зеркало из https://github.com/github/ruby.git
43 строки
823 B
Ruby
43 строки
823 B
Ruby
#!/usr/bin/ruby
|
|
#
|
|
# The Great Computer Language Shootout
|
|
# http://shootout.alioth.debian.org/
|
|
#
|
|
# nsieve-bits in Ruby
|
|
# Contributed by Glenn Parker, March 2005
|
|
|
|
CharExponent = 3
|
|
BitsPerChar = 1 << CharExponent
|
|
LowMask = BitsPerChar - 1
|
|
|
|
def sieve(m)
|
|
items = "\xFF" * ((m / BitsPerChar) + 1)
|
|
masks = ""
|
|
BitsPerChar.times do |b|
|
|
masks << (1 << b).chr
|
|
end
|
|
|
|
count = 0
|
|
pmax = m - 1
|
|
2.step(pmax, 1) do |p|
|
|
if items[p >> CharExponent][p & LowMask] == 1
|
|
count += 1
|
|
p.step(pmax, p) do |mult|
|
|
a = mult >> CharExponent
|
|
b = mult & LowMask
|
|
items[a] -= masks[b] if items[a][b] != 0
|
|
end
|
|
end
|
|
end
|
|
count
|
|
end
|
|
|
|
n = 9 # (ARGV[0] || 2).to_i
|
|
n.step(n - 2, -1) do |exponent|
|
|
break if exponent < 0
|
|
m = 2 ** exponent * 10_000
|
|
count = sieve(m)
|
|
printf "Primes up to %8d %8d\n", m, count
|
|
end
|
|
|