A good piece of research, however the possibility exists that the two results are related and generating the first one also pre-generates the second one. I suggest that tests like these are best done in separate methods on separate data just to be sure.
#!/usr/bin/perl
use strict;
use warnings;
use Benchmark qw(:all) ;
my $n = 100000;
our %hash1;
@hash1{1..$n} = 1 x $n;
my $n2 = 100000;
our %hash2;
@hash2{1..$n2} = 1 x $n2;
my $n3 = 1000000;
our %hash3;
@hash3{1..$n3} = 1 x $n3;
cmpthese( 1000, {
'Method 1' => sub {
my @k = keys %hash1;
my $v = scalar @k;
},
'100K' => sub {
my $v = scalar keys %hash2;
},
'1 Mill' => sub {
my $v = scalar keys %hash3;
}
}
);
Results:
Rate Method 1 1 Mill
+ 100K
Method 1 15.0/s -- -100%
+ -100%
1 Mill 999999999999999872/s 6645700000000000000% --
+ 0%
100K 999999999999999872/s 6645700000000000000% 0%
+ --
Note result appears to be same for 100k and 1Million entries in hash.
If you spot any bugs in my solutions, it's because I've deliberately left them in as an exercise for the reader! :-)
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