4 ms·

You don't need arbitrary precision, use a spigot https://en.wikipedia.org/wiki/Pi#Spigot_algorithms https://en.wikipedia.org/wiki/Pi#Spigot_algorithms

• ajuc 8y ago
  Wow, this blew my mind. And it's so simple, too. def nthHexDigitOfPI(n): return 4/(8*n+1) - 2/(8*n+4) - 1/(8*n+5) - 1/(8*n+6)
  • leni536 8y ago
    What you wrote just returns 0 for a large enough n.
    • ajuc 8y ago
      Serves me right for stopping the reading on the first line :)
• leni536 8y ago
  I took a look at a spigot algorithm[1]. I still think it needs arbitrary precision arithmetics but maybe I miss something obvious. [1] https://en.wikipedia.org/wiki/Bailey%E2%80%93Borwein%E2%80%93Plouffe_formula#BBP_digit-extraction_algorithm_for_%CF%80 https://en.wikipedia.org/wiki/Bailey%E2%80%93Borwein%E2%80%9...
  • dhartmei 8y ago
    Here's an example if you want to try http://www.benzedrine.ch/pi-spigot.c http://www.benzedrine.ch/pi-spigot.c
    • leni536 8y ago
      This doesn't look like a spigot algorithm. It has a link in the comments[1], it calculates the digits of PI from the beginning. The code you linked seems to implement the exact same algorithm. I don't fully comprehend the code still, but the SCALE parameter suggest that it handles the elements of the array as a fixed point representation of real numbers. I wonder if it's correct for large number of digits. [1] http://www.codecodex.com/wiki/Calculate_digits_of_pi#C http://www.codecodex.com/wiki/Calculate_digits_of_pi#C