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in reply to Re: Find unique elements in an array
in thread Find unique elements in an array

Calling undef on a hash slice is faster still. 
use Benchmark qw(:all) ;

my @a;
push @a, int (rand(10)) foreach 1..100;
my %unique;
my @awd;
cmpthese($1000, {
                  'jc' =>
                  sub { foreach my $thingy (@a) { $unique{$thingy} = 1
+; }
                        @awd = keys %unique;
                     },
                  'mk' =>
                  sub { @unique{ @a} = 1;
                        @awd = keys %unique;
                     },
                   'bt' =>
                  sub { undef(@unique{@a});
                        @awd = keys %unique;
                     },
                 });

[download]
gives me 
      Rate   jc   mk   bt
jc 16556/s   -- -54% -62%
mk 36080/s 118%   -- -18%
bt 44007/s 166%  22%   --

[download]
(Incidentally that is a truely bizarre indent style.)

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Re: Re: Re: Find unique elements in an array
by BrowserUk (Patriarch) on Apr 04, 2004 at 22:28 UTC

    What is the purpose of using undef as the iteration count for cmpthese( $1000, ... );?

    Is that what causes the warnings? 

    Use of uninitialized value in numeric gt (>) at c:/Perl/lib/Benchmark.
+pm line 831.
Use of uninitialized value in numeric gt (>) at c:/Perl/lib/Benchmark.
+pm line 838.
Use of uninitialized value in numeric eq (==) at c:/Perl/lib/Benchmark
+.pm line 776.
Use of uninitialized value in numeric gt (>) at c:/Perl/lib/Benchmark.
+pm line 840.
Use of uninitialized value in numeric gt (>) at c:/Perl/lib/Benchmark.
+pm line 791.
Use of uninitialized value in numeric eq (==) at c:/Perl/lib/Benchmark
+.pm line 776.
Use of uninitialized value in numeric gt (>) at c:/Perl/lib/Benchmark.
+pm line 791.
Use of uninitialized value in numeric eq (==) at c:/Perl/lib/Benchmark
+.pm line 776.
Use of uninitialized value in numeric gt (>) at c:/Perl/lib/Benchmark.
+pm line 791.
Use of uninitialized value in numeric eq (==) at c:/Perl/lib/Benchmark
+.pm line 776.

    [download]
    Examine what is said, not who speaks.
    "Efficiency is intelligent laziness." -David Dunham
    "Think for yourself!" - Abigail
[reply]
[d/l]
[select]
      You'll have to ask kvale that question, not me. I copied everything except the last test from him.

      I'd guessed that he meant to type "1000" and messed up. I noticed wondered about that as I was copying it back, but didn't care enough to modify the code and re-run it...

[reply]

        Sorry about the mis-attribution. I came in on your post and didn't think to look back.

        Examine what is said, not who speaks.
        "Efficiency is intelligent laziness." -David Dunham
        "Think for yourself!" - Abigail
[reply]

In Section Cool Uses for Perl