Re^4: Making a hash with lists

Try this variation of your benchmark:

#! perl

use strict;
use warnings;
use Benchmark 'cmpthese';
use List::MoreUtils 'zip'; # Hands up if you can predict the result? :
+)

sub zip1 {
  my @list1 = @{shift()};
  my @list2 = @{shift()};
  my @zip;
  while (@list1+@list2) {
    push(@zip, shift(@list1), shift(@list2));
  }
  @zip
}

sub zip2 {
    my( $r1, $r2 ) = @_;
    map {
        $r1->[ $_ ], $r2->[ $_ ]
    } 0 .. ( $#$r1 > $#$r2 ? $#$r1 : $#$r2 );
}

for my $length (10, 1000, 10000, 100000) {
    my @a = 1 .. $length;
    my @b = reverse @a;
    print "For $length elements:\n";
    cmpthese(-3, {
        copy  => sub{ my @res = zip1( \@a, \@b ) },
        deref => sub{ my @res = zip2( \@a, \@b ) },
        CPAN  => sub{ my @res = zip(   @a,  @b ) },
    });
    print "\n";
}
[download]

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

"Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."

Comment on Re^4: Making a hash with lists Download Code

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Re^5: Making a hash with lists by Porculus (Hermit) on Jun 28, 2008 at 16:29 UTC
Oops. I thought those results looked fishy. Thanks; I've learnt something today. (This must be quite a common mistake to make. I would have expected the "strict" pragma to pick up the scoping error, but it looks like 'strict' isn't active within the evalled code by default.)	[reply]
Re^6: Making a hash with lists by BrowserUk (Patriarch) on Jun 28, 2008 at 19:08 UTC
but it looks like 'strict' isn't active within the evalled code by default By default it isn't, due to this piece of nonsense from Benchmark.pm: `# evaluate something in a clean lexical environment sub _doeval { no strict; eval shift }` [download] If you remove the `no strict;` as I have, then you'd have got: `For 10 elements: runloop unable to compile ' my @res = zip( @a, @b ) ': Global symbol "@a" requires explicit package name at (eval 4) line 1. Global symbol "@b" requires explicit package name at (eval 4) line 1. code: sub { for (1 .. 1) { local $_; package main; my @res = zip( @ +a, @b ) ;} } at c:\test\junk9.pl line 29` [download] Which seems far more useful than the current behaviour. I'm not sure what the author hoped to achieve by adding it? The other thing to note in my version is the assignment of the result. Without this, Perl may optimise away code that appears in a void context. In 5.10 for example, map called in a void context doesn't bother stacking the results which would further skew the benchmark. Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. "Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."	[reply] [d/l] [select]