Re: Re: Re: eq vs. ==

Actually i think i read it in Mastering Algorithms with Perl even though i cannot find it right now.

Anyway to wipe out your doubts you can try a benchmark:

#!/usr/bin/perl

use strict;
use Benchmark qw(:all);

cmpthese(10, {
    'eq'    =>  sub {
        for (my ($i, $j) = (0, 0); $i < 1_000_000; $i++) {
            $j++ if ($i % 3) eq 2;
        }
    },
    '=='    =>  sub {
        for (my ($i, $j) = (0, 0); $i < 1_000_000; $i++) {
            $j++ if ($i % 3) == 2;
        }
    },
});

__END__
Benchmark: timing 10 iterations of ==, eq...
        ==: 28 wallclock secs (27.91 usr +  0.00 sys = 27.91 CPU) @  0
+.36/s (n=10)
        eq: 36 wallclock secs (36.16 usr +  0.01 sys = 36.17 CPU) @  0
+.28/s (n=10)
   s/iter   eq   ==
eq   3.62   -- -23%
==   2.79  30%   --
[download]

The test was run on my Powerbook G3 with Perl v5.8.0 built for powerpc-linux-thread-multi.

I agree we shouldn't program for speed only, but here speed and good form comes from the same expression. Also you may note how my first post in this thread started out with "Also": it wasn't meant to be a comprehensive response to c's problem, but instead my 2 cents to what already said.

$|=$_="1g2i1u1l2i4e2n0k",map{print"\7",chop;select$,,$,,$,,$_/7}m{..}g

Comment on Re: Re: Re: eq vs. == Download Code

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Re: eq vs. ==
by Abigail-II (Bishop) on Jul 21, 2003 at 13:45 UTC

atoi

%

Here's a different benchmark. One that used both numbers and string, and both == and eq. You will see that the fastest cases are when no conversions needs to take place. Conclusion: use eq when comparing strings, and == when comparing numbers if speed is your main motivation.

#!/usr/bin/perl

use strict;
use warnings;
use Benchmark qw /cmpthese/;

our ($a, $b, $c, $d);

cmpthese -10 => {
    '==-num' => '$::a = 0;
                 for my $i (0 .. 1000000) {
                     $::a ++ if $i == 100;
                 }',
    'eq-num' => '$::b = 0;
                 for my $i (0 .. 1000000) {
                     $::b ++ if $i eq "100";
                 }',
    '==-str' => '$::c = 0;
                 for my $i ("0" .. "1000000") {
                     $::c ++ if $i == 100;
                 }',
    'eq-str' => '$::d = 0;
                 for my $i (0 .. "1000000") {
                     $::d ++ if $i eq "100";
                 }',
};

print "[$a] [$b] [$c] [$d]\n";

__END__
Benchmark: running ==-num, ==-str, eq-num, eq-str, each for at least 1
+0 CPU seconds...
    ==-num: 10 wallclock secs (10.02 usr +  0.00 sys = 10.02 CPU) @  4
+.19/s (n=42)
    ==-str: 10 wallclock secs (10.25 usr +  0.01 sys = 10.26 CPU) @  1
+.75/s (n=18)
    eq-num: 10 wallclock secs (10.06 usr +  0.01 sys = 10.07 CPU) @  2
+.38/s (n=24)
    eq-str: 10 wallclock secs (10.28 usr +  0.00 sys = 10.28 CPU) @  2
+.43/s (n=25)
         Rate ==-str eq-num eq-str ==-num
==-str 1.75/s     --   -26%   -28%   -58%
eq-num 2.38/s    36%     --    -2%   -43%
eq-str 2.43/s    39%     2%     --   -42%
==-num 4.19/s   139%    76%    72%     --
[1] [1] [1] [1]
[download]

Abigail

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