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HotspotIntegerGenerator.java
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Wed, May 22, 10:51

HotspotIntegerGenerator.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;
import java.util.Random;
import com.yahoo.ycsb.Utils;
/**
* Generate integers resembling a hotspot distribution where x% of operations
* access y% of data items. The parameters specify the bounds for the numbers,
* the percentage of the of the interval which comprises the hot set and
* the percentage of operations that access the hot set. Numbers of the hot set are
* always smaller than any number in the cold set. Elements from the hot set and
* the cold set are chose using a uniform distribution.
*
* @author sudipto
*
*/
public class HotspotIntegerGenerator extends NumberGenerator {
private final int lowerBound;
private final int upperBound;
private final int hotInterval;
private final int coldInterval;
private final double hotsetFraction;
private final double hotOpnFraction;
/**
* Create a generator for Hotspot distributions.
*
* @param lowerBound lower bound of the distribution.
* @param upperBound upper bound of the distribution.
* @param hotsetFraction percentage of data item
* @param hotOpnFraction percentage of operations accessing the hot set.
*/
public HotspotIntegerGenerator(int lowerBound, int upperBound,
double hotsetFraction, double hotOpnFraction) {
if (hotsetFraction < 0.0 || hotsetFraction > 1.0) {
System.err.println("Hotset fraction out of range. Setting to 0.0");
hotsetFraction = 0.0;
}
if (hotOpnFraction < 0.0 || hotOpnFraction > 1.0) {
System.err.println("Hot operation fraction out of range. Setting to 0.0");
hotOpnFraction = 0.0;
}
if (lowerBound > upperBound) {
System.err.println("Upper bound of Hotspot generator smaller than the lower bound. " +
"Swapping the values.");
int temp = lowerBound;
lowerBound = upperBound;
upperBound = temp;
}
this.lowerBound = lowerBound;
this.upperBound = upperBound;
this.hotsetFraction = hotsetFraction;
int interval = upperBound - lowerBound + 1;
this.hotInterval = (int)(interval * hotsetFraction);
this.coldInterval = interval - hotInterval;
this.hotOpnFraction = hotOpnFraction;
}
@Override
public Integer nextValue() {
int value = 0;
Random random = Utils.random();
if (random.nextDouble() < hotOpnFraction) {
// Choose a value from the hot set.
value = lowerBound + random.nextInt(hotInterval);
} else {
// Choose a value from the cold set.
value = lowerBound + hotInterval + random.nextInt(coldInterval);
}
setLastValue(value);
return value;
}
/**
* @return the lowerBound
*/
public int getLowerBound() {
return lowerBound;
}
/**
* @return the upperBound
*/
public int getUpperBound() {
return upperBound;
}
/**
* @return the hotsetFraction
*/
public double getHotsetFraction() {
return hotsetFraction;
}
/**
* @return the hotOpnFraction
*/
public double getHotOpnFraction() {
return hotOpnFraction;
}
@Override
public double mean() {
return hotOpnFraction * (lowerBound + hotInterval/2.0)
+ (1 - hotOpnFraction) * (lowerBound + hotInterval + coldInterval/2.0);
}
}

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