modified the hueristic for taking over blocks slightly, added logging

src/peer_connection.cpp

@@ -1041,8 +1041,9 @@ namespace libtorrent
 				// peer that has taken over it.
 				boost::optional<tcp::endpoint> peer
 					= t->picker().get_downloader(block_finished);
-				if (!t->picker().is_finished(block_finished) && peer)
+				if (peer)
 				{
+					assert(!t->picker().is_finished(block_finished));
 					peer_connection* pc = t->connection_for(*peer);
 					if (pc && pc != this)
 					{

src/piece_picker.cpp

@@ -1163,14 +1163,17 @@ namespace libtorrent
 
 		assert(block.block_index < blocks_in_piece(block.piece_index));
 #ifndef NDEBUG
-		if (i->requested_blocks[block.block_index] != 1)
+		if (i->requested_blocks[block.block_index] == false)
 		{
 			assert(false);
 		}
 #endif
 
 		// clear this block as being downloaded
-		i->requested_blocks[block.block_index] = 0;
+		i->requested_blocks[block.block_index] = false;
+		
+		// clear the downloader of this block
+		i->info[block.block_index].peer = tcp::endpoint();
 
 		// if there are no other blocks in this piece
 		// that's being downloaded, remove it from the list

src/policy.cpp

@@ -181,25 +181,35 @@ namespace
 				const std::deque<piece_block>& request_queue = i->second->request_queue();
 				const int queue_size = (int)i->second->download_queue().size()
 					+ (int)i->second->request_queue().size();
-				const float weight = queue_size == 0
+
+				bool in_request_queue = std::find_first_of(
+						busy_pieces.begin()
+						, busy_pieces.end()
+						, request_queue.begin()
+						, request_queue.end()) != busy_pieces.end();
+						
+				bool in_download_queue = std::find_first_of(
+						busy_pieces.begin()
+						, busy_pieces.end()
+						, download_queue.begin()
+						, download_queue.end()) != busy_pieces.end();
+
+				// if the block is in the request queue rather than the download queue
+				// (i.e. the request message hasn't been sent yet) lower the weight in
+				// order to prioritize it. Taking over a block in the request queue is
+				// free in terms of redundant download. A block that already has been
+				// requested is likely to be in transit already, and would in that case
+				// mean redundant data to receive.
+				const float weight = (queue_size == 0)
 					? std::numeric_limits<float>::max()
-					: i->second->statistics().download_payload_rate() / queue_size;
+					: i->second->statistics().download_payload_rate() / queue_size
+						* in_request_queue ? .1f : 1.f;
 
 				// if the peer's (i) weight is less than the lowest we've found so
 				// far (weight == priority) and it has blocks in its request-
 				// or download queue that we could request from this peer (c),
 				// replace the currently lowest ranking peer.
-				if (weight < min_weight
-					&& (std::find_first_of(
-						busy_pieces.begin()
-						, busy_pieces.end()
-						, request_queue.begin()
-						, request_queue.end()) != busy_pieces.end()
-					|| std::find_first_of(
-						busy_pieces.begin()
-						, busy_pieces.end()
-						, download_queue.begin()
-						, download_queue.end()) != busy_pieces.end()))
+				if (weight < min_weight && (in_request_queue || in_download_queue))
 				{
 					peer = i->second;
 					min_weight = weight;

src/torrent.cpp

@@ -209,6 +209,7 @@ namespace
 			<< "16. bytes received 10 seconds mean\n"
 			<< "17. total payload download\n"
 			<< "18. total web seed payload download\n"
+			<< "19. total redundant bytes downloaded\n"
 			<< "\n";
 	}
 #endif
@@ -2015,6 +2016,7 @@ namespace libtorrent
 			<< mean_dl << "\t"
 			<< m_stat.total_payload_download() << "\t"
 			<< m_web_stat.total_payload_download() << "\t"
+			<< m_total_redundant_bytes
 			<< "\n";
 
 		(*m_log)