A simple Ruby script to calculate using the Chudnovsky algorithm. Seems to only be accurate to 69 d.p. according to http://www.angio.net/pi/bigpi.cgi - likely an issue with the 10005^0.5 precision and perhaps some proper floating point errors?

cookπ

#!/usr/bin/env ruby

require 'bigdecimal';

class Integer
  def factorial
    f = 1; for i in 1..self; f *= i; end; f
  end
end

iterations = 500;

multIPi = BigDecimal.new("0");

for k in (0..iterations)
  multIPi += 
    (
      BigDecimal.new((6*k).factorial.to_s) *
      BigDecimal.new((13591409 + 545140134 * k).to_s)
    ) / 
    (
      BigDecimal.new((3*k).factorial.to_s) *
      BigDecimal.new(k.factorial.to_s)**3 *
      BigDecimal.new(((-640320)**(3*k)).to_s)
    );
end

pi = BigDecimal.new("426880") * BigDecimal.new("10005").sqrt(iterations * 200) / multIPi;

puts pi.to_s("F")