FlowStat: Replace btree_map with flat map which is inlined in small case

Inline storage for size <= 2
Size = 1 is ~90%
Size = 2 is ~9%
Size >=3 is ~1% and gets a separate allocation

src/cargopacket.cpp

@@ -663,10 +663,10 @@ bool VehicleCargoList::Stage(bool accepted, StationID current_station, StationID
 				FlowStat new_shares = *flow_it;
 				new_shares.ChangeShare(current_station, INT_MIN);
 				StationIDStack excluded = next_station;
-				while (!excluded.IsEmpty() && !new_shares.GetShares()->empty()) {
+				while (!excluded.IsEmpty() && !new_shares.empty()) {
 					new_shares.ChangeShare(excluded.Pop(), INT_MIN);
 				}
-				if (new_shares.GetShares()->empty()) {
+				if (new_shares.empty()) {
 					cargo_next = INVALID_STATION;
 				} else {
 					cargo_next = new_shares.GetVia();

src/linkgraph/linkgraphjob.cpp

@@ -155,8 +155,8 @@ void LinkGraphJob::FinaliseJob()
 					FlowStat shares(INVALID_STATION, INVALID_STATION, 1);
 					it->SwapShares(shares);
 					it = ge.flows.erase(it);
-					for (FlowStat::SharesMap::const_iterator shares_it(shares.GetShares()->begin());
-							shares_it != shares.GetShares()->end(); ++shares_it) {
+					for (FlowStat::const_iterator shares_it(shares.begin());
+							shares_it != shares.end(); ++shares_it) {
 						RerouteCargo(st, this->Cargo(), shares_it->second, st->index);
 					}
 				}

src/linkgraph/mcf.cpp

@@ -156,10 +156,10 @@ private:
 	std::vector<NodeID> station_to_node;
 
 	/** Current iterator in the shares map. */
-	FlowStat::SharesMap::const_iterator it;
+	FlowStat::const_iterator it;
 
 	/** End of the shares map. */
-	FlowStat::SharesMap::const_iterator end;
+	FlowStat::const_iterator end;
 public:
 
 	/**
@@ -187,11 +187,11 @@ public:
 		const FlowStatMap &flows = this->job[node].Flows();
 		FlowStatMap::const_iterator it = flows.find(this->job[source].Station());
 		if (it != flows.end()) {
-			this->it = it->GetShares()->begin();
-			this->end = it->GetShares()->end();
+			this->it = it->begin();
+			this->end = it->end();
 		} else {
-			this->it = FlowStat::empty_sharesmap.begin();
-			this->end = FlowStat::empty_sharesmap.end();
+			this->it = nullptr;
+			this->end = nullptr;
 		}
 	}
 

src/saveload/station_sl.cpp

@@ -523,15 +523,16 @@ static void RealSave_STNN(BaseStation *bst)
 			_num_dests = (uint32)st->goods[i].cargo.Packets()->MapSize();
 			_num_flows = 0;
 			for (FlowStatMap::const_iterator it(st->goods[i].flows.begin()); it != st->goods[i].flows.end(); ++it) {
-				_num_flows += (uint32)it->GetShares()->size();
+				_num_flows += (uint32)it->size();
 			}
 			SlObjectSaveFiltered(&st->goods[i], _filtered_goods_desc.data());
 			for (FlowStatMap::const_iterator outer_it(st->goods[i].flows.begin()); outer_it != st->goods[i].flows.end(); ++outer_it) {
-				const FlowStat::SharesMap *shares = outer_it->GetShares();
 				uint32 sum_shares = 0;
 				FlowSaveLoad flow;
 				flow.source = outer_it->GetOrigin();
-				for (FlowStat::SharesMap::const_iterator inner_it(shares->begin()); inner_it != shares->end(); ++inner_it) {
+				FlowStat::const_iterator inner_it(outer_it->begin());
+				const FlowStat::const_iterator end(outer_it->end());
+				for (; inner_it != end; ++inner_it) {
 					flow.via = inner_it->second;
 					flow.share = inner_it->first - sum_shares;
 					flow.restricted = inner_it->first > outer_it->GetUnrestricted();

