If you need to generate the intersection between your array1 and another array more than once, then there is a way of speeding this process up by a huge factor (over 10000%!) relative to using the FAQ intersection method.

Instead of generating a new hash from array's 1 & 2 each time you need to do this, you can use a %hash1 in place of @array1. In use, you would need to swap your array1 references from $array1[n] to $aryHash1{n};, you wouldn't be able to have duplicates in aryHash1, and it would use additional memory, but less than the combined space of an array and a temporary hash for doing the intersection.

Benchmark 

#! perl -sw
use strict;
use Benchmark::Timer;
my $timer = Benchmark::Timer->new(skip => 1);

local $\=$/;

sub intersect (\@\@) {
    my ($aryRef1, $aryRef2) = @_;
    my %count = ();
    $count{$_}++ foreach @$aryRef1, @$aryRef2;
    return grep{ $count{$_} == 1 } keys %count;
}

my @aryBase = (1 .. 28000);
my %hashBase;
@hashBase{@aryBase} = undef;

my @array2 = (1..1000, 1..100); # create some duplicates with duplicat
+es

for (0..100){
    my @array1 = @aryBase;
    $timer->start('faq');
    my @dup = intersect( @array1, @array2 );
    $timer->stop('faq');
}

for (0..100){
    my %hashAry = %hashBase;
    $timer->start('delete');
    my @dup = delete @hashAry{@array2};
    $timer->stop('delete');
}

$timer->report;

@aryBase = intersect( @aryBase, @array2 );
print '\@aryBase contains ', scalar @aryBase, ' elements after interse
+ct';

delete @hashBase{@array2};
print '\@hashBase contains ', scalar keys %hashBase, ' elements after 
+intersect';

__END__
#output
C:\test>207632
100 trials of faq (103.692s total), 1.037s/trial

100 trials of delete (881.000ms total), 8.810ms/trial

\@aryBase contains 27000 elements after intersect
\@hashBase contains 27000 elements after intersect

C:\test>

[download]

By my calculation, this is an 1037/8.81*100 = 11770% faster! Did I make a mistake?

Cor! Like yer ring! ... HALO dammit! ... 'Ave it yer way! Hal-lo, Mister la-de-da. ... Like yer ring!

In reply to Re: How to splice out multiple entries from an array by BrowserUk
in thread How to splice out multiple entries from an array by Ya

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.