/**
* 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.Vector;
import java.util.Random;
import com.yahoo.ycsb.Utils;
import com.yahoo.ycsb.WorkloadException;
/**
* Generates a distribution by choosing from a discrete set of values.
*/
public class DiscreteGenerator extends Generator
{
class Pair
{
public double _weight;
public String _value;
Pair(double weight, String value)
{
_weight=weight;
_value=value;
}
}
Vector<Pair> _values;
String _lastvalue;
public DiscreteGenerator()
{
_values=new Vector<Pair>();
_lastvalue=null;
}
/**
* Generate the next string in the distribution.
*/
public String nextString()
{
double sum=0;
for (Pair p : _values)
{
sum+=p._weight;
}
double val=Utils.random().nextDouble();
for (Pair p : _values)
{
if (val<p._weight/sum)
{
return p._value;
}
val-=p._weight/sum;
}
//should never get here.
System.out.println("oops. should not get here.");
System.exit(0);
return null;
}
/**
* If the generator returns numeric (integer) values, return the next value as an int. Default is to return -1, which
* is appropriate for generators that do not return numeric values.
*
* @throws WorkloadException if this generator does not support integer values
*/
public int nextInt() throws WorkloadException
{
throw new WorkloadException("DiscreteGenerator does not support nextInt()");
}
/**
* Return the previous string generated by the distribution; e.g., returned from the last nextString() call.
* Calling lastString() should not advance the distribution or have any side effects. If nextString() has not yet
* been called, lastString() should return something reasonable.
*/
public String lastString()
{
if (_lastvalue==null)
{
_lastvalue=nextString();
}
return _lastvalue;
}
public void addValue(double weight, String value)
{
_values.add(new Pair(weight,value));
}
}