benchmark/so_nsieve.yml


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prelude: |
  # The Computer Language Shootout
  # http://shootout.alioth.debian.org/
benchmark:
  so_nsieve: |
    #
    # 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
loop_count: 1