Java List Distinct Value addWithExpDecay(List distinctVals)

Description

add With Exp Decay

License

Apache License

Declaration

public static Long addWithExpDecay(List<Long> distinctVals) 

Method Source Code

//package com.java2s;
/**// ww w  . j  a  va  2  s  .co  m
 * 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.
 */

import java.util.Collections;

import java.util.List;

public class Main {
    public static Long addWithExpDecay(List<Long> distinctVals) {
        // Exponential back-off for NDVs.
        // 1) Descending order sort of NDVs
        // 2) denominator = NDV1 * (NDV2 ^ (1/2)) * (NDV3 ^ (1/4))) * ....
        Collections.sort(distinctVals, Collections.reverseOrder());

        long denom = distinctVals.get(0);
        for (int i = 1; i < distinctVals.size(); i++) {
            denom = (long) (denom * Math.pow(distinctVals.get(i), 1.0 / (1 << i)));
        }

        return denom;
    }
}

Related

1. addDistinctEntry(List sourceList, V entry)
2. addDistinctItems(List fromItems, List toItems)
3. addDistinctList(List sourceList, List entryList)
4. constructDistinctClause(StringBuffer selectClause, List attributes, boolean isCountOnly)
5. distinct(List list)
6. distinct(List list)
7. distinct(List vector)