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/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.mahout.math.hadoop.stochasticsvd;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.io.Serializable;

import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.io.WritableComparator;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.mahout.math.Varint;

/**
 * a key for vectors allowing to identify them by their coordinates in original
 * split of A.
 * 
 * We assume all passes over A results in the same splits, thus, we can always
 * prepare side files that come into contact with A, sp that they are sorted and
 * partitioned same way.
 * 

* * Hashcode is defined the way that all records of the same split go to the same * reducer. *

* * In addition, we are defining a grouping comparator allowing group one split * into the same reducer group. *

* */ public class SplitPartitionedWritable implements WritableComparable { private int taskId; private long taskItemOrdinal; public SplitPartitionedWritable(Mapper.Context mapperContext) { // this is basically a split # if i understand it right taskId = mapperContext.getTaskAttemptID().getTaskID().getId(); } public SplitPartitionedWritable() { } public int getTaskId() { return taskId; } public long getTaskItemOrdinal() { return taskItemOrdinal; } public void incrementItemOrdinal() { taskItemOrdinal++; } public void setTaskItemOrdinal(long taskItemOrdinal) { this.taskItemOrdinal = taskItemOrdinal; } @Override public void readFields(DataInput in) throws IOException { taskId = Varint.readUnsignedVarInt(in); taskItemOrdinal = Varint.readUnsignedVarLong(in); } @Override public void write(DataOutput out) throws IOException { Varint.writeUnsignedVarInt(taskId, out); Varint.writeUnsignedVarLong(taskItemOrdinal, out); } @Override public int hashCode() { int prime = 31; int result = 1; result = prime * result + taskId; return result; } @Override public boolean equals(Object obj) { if (this == obj) { return true; } if (obj == null) { return false; } if (getClass() != obj.getClass()) { return false; } SplitPartitionedWritable other = (SplitPartitionedWritable) obj; return taskId == other.taskId; } @Override public int compareTo(SplitPartitionedWritable o) { if (taskId < o.taskId) { return -1; } if (taskId > o.taskId) { return 1; } if (taskItemOrdinal < o.taskItemOrdinal) { return -1; } if (taskItemOrdinal > o.taskItemOrdinal) { return 1; } return 0; } public static final class SplitGroupingComparator extends WritableComparator implements Serializable { public SplitGroupingComparator() { super(SplitPartitionedWritable.class, true); } @Override public int compare(Object a, Object b) { SplitPartitionedWritable o1 = (SplitPartitionedWritable) a; SplitPartitionedWritable o2 = (SplitPartitionedWritable) b; if (o1.taskId < o2.taskId) { return -1; } if (o1.taskId > o2.taskId) { return 1; } return 0; } } }





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