Comparing refs is fast, yes. Taking references isn't.

Try precomputing the references to $sym1-$sym4...

Of course, that still winds up being about the same speed as string refs. I suspect that's because the ref comparison has to compare the type of the ref as well as the pointer? 


use strict;
use warnings;
use Benchmark 'cmpthese';

my ($sym1, $sym2, $sym3, $sym4);
my ($sym1_r, $sym2_r, $sym3_r, $sym4_r)=
   \($sym1, $sym2, $sym3, $sym4);

sub strings
 {
 if ($_[0] eq "yes")  { return 1; }
 elsif ($_[0] eq "no")  { return 0; }
 elsif ($_[0] eq "maybe")  { return 2; }
 elsif ($_[0] eq "foo")  { return 3; }
 return undef;
 }

sub numbers
 {
 if ($_[0] == 42)  { return 1; }
 elsif ($_[0] == 33)  { return 0; }
 elsif ($_[0] == 99)  { return 2; }
 elsif ($_[0] == 69)  { return 3; }
 return undef;
 }

sub refs
 {
 if ($_[0] == \$sym1)  { return 1; }
 elsif ($_[0] == \$sym2)  { return 0; }
 elsif ($_[0] == \$sym3)  { return 2; }
 elsif ($_[0] == \$sym4)  { return 3; }
 return undef;
 }


sub quick_refs
 {
 if ($_[0] == $sym1_r)  { return 1; }
 elsif ($_[0] == $sym2_r)  { return 0; }
 elsif ($_[0] == $sym3_r)  { return 2; }
 elsif ($_[0] == $sym4_r)  { return 3; }
 return undef;
 }

my $ref_r=\&refsl;

cmpthese (0,
 { 'strings 2' => sub { strings ("no") },
 'strings 4' => sub { strings ("notfound") },
 'numbers 2' => sub { numbers (33) },
 'numbers 4' => sub { numbers (99999) },
 'refs 2' => sub { refs (\$sym2); },
 'refs 4' => sub { refs (\&refs); },
 'qrefs 2' => sub { quick_refs ($sym2_r); },
 'qrefs 4' => sub { quick_refs ($ref_r); },
 });

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--
Mike

In reply to Re: speed of comparisons of things by RMGir
in thread speed of comparisons of things by John M. Dlugosz

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