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SkewedLatestGenerator.java
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Mon, May 20, 00:39

SkewedLatestGenerator.java
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/**
* Copyright (c) 2010 Yahoo! Inc. All rights reserved.
*
* 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. See accompanying
* LICENSE file.
*/
package com.yahoo.ycsb.generator;
/**
* Generate a popularity distribution of items, skewed to favor recent items significantly more than older items.
*/
public class SkewedLatestGenerator extends IntegerGenerator
{
CounterGenerator _basis;
ZipfianGenerator _zipfian;
public SkewedLatestGenerator(CounterGenerator basis)
{
_basis=basis;
_zipfian=new ZipfianGenerator(_basis.lastInt());
nextInt();
}
/**
* Generate the next string in the distribution, skewed Zipfian favoring the items most recently returned by the basis generator.
*/
public int nextInt()
{
int max=_basis.lastInt();
int nextint=max-_zipfian.nextInt(max);
setLastInt(nextint);
return nextint;
}
public static void main(String[] args)
{
SkewedLatestGenerator gen=new SkewedLatestGenerator(new CounterGenerator(1000));
for (int i=0; i<Integer.parseInt(args[0]); i++)
{
System.out.println(gen.nextString());
}
}
@Override
public double mean() {
throw new UnsupportedOperationException("Can't compute mean of non-stationary distribution!");
}
}

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