Merge pull request #890 from mridulm/master

Fix hash bug

core/src/main/scala/org/apache/spark/network/netty/ShuffleSender.scala

@@ -20,6 +20,7 @@ package org.apache.spark.network.netty
 import java.io.File
 
 import org.apache.spark.Logging
+import org.apache.spark.util.Utils
 
 
 private[spark] class ShuffleSender(portIn: Int, val pResolver: PathResolver) extends Logging {
@@ -57,7 +58,7 @@ private[spark] object ShuffleSender {
           throw new Exception("Block " + blockId + " is not a shuffle block")
         }
         // Figure out which local directory it hashes to, and which subdirectory in that
-        val hash = math.abs(blockId.hashCode)
+        val hash = Utils.nonNegativeHash(blockId)
         val dirId = hash % localDirs.length
         val subDirId = (hash / localDirs.length) % subDirsPerLocalDir
         val subDir = new File(localDirs(dirId), "%02x".format(subDirId))

core/src/main/scala/org/apache/spark/storage/DiskStore.scala

@@ -238,7 +238,7 @@ private class DiskStore(blockManager: BlockManager, rootDirs: String)
     logDebug("Getting file for block " + blockId)
 
     // Figure out which local directory it hashes to, and which subdirectory in that
-    val hash = math.abs(blockId.hashCode)
+    val hash = Utils.nonNegativeHash(blockId)
     val dirId = hash % localDirs.length
     val subDirId = (hash / localDirs.length) % subDirsPerLocalDir
 

core/src/main/scala/org/apache/spark/util/Utils.scala

@@ -778,4 +778,18 @@ private[spark] object Utils extends Logging {
     val rawMod = x % mod
     rawMod + (if (rawMod < 0) mod else 0)
   }
+
+  // Handles idiosyncracies with hash (add more as required)
+  def nonNegativeHash(obj: AnyRef): Int = {
+
+    // Required ?
+    if (obj eq null) return 0
+
+    val hash = obj.hashCode
+    // math.abs fails for Int.MinValue
+    val hashAbs = if (Int.MinValue != hash) math.abs(hash) else 0
+
+    // Nothing else to guard against ?
+    hashAbs
+  }
 }