gistfile1.rb

require "benchmark"
require "inline"
class Integer
  def count_set_bits(use_c = false)
    return csb(self) if use_c
    return 0 if self.zero?
    bits, x = 1, self
    bits += 1 while (x = x & (x - 1)).nonzero?
    bits
  end
  inline do |builder|
    builder.c "int csb(long x) {
    if (x == 0) return (x);
    int bits = 1;
    while ((x = x & (x - 1))) bits++;
    return (bits);
    }"
  end
end
Benchmark.bmbm do |b|
  b.report("ruby") { 100_000.times { 152363.count_set_bits } }
  b.report("c") { 100_000.times { 152363.count_set_bits(true) } }
end