(svn r20857) -Fix [FS#3637]: The station with the second highest rating was doubly penalised when distributing cargo. Now the penalty is completely removed and the granularity/precision of the distribution in increased by using fractional cargo. This should make competing stations less "all-or-nothing".

src/saveload/saveload.cpp

@@ -212,8 +212,9 @@
  *  147   20621
  *  148   20659
  *  149   20832
+ *  150   20857
  */
-extern const uint16 SAVEGAME_VERSION = 149; ///< current savegame version of OpenTTD
+extern const uint16 SAVEGAME_VERSION = 150; ///< current savegame version of OpenTTD
 
 SavegameType _savegame_type; ///< type of savegame we are loading
 

src/saveload/station_sl.cpp

@@ -238,6 +238,7 @@ const SaveLoad *GetGoodsDesc()
 		     SLE_VAR(GoodsEntry, last_age,            SLE_UINT8),
 		SLEG_CONDVAR(            _cargo_feeder_share, SLE_FILE_U32 | SLE_VAR_I64, 14, 64),
 		SLEG_CONDVAR(            _cargo_feeder_share, SLE_INT64,                  65, 67),
+		 SLE_CONDVAR(GoodsEntry, amount_fract,        SLE_UINT8,                 150, SL_MAX_VERSION),
 		 SLE_CONDLST(GoodsEntry, cargo.packets,       REF_CARGO_PACKET,           68, SL_MAX_VERSION),
 
 		SLE_END()

src/station_base.h

@@ -42,6 +42,7 @@ struct GoodsEntry {
 	byte rating;
 	byte last_speed;
 	byte last_age;
+	byte amount_fract;      ///< Fractional part of the amount in the cargo list
 	StationCargoList cargo; ///< The cargo packets of cargo waiting in this station
 };
 

src/station_cmd.cpp

@@ -3188,8 +3188,15 @@ void ModifyStationRatingAround(TileIndex tile, Owner owner, int amount, uint rad
 	}
 }
 
-static void UpdateStationWaiting(Station *st, CargoID type, uint amount, SourceType source_type, SourceID source_id)
+static uint UpdateStationWaiting(Station *st, CargoID type, uint amount, SourceType source_type, SourceID source_id)
 {
+	amount += st->goods[type].amount_fract;
+	st->goods[type].amount_fract = GB(amount, 0, 8);
+
+	amount >>= 8;
+	/* No new "real" cargo item yet. */
+	if (amount == 0) return 0;
+
 	st->goods[type].cargo.Append(new CargoPacket(st->index, st->xy, amount, source_type, source_id));
 	SetBit(st->goods[type].acceptance_pickup, GoodsEntry::PICKUP);
 
@@ -3198,6 +3205,7 @@ static void UpdateStationWaiting(Station *st, CargoID type, uint amount, SourceT
 
 	SetWindowDirty(WC_STATION_VIEW, st->index);
 	st->MarkTilesDirty(true);
+	return amount;
 }
 
 static bool IsUniqueStationName(const char *name)
@@ -3328,11 +3336,13 @@ uint MoveGoodsToStation(CargoID type, uint amount, SourceType source_type, Sourc
 	/* no stations around at all? */
 	if (st1 == NULL) return 0;
 
+	/* From now we'll calculate with fractal cargo amounts.
+	 * First determine how much cargo we really have. */
+	amount *= best_rating1 + 1;
+
 	if (st2 == NULL) {
 		/* only one station around */
-		uint moved = amount * best_rating1 / 256 + 1;
-		UpdateStationWaiting(st1, type, moved, source_type, source_id);
-		return moved;
+		return UpdateStationWaiting(st1, type, amount, source_type, source_id);
 	}
 
 	/* several stations around, the best two (highest rating) are in st1 and st2 */
@@ -3340,26 +3350,19 @@ uint MoveGoodsToStation(CargoID type, uint amount, SourceType source_type, Sourc
 	assert(st2 != NULL);
 	assert(best_rating1 != 0 || best_rating2 != 0);
 
-	/* the 2nd highest one gets a penalty */
-	best_rating2 >>= 1;
-
-	/* amount given to station 1 */
-	uint t = (best_rating1 * (amount + 1)) / (best_rating1 + best_rating2);
-
-	uint moved = 0;
-	if (t != 0) {
-		moved = t * best_rating1 / 256 + 1;
-		amount -= t;
-		UpdateStationWaiting(st1, type, moved, source_type, source_id);
-	}
-
-	if (amount != 0) {
-		amount = amount * best_rating2 / 256 + 1;
-		moved += amount;
-		UpdateStationWaiting(st2, type, amount, source_type, source_id);
-	}
-
-	return moved;
+	/* Then determine the amount the worst station gets. We do it this way as the
+	 * best should get a bonus, which in this case is the rounding difference from
+	 * this calculation. In reality that will mean the bonus will be pretty low.
+	 * Nevertheless, the best station should always get the most cargo regardless
+	 * of rounding issues. */
+	uint worst_cargo = amount * best_rating2 / (best_rating1 + best_rating2);
+	assert(worst_cargo <= (amount - worst_cargo));
+
+	/* And then send the cargo to the stations! */
+	uint moved = UpdateStationWaiting(st1, type, amount - worst_cargo, source_type, source_id);
+	/* These two UpdateStationWaiting's can't be in the statement as then the order
+	 * of execution would be undefined and that could cause desyncs with callbacks. */
+	return moved + UpdateStationWaiting(st2, type, worst_cargo, source_type, source_id);
 }
 
 void BuildOilRig(TileIndex tile)