com.splout.db.benchmark
Class PositiveHistogram

java.lang.Object
  com.splout.db.benchmark.PositiveHistogram

Direct Known Subclasses:

HistogramWithStats

public class PositiveHistogram
extends java.lang.Object

A class for computing approximated histograms, keeping a constant resolution, constant amount of memory, and without the needed of pre or post processing. WARNING: It only works for positive values. And if they are distributed far from 0, then will not work properly as well.

Field Summary

protected int[]	buckets
protected long	count
protected double	upperLimit

Constructor Summary

PositiveHistogram(int bits, double initialUpperLimit)
2^bits will be number of buckets.

Method Summary

void	add(double value) Add a new value to the histogram
int	bucketFor(java.lang.Double value) Return the bucket index for a given value.
int[]	getBuckets() Return the list of buckets.
double	getBucketSize()
long	getCount() Returns the number of elements that was added to the histogram.
double	getLeftAccumulatedProbability(double value) Computes the accumulated probability for the values at the left of the provided value
double[]	getNormalizedHistogram()
double	getRigthAccumulatedProbability(double value) Computes the accumulated probability for the values at the right of the provided value
double	getUpperLimit() Returns the maximum value that can be keep if the current histogram without needing to redistribute the buckets.
protected void	resize(double value)
java.lang.String	toTSV()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

buckets

protected int[] buckets

upperLimit

protected double upperLimit

count

protected long count

Constructor Detail

PositiveHistogram

public PositiveHistogram(int bits,
                         double initialUpperLimit)

2^bits will be number of buckets. If known, it is useful to provide an initialUpperLimit. If it is not known, just set it as 0

Method Detail

add

public void add(double value)

Add a new value to the histogram

resize

protected void resize(double value)

bucketFor

public int bucketFor(java.lang.Double value)

Return the bucket index for a given value.

getUpperLimit

public double getUpperLimit()

Returns the maximum value that can be keep if the current histogram without needing to redistribute the buckets.

getBuckets

public int[] getBuckets()

Return the list of buckets. They represent the values between 0 and getUpperLimit()

getCount

public long getCount()

Returns the number of elements that was added to the histogram.

getRigthAccumulatedProbability

public double getRigthAccumulatedProbability(double value)

Computes the accumulated probability for the values at the right of the provided value

getLeftAccumulatedProbability

public double getLeftAccumulatedProbability(double value)

Computes the accumulated probability for the values at the left of the provided value

getNormalizedHistogram

public double[] getNormalizedHistogram()

getBucketSize

public double getBucketSize()

toTSV

public java.lang.String toTSV()