src/script/api/script_stationlist.cpp

@@ -195,10 +195,9 @@ void ScriptStationList_CargoPlanned::Add(StationID station_id, CargoID cargo, St
 	FlowStatMap::const_iterator iter = collector.GE()->flows.begin();
 	FlowStatMap::const_iterator end = collector.GE()->flows.end();
 	for (; iter != end; ++iter) {
-		const FlowStat::SharesMap *shares = iter->GetShares();
 		uint prev = 0;
-		for (FlowStat::SharesMap::const_iterator flow_iter = shares->begin();
-				flow_iter != shares->end(); ++flow_iter) {
+		for (FlowStat::const_iterator flow_iter = iter->begin();
+				flow_iter != iter->end(); ++flow_iter) {
 			collector.Update<Tselector>(iter->GetOrigin(), flow_iter->second, flow_iter->first - prev);
 			prev = flow_iter->first;
 		}
@@ -265,10 +264,9 @@ ScriptStationList_CargoPlannedFromByVia::ScriptStationList_CargoPlannedFromByVia
 
 	FlowStatMap::const_iterator iter = collector.GE()->flows.find(from);
 	if (iter == collector.GE()->flows.end()) return;
-	const FlowStat::SharesMap *shares = iter->GetShares();
 	uint prev = 0;
-	for (FlowStat::SharesMap::const_iterator flow_iter = shares->begin();
-			flow_iter != shares->end(); ++flow_iter) {
+	for (FlowStat::const_iterator flow_iter = iter->begin();
+			flow_iter != iter->end(); ++flow_iter) {
 		collector.Update<CS_FROM_BY_VIA>(iter->GetOrigin(), flow_iter->second, flow_iter->first - prev);
 		prev = flow_iter->first;
 	}

src/station_base.h

@@ -22,10 +22,12 @@
 #include "3rdparty/cpp-btree/btree_map.h"
 #include "3rdparty/cpp-btree/btree_set.h"
 #include "bitmap_type.h"
+#include "core/endian_type.hpp"
 #include <map>
 #include <vector>
 #include <iterator>
 #include <functional>
+#include <algorithm>
 
 typedef Pool<BaseStation, StationID, 32, 64000> StationPool;
 extern StationPool _station_pool;
@@ -44,9 +46,28 @@ class FlowStatMap;
 class FlowStat {
 	friend FlowStatMap;
 public:
-	typedef btree::btree_map<uint32, StationID> SharesMap;
+	struct ShareEntry {
+#if OTTD_ALIGNMENT == 0
+		unaligned_uint32 first;
+#else
+		uint32 first;
+#endif
+		StationID second;
+	};
+	static_assert(sizeof(ShareEntry) == 6, "");
+
+	friend bool operator<(const ShareEntry &a, const ShareEntry &b) noexcept
+	{
+		return a.first < b.first;
+	}
+
+	friend bool operator<(uint a, const ShareEntry &b) noexcept
+	{
+		return a < b.first;
+	}
 
-	static const SharesMap empty_sharesmap;
+	typedef ShareEntry* iterator;
+	typedef const ShareEntry* const_iterator;
 
 	/**
 	 * Invalid constructor. This can't be called as a FlowStat must not be
@@ -65,11 +86,92 @@ public:
 	inline FlowStat(StationID origin, StationID via, uint flow, bool restricted = false)
 	{
 		assert(flow > 0);
-		this->shares[flow] = via;
+		this->storage.inline_shares[0].first = flow;
+		this->storage.inline_shares[0].second = via;
 		this->unrestricted = restricted ? 0 : flow;
+		this->count = 1;
 		this->origin = origin;
 	}
 
