Re^2: Macro in perl code?

Here is a benchmark attempt for a few variations:


#!/usr/bin/perl

use strict;
use warnings;

use Benchmark;

our $verbosity = 7;
our $volume    = 1;
our $holy_crap = "Hmmmm.. here's the problem!";

timethese(10000000, {
     'Name1' => ' v_print0( 1, "Holy Crap = holy_crap\n"); ',
     'Name2' => ' v_print0( 1, "Holy Crap = $holy_crap\n"); ',
     'Name3' => ' v_print1( 1, sub { "Holy Crap = holy_crap\n"  } ); '
+,
     'Name4' => ' v_print1( 1, sub { "Holy Crap = $holy_crap\n" } ); '
+,
     'Name5' => ' v_print2( 1, \'"Holy Crap = holy_crap\n"\'  ); ',
     'Name6' => ' v_print2( 1, \'"Holy Crap = $holy_crap\n"\' ); ',
     'Name7' => ' if ( $volume >= $verbosity ) { v_print3( "Holy Crap 
+ $holy_crap\n" ) }; ',
});
[download]

sub v_print0 {
    my $volume  = shift;
    my $message = shift;
    if ( $volume >= $verbosity ) {
        print $message;
    }
}

sub v_print1 {
    my $volume = shift;
    my $code   = shift;
    if ( $volume >= $verbosity ) {
        print &$code;
    }
}

sub v_print2 {
    my $volume = shift;
    my $code   = shift;
    if ( $volume >= $verbosity ) {
        print eval( $code );
    }
}

sub v_print3 {
    my $message = shift;
    print $message;
}
[download]

And here the results:

Benchmark: timing 10000000 iterations of Name1, Name2, Name3, Name4, N
+ame5, Name6, Name7...
     Name1: 12 wallclock secs (11.24 usr +  0.01 sys = 11.25 CPU) @ 88
+8888.89/s (n=10000000)
     Name2: 16 wallclock secs (16.08 usr +  0.00 sys = 16.08 CPU) @ 62
+1890.55/s (n=10000000)
     Name3: 14 wallclock secs (13.93 usr + -0.01 sys = 13.92 CPU) @ 71
+8390.80/s (n=10000000)
     Name4: 13 wallclock secs (14.10 usr +  0.00 sys = 14.10 CPU) @ 70
+9219.86/s (n=10000000)
     Name5: 11 wallclock secs (11.26 usr +  0.00 sys = 11.26 CPU) @ 88
+8099.47/s (n=10000000)
     Name6: 12 wallclock secs (11.00 usr +  0.01 sys = 11.01 CPU) @ 90
+8265.21/s (n=10000000)
     Name7:  1 wallclock secs ( 1.24 usr +  0.00 sys =  1.24 CPU) @ 80
+64516.13/s (n=10000000)
[download]

Conclusions seem to be, as you mentioned:

avoid calling subs in the first place, if possible

postpone string interpolation to happen only in the called sub, not before the call

The initial surprise diminished a bit after thinking about the benchmarks - but it's good to know it anyway;)

Comment on Re^2: Macro in perl code? Select or Download Code

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Re^3: Macro in perl code? by andreas1234567 (Vicar) on Oct 17, 2007 at 07:47 UTC
One can improve performance even further by using constant. `$ cat 645310.pl use strict; use warnings; use Benchmark qw/ cmpthese /; our $verbosity = 7; our $volume = 1; use constant VERBOSE => 0; cmpthese( -1, { 'Name7' => ' if ( $volume >= $verbosity ) { v_print3( "foo" ) }; ' +, 'Name8' => ' if ( VERBOSE ) { v_print3( "foo" ) }; ' +, } ); sub v_print3 { my $message = shift; print $message; } __END__ $ perl 645310.pl Rate Name7 Name8 Name7 9442579/s -- -74% Name8 35826879/s 279% --` [download] The whole subroutine call gets optimized away: `$ perl -MO=Deparse,-x,-p -e 'use constant VERBOSE => 0; if ( VERBOSE ) + { v_print3( "foo" ) }; ' use constant ('VERBOSE', 0); '???'; -e syntax OK` [download] -- Andreas	[reply] [d/l] [select]

Replies are listed 'Best First'.

Re^3: Macro in perl code?
by andreas1234567 (Vicar) on Oct 17, 2007 at 07:47 UTC

constant

$ cat 645310.pl
use strict;
use warnings;
use Benchmark qw/ cmpthese /;

our $verbosity = 7;
our $volume    = 1;
use constant VERBOSE => 0;

cmpthese(
  -1,
  {
    'Name7' => ' if ( $volume >= $verbosity ) { v_print3( "foo" ) }; '
+,
    'Name8' => ' if ( VERBOSE )               { v_print3( "foo" ) }; '
+,
  }
);

sub v_print3 { my $message = shift; print $message; }
__END__
$ perl 645310.pl
            Rate Name7 Name8
Name7  9442579/s    --  -74%
Name8 35826879/s  279%    --
[download]

$ perl -MO=Deparse,-x,-p -e 'use constant VERBOSE => 0; if ( VERBOSE )
+ { v_print3( "foo" ) }; '
use constant ('VERBOSE', 0);
'???';
-e syntax OK
[download]

--
Andreas

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