Re: How can I tell if a number is a power of 2?

[larryk]

Of course implementation is everything:

#!perl
use strict;
use warnings;

use Benchmark qw/cmpthese/;

sub tye {
    my $x = shift;
    0 == ( $x & ($x-1) ) ? 1 : 0;
}

sub tye2 {
    my $x = shift;
    !( $x & ($x-1) );
}

cmpthese( -5,
    {
        tye => q!tye(rand 1000000)!,
        tye2 => q!tye2(rand 1000000)!,
    }
);

__END__
Benchmark: running tye, tye2, each for at least 5 CPU seconds...
  tye :  6 wallclock secs ( 5.07 usr +  0.00 sys =  5.07 CPU) @ 200612
+.27/s (n=1016703)
  tye2:  6 wallclock secs ( 5.02 usr +  0.00 sys =  5.02 CPU) @ 225545
+.83/s (n=1131789)
         Rate  tye tye2
tye  200612/s   -- -11%
tye2 225546/s  12%   --