cpp/openttd-patchpack/source Changeset - r19229:5550f5cdc59d

Changeset - r19229:5550f5cdc59d

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michi_cc - 12 years ago 2012-04-17 19:43:43
michi_cc@openttd.org

(svn r24132) -Change [FS#4713]: Improve randomness of tile order in the tile loop. (monoid)

4 files changed with 36 insertions and 20 deletions:

src/genworld.cpp

src/landscape.cpp

src/misc.cpp

src/saveload/afterload.cpp

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src/genworld.cpp

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@@ @@ -159,6 +159,7 @@ static void _GenerateWorld(void *) @@
 			SetGeneratingWorldProgress(GWP_RUNTILELOOP, 0x500);
 			for (i = 0; i < 0x500; i++) {
 				RunTileLoop();
 				_tick_counter++;
 				IncreaseGeneratingWorldProgress(GWP_RUNTILELOOP);
+			}

src/landscape.cpp

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@@ @@ -712,32 +712,43 @@ CommandCost CmdClearArea(TileIndex tile, @@
 TileIndex _cur_tileloop_tile;
 #define TILELOOP_BITS 4
 #define TILELOOP_SIZE (1 << TILELOOP_BITS)
 #define TILELOOP_ASSERTMASK ((TILELOOP_SIZE - 1) + ((TILELOOP_SIZE - 1) << MapLogX()))
 #define TILELOOP_CHKMASK (((1 << (MapLogX() - TILELOOP_BITS))-1) << TILELOOP_BITS)
 /**
  * Gradually iterate over all tiles on the map, calling their TileLoopProcs once every 256 ticks.
  */
 void RunTileLoop()
+{
 	TileIndex tile = _cur_tileloop_tile;
 	/* The pseudorandom sequence of tiles is generated using a Galois linear feedback
 	 * shift register (LFSR). This allows a deterministic pseudorandom ordering, but
 	 * still with minimal state and fast iteration. */
 	/* Maximal length LFSR feedback terms, from 12-bit (for 64x64 maps) to 22-bit (for 2048x2048 maps).
 	 * Extracted from http://www.ece.cmu.edu/~koopman/lfsr/ */
 	static const uint32 feedbacks[] = {
 xD8F, 0x1296, 0x2496, 0x4357, 0x8679, 0x1030E, 0x206CD, 0x403FE, 0x807B8, 0x1004B2, 0x2006A8
 	};
 	const uint32 feedback = feedbacks[MapLogX() + MapLogY() - 12];
 	assert((tile & ~TILELOOP_ASSERTMASK) == 0);
 	uint count = (MapSizeX() / TILELOOP_SIZE) * (MapSizeY() / TILELOOP_SIZE);
 	do {
 	/* We update every tile every 256 ticks, so divide the map size by 2^8 = 256 */
 	uint count = 1 << (MapLogX() + MapLogY() - 8);
 	TileIndex tile = _cur_tileloop_tile;
 	/* The LFSR cannot have a zeroed state. */
 	assert(tile != 0);
 	/* Manually update tile 0 every 256 ticks - the LFSR never iterates over it itself.  */
 	if (_tick_counter % 256 == 0) {
 		_tile_type_procs[GetTileType(0)]->tile_loop_proc(0);
 		count--;
+	}
 	while (count--) {
 		_tile_type_procs[GetTileType(tile)]->tile_loop_proc(tile);
 		if (TileX(tile) < MapSizeX() - TILELOOP_SIZE) {
 			tile += TILELOOP_SIZE; // no overflow
 		} else {
 			tile = TILE_MASK(tile - TILELOOP_SIZE * (MapSizeX() / TILELOOP_SIZE - 1) + TileDiffXY(0, TILELOOP_SIZE)); // x would overflow, also increase y
+		}
 	} while (--count != 0);
 	assert((tile & ~TILELOOP_ASSERTMASK) == 0);
 		/* Get the next tile in sequence using a Galois LFSR. */
 		tile = (tile >> 1) ^ (-(int32)(tile & 1) & feedback);
+	}
 	tile += 9;
 	if (tile & TILELOOP_CHKMASK) {
 		tile = (tile + MapSizeX()) & TILELOOP_ASSERTMASK;
+	}
 	_cur_tileloop_tile = tile;
+}

src/misc.cpp

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@@ @@ -59,7 +59,7 @@ void InitializeGame(uint size_x, uint si @@
 	_pause_mode = PM_UNPAUSED;
 	_fast_forward = 0;
 	_tick_counter = 0;
-	_cur_tileloop_tile = 0;
+	_cur_tileloop_tile = 1;
 	_thd.redsq = INVALID_TILE;
 	if (reset_settings) MakeNewgameSettingsLive();

src/saveload/afterload.cpp

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@@ @@ -483,6 +483,10 @@ bool AfterLoadGame() @@
 	TileIndex map_size = MapSize();
 	extern TileIndex _cur_tileloop_tile; // From landscape.cpp.
 	/* The LFSR used in RunTileLoop iteration cannot have a zeroed state, make it non-zeroed. */
 	if (_cur_tileloop_tile == 0) _cur_tileloop_tile = 1;
 	if (IsSavegameVersionBefore(98)) GamelogOldver();
 	GamelogTestRevision();

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