content: /*
   * Licensed 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.clearspring.analytics.stream.frequency;
  
  import com.clearspring.analytics.stream.membership.Filter;
  
  /**
   * A more accurate (by some large, but ill-defined amount), but slower (by some
   * small, but equally ill-defined amount) count min sketch. It seemed like a
   * simple optimization and later internet searching suggested it might be
   * called something like a conservative adding variant.
   */
  public class ConservativeAddSketch extends CountMinSketch {
  
      ConservativeAddSketch() {
          super();
      }
  
      public ConservativeAddSketch(int depth, int width, int seed) {
          super(depth, width, seed);
      }
  
      public ConservativeAddSketch(double epsOfTotalCount, double confidence, int seed) {
          super(epsOfTotalCount, confidence, seed);
      }
  
      ConservativeAddSketch(int depth, int width, long size, long[] hashA, long[][] table) {
          super(depth, width, size, hashA, table);
      }
  
      @Override
      public void add(long item, long count) {
          if (count < 0) {
              // Negative values are not implemented in the regular version, and do not
              // play nicely with this algorithm anyway
              throw new IllegalArgumentException("Negative increments not implemented");
          }
          int[] buckets = new int[depth];
          for (int i = 0; i < depth; ++i) {
              buckets[i] = hash(item, i);
          }
          long min = table[0][buckets[0]];
          for (int i = 1; i < depth; ++i) {
              min = Math.min(min, table[i][buckets[i]]);
          }
          for (int i = 0; i < depth; ++i) {
              long newVal = Math.max(table[i][buckets[i]], min + count);
              table[i][buckets[i]] = newVal;
          }
          size += count;
      }
  
      @Override
      public void add(String item, long count) {
          if (count < 0) {
              // Negative values are not implemented in the regular version, and do not
              // play nicely with this algorithm anyway
              throw new IllegalArgumentException("Negative increments not implemented");
          }
          int[] buckets = Filter.getHashBuckets(item, depth, width);
          long min = table[0][buckets[0]];
          for (int i = 1; i < depth; ++i) {
              min = Math.min(min, table[i][buckets[i]]);
          }
          for (int i = 0; i < depth; ++i) {
              long newVal = Math.max(table[i][buckets[i]], min + count);
              table[i][buckets[i]] = newVal;
          }
          size += count;
      }
  }
  