source code
# The Computer Language Benchmarks Game
# http://benchmarksgame.alioth.debian.org/
# Contributed by Sebastien Loisel
# Fixed by Isaac Gouy
# Sped up by Josh Goldfoot
# Dirtily sped up by Simon Descarpentries
# Concurrency by Jason Stitt
# 2to3
from multiprocessing import Pool
from math import sqrt
from sys import argv
def eval_A (i, j):
return 1.0 / ((i + j) * (i + j + 1) / 2 + i + 1)
def eval_A_times_u (u):
args = ((i,u) for i in range(len(u)))
return pool.map(part_A_times_u, args)
def eval_At_times_u (u):
args = ((i,u) for i in range(len(u)))
return pool.map(part_At_times_u, args)
def eval_AtA_times_u (u):
return eval_At_times_u (eval_A_times_u (u))
def part_A_times_u(xxx_todo_changeme):
(i,u) = xxx_todo_changeme
partial_sum = 0
for j, u_j in enumerate(u):
partial_sum += eval_A (i, j) * u_j
return partial_sum
def part_At_times_u(xxx_todo_changeme1):
(i,u) = xxx_todo_changeme1
partial_sum = 0
for j, u_j in enumerate(u):
partial_sum += eval_A (j, i) * u_j
return partial_sum
def main():
n = int(argv[1])
u = [1] * n
for dummy in range (10):
v = eval_AtA_times_u (u)
u = eval_AtA_times_u (v)
vBv = vv = 0
for ue, ve in zip (u, v):
vBv += ue * ve
vv += ve * ve
print("%0.9f" % (sqrt(vBv/vv)))
if __name__ == '__main__':
pool = Pool(processes=4)
main()