From ffd66c3f528623fbd03430b62caf733e64346757 Mon Sep 17 00:00:00 2001
From: leventov <leventov@ya.ru>
Date: Sat, 25 Oct 2014 01:58:05 +0400
Subject: [PATCH] Improved estimateSegments() heuristic and fix tests

---
 .../openhft/chronicle/map/ChronicleMapBuilder.java | 14 ++++++++------
 .../chronicle/map/ReplicatedChronicleMapTest.java  |  2 +-
 2 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/src/main/java/net/openhft/chronicle/map/ChronicleMapBuilder.java b/src/main/java/net/openhft/chronicle/map/ChronicleMapBuilder.java
index 11f29490d..0b2bfe620 100644
--- a/src/main/java/net/openhft/chronicle/map/ChronicleMapBuilder.java
+++ b/src/main/java/net/openhft/chronicle/map/ChronicleMapBuilder.java
@@ -422,14 +422,16 @@ public class ChronicleMapBuilder<K, V> implements Cloneable,
         return Math.max(estimateSegments(), minSegments);
     }
 
-    /**
-     * Heuristic -- number of segments ~= cube root from number of entries seems optimal
-     */
     private int estimateSegments() {
+        for (int power = 0; power < 7; power++) {
+            if (entries < (1L << (7 + (2 * power))))
+                return 1 << power;
+        }
+        // Heuristic -- number of segments ~= cube root from number of entries seems optimal
         int maxSegments = 65536;
-        for (int i = 4; i < maxSegments; i <<= 1) {
-            if (((long) i) * i * i >= entries)
-                return i;
+        for (int segments = 4; segments < maxSegments; segments <<= 1) {
+            if (((long) segments) * segments * segments >= entries)
+                return segments;
         }
         return maxSegments;
     }
diff --git a/src/test/java/net/openhft/chronicle/map/ReplicatedChronicleMapTest.java b/src/test/java/net/openhft/chronicle/map/ReplicatedChronicleMapTest.java
index a7d5d7d50..f67549868 100644
--- a/src/test/java/net/openhft/chronicle/map/ReplicatedChronicleMapTest.java
+++ b/src/test/java/net/openhft/chronicle/map/ReplicatedChronicleMapTest.java
@@ -96,7 +96,7 @@ public class ReplicatedChronicleMapTest extends JSR166TestCase {
      * Returns a new map from Integers 1-5 to Strings "A"-"E".
      */
     private ChronicleMap map5() throws IOException {
-        ChronicleMap<Integer, CharSequence> map = newShmIntString(5);
+        ChronicleMap<Integer, CharSequence> map = newShmIntString(10);
         assertTrue(map.isEmpty());
         map.put(JSR166TestCase.one, "A");
         map.put(JSR166TestCase.two, "B");