but empty loop body) is subtracted
from the time of the real loop.
-The null loop times are cached, the key being the
+The null loop times can be cached, the key being the
number of rounds. The caching can be controlled using
calls like these:
disablecache();
enablecache();
+Caching is off by default, as it can (usually slightly) decrease
+accuracy and does not usually noticably affect runtimes.
+
+=head1 EXAMPLES
+
+For example,
+
+ use Benchmark;$x=3;cmpthese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
+
+outputs something like this:
+
+ Benchmark: running a, b, each for at least 5 CPU seconds...
+ a: 10 wallclock secs ( 5.14 usr + 0.13 sys = 5.27 CPU) @ 3835055.60/s (n=20210743)
+ b: 5 wallclock secs ( 5.41 usr + 0.00 sys = 5.41 CPU) @ 1574944.92/s (n=8520452)
+ Rate b a
+ b 1574945/s -- -59%
+ a 3835056/s 144% --
+
+while
+
+ use Benchmark;
+ $x=3;
+ $r=timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}},'none');
+ cmpthese($r);
+
+outputs something like this:
+
+ Rate b a
+ b 1559428/s -- -62%
+ a 4152037/s 166% --
+
+
=head1 INHERITANCE
Benchmark inherits from no other class, except of course
=head1 CAVEATS
Comparing eval'd strings with code references will give you
-inaccurate results: a code reference will show a slower
+inaccurate results: a code reference will show a slightly slower
execution time than the equivalent eval'd string.
The real time timing is done using time(2) and
more than the system time of the loop with the actual
code and therefore the difference might end up being E<lt> 0.
+=head1 SEE ALSO
+
+L<Devel::DProf> - a Perl code profiler
+
=head1 AUTHORS
Jarkko Hietaniemi <F<jhi@iki.fi>>, Tim Bunce <F<Tim.Bunce@ig.co.uk>>
April 04-07th, 1997: by Jarkko Hietaniemi, added the run-for-some-time
functionality.
+September, 1999; by Barrie Slaymaker: math fixes and accuracy and
+efficiency tweaks. Added cmpthese(). A result is now returned from
+timethese(). Exposed countit() (was runfor()).
+
=cut
# evaluate something in a clean lexical environment
use Carp;
use Exporter;
@ISA=(Exporter);
-@EXPORT=qw(timeit timethis timethese timediff timesum timestr);
-@EXPORT_OK=qw(clearcache clearallcache disablecache enablecache);
+@EXPORT=qw(timeit timethis timethese timediff timestr);
+@EXPORT_OK=qw(timesum cmpthese countit
+ clearcache clearallcache disablecache enablecache);
+
+$VERSION = 1.01;
&init;
sub cpu_c { my($r,$pu,$ps,$cu,$cs) = @{$_[0]}; $cu+$cs ; }
sub cpu_a { my($r,$pu,$ps,$cu,$cs) = @{$_[0]}; $pu+$ps+$cu+$cs ; }
sub real { my($r,$pu,$ps,$cu,$cs) = @{$_[0]}; $r ; }
+sub iters { $_[0]->[5] ; }
sub timediff {
my($a, $b) = @_;
my @t = @$tr;
warn "bad time value (@t)" unless @t==6;
my($r, $pu, $ps, $cu, $cs, $n) = @t;
- my($pt, $ct, $t) = ($tr->cpu_p, $tr->cpu_c, $tr->cpu_a);
+ my($pt, $ct, $tt) = ($tr->cpu_p, $tr->cpu_c, $tr->cpu_a);
$f = $defaultfmt unless defined $f;
# format a time in the required style, other formats may be added here
$style ||= $defaultstyle;
$style = ($ct>0) ? 'all' : 'noc' if $style eq 'auto';
my $s = "@t $style"; # default for unknown style
$s=sprintf("%2d wallclock secs (%$f usr %$f sys + %$f cusr %$f csys = %$f CPU)",
- @t,$t) if $style eq 'all';
+ $r,$pu,$ps,$cu,$cs,$tt) if $style eq 'all';
$s=sprintf("%2d wallclock secs (%$f usr + %$f sys = %$f CPU)",
$r,$pu,$ps,$pt) if $style eq 'noc';
$s=sprintf("%2d wallclock secs (%$f cusr + %$f csys = %$f CPU)",
$r,$cu,$cs,$ct) if $style eq 'nop';
- $s .= sprintf(" @ %$f/s (n=$n)", $n / ( $pu + $ps )) if $n;
+ $s .= sprintf(" @ %$f/s (n=$n)", $n / ( $pu + $ps )) if $n && $pu+$ps;
$s;
}
croak "runloop unable to compile '$c': $@\ncode: $subcode\n" if $@;
print STDERR "runloop $n '$subcode'\n" if $debug;
- # Wait for the user timer to tick. This makes the error range more like -0.01, +0. If
- # we don't wait, then it's more like -0.01, +0.01. This may not seem important, but it
- # significantly reduces the chances of getting too low initial $n in the initial, 'find
- # the minimum' loop in &runfor. This, in turn, can reduce the number of calls to
