Comper ruby's log and math.h log

compare.rb

require 'benchmark'
require 'inline'

class Test
  include Math
  inline do |builder|
    builder.include('<math.h>')
    builder.c <<-EOF
    double
    log_c(int i)
    {
      return log(i);
    }
    EOF
  end
end

Benchmark.bmbm do |x|
  t = Test.new
  rands = []
  10_000_000.times do
    rands << rand(1000)
  end

  x.report('ruby') do
    rands.each do |int|
      Math.log(int)
    end
  end

  x.report('inline') do
    rands.each do |int|
      t.log_c(int)
    end
  end

end

# Rehearsal ------------------------------------------
# ruby     9.840000   0.000000   9.840000 (  9.842299)
# inline   2.650000   0.010000   2.660000 (  2.667835)
# -------------------------------- total: 12.500000sec

#              user     system      total        real
# ruby    10.410000   0.010000  10.420000 ( 10.437814)
# inline   2.420000   0.000000   2.420000 (  2.422468)