com.datatorrent.lib.util.AbstractBaseFrequentKey.java Source code

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Here is the source code for com.datatorrent.lib.util.AbstractBaseFrequentKey.java

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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 com.datatorrent.lib.util;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;

import org.apache.commons.lang.mutable.MutableInt;

/**
 * This is the base implementation of an operator, which counts the number of times each tuple occurs. 
 * The counts of tuples are then compared at the end of each window and the winning tuple(s) are emitted. 
 * Subclasses should implement the methods that are used to emit tuples, as well as the comparison method used
 * to determine the winning tuple(s).
 * <p>
 * This module is an end of window module.
 * </p>
 *
 * @displayName Emit Winning Value(s)
 * @category Algorithmic
 * @tags count, compare
 * @since 0.3.2
 */
public abstract class AbstractBaseFrequentKey<K> extends BaseKeyOperator<K> {
    /**
     * Counts frequency of a key
     * @param tuple
     */
    public void processTuple(K tuple) {
        MutableInt count = keycount.get(tuple);
        if (count == null) {
            count = new MutableInt(0);
            keycount.put(cloneKey(tuple), count);
        }
        count.increment();
    }

    protected HashMap<K, MutableInt> keycount = new HashMap<K, MutableInt>();

    /**
     * override emitTuple to decide the port to emit to
     * @param tuple
     */
    public abstract void emitTuple(HashMap<K, Integer> tuple);

    /**
     * Overide emitList to specify the emit schema
     * @param tlist
     */
    public abstract void emitList(ArrayList<HashMap<K, Integer>> tlist);

    /**
     * Override compareCount to decide most vs least
     * @param val1
     * @param val2
     * @return result of compareCount to be done by subclass
     */
    public abstract boolean compareCount(int val1, int val2);

    /**
     * Emits the result.
     */
    @Override
    public void endWindow() {
        // Compute least frequent
        K key = null;
        int kval = -1;
        HashMap<K, Object> map = new HashMap<K, Object>();
        for (Map.Entry<K, MutableInt> e : keycount.entrySet()) {
            if ((kval == -1)) {
                key = e.getKey();
                kval = e.getValue().intValue();
                map.put(key, null);
            } else if (compareCount(e.getValue().intValue(), kval)) {
                key = e.getKey();
                kval = e.getValue().intValue();
                map.clear();
                map.put(key, null);
            } else if (e.getValue().intValue() == kval) {
                map.put(e.getKey(), null);
            }
        }

        // Emit least frequent key, emit all least frequent keys list
        // on other ports.
        HashMap<K, Integer> tuple;
        if ((key != null) && (kval > 0)) {
            tuple = new HashMap<K, Integer>(1);
            tuple.put(key, new Integer(kval));
            emitTuple(tuple);
            ArrayList<HashMap<K, Integer>> elist = new ArrayList<HashMap<K, Integer>>();
            for (Map.Entry<K, Object> e : map.entrySet()) {
                tuple = new HashMap<K, Integer>(1);
                tuple.put(e.getKey(), kval);
                elist.add(tuple);
            }
            emitList(elist);
        }
        keycount.clear();
    }
}