+ # Wait for the user timer to tick. This makes the error range more like
+ # -0.01, +0. If we don't wait, then it's more like -0.01, +0.01. This
+ # may not seem important, but it significantly reduces the chances of
+ # getting a too low initial $n in the initial, 'find the minimum' loop
+ # in &countit. This, in turn, can reduce the number of calls to
# &runloop a lot, and thus reduce additive errors.
my $tbase = Benchmark->new(0)->[1];
- do {
- $t0 = Benchmark->new(0);
- } while ( $t0->[1] == $tbase ) ;
+ while ( ( $t0 = Benchmark->new(0) )->[1] == $tbase ) {} ;
&$subref;
$t1 = Benchmark->new($n);
$td = &timediff($t1, $t0);
my($wn, $wc, $wd);
printf STDERR "timeit $n $code\n" if $debug;
- my $cache_key = $n . ( ref( $code ) ? 'c' : 's' ) ;
+ my $cache_key = $n . ( ref( $code ) ? 'c' : 's' );
if ($cache && exists $cache{$cache_key} ) {
$wn = $cache{$cache_key};
} else {
$wn = &runloop($n, ref( $code ) ? sub { undef } : '' );
+ # Can't let our baseline have any iterations, or they get subtracted
+ # out of the result.
+ $wn->[5] = 0;
$cache{$cache_key} = $wn;
}
$wc = &runloop($n, $code);
$wd = timediff($wc, $wn);
-
timedebug("timeit: ",$wc);
timedebug(" - ",$wn);
timedebug(" = ",$wd);
my $default_for = 3;
my $min_for = 0.1;
-sub runfor {
- my ($code, $tmax) = @_;
+
+sub countit {
+ my ( $tmax, $code ) = @_;
if ( not defined $tmax or $tmax == 0 ) {
$tmax = $default_for;
$tmax = -$tmax;
}
- die "runfor(..., $tmax): timelimit cannot be less than $min_for.\n"
+ die "countit($tmax, ...): timelimit cannot be less than $min_for.\n"
if $tmax < $min_for;
- my ($n, $td, $tc, $ntot, $rtot, $utot, $stot, $cutot, $cstot );
+ my ($n, $tc);
# First find the minimum $n that gives a significant timing.
-
- my $nmin;
-
- for ($n = 1, $tc = 0; ; $n *= 2 ) {
- $td = timeit($n, $code);
+ for ($n = 1; ; $n *= 2 ) {
+ my $td = timeit($n, $code);
$tc = $td->[1] + $td->[2];
- last if $tc > 0.1 ;
+ last if $tc > 0.1;
}
- $nmin = $n;
-
- my $ttot = 0;
- my $tpra = 0.05 * $tmax; # Target/time practice.
- # Double $n until we have think we have practiced enough.
- for ( ; $ttot < $tpra; $n *= 2 ) {
- $td = timeit($n, $code);
- $ntot += $n;
- $rtot += $td->[0];
- $utot += $td->[1];
- $stot += $td->[2];
- $ttot = $utot + $stot;
- $cutot += $td->[3];
- $cstot += $td->[4];
+ my $nmin = $n;
+
+ # Get $n high enough that we can guess the final $n with some accuracy.
+ my $tpra = 0.1 * $tmax; # Target/time practice.
