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HistogramGenerator.java
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Wed, May 22, 18:57

HistogramGenerator.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.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import com.yahoo.ycsb.Utils;
import com.yahoo.ycsb.generator.NumberGenerator;
/**
* Generate integers according to a histogram distribution. The histogram
* buckets are of width one, but the values are multiplied by a block size.
* Therefore, instead of drawing sizes uniformly at random within each
* bucket, we always draw the largest value in the current bucket, so the value
* drawn is always a multiple of block_size.
*
* The minimum value this distribution returns is block_size (not zero).
*
* Modified Nov 19 2010 by sears
*
* @author snjones
*
*/
public class HistogramGenerator extends NumberGenerator {
private final long block_size;
private final long[] buckets;
private long area;
private long weighted_area = 0;
private double mean_size = 0;
public HistogramGenerator(String histogramfile) throws IOException {
try (BufferedReader in = new BufferedReader(new FileReader(histogramfile))) {
String str;
String[] line;
ArrayList<Integer> a = new ArrayList<Integer>();
str = in.readLine();
if(str == null) {
throw new IOException("Empty input file!\n");
}
line = str.split("\t");
if(line[0].compareTo("BlockSize") != 0) {
throw new IOException("First line of histogram is not the BlockSize!\n");
}
block_size = Integer.parseInt(line[1]);
while((str = in.readLine()) != null){
// [0] is the bucket, [1] is the value
line = str.split("\t");
a.add(Integer.parseInt(line[0]), Integer.parseInt(line[1]));
}
buckets = new long[a.size()];
for(int i = 0; i < a.size(); i++) {
buckets[i] = a.get(i);
}
}
init();
}
public HistogramGenerator(long[] buckets, int block_size) {
this.block_size = block_size;
this.buckets = buckets;
init();
}
private void init() {
for(int i = 0; i < buckets.length; i++) {
area += buckets[i];
weighted_area = i * buckets[i];
}
// calculate average file size
mean_size = ((double)block_size) * ((double)weighted_area) / (area);
}
@Override
public Long nextValue() {
int number = Utils.random().nextInt((int)area);
int i;
for(i = 0; i < (buckets.length - 1); i++){
number -= buckets[i];
if(number <= 0){
return (i+1)*block_size;
}
}
return i * block_size;
}
@Override
public double mean() {
return mean_size;
}
}

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