Tweek the sizing rules as well as optimise the hashing algo so it creates a more even distribution (for at least one set of test cases)

src/main/java/net/openhft/chronicle/common/serialization/Hasher.java

@@ -23,11 +23,12 @@ import sun.misc.Unsafe;
 import static java.nio.ByteOrder.LITTLE_ENDIAN;
 import static java.nio.ByteOrder.nativeOrder;
 
-public final class Hasher {
+public enum Hasher {
+    ;
 
     private static final long LONG_LEVEL_PRIME_MULTIPLE = 1011001110001111L;
-    private static final int SHORT_LEVEL_PRIME_MULTIPLE = 101111;
-    private static final long BYTE_LEVEL_PRIME_MULTIPLE = 2111;
+    private static final short SHORT_LEVEL_PRIME_MULTIPLE = 10191;
+    private static final byte BYTE_LEVEL_PRIME_MULTIPLE = 109;
 
     private static final int INT_HASH_LOW_SHORT_MULTIPLE =
             nativeOrder() == LITTLE_ENDIAN ? SHORT_LEVEL_PRIME_MULTIPLE : 1;
@@ -72,10 +73,8 @@ public final class Hasher {
     }
 
     public static long hash(long value) {
-        value *= 11018881818881011L;
-        value ^= (value >>> 41) ^ (value >>> 21);
+        value ^= (value >>> 41) - (value >>> 21);
+        value ^= (value >>> 15) + (value >>> 7);
         return value;
     }
-
-    private Hasher() {}
 }

src/main/java/net/openhft/chronicle/map/ChronicleMapBuilder.java

@@ -390,10 +390,10 @@ public class ChronicleMapBuilder<K, V> implements Cloneable,
         if (actualEntriesPerSegment > 0)
             return actualEntriesPerSegment;
         int as = actualSegments();
-        long actualEntries =
-                as == 1 ? entries + 1 :        // The extra 1 might not be needed.
-                        as <= 4 ? entries * 10L / 9 :  // 10%, assumes you are trying to be tight.
-                                entries * 5L / 4;      // 25%
+        long actualEntries = entries +
+                (as == 1 ? 1 :        // The extra 1 might not be needed.
+                        as <= 8 ? entries / 12 :  // 6%, (3% was min for tests)
+                                entries / 6);      // 16% (8% was min for tests)
 
         // round up to the next multiple of 64.
         return (int) (Math.max(1, actualEntries / as) + 63) & ~63;

src/main/java/net/openhft/chronicle/map/ReplicatedChronicleMap.java

@@ -262,7 +262,7 @@ class ReplicatedChronicleMap<K, KI, MKI extends MetaBytesInterop<K, KI>,
         int segmentNum = getSegment(hash);
         int segmentHash = segmentHash(hash);
         return segment(segmentNum).acquire(copies, metaKeyWriter, keyWriter, key, value,
-                segmentHash, create, timeProvider.currentTimeMillis());
+                segmentHash, create, create ? timeProvider.currentTimeMillis() : 0L);
     }
 
     @Override

src/main/java/net/openhft/chronicle/map/VanillaChronicleMap.java

@@ -17,9 +17,9 @@
 package net.openhft.chronicle.map;
 
 import net.openhft.chronicle.common.ChronicleHashErrorListener;
+import net.openhft.chronicle.common.serialization.*;
 import net.openhft.chronicle.common.threadlocal.Provider;
 import net.openhft.chronicle.common.threadlocal.ThreadLocalCopies;
-import net.openhft.chronicle.common.serialization.*;
 import net.openhft.lang.Maths;
 import net.openhft.lang.collection.DirectBitSet;
 import net.openhft.lang.collection.SingleThreadedDirectBitSet;
@@ -910,10 +910,10 @@ class VanillaChronicleMap<K, KI, MKI extends MetaBytesInterop<K, KI>,
                 ret = (int) freeList.setNextNContinuousClearBits(0, blocks);
                 if (ret == DirectBitSet.NOT_FOUND) {
                     if (blocks == 1) {
-                        throw new IllegalArgumentException(
+                        throw new IllegalStateException(
                                 "Segment is full, no free entries found");
                     } else {
-                        throw new IllegalArgumentException(
+                        throw new IllegalStateException(
                                 "Segment is full or has no ranges of " + blocks
                                         + " continuous free blocks"
                         );
@@ -970,7 +970,7 @@ class VanillaChronicleMap<K, KI, MKI extends MetaBytesInterop<K, KI>,
 
         /**
          * Removes a key (or key-value pair) from the Segment.
-         *
+         * <p/>
          * <p>The entry will only be removed if {@code expectedValue} equals to {@code null}
          * or the value previously corresponding to the specified key.
          *
@@ -1446,4 +1446,11 @@ class VanillaChronicleMap<K, KI, MKI extends MetaBytesInterop<K, KI>,
             return super.setValue(value);
         }
     }
+
+    int[] segmentSizes() {
+        int[] sizes = new int[segments.length];
+        for (int i = 0; i < segments.length; i++)
+            sizes[i] = segments[i].getSize();
+        return sizes;
+    }
 }