1 files changed, 46 insertions, 0 deletions
diff --git a/benchmark/so_nsieve_bits.yml b/benchmark/so_nsieve_bits.yml
new file mode 100644
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+++ b/benchmark/so_nsieve_bits.yml
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+prelude: |
+  #!/usr/bin/ruby
+  #coding: us-ascii
+benchmark:
+  so_nsieve_bits: |
+    #
+    # 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
+loop_count: 1