package Benchmark; =head1 NAME Benchmark - benchmark running times of Perl code =head1 SYNOPSIS timethis ($count, "code"); # Use Perl code in strings... timethese($count, { 'Name1' => '...code1...', 'Name2' => '...code2...', }); # ... or use subroutine references. timethese($count, { 'Name1' => sub { ...code1... }, 'Name2' => sub { ...code2... }, }); # cmpthese can be used both ways as well cmpthese($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 =item 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"; =item debug Enables or disable debugging by setting the C<$Benchmark::Debug> flag: debug Benchmark 1; $t = timeit(10, ' 5 ** $Global '); debug Benchmark 0; =item iters Returns the number of iterations. =back =head2 Standard Exports The following routines will be exported into your namespace if you use the Benchmark module: =over 10 =item 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. =item 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. The COUNT can be zero or negative: this means the I to run. A zero signifies the default of 3 seconds. For example to run at least for 10 seconds: timethis(-10, $code) or to run two pieces of code tests for at least 3 seconds: timethese(0, { test1 => '...', test2 => '...'}) CPU seconds is, in UNIX terms, the user time plus the system time of the process itself, as opposed to the real (wallclock) time and the time spent by the child processes. Less than 0.1 seconds is not accepted (-0.01 as the count, for example, will cause a fatal runtime exception). Note that the CPU seconds is the B time: CPU scheduling and other operating system factors may complicate the attempt so that a little bit more time is spent. The benchmark output will, however, also tell the number of C<$code> runs/second, which should be a more interesting number than the actually spent seconds. Returns a Benchmark object. =item 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) The routines are called in string comparison order of KEY. 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 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', '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-style format specifier (without the leading '%') to use to print the times. It defaults to '5.2f'. =back =head2 Optional Exports The following routines will be exported into your namespace if you specifically ask that they be imported: =over 10 =item clearcache ( COUNT ) Clear the cached time for COUNT rounds of the null loop. =item clearallcache ( ) 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( $results ); Returns the data structure returned by timethese() (or passed in). =item countit(TIME, CODE) Arguments: TIME is the minimum length of time to run CODE for, and CODE is the code to run. CODE may be either a code reference or a string to be eval'd; either way it will be run in the caller's package. TIME is I negative. countit() will run the loop many times to calculate the speed of CODE before running it for TIME. The actual time run for will usually be greater than TIME due to system clock resolution, so it's best to look at the number of iterations divided by the times that you are concerned with, not just the iterations. Returns: a Benchmark object. =item disablecache ( ) Disable caching of timings for the null loop. This will force Benchmark to recalculate these timings for each new piece of code timed. =item enablecache ( ) Enable caching of timings for the null loop. The time taken for COUNT rounds of the null loop will be calculated only once for each different COUNT used. =item timesum ( T1, T2 ) Returns the sum of two Benchmark times as a Benchmark object suitable for passing to timestr(). =back =head1 NOTES The data is stored as a list of values from the time and times functions: ($real, $user, $system, $children_user, $children_system, $iters) in seconds for the whole loop (not divided by the number of rounds). The timing is done using time(3) and times(3). Code is executed in the caller's package. The time of the null loop (a loop with the same number of rounds but empty loop body) is subtracted from the time of the real loop. The null loop times can be cached, the key being the number of rounds. The caching can be controlled using calls like these: clearcache($key); clearallcache(); 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 for Exporter. =head1 CAVEATS Comparing eval'd strings with code references will give you 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 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 E 0. =head1 SEE ALSO L - a Perl code profiler =head1 AUTHORS Jarkko Hietaniemi >, Tim Bunce > =head1 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. 