/*
* Created on Apr 5, 2005
* Created by Alon Rohter
* Copyright (C) 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 com.aelitis.azureus.core.peermanager.unchoker;
import java.util.*;
import org.gudy.azureus2.core3.peer.PEPeer;
import org.gudy.azureus2.core3.peer.impl.PEPeerTransport;
import org.gudy.azureus2.core3.util.RandomUtils;
/**
* Utility collection for unchokers.
*/
public class UnchokerUtil {
/**
* Test whether or not the given peer is allowed to be unchoked.
* @param peer to test
* @param allow_snubbed if true, ignore snubbed state
* @return true if peer is allowed to be unchoked, false if not
*/
public static boolean isUnchokable( PEPeer peer, boolean allow_snubbed ) {
return peer.getPeerState() == PEPeer.TRANSFERING && !peer.isSeed() && !peer.isRelativeSeed() && peer.isInterested() && ( !peer.isSnubbed() || allow_snubbed );
}
/**
* Update (if necessary) the given list with the given value while maintaining a largest-value-first (as seen so far) sort order.
* NOTE: You will need to initialize the values array to Long.MIN_VALUE if you want to store negative values!
* @param new_value to use
* @param values existing values array
* @param new_item to insert
* @param items existing items
* @param start_pos index at which to start compare
*/
public static void updateLargestValueFirstSort( long new_value, long[] values, PEPeer new_item, ArrayList items, int start_pos ) {
items.ensureCapacity( values.length );
for( int i=start_pos; i < values.length; i++ ) {
if( new_value >= values[ i ] ) {
for( int j = values.length - 2; j >= i; j-- ) { //shift displaced values to the right
values[j + 1] = values[ j ];
}
if( items.size() == values.length ) { //throw away last item if list too large
items.remove( values.length - 1 );
}
values[ i ] = new_value;
items.add( i, new_item );
return;
}
}
}
/**
* Choose the next peer, optimistically, that should be unchoked.
* @param all_peers list of peer to choose from
* @param factor_reciprocated if true, factor in how much (if any) this peer has reciprocated when choosing
* @param allow_snubbed allow the picking of snubbed-state peers as last resort
* @return the next peer to optimistically unchoke, or null if there are no peers available
*/
public static PEPeer getNextOptimisticPeer( ArrayList<PEPeer> all_peers, boolean factor_reciprocated, boolean allow_snubbed ) {
ArrayList<PEPeer> peers = getNextOptimisticPeers( all_peers, factor_reciprocated, allow_snubbed, 1 );
if ( peers != null ){
return((PEPeerTransport)peers.get(0));
}
return( null );
}
public static ArrayList<PEPeer> getNextOptimisticPeers( ArrayList<PEPeer> all_peers, boolean factor_reciprocated, boolean allow_snubbed, int num_needed ) {
//find all potential optimistic peers
ArrayList<PEPeer> optimistics = new ArrayList<PEPeer>();
for( int i=0; i < all_peers.size(); i++ ) {
PEPeer peer = all_peers.get( i );
if( isUnchokable( peer, false ) && peer.isChokedByMe() ) {
optimistics.add( peer );
}
}
if( optimistics.isEmpty() && allow_snubbed ) { //try again, allowing snubbed peers as last resort
for( int i=0; i < all_peers.size(); i++ ) {
PEPeer peer = all_peers.get( i );
if( isUnchokable( peer, true ) && peer.isChokedByMe() ) {
optimistics.add( peer );
}
}
}
if( optimistics.isEmpty() ) return null; //no unchokable peers avail
//factor in peer reciprocation ratio when picking optimistic peers
ArrayList<PEPeer> result = new ArrayList<PEPeer>(optimistics.size());
if ( factor_reciprocated ){
ArrayList<PEPeerTransport> ratioed_peers = new ArrayList<PEPeerTransport>( optimistics.size() );
long[] ratios = new long[ optimistics.size() ];
Arrays.fill( ratios, Long.MIN_VALUE );
//order by upload ratio
for( int i=0; i < optimistics.size(); i++ ) {
PEPeer peer = optimistics.get( i );
//score of >0 means we've uploaded more, <0 means we've downloaded more
long score = peer.getStats().getTotalDataBytesSent() - peer.getStats().getTotalDataBytesReceived();
UnchokerUtil.updateLargestValueFirstSort( score, ratios, peer, ratioed_peers, 0 ); //higher value = worse score
}
for (int i=0;i<num_needed && ratioed_peers.size() > 0;i++ ){
double factor = 1F / ( 0.8 + 0.2 * Math.pow( RandomUtils.nextFloat(), -1 ) ); //map to sorted list using a logistic curve
int pos = (int)(factor * ratioed_peers.size());
result.add(ratioed_peers.remove( pos ));
}
}else{
for (int i=0;i<num_needed && optimistics.size() > 0;i++ ){
int rand_pos = new Random().nextInt( optimistics.size() );
result.add( optimistics.remove( rand_pos ));
}
}
return( result );
//TODO:
//in downloading mode, we would be better off optimistically unchoking just peers we are interested in ourselves,
//as they could potentially reciprocate. however, new peers have no pieces to share, and are not interesting to
//us, and would never be unchoked, and thus would never get any data.
//we could use a deterministic method for new peers to get their very first piece from us
}
/**
* Send choke/unchoke messages to the given peers.
* @param peers_to_choke
* @param peers_to_unchoke
*/
public static void performChokes( ArrayList<PEPeer> peers_to_choke, ArrayList<PEPeer> peers_to_unchoke ) {
//do chokes
if( peers_to_choke != null ) {
for( int i=0; i < peers_to_choke.size(); i++ ) {
final PEPeerTransport peer = (PEPeerTransport)peers_to_choke.get( i );
if( !peer.isChokedByMe() ) {
peer.sendChoke();
}
}
}
//do unchokes
if( peers_to_unchoke != null ) {
for( int i=0; i < peers_to_unchoke.size(); i++ ) {
final PEPeer peer = peers_to_unchoke.get( i );
if( peer.isChokedByMe() ) { //TODO add UnchokerUtil.isUnchokable() test here to be safe?
peer.sendUnChoke();
}
}
}
}
public static void performChokeUnchoke( PEPeer to_choke, PEPeer to_unchoke ) {
if( to_choke != null && !to_choke.isChokedByMe() ) {
to_choke.sendChoke();
}
if( to_unchoke != null && to_unchoke.isChokedByMe() ) {
to_unchoke.sendUnChoke();
}
}
}