content: /**
   * 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.asterix.fuzzyjoin;
  
  public class FuzzyFiltersJaccard {
  
      /**
       * type is double because with float .8 / (1 + .8) * (8 + 10) = 8.0...01
       */
      protected final double simThr;
      protected final double simThrExpr;
  
      public FuzzyFiltersJaccard(double similarityThreshold) {
          simThr = similarityThreshold;
          simThrExpr = simThr / (1 + simThr);
      }
  
      public int getIndexPrefixLength(int length) {
          return length - (int) Math.ceil(2 * simThrExpr * length) + 1;
      }
  
      public int getIntersectLowerBound(int lengthX, int lengthY) {
          return (int) Math.ceil(simThrExpr * (lengthX + lengthY));
      }
  
      public long getIntersectLowerBound(long lengthX, long lengthY) {
          return (long) Math.ceil(simThrExpr * (lengthX + lengthY));
      }
  
      public int getIntersectUpperBound(int noGramsCommon, int positionX, int positionY, int lengthX, int lengthY) {
          return noGramsCommon + Math.min(lengthX - positionX - 1, lengthY - positionY - 1);
      }
  
      public long getIntersectUpperBound(int noGramsCommon, long positionX, long positionY, long lengthX, long lengthY) {
          return noGramsCommon + Math.min(lengthX - positionX - 1, lengthY - positionY - 1);
      }
  
      public int getLengthLowerBound(int length) {
          return (int) Math.ceil(simThr * length);
      }
  
      public long getLengthLowerBound(long length) {
          return (long) Math.ceil(simThr * length);
      }
  
      public int getPrefixLength(int length) {
          return length - (int) Math.ceil(simThr * length) + 1;
      }
  
      public long getPrefixLength(long length) {
          return length - (long) Math.ceil(simThr * length) + 1;
      }
  
      public double getSimilarityThreshold() {
          return simThr;
      }
  
      public boolean passLengthFilter(int lengthX, int lengthY) {
          return getLengthLowerBound(lengthX) <= lengthY && lengthY <= 1 / simThr * lengthX;
      }
  
      public boolean passLengthFilter(long lengthX, long lengthY) {
          return getLengthLowerBound(lengthX) <= lengthY && lengthY <= 1 / simThr * lengthX;
      }
  
      /**
       * @param noGramsCommon
       *            number of grams in common
       * @param positionX
       *            position of the last gram in common on X
       * @param positionY
       *            position of the last gram in common on X
       * @param lengthX
       * @param lengthY
       * @return
       */
      public boolean passPositionFilter(int noGramsCommon, int positionX, int positionY, int lengthX, int lengthY) {
          return getIntersectUpperBound(noGramsCommon, positionX, positionY, lengthX,
                  lengthY) >= getIntersectLowerBound(lengthX, lengthY);
      }
  
      public boolean passPositionFilter(int noGramsCommon, long positionX, long positionY, long lengthX, long lengthY) {
          return getIntersectUpperBound(noGramsCommon, positionX, positionY, lengthX,
                  lengthY) >= getIntersectLowerBound(lengthX, lengthY);
      }
  
  }
  