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Re^3: Does @{ } copy arrays?

by bv (Friar)
on Oct 17, 2009 at 16:34 UTC ( #801770=note: print w/replies, xml ) Need Help??


in reply to Re^2: Does @{ } copy arrays?
in thread Does @{ } copy arrays?

Interesting! That's the kind of answer I was hoping someone would post. For anyone who's keeping score, here's a benchmark and my results:

#!/usr/bin/perl use strict; use warnings; use Benchmark qw(cmpthese); my $i=0; cmpthese(-10, { deref => sub { my $aryptr = [qw(Once upon a time in a galaxy far far away +)]; if ( @{ $aryptr } ) { $i=1; } $aryptr = []; if ( @{ $aryptr } ) { $i=-1; } }, arylen => sub { my $aryptr = [qw(Once upon a time in a galaxy far far away +)]; if ( $#{ $aryptr } >= 0 ) { $i=1; } $aryptr = []; if ( $#{ $aryptr } >= 0 ) { $i=-1; } }, } ); __END__ Rate arylen deref arylen 95903/s -- -28% deref 132418/s 38% --

print pack("A25",pack("V*",map{1919242272+$_}(34481450,-49737472,6228,0,-285028276,6979,-1380265972)))

Replies are listed 'Best First'.
Re^4: Does @{ } copy arrays?
by ikegami (Pope) on Oct 23, 2009 at 20:57 UTC

    The point is that $#a should be faster than @a-1. That's not what you are testing. You have have an extra operation in your $#a test instead of having one less.

    #!/usr/bin/perl use strict; use warnings; use Benchmark qw(cmpthese); our @a = qw( Once upon a time in a galaxy far far away ); cmpthese(-3, { cnt_minus_1 => 'my $x = @a-1;', last_idx => 'my $x = $#a;', });
    Rate last_idx cnt_minus_1 last_idx 3225597/s -- -25% cnt_minus_1 4308243/s 34% --

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