# Pi - Calculate pi using the Leibniz series with a specified number of iterations.
# See: http://en.wikipedia.org/wiki/Leibniz_formula_for_pi.
# and: http://derekwilliams.us/?p=4886.

class Pi

  attr_accessor :iterations

  def initialize(iterations)
    @iterations = iterations
  end

  def calculate
    numerator = 4.0
    denominator = 1.0
    negval = 1.0
    answer = 0.0

    iterations.times do
      answer += (negval) * (numerator/denominator)
      negval *= -1
      denominator += 2
    end
    return answer
  end

end

start = Time.now
threads = []
10.times do
  threads << Thread.new do
    puts Pi.new(1000000000).calculate
  end
end
threads.each { |thr| thr.join }
printf("Time: %d seconds\n", Time.now - start);