/**
* 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.fpm.pfpgrowth;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.mahout.common.IntegerTuple;
import org.apache.mahout.common.Pair;
import org.apache.mahout.common.Parameters;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.Map.Entry;
import java.util.regex.Pattern;
/**
* {@link ParallelFPGrowthMapper} maps each transaction to all unique items
* groups in the transaction. mapper outputs the group id as key and the
* transaction as value
*
*/
public class ParallelFPGrowthMapper extends
Mapper<LongWritable, Text, LongWritable, IntegerTuple> {
private final Map<String, Integer> fMap = new HashMap<String, Integer>();
private final Map<Integer, Long> gListInt = new HashMap<Integer, Long>();
private Pattern splitter = null;
@Override
protected void map(LongWritable offset, Text input, Context context)
throws IOException, InterruptedException {
String[] items = splitter.split(input.toString());
List<Integer> itemSet = new ArrayList<Integer>();
for (String item : items) // remove items not in the fList
{
if (fMap.containsKey(item) && item.trim().length() != 0)
itemSet.add(fMap.get(item));
}
Collections.sort(itemSet);
Integer[] prunedItems = itemSet.toArray(new Integer[itemSet.size()]);
Set<Long> groups = new HashSet<Long>();
for (int j = prunedItems.length - 1; j >= 0; j--) { // generate group
// dependent
// shards
Integer item = prunedItems[j];
Long groupID = gListInt.get(item);
if (groups.contains(groupID) == false) {
Integer[] tempItems = new Integer[j + 1];
System.arraycopy(prunedItems, 0, tempItems, 0, j + 1);
context
.setStatus("Parallel FPGrowth: Generating Group Dependent transactions for: "
+ item);
context.write(new LongWritable(groupID), new IntegerTuple(tempItems));
}
groups.add(groupID);
}
}
@Override
protected void setup(Context context) throws IOException,
InterruptedException {
super.setup(context);
Parameters params = Parameters.fromString(context.getConfiguration().get(
"pfp.parameters", ""));
int i = 0;
for (Pair<String, Long> e : PFPGrowth.deserializeList(params, "fList",
context.getConfiguration())) {
fMap.put(e.getFirst(), i++);
}
for (Entry<String, Long> e : PFPGrowth.deserializeMap(params, "gList",
context.getConfiguration()).entrySet()) {
gListInt.put(fMap.get(e.getKey()), e.getValue());
}
splitter = Pattern.compile(params.get("splitPattern", PFPGrowth.SPLITTER
.toString()));
}
}