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# The Computer Language Shootout
# http://shootout.alioth.debian.org/
#
# contributed by Glenn Parker, March 2005
# modified by Evan Phoenix, Sept 2006
def sieve(m)
flags = Flags.dup[0,m]
count = 0
pmax = m - 1
p = 2
while p <= pmax
unless flags[p].zero?
count += 1
mult = p
while mult <= pmax
flags[mult] = 0
mult += p
end
end
p += 1
end
count
end
n = 9 # (ARGV[0] || 2).to_i
Flags = ("\x1" * ( 2 ** n * 10_000)).unpack("c*")
n.downto(n-2) do |exponent|
break if exponent < 0
m = (1 << exponent) * 10_000
# m = (2 ** exponent) * 10_000
count = sieve(m)
printf "Primes up to %8d %8d\n", m, count
end
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