Thanks for the reply GrandFather. Not that I didn't believe you, but here's the proof:
#! /usr/bin/perl
use strict;
use warnings;
use File::Spec;
use Data::Dumper;
use Benchmark qw( timethese cmpthese );
my ( undef, undef, $app ) = File::Spec->splitpath( $0 );
open my $DATA, '<', './AXP_FACS.DAT' or die "Error opening file: $!";
my @faclist = (<$DATA>);
chomp @faclist;
close $DATA;
sub grep_by_array {
my ( $ref ) = @_;
my @faclist = @$ref;
my @found;
foreach my $integer ( 1..5000 ) {
if ( grep { /\b$integer\b/ } @faclist ) {
unshift @found, $integer;
}
}
return \@found;
}
# Convert the array to a hash with the numbers as keys
my %list = map { $_ => 1 } @faclist;
sub grep_by_hash {
my ( $ref ) = @_;
my %faclist = %$ref;
my @found;
foreach my $integer( 1..5000 ) {
if ( exists $faclist{$integer} ) {
unshift @found, $integer;
}
}
return \@found;
}
# Benchmark the 2 subs
my $r = timethese( 1000, {
'array' => sub{ grep_by_array(\@faclist) },
'hash' => sub{ grep_by_hash(\%list) },
}
);
cmpthese( $r );
RESULTS:
Benchmark: timing 5000 iterations of array, hash...
array: 339 wallclock secs (339.02 usr + 0.04 sys = 339.06 CPU) @ 14.75/s (n=5000)
hash: 8 wallclock secs ( 8.27 usr + 0.00 sys = 8.27 CPU) @ 604.59/s (n=5000)
Rate array hash
array 14.7/s -- -98%
hash 605/s 4000% --
That's quite an improvement using a hash!
You learn something every day...
njcodewarrior
In reply to Re^3: Hash checking
by njcodewarrior
in thread Hash checking
by Anonymous Monk
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