Otherwise, cache the values %whop as hash keys, and do your lookups there.

Using reverse is faster than values (unless I've misunderstood how you'd do this), especially for larger hashes (I'm using Perl 5.005_03 on FreeBSD 4.2): 

use Benchmark qw(timethese);

use constant VALUE => 5000;
my %hash = ( 1..VALUE);

timethese(1_000_000 / VALUE, {
    'reverse' => sub {
        my %values = reverse %hash;
    },
    'map_values' => sub {
        my %values = map {$_ => undef} values %hash;
    }
});

[download]

For VALUE => 5000:
Benchmark: timing 200 iterations of map_values, reverse...
map_values: 10 wallclock secs ( 9.40 usr + 0.00 sys = 9.40 CPU)
reverse: 4 wallclock secs ( 3.51 usr + 0.01 sys = 3.52 CPU)

For VALUE => 50:
Benchmark: timing 20000 iterations of map_values, reverse...
map_values: 3 wallclock secs ( 2.95 usr + 0.00 sys = 2.95 CPU)
reverse: 3 wallclock secs ( 2.55 usr + 0.01 sys = 2.55 CPU)

In reply to Re: Re: Looking up a hash by value by tomhukins
in thread Looking up a hash by value by tanger

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