+ while ( $tc < $tpra ) {
+ # The 5% fudge is to keep us from iterating again all
+ # that often (this speeds overall responsiveness when $tmax is big
+ # and we guess a little low). This does not noticably affect
+ # accuracy since we're not couting these times.
+ $n = int( $tpra * 1.05 * $n / $tc ); # Linear approximation.
+ my $td = timeit($n, $code);
+ my $new_tc = $td->[1] + $td->[2];
+ # Make sure we are making progress.
+ $tc = $new_tc > 1.2 * $tc ? $new_tc : 1.2 * $tc;
}
- my $r;
+ # Now, do the 'for real' timing(s), repeating until we exceed
+ # the max.
+ my $ntot = 0;
+ my $rtot = 0;
+ my $utot = 0.0;
+ my $stot = 0.0;
+ my $cutot = 0.0;
+ my $cstot = 0.0;
+ my $ttot = 0.0;
+
+ # The 5% fudge is because $n is often a few % low even for routines
+ # with stable times and avoiding extra timeit()s is nice for
+ # accuracy's sake.
+ $n = int( $n * ( 1.05 * $tmax / $tc ) );
+
+ while () {
+ my $td = timeit($n, $code);
+ $ntot += $n;
+ $rtot += $td->[0];
+ $utot += $td->[1];
+ $stot += $td->[2];
+ $cutot += $td->[3];
+ $cstot += $td->[4];
+ $ttot = $utot + $stot;
+ last if $ttot >= $tmax;
- # Then iterate towards the $tmax.
- while ( $ttot < $tmax ) {
- $r = $tmax / $ttot - 1; # Linear approximation.
+ $ttot = 0.01 if $ttot < 0.01;
+ my $r = $tmax / $ttot - 1; # Linear approximation.
$n = int( $r * $ntot );
$n = $nmin if $n < $nmin;
- $td = timeit($n, $code);
- $ntot += $n;
- $rtot += $td->[0];
- $utot += $td->[1];
- $stot += $td->[2];
- $ttot = $utot + $stot;
- $cutot += $td->[3];
- $cstot += $td->[4];
}
return bless [ $rtot, $utot, $stot, $cutot, $cstot, $ntot ];
$title = "timethis $n" unless defined $title;
} else {
$fort = n_to_for( $n );
- $t = runfor($code, $fort);
+ $t = countit( $fort, $code );
$title = "timethis for $fort" unless defined $title;
$forn = $t->[-1];
}
local $| = 1;
$style = "" unless defined $style;
- printf("%10s: ", $title);
- print timestr($t, $style, $defaultfmt),"\n";
+ printf("%10s: ", $title) unless $style eq 'none';
+ print timestr($t, $style, $defaultfmt),"\n" unless $style eq 'none';
$n = $forn if defined $forn;
unless ref $alt eq HASH;
my @names = sort keys %$alt;
$style = "" unless defined $style;
- print "Benchmark: ";
+ print "Benchmark: " unless $style eq 'none';
if ( $n > 0 ) {
croak "non-integer loopcount $n, stopped" if int($n)<$n;
- print "timing $n iterations of";
+ print "timing $n iterations of" unless $style eq 'none';
} else {
- print "running";
+ print "running" unless $style eq 'none';
}
- print " ", join(', ',@names);
+ print " ", join(', ',@names) unless $style eq 'none';
unless ( $n > 0 ) {
my $for = n_to_for( $n );
- print ", each for at least $for CPU seconds";
+ print ", each for at least $for CPU seconds" unless $style eq 'none';
}
- print "...\n";
+ print "...\n" unless $style eq 'none';
# we could save the results in an array and produce a summary here
# sum, min, max, avg etc etc
+ my %results;
foreach my $name (@names) {
- timethis ($n, $alt -> {$name}, $name, $style);
+ $results{$name} = timethis ($n, $alt -> {$name}, $name, $style);
}
+
+ return \%results;
}
+sub cmpthese{
+ my $results = ref $_[0] ? $_[0] : timethese( @_ );
+
+ return $results
+ if defined $_[2] && $_[2] eq 'none';
+
+ # Flatten in to an array of arrays with the name as the first field
+ my @vals = map{ [ $_, @{$results->{$_}} ] } keys %$results;
+
+ for (@vals) {
+ # The epsilon fudge here is to prevent div by 0. Since clock
+ # resolutions are much larger, it's below the noise floor.
