in reply to Re^2: Fast Sets of Scalars in Perl
in thread Fast Sets of Scalars in Perl

I stand corrected.

my %set; my $how_many = 10_000_000; for( my $i = 0; $i < $how_many; $i++ ) { $set{$i} = undef; } print 'mem usage: ', my_mem(), "\n"; sub my_mem { my ($proc_info) = grep { $_->[2] == $$ } map { [ split ] } `ps l | tail -n +2` +; return $proc_info->[6]; } __END__ mem usage: 1323312

Changing $set{$i}=undef to $set{$i}=1:

mem usage: 1402268

Using undef instead of 1, you save about 78M on ten million items—about a 6% difference. Or you could look at it as 8 bytes per item, unless I did my math wrong (which becomes more and more probable as time t approaches lunch).

When $set{$i}=10 (no chance of using sv_yes):

mem usage: 1402268

When $set{$i}='' (empty string):

mem usage: 1872484

And finally, Set::Light:

use Set::Light; my $set = Set::Light->new(); my $how_many = 10_000_000; for( my $i = 0; $i < $how_many; $i++ ) { $set->insert( $i ); } __END__ mem usage: 1127960

It beats them all! It beats the undef case by 195M. Note, however, that most of my tests ran in 20–25 seconds. The Set::Light test took much much longer—almost four minutes. I'm pretty sure all that time is spent in destruction, because the test reports its results fairly quickly and then takes a long time to exit.