code: /**
   * Copyright 2009 Saptarshi Guha
   *
   *   Licensed under the Apache License, Version 2.0 (the "License");
   *  you may not use this file except in compliance with the License.
   *  You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package org.godhuli.rhipe;
  
  
  import com.google.protobuf.InvalidProtocolBufferException;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.mapreduce.Partitioner;
  import org.godhuli.rhipe.REXPProtos.REXP;
  
  public class RHPartitionerNumeric extends Partitioner<RHBytesWritable, RHBytesWritable> {
  
      protected static final Log LOG = LogFactory.getLog(RHPartitionerNumeric.class);
  
      public int getPartition(final RHBytesWritable key, final RHBytesWritable value, final int numReduceTasks) {
          int hashCode = 1;
          // taken from http://alias-i.com/lingpipe/docs/api/com/aliasi/matrix/Vector.html#hashCode%28%29
          // double hash2 = 0;
          // this is a crude and almost uses paritioning scheme.
          try {
              final REXP r = key.getParsed();
              for (int i = RHMRHelper.PARTITION_START; i <= RHMRHelper.PARTITION_END; i++) {
                  final long v = Double.doubleToLongBits(r.getRealValue(i));
                  final int valHash = (int) (v ^ (v >>> 32));
                  hashCode = 31 * hashCode + valHash;
              }
              // hashcode = ((int)Double.doubleToLongBits(hash2));
          }
          catch (InvalidProtocolBufferException e) {
              LOG.error(e);
          }
          return (hashCode & Integer.MAX_VALUE) % numReduceTasks;
      }
      // protected int hashCode(byte[] b, int currentHash) {
      //   for (int i = 0; i < b.length; i++) {
      //     currentHash = 31*currentHash + b[i];
      //   }
      //   return currentHash;
      // }
  
  }
  