Re^2: Sorting by Array values, obtaining indices

Though I question the argument that hashes take up more space as a legitimate reason not to use them?

Do you?

use strict;
use Devel::Size qw(total_size);

my %hash = ( 0 => 3,
             1 => 7,
             2 => 5,
             3 => 0,
             4 => 2,
           );

my @vals = qw(3 7 5 0 2);

print 'T1: ', total_size(\%hash),"\n";
print 'T2: ', total_size(\@vals),"\n";
[download]

30% less space for the array, same access speed. There need to be as many of these data structures in memory as possible. qed

Bye
PetaMem All Perl: MT, NLP, NLU

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Re^3: Sorting by Array values, obtaining indices by waswas-fng (Curate) on Jun 27, 2005 at 17:08 UTC
And hashes can be more efficient if there are holes in the index. `use strict; use Devel::Size qw(total_size); my %hash = ( 0 => 3, 1 => 7, 2 => 5, 3 => 0, 20202 => 2, ); my @vals = qw(3 7 5 0); $vals[20202] = 2; print 'T1: ', total_size(\%hash),"\n"; print 'T2: ', total_size(\@vals),"\n"; [waswas:/var/tmp] waswas% perl hah T1: 291 T2: 131228` [download] -Waswas	[reply] [d/l]
Re^3: Sorting by Array values, obtaining indices by Limbic~Region (Chancellor) on Jun 27, 2005 at 16:44 UTC
PetaMem, Yeah. I know they take up more space and can be slower than arrays WRT accessing. The work involved in making an array work when a hash makes natural sense almost always outweighs the benefit gained by not using the hash. Let me put it another way. When you need to access something by key then a hash is almost always the way to go. I feel that with the amount of information originally given, it was not unexpected to question the motives of using an array over a hash. I am not saying there is never a reason not to use a hash - it is just good to get a sanity check first. Cheers - L~R	[reply]