made the sequential download mode slightly more sequential (by letting more categories of peers request early pieces). Disabled speed affinity and prefer_whole_pieces when in sequential download mode

include/libtorrent/piece_picker.hpp

@@ -129,7 +129,11 @@ namespace libtorrent
 			// always pick partial pieces before any other piece
 			prioritize_partials = 8,
 			// pick pieces in sequential order
-			sequential = 16
+			sequential = 16,
+			// have affinity to pieces with the same speed category
+			speed_affinity = 32,
+			// ignore the prefer_whole_pieces parameter
+			ignore_whole_pieces = 64
 		};
 
 		struct downloading_piece

src/peer_connection.cpp

@@ -617,7 +617,7 @@ namespace libtorrent
 
 		if (t->is_sequential_download())
 		{
-			ret |= piece_picker::sequential;
+			ret |= piece_picker::sequential | piece_picker::ignore_whole_pieces;
 		}
 		else if (t->num_have() < t->settings().initial_picker_threshold)
 		{
@@ -628,7 +628,7 @@ namespace libtorrent
 		}
 		else
 		{
-			ret |= piece_picker::rarest_first;
+			ret |= piece_picker::rarest_first | piece_picker::speed_affinity;
 		}
 
 		if (m_snubbed)

src/piece_picker.cpp

@@ -1319,6 +1319,12 @@ namespace libtorrent
 	//     peer
 	// * prioritize_partials
 	//     pick blocks from downloading pieces first
+	// * speed_affinity
+	//     have an affinity to pick pieces in the same speed
+	//     category.
+	// * ignore_whole_pieces
+	//     ignores the prefer_whole_pieces parameter (as if
+	//     it was 0)
 
 	// only one of rarest_first, sequential can be set
 
@@ -1330,6 +1336,8 @@ namespace libtorrent
 		// prevent the number of partial pieces to grow indefinitely
 		if (m_downloads.size() > 20) options |= prioritize_partials;
 
+		if (options & ignore_whole_pieces) prefer_whole_pieces = 0;
+
 		// only one of rarest_first and sequential can be set.
 		TORRENT_ASSERT(bool(options & rarest_first)
 			+ bool(options & sequential) <= 1);
@@ -1812,7 +1820,7 @@ namespace libtorrent
 			// if the state of the piece is none (the
 			// piece will in that case change state).
 			if (dp.state != none && dp.state != speed
-				&& !exclusive_active)
+				&& !exclusive_active && (options & speed_affinity))
 			{
 				if (abs(dp.state - speed) == 1)
 				{