From 30b2cb380e0a8f777a2fc2d736c2ccddf3362fcd Mon Sep 17 00:00:00 2001
From: ko1 <ko1@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Fri, 28 Sep 2007 10:18:53 +0000
Subject: * benchmark/driver.rb: fix notations. *
 benchmark/bm_loop_whileloop.rb: ditto. * benchmark/bm_loop_whileloop2.rb:
 ditto. * benchmark/bm_app_uri.rb: added. * benchmark/bm_vm1_ivar_set.rb:
 ditto. * benchmark/bm_so_binary_trees.rb: added from Computer Language  
 Benchmarks Game (http://shootout.alioth.debian.org/). *
 benchmark/bm_so_fannkuch.rb: ditto. * benchmark/bm_so_mandelbrot.rb: ditto. *
 benchmark/bm_so_meteor_contest.rb: ditto. * benchmark/bm_so_nbody.rb: ditto.
 * benchmark/bm_so_nsieve.rb: ditto. * benchmark/bm_so_nsieve_bits.rb: ditto.
 * benchmark/bm_so_partial_sums.rb: ditto. * benchmark/bm_so_pidigits.rb:
 ditto. * benchmark/bm_so_spectralnorm.rb: ditto.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@13548 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 benchmark/bm_so_nsieve_bits.rb | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)
 create mode 100644 benchmark/bm_so_nsieve_bits.rb

(limited to 'benchmark/bm_so_nsieve_bits.rb')

diff --git a/benchmark/bm_so_nsieve_bits.rb b/benchmark/bm_so_nsieve_bits.rb
new file mode 100644
index 0000000000..693b2f246d
--- /dev/null
+++ b/benchmark/bm_so_nsieve_bits.rb
@@ -0,0 +1,42 @@
+#!/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
+
-- 
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