# ignite-47 Use Integer.highestOneBit() to calculate table size, Integer.highestOneBit() works fast because JIT translate it to one processor instruction. (cherry picked from commit de1f71f)
Project: http://git-wip-us.apache.org/repos/asf/incubator-ignite/repo Commit: http://git-wip-us.apache.org/repos/asf/incubator-ignite/commit/a46067a4 Tree: http://git-wip-us.apache.org/repos/asf/incubator-ignite/tree/a46067a4 Diff: http://git-wip-us.apache.org/repos/asf/incubator-ignite/diff/a46067a4 Branch: refs/heads/ignite-45 Commit: a46067a464c80d07f0cc0b31b34b3afd3db15a8a Parents: c799054 Author: sevdokimov <sevdoki...@gridgain.com> Authored: Tue Mar 10 16:25:39 2015 +0300 Committer: sevdokimov <sevdoki...@gridgain.com> Committed: Wed Mar 11 18:34:53 2015 +0300 ---------------------------------------------------------------------- .../java/org/jdk8/backport/ConcurrentHashMap8.java | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-) ---------------------------------------------------------------------- http://git-wip-us.apache.org/repos/asf/incubator-ignite/blob/a46067a4/modules/core/src/main/java/org/jdk8/backport/ConcurrentHashMap8.java ---------------------------------------------------------------------- diff --git a/modules/core/src/main/java/org/jdk8/backport/ConcurrentHashMap8.java b/modules/core/src/main/java/org/jdk8/backport/ConcurrentHashMap8.java index e944961..91181d5 100644 --- a/modules/core/src/main/java/org/jdk8/backport/ConcurrentHashMap8.java +++ b/modules/core/src/main/java/org/jdk8/backport/ConcurrentHashMap8.java @@ -2001,16 +2001,14 @@ public class ConcurrentHashMap8<K, V> /** * Returns a power of two table size for the given desired capacity. - * See Hackers Delight, sec 3.2 */ private static final int tableSizeFor(int c) { - int n = c - 1; - n |= n >>> 1; - n |= n >>> 2; - n |= n >>> 4; - n |= n >>> 8; - n |= n >>> 16; - return (n < 0) ? 1 : (n >= MAXIMUM_CAPACITY) ? MAXIMUM_CAPACITY : n + 1; + if (c <= 0) + return 1; + + int n = Integer.highestOneBit(c - 1) << 1; + + return (n >= MAXIMUM_CAPACITY) ? MAXIMUM_CAPACITY : n; } /**
