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root/jsr166/jsr166/src/jsr166e/StripedAdder.java

Comparing jsr166/src/jsr166e/StripedAdder.java (file contents):
Revision 1.1 by dl, Wed Jul 20 15:00:56 2011 UTC vs.
Revision 1.2 by jsr166, Wed Jul 20 16:06:19 2011 UTC

#	Line 22 | Line 22 | import java.io.ObjectOutputStream;
22		* <em>NOT</em> an atomic snapshot (concurrent updates may occur while
23		* the sum is being calculated), and so cannot be used alone for
24		* fine-grained synchronization control.
25	<	*
25	>	*
26		* <p> This class may be applicable when many threads frequently
27		* update a common sum that is used for purposes such as collecting
28		* statistics. In this case, performance may be significantly faster
#	Line 31 | Line 31 | import java.io.ObjectOutputStream;
31		* only one thread can ever update the sum, performance may be
32		* significantly slower than just updating a local variable.
33		*
34	<	* @author Doug Lea
34	>	* @author Doug Lea
35		*/
36		public class StripedAdder implements Serializable {
37		private static final long serialVersionUID = 7249069246863182397L;
#	Line 52 | Line 52 | public class StripedAdder implements Ser
52		* candidate Adder.
53		*/
54
55	<	/**
55	>	/**
56		* Number of processors, to place a cap on table growth.
57		*/
58		static final int NCPU = Runtime.getRuntime().availableProcessors();
#	Line 66 | Line 66 | public class StripedAdder implements Ser
66		Adder(long x) { super(x); }
67		}
68
69	<	/**
69	>	/**
70		* Holder for the thread-local hash code.
71		*/
72		static final class HashCode {
#	Line 79 | Line 79 | public class StripedAdder implements Ser
79		*/
80		static final class ThreadHashCode extends ThreadLocal<HashCode> {
81		static final Random rng = new Random();
82	<	public HashCode initialValue() {
82	>	public HashCode initialValue() {
83		int h = rng.nextInt();
84		return new HashCode((h == 0) ? 1 : h); // ensure nonzero
85		}
#	Line 107 | Line 107 | public class StripedAdder implements Ser
107		/**
108		* Marsaglia XorShift for rehashing on collisions
109		*/
110	<	private static int xorShift(int r) {
110	>	private static int xorShift(int r) {
111		r ^= r << 13;
112		r ^= r >>> 17;
113		return r ^ (r << 5);
#	Line 172 | Line 172 | public class StripedAdder implements Ser
172		* Returns an estimate of the current sum.  The result is
173		* calculated by summing multiple variables, so may not be
174		* accurate if updates occur concurrently with this method.
175	<	*
175	>	*
176		* @return the estimated sum
177		*/
178		public long sum() {

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