+ my $rate = $_->[6] / ( $_->[2] + $_->[3] + 0.000000000000001 );
+ $_->[7] = $rate;
+ }
+
+ # Sort by rate
+ @vals = sort { $a->[7] <=> $b->[7] } @vals;
+
+ # If more than half of the rates are greater than one...
+ my $display_as_rate = $vals[$#vals>>1]->[7] > 1;
+
+ my @rows;
+ my @col_widths;
+
+ my @top_row = (
+ '',
+ $display_as_rate ? 'Rate' : 's/iter',
+ map { $_->[0] } @vals
+ );
+
+ push @rows, \@top_row;
+ @col_widths = map { length( $_ ) } @top_row;
+
+ # Build the data rows
+ # We leave the last column in even though it never has any data. Perhaps
+ # it should go away. Also, perhaps a style for a single column of
+ # percentages might be nice.
+ for my $row_val ( @vals ) {
+ my @row;
+
+ # Column 0 = test name
+ push @row, $row_val->[0];
+ $col_widths[0] = length( $row_val->[0] )
+ if length( $row_val->[0] ) > $col_widths[0];
+
+ # Column 1 = performance
+ my $row_rate = $row_val->[7];
+
+ # We assume that we'll never get a 0 rate.
+ my $a = $display_as_rate ? $row_rate : 1 / $row_rate;
+
+ # Only give a few decimal places before switching to sci. notation,
+ # since the results aren't usually that accurate anyway.
+ my $format =
+ $a >= 100 ?
+ "%0.0f" :
+ $a >= 10 ?
+ "%0.1f" :
+ $a >= 1 ?
+ "%0.2f" :
+ $a >= 0.1 ?
+ "%0.3f" :
+ "%0.2e";
+
+ $format .= "/s"
+ if $display_as_rate;
+ # Using $b here due to optimizing bug in _58 through _61
+ my $b = sprintf( $format, $a );
+ push @row, $b;
+ $col_widths[1] = length( $b )
+ if length( $b ) > $col_widths[1];
+
+ # Columns 2..N = performance ratios
+ my $skip_rest = 0;
+ for ( my $col_num = 0 ; $col_num < @vals ; ++$col_num ) {
+ my $col_val = $vals[$col_num];
+ my $out;
+ if ( $skip_rest ) {
+ $out = '';
+ }
+ elsif ( $col_val->[0] eq $row_val->[0] ) {
+ $out = "--";
+ # $skip_rest = 1;
+ }
+ else {
+ my $col_rate = $col_val->[7];
+ $out = sprintf( "%.0f%%", 100*$row_rate/$col_rate - 100 );
+ }
+ push @row, $out;
+ $col_widths[$col_num+2] = length( $out )
+ if length( $out ) > $col_widths[$col_num+2];
+
+ # A little wierdness to set the first column width properly
+ $col_widths[$col_num+2] = length( $col_val->[0] )
+ if length( $col_val->[0] ) > $col_widths[$col_num+2];
+ }
+ push @rows, \@row;
+ }
+
+ # Equalize column widths in the chart as much as possible without
+ # exceeding 80 characters. This does not use or affect cols 0 or 1.
+ my @sorted_width_refs =
+ sort { $$a <=> $$b } map { \$_ } @col_widths[2..$#col_widths];
+ my $max_width = ${$sorted_width_refs[-1]};
+
+ my $total = @col_widths - 1 ;
+ for ( @col_widths ) { $total += $_ }
+
+ STRETCHER:
+ while ( $total < 80 ) {
+ my $min_width = ${$sorted_width_refs[0]};
+ last
+ if $min_width == $max_width;
+ for ( @sorted_width_refs ) {
+ last
+ if $$_ > $min_width;
+ ++$$_;
+ ++$total;
+ last STRETCHER
+ if $total >= 80;
+ }
+ }
+
+ # Dump the output
+ my $format = join( ' ', map { "%${_}s" } @col_widths ) . "\n";
+ substr( $format, 1, 0 ) = '-';
+ for ( @rows ) {
+ printf $format, @$_;
+ }
+
+ return $results;
+}
+
+
1;
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