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From rama...@apache.org
Subject [1/2] incubator-apex-malhar git commit: - MLHR-1868 improved the hashcode function to produce better hashes.
Date Wed, 14 Oct 2015 22:10:22 GMT
Repository: incubator-apex-malhar
Updated Branches:
  refs/heads/devel-3 38c895292 -> 893ac3505


 - MLHR-1868 improved the hashcode function to produce better hashes.


Project: http://git-wip-us.apache.org/repos/asf/incubator-apex-malhar/repo
Commit: http://git-wip-us.apache.org/repos/asf/incubator-apex-malhar/commit/dbdc9cad
Tree: http://git-wip-us.apache.org/repos/asf/incubator-apex-malhar/tree/dbdc9cad
Diff: http://git-wip-us.apache.org/repos/asf/incubator-apex-malhar/diff/dbdc9cad

Branch: refs/heads/devel-3
Commit: dbdc9cadce46e5a8d5ec420e6c8695349fc0ada0
Parents: e1a4550
Author: Timothy Farkas <tim@datatorrent.com>
Authored: Mon Oct 12 10:06:12 2015 -0700
Committer: Timothy Farkas <tim@datatorrent.com>
Committed: Wed Oct 14 14:58:26 2015 -0700

----------------------------------------------------------------------
 .../datatorrent/lib/appdata/gpo/GPOUtils.java   | 42 +++++++++++++++-----
 1 file changed, 31 insertions(+), 11 deletions(-)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/incubator-apex-malhar/blob/dbdc9cad/library/src/main/java/com/datatorrent/lib/appdata/gpo/GPOUtils.java
----------------------------------------------------------------------
diff --git a/library/src/main/java/com/datatorrent/lib/appdata/gpo/GPOUtils.java b/library/src/main/java/com/datatorrent/lib/appdata/gpo/GPOUtils.java
index 290d814..239dab7 100644
--- a/library/src/main/java/com/datatorrent/lib/appdata/gpo/GPOUtils.java
+++ b/library/src/main/java/com/datatorrent/lib/appdata/gpo/GPOUtils.java
@@ -1748,10 +1748,25 @@ public class GPOUtils
     return hashCode;
   }
 
+  /**
+   * This function computes the hashcode of a {@link GPOMutable} based on a specified subset
of its data.
+   * <br/>
+   * <br/>
+   * <b>Note:</b> In some cases a {@link GPOMutable} object contains a field
which is bucketed. In the case of
+   * bucketed fields, you may want to preserve the original value of the field, but only
use the bucketed value
+   * of the field for computing a hashcode. In order to do this you can store the original
value of {@link GPOMutable}'s
+   * field before calling this function, and replace it with the bucketed value. Then after
the hashcode is computed, the
+   * original value of the field can be restored.
+   *
+   * @param gpo The {@link GPOMutable} to compute a hashcode for.
+   * @param indexSubset The subset of the {@link GPOMutable} used to compute the hashcode.
+   * @return The hashcode for the given {@link GPOMutable} computed from the specified subset
of its data.
+   */
   public static int indirectHashcode(GPOMutable gpo,
                                      IndexSubset indexSubset)
   {
-    int hashCode = 0;
+    int hashCode = 7;
+    final int hashMultiplier = 23;
 
     {
       String[] stringArray = gpo.getFieldsString();
@@ -1763,7 +1778,7 @@ public class GPOUtils
           if(srcIndex[index] == -1) {
             continue;
           }
-          hashCode ^= stringArray[srcIndex[index]].hashCode();
+          hashCode = hashMultiplier * hashCode + stringArray[srcIndex[index]].hashCode();
         }
       }
     }
@@ -1778,7 +1793,7 @@ public class GPOUtils
           if(srcIndex[index] == -1) {
             continue;
           }
-          hashCode ^= booleanArray[srcIndex[index]] ? 1: 0;
+          hashCode = hashMultiplier * hashCode + (booleanArray[srcIndex[index]] ? 1: 0);
         }
       }
     }
@@ -1793,7 +1808,7 @@ public class GPOUtils
           if(srcIndex[index] == -1) {
             continue;
           }
-          hashCode ^= Character.getNumericValue(charArray[srcIndex[index]]);
+          hashCode = hashMultiplier * hashCode + Character.getNumericValue(charArray[srcIndex[index]]);
         }
       }
     }
@@ -1808,7 +1823,7 @@ public class GPOUtils
           if(srcIndex[index] == -1) {
             continue;
           }
-          hashCode ^= byteArray[srcIndex[index]];
+          hashCode = hashMultiplier * hashCode + byteArray[srcIndex[index]];
         }
       }
     }
@@ -1823,7 +1838,7 @@ public class GPOUtils
           if(srcIndex[index] == -1) {
             continue;
           }
-          hashCode ^= shortArray[srcIndex[index]];
+          hashCode = hashMultiplier * hashCode + shortArray[srcIndex[index]];
         }
       }
     }
@@ -1838,7 +1853,7 @@ public class GPOUtils
           if(srcIndex[index] == -1) {
             continue;
           }
-          hashCode ^= integerArray[srcIndex[index]];
+          hashCode = hashMultiplier * hashCode + integerArray[srcIndex[index]];
         }
       }
     }
@@ -1853,7 +1868,9 @@ public class GPOUtils
           if(srcIndex[index] == -1) {
             continue;
           }
-          hashCode ^= longArray[srcIndex[index]];
+          long element = longArray[srcIndex[index]];
+          int elementHash = (int) (element ^ (element >>> 32));
+          hashCode = hashMultiplier * hashCode + elementHash;
         }
       }
     }
@@ -1868,7 +1885,7 @@ public class GPOUtils
           if(srcIndex[index] == -1) {
             continue;
           }
-          hashCode ^= Float.floatToIntBits(floatArray[srcIndex[index]]);
+          hashCode = hashMultiplier * hashCode + Float.floatToIntBits(floatArray[srcIndex[index]]);
         }
       }
     }
@@ -1883,7 +1900,9 @@ public class GPOUtils
           if(srcIndex[index] == -1) {
             continue;
           }
-          hashCode ^= Double.doubleToLongBits(doubleArray[srcIndex[index]]);
+          long element = Double.doubleToLongBits(doubleArray[srcIndex[index]]);
+          int elementHash = (int) (element ^ (element >>> 32));
+          hashCode = hashMultiplier * hashCode + elementHash;
         }
       }
     }
@@ -1898,7 +1917,8 @@ public class GPOUtils
           if(srcIndex[index] == -1) {
             continue;
           }
-          hashCode ^= objectArray[srcIndex[index]].hashCode();
+
+          hashCode = hashMultiplier * hashCode + objectArray[srcIndex[index]].hashCode();
         }
       }
     }


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