hamming.rb

#!/usr/bin/env rvm 1.9.3 do ruby
require 'pp'

def hamming(i)
	dist = 0
	v = i
	while v != 0
		dist += 1 if (v & 1 != 0)
		v >>= 1
	end
	dist
end


$alphabet_size = 32
$log = Math.log2($alphabet_size).ceil.to_i

$hammings = []
(0..(1 << $log)).each do |i|
	$hammings[i] = hamming(i)
end

def hamming_cached(i)
	return $hammings[i]
end

sample = 10 * 1000
choices = 4
hist = [0] * (Math.log2($alphabet_size).ceil + 1)

sample.times do
	x = 0
	choices.times { x ^= rand($alphabet_size) }
	hist[hamming_cached(x)] += 1
end

pp hist