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 sub _doeval { eval shift } # # put any lexicals at file scope AFTER here # use Carp; use Exporter; @ISA=(Exporter); @EXPORT=qw(timeit timethis timethese timediff timestr); @EXPORT_OK=qw(timesum cmpthese countit clearcache clearallcache disablecache enablecache); $VERSION = 1.00; &init; sub init { $debug = 0; $min_count = 4; $min_cpu = 0.4; $defaultfmt = '5.2f'; $defaultstyle = 'auto'; # The cache can cause a slight loss of sys time accuracy. If a # user does many tests (>10) with *very* large counts (>10000) # or works on a very slow machine the cache may be useful. &disablecache; &clearallcache; } sub debug { $debug = ($_[1] != 0); } # The cache needs two branches: 's' for strings and 'c' for code. The # emtpy loop is different in these two cases. sub clearcache { delete $cache{"$_[0]c"}; delete $cache{"$_[0]s"}; } sub clearallcache { %cache = (); } sub enablecache { $cache = 1; } sub disablecache { $cache = 0; } # --- Functions to process the 'time' data type sub new { my @t = (time, times, @_ == 2 ? $_[1] : 0); print "new=@t\n" if $debug; bless \@t; } sub cpu_p { my($r,$pu,$ps,$cu,$cs) = @{$_[0]}; $pu+$ps ; } 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 @r; for (my $i=0; $i < @$a; ++$i) { push(@r, $a->[$i] - $b->[$i]); } bless \@r; } sub timesum { my($a, $b) = @_; my @r; for (my $i=0; $i < @$a; ++$i) { push(@r, $a->[$i] + $b->[$i]); } bless \@r; } sub timestr { my($tr, $style, $f) = @_; my @t = @$tr; warn "bad time value (@t)" unless @t==6; my($r, $pu, $ps, $cu, $cs, $n) = @t; my($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)", $r,$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 && $pu+$ps; $s; } sub timedebug { my($msg, $t) = @_; print STDERR "$msg",timestr($t),"\n" if $debug; } # --- Functions implementing low-level support for timing loops sub runloop { my($n, $c) = @_; $n+=0; # force numeric now, so garbage won't creep into the eval croak "negative loopcount $n" if $n<0; confess "Usage: runloop(number, [string | coderef])" unless defined $c; my($t0, $t1, $td); # before, after, difference # find package of caller so we can execute code there my($curpack) = caller(0); my($i, $pack)= 0; while (($pack) = caller(++$i)) { last if $pack ne $curpack; } my ($subcode, $subref); if (ref $c eq 'CODE') { $subcode = "sub { for (1 .. $n) { local \$_; package $pack; &\$c; } }"; $subref = eval $subcode; } else { $subcode = "sub { for (1 .. $n) { local \$_; package $pack; $c;} }"; $subref = _doeval($subcode); } 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 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]; while ( ( $t0 = Benchmark->new(0) )->[1] == $tbase ) {} ; &$subref; $t1 = Benchmark->new($n); $td = &timediff($t1, $t0); timedebug("runloop:",$td); $td; } sub timeit { my($n, $code) = @_; my($wn, $wc, $wd); printf STDERR "timeit $n $code\n" if $debug; 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); $wd; } my $default_for = 3; my $min_for = 0.1; sub countit { my ( $tmax, $code ) = @_; if ( not defined $tmax or $tmax == 0 ) { $tmax = $default_for; } elsif ( $tmax < 0 ) { $tmax = -$tmax; } die "countit($tmax, ...): timelimit cannot be less than $min_for.\n" if $tmax < $min_for; my ($n, $tc); # First find the minimum $n that gives a significant timing. for ($n = 1; ; $n *= 2 ) { my $td = timeit($n, $code); $tc = $td->[1] + $td->[2]; last if $tc > 0.1; } 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; } # 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; $ttot = 0.01 if $ttot < 0.01; my $r = $tmax / $ttot - 1; # Linear approximation. $n = int( $r * $ntot ); $n = $nmin if $n < $nmin; } return bless [ $rtot, $utot, $stot, $cutot, $cstot, $ntot ]; } # --- Functions implementing high-level time-then-print utilities sub n_to_for { my $n = shift; return $n == 0 ? $default_for : $n < 0 ? -$n : undef; } sub timethis{ my($n, $code, $title, $style) = @_; my($t, $for, $forn); if ( $n > 0 ) { croak "non-integer loopcount $n, stopped" if int($n)<$n; $t = timeit($n, $code); $title = "timethis $n" unless defined $title; } else { $fort = n_to_for( $n ); $t = countit( $fort, $code ); $title = "timethis for $fort" unless defined $title; $forn = $t->[-1]; } local $| = 1; $style = "" unless defined $style; printf("%10s: ", $title) unless $style eq 'none'; print timestr($t, $style, $defaultfmt),"\n" unless $style eq 'none'; $n = $forn if defined $forn; # A conservative warning to spot very silly tests. # Don't assume that your benchmark is ok simply because # you don't get this warning! print " (warning: too few iterations for a reliable count)\n" if $n < $min_count || ($t->real < 1 && $n < 1000) || $t->cpu_a < $min_cpu; $t; } sub timethese{ my($n, $alt, $style) = @_; die "usage: timethese(count, { 'Name1'=>'code1', ... }\n" unless ref $alt eq HASH; my @names = sort keys %$alt; $style = "" unless defined $style; print "Benchmark: " unless $style eq 'none'; if ( $n > 0 ) { croak "non-integer loopcount $n, stopped" if int($n)<$n; print "timing $n iterations of" unless $style eq 'none'; } else { print "running" unless $style eq 'none'; } print " ", join(', ',@names) unless $style eq 'none'; unless ( $n > 0 ) { my $for = n_to_for( $n ); print ", each for at least $for CPU seconds" unless $style eq 'none'; } 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) { $results{$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;