org.apache.mahout.fpm.pfpgrowth.fpgrowth.Pattern.java Source code

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Here is the source code for org.apache.mahout.fpm.pfpgrowth.fpgrowth.Pattern.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 org.apache.mahout.fpm.pfpgrowth.fpgrowth;

import com.google.common.primitives.Longs;

import java.util.Arrays;

/**
 * A  in FPGrowth is a list of items (here int) and the
 * support(the number of times the pattern is seen in the dataset)
 * 
 */
public class Pattern implements Comparable<Pattern> {

    private static final int DEFAULT_INITIAL_SIZE = 2;

    private static final float GROWTH_RATE = 1.5f;

    private boolean dirty = true;

    private int hashCode;

    private int length;

    private int[] pattern;

    private long support = Long.MAX_VALUE;

    public Pattern() {
        this(DEFAULT_INITIAL_SIZE);
    }

    private Pattern(int size) {
        if (size < DEFAULT_INITIAL_SIZE) {
            size = DEFAULT_INITIAL_SIZE;
        }
        this.pattern = new int[size];
        dirty = true;
    }

    public final void add(int id, long supportCount) {
        dirty = true;
        if (length >= pattern.length) {
            resize();
        }
        this.pattern[length++] = id;
        Arrays.sort(this.pattern, 0, length);
        this.support = supportCount > this.support ? this.support : supportCount;
    }

    public final int[] getPattern() {
        return this.pattern;
    }

    public final boolean isSubPatternOf(Pattern frequentPattern) {
        int[] otherPattern = frequentPattern.getPattern();
        int otherLength = frequentPattern.length();
        if (this.length() > frequentPattern.length()) {
            return false;
        }
        int i = 0;
        int otherI = 0;
        while (i < length && otherI < otherLength) {
            if (otherPattern[otherI] == pattern[i]) {
                otherI++;
                i++;
            } else if (otherPattern[otherI] < pattern[i]) {
                otherI++;
            } else {
                return false;
            }
        }
        return otherI != otherLength || i == length;
    }

    public final int length() {
        return this.length;
    }

    public final long support() {
        return this.support;
    }

    private void resize() {
        int size = (int) (GROWTH_RATE * length);
        if (size < DEFAULT_INITIAL_SIZE) {
            size = DEFAULT_INITIAL_SIZE;
        }
        int[] oldpattern = pattern;
        this.pattern = new int[size];
        System.arraycopy(oldpattern, 0, this.pattern, 0, length);
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }
        if (obj == null) {
            return false;
        }
        if (getClass() != obj.getClass()) {
            return false;
        }
        Pattern other = (Pattern) obj;
        // expensive check done only if length and support matches    
        return length == other.length && support == other.support && Arrays.equals(pattern, other.pattern);
    }

    @Override
    public int hashCode() {
        if (!dirty) {
            return hashCode;
        }
        int result = Arrays.hashCode(pattern);
        result = 31 * result + Longs.hashCode(support);
        result = 31 * result + length;
        hashCode = result;
        return result;
    }

    @Override
    public final String toString() {
        int[] arr = new int[length];
        System.arraycopy(pattern, 0, arr, 0, length);
        return Arrays.toString(arr) + '-' + support;
    }

    @Override
    public int compareTo(Pattern cr2) {
        long support2 = cr2.support();
        int length2 = cr2.length();
        if (support == support2) {
            if (length < length2) {
                return -1;
            } else if (length > length2) {
                return 1;
            } else {
                return 0;
            }
        } else {
            return support > support2 ? 1 : -1;
        }
    }

}