/*
* Created on june 12th, 2003
* Copyright (C) 2003, 2004, 2005, 2006 Aelitis, All Rights Reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* AELITIS, SAS au capital de 46,603.30 euros
* 8 Allee Lenotre, La Grille Royale, 78600 Le Mesnil le Roi, France.
*
*/
package org.gudy.azureus2.core3.util;
/**
*
* This class is used to compute average (mostly for speed transfer).
*
* @author Olivier
*
*/
public class Average {
/**
* It uses a simple array of longs to store values in a cycling way.
* The array has 2 more elements than really needed to compute the average.
* One is the next one to be filled, and its value is always 0,
* and the other one is the one currently filled,
* which value is not taken into account for the average.
*/
//The refresh rate of the average (ms)
private int refreshRate;
//the period (in ms)
private int period;
//The number of elements in the average
private int nbElements;
//The time the average was last updated (divided by the refreshRate).
private long lastUpdate;
//The values
private long values[];
/**
* Private constructor for an Average
* @param _refreshRate the refresh rate in ms
* @param _period the period in s
*/
protected Average(int _refreshRate, int _period) {
this.refreshRate = _refreshRate;
this.period = _period;
this.nbElements = (_period * 1000) / _refreshRate + 2;
this.lastUpdate = getEffectiveTime() / _refreshRate;
this.values = new long[this.nbElements];
}
/**
* The way to get a new Average Object, it does some parameter checking.
* refreshRate must be greater than 100,
* and period*1000 must be greater than refreshRate
* @param refreshRate in ms
* @param period in s
* @return the newlly created Average, or null if parameters are wrong
*/
public static Average getInstance(int refreshRate, int period) {
if (refreshRate < 100)
return null;
if ((period * 1000) < refreshRate)
return null;
return new Average(refreshRate, period);
}
/**
* This method is used to update the buffer tha stores the values,
* in fact it mostly does clean-up over this buffer,
* erasing all values that have not been updated.
* @param timeFactor which is the currentTime divided by the refresh Rate
*/
private synchronized void update(long timeFactor) {
//If we have a really OLD lastUpdate, we could erase the buffer a
//huge number of time, so if it's really old, we change it so we'll only
//erase the buffer once.
if (lastUpdate < timeFactor - nbElements)
lastUpdate = timeFactor - nbElements - 1;
//For all values between lastUpdate + 1 (next value than last updated)
//and timeFactor (which is the new value insertion position)
for (long i = lastUpdate + 1; i <= timeFactor; i++) {
//We set the value to 0.
values[(int) (i % nbElements)] = 0;
}
//We also clear the next value to be inserted (so on next time change...)
values[(int) ((timeFactor + 1) % nbElements)] = 0;
//And we update lastUpdate.
lastUpdate = timeFactor;
}
/**
* Public method to add a value to the average,
* the time it is added is the time this method is called.
* @param value the value to be added to the Average
*/
public void addValue(long value) {
//We get the current time factor.
long timeFactor = getEffectiveTime() / refreshRate;
//We first update the buffer.
update(timeFactor);
//And then we add our value to current element
values[(int) (timeFactor % nbElements)] += value;
}
/**
* This method can be called to get the current average value.
* @return the current Average computed.
*/
public long getAverage() {
return( getSum() / period );
}
public double getDoubleAverage() {
return( (double)getSum() / period );
}
public String getDoubleAverageAsString( int precision ) {
return( DisplayFormatters.formatDecimal( getDoubleAverage(), precision ));
}
public long getAverage(int average_period )
{
int slots = average_period<=0?(nbElements - 2):(average_period / refreshRate);
if ( slots <= 0 ){
slots = 1;
}else if ( slots > nbElements - 2 ){
slots = nbElements - 2;
}
if ( slots == 1 ){
return( getPointValue());
}
long res = getSum(slots) / ( period * slots / ( nbElements - 2 ));
return( res );
}
public long
getPointValue()
{
long timeFactor = getEffectiveTime() / refreshRate;
//We first update the buffer
update(timeFactor);
return(values[(int)((timeFactor-1)% nbElements)]);
}
protected final long getSum() {
//We get the current timeFactor
long timeFactor = getEffectiveTime() / refreshRate;
//We first update the buffer
update(timeFactor);
//The sum of all elements used for the average.
long sum = 0;
//Starting on oldest one (the one after the next one)
//Ending on last one fully updated (the one previous current one)
for (long i = timeFactor + 2; i < timeFactor + nbElements; i++) {
//Simple addition
sum += values[(int) (i % nbElements)];
}
//We return the sum divided by the period
return(sum);
}
protected final long getSum(int slots) {
//We get the current timeFactor
long timeFactor = getEffectiveTime() / refreshRate;
//We first update the buffer
update(timeFactor);
//The sum of all elements used for the average.
long sum = 0;
if ( slots < 1 ){
slots = 1;
}else if ( slots > nbElements-2 ){
slots = nbElements-2;
}
//Starting on oldest one (the one after the next one)
//Ending on last one fully updated (the one previous current one)
long end_slot = timeFactor + nbElements;
long start_slot = end_slot - slots;
for (long i = start_slot; i< end_slot;i++ ){
sum += values[(int) (i % nbElements)];
}
//We return the sum divided by the period
return(sum);
}
protected long
getEffectiveTime()
{
return( SystemTime.getCurrentTime());
}
}
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