+private:
+	inline bool inline_mode() const
+	{
+		return this->count <= 2;
+	}
+
+	inline const ShareEntry *data() const
+	{
+		return this->inline_mode() ? this->storage.inline_shares : this->storage.ptr_shares.buffer;
+	}
+
+	inline ShareEntry *data()
+	{
+		return const_cast<ShareEntry *>(const_cast<const FlowStat*>(this)->data());
+	}
+
+	inline void clear()
+	{
+		if (!inline_mode()) {
+			free(this->storage.ptr_shares.buffer);
+		}
+		this->count = 0;
+	}
+
+	iterator erase_item(iterator iter, uint flow_reduction);
+
+	inline void CopyCommon(const FlowStat &other)
+	{
+		this->count = other.count;
+		if (!other.inline_mode()) {
+			this->storage.ptr_shares.elem_capacity = other.storage.ptr_shares.elem_capacity;
+			this->storage.ptr_shares.buffer = MallocT<ShareEntry>(other.storage.ptr_shares.elem_capacity);
+		}
+		MemCpyT(this->data(), other.data(), this->count);
+		this->unrestricted = other.unrestricted;
+		this->origin = other.origin;
+	}
+
+public:
+	inline FlowStat(const FlowStat &other)
+	{
+		this->CopyCommon(other);
+	}
+
+	inline FlowStat(FlowStat &&other) noexcept
+	{
+		this->count = 0;
+		this->SwapShares(other);
+		this->origin = other.origin;
+	}
+
+	inline ~FlowStat()
+	{
+		this->clear();
+	}
+
+	inline FlowStat &operator=(const FlowStat &other)
+	{
+		this->clear();
+		this->CopyCommon(other);
+		return *this;
+	}
+
+	inline FlowStat &operator=(FlowStat &&other) noexcept
+	{
+		this->SwapShares(other);
+		this->origin = other.origin;
+		return *this;
+	}
+
+	inline size_t size() const { return this->count; }
+	inline bool empty() const { return this->count == 0; }
+	inline iterator begin() { return this->data(); }
+	inline const_iterator begin() const { return this->data(); }
+	inline iterator end() { return this->data() + this->count; }
+	inline const_iterator end() const { return this->data() + this->count; }
+	inline iterator upper_bound(uint32 key) { return std::upper_bound(this->begin(), this->end(), key); }
+	inline const_iterator upper_bound(uint32 key) const { return std::upper_bound(this->begin(), this->end(), key); }
+
 	/**
 	 * Add some flow to the end of the shares map. Only do that if you know
 	 * that the station isn't in the map yet. Anything else may lead to
@@ -81,8 +183,26 @@ public:
 	inline void AppendShare(StationID st, uint flow, bool restricted = false)
 	{
 		assert(flow > 0);
-		uint32 key = (--this->shares.end())->first + flow;
-		this->shares.insert(this->shares.end(), std::make_pair(key, st));
+		uint32 key = this->GetLastKey() + flow;
+		if (unlikely(this->count >= 2)) {
+			if (this->count == 2) {
+				// convert inline buffer to ptr
+				ShareEntry *ptr = MallocT<ShareEntry>(4);
+				ptr[0] = this->storage.inline_shares[0];
+				ptr[1] = this->storage.inline_shares[1];
+				this->storage.ptr_shares.buffer = ptr;
+				this->storage.ptr_shares.elem_capacity = 4;
+			} else if (this->count == this->storage.ptr_shares.elem_capacity) {
+				// grow buffer
+				uint16 new_size = this->storage.ptr_shares.elem_capacity * 2;
+				this->storage.ptr_shares.buffer = ReallocT<ShareEntry>(this->storage.ptr_shares.buffer, new_size);
+				this->storage.ptr_shares.elem_capacity = new_size;
+			}
+			this->storage.ptr_shares.buffer[this->count] = { key, st };
+		} else {
+			this->storage.inline_shares[this->count] = { key, st };
+		}
+		this->count++;
 		if (!restricted) this->unrestricted += flow;
 	}
 
@@ -96,13 +216,6 @@ public:
 
 	void ScaleToMonthly(uint runtime);
 
-	/**
-	 * Get the actual shares as a const pointer so that they can be iterated
-	 * over.
-	 * @return Actual shares.
-	 */
-	inline const SharesMap *GetShares() const { return &this->shares; }
-
 	/**
 	 * Return total amount of unrestricted shares.
 	 * @return Amount of unrestricted shares.
@@ -116,8 +229,9 @@ public:
 	 */
 	inline void SwapShares(FlowStat &other)
 	{
-		this->shares.swap(other.shares);
-		Swap(this->unrestricted, other.unrestricted);
+		std::swap(this->storage, other.storage);
+		std::swap(this->unrestricted, other.unrestricted);
+		std::swap(this->count, other.count);
 	}
 
 	/**
@@ -130,10 +244,10 @@ public:
 	 */
 	inline StationID GetViaWithRestricted(bool &is_restricted) const
 	{
-		assert(!this->shares.empty());
-		uint rand = RandomRange((--this->shares.end())->first);
+		assert(!this->empty());
+		uint rand = RandomRange(this->GetLastKey());
 		is_restricted = rand >= this->unrestricted;
-		return this->shares.upper_bound(rand)->second;
+		return this->upper_bound(rand)->second;
 	}
 
 	/**
@@ -145,9 +259,9 @@ public:
 	 */
 	inline StationID GetVia() const
 	{
-		assert(!this->shares.empty());
+		assert(!this->empty());
 		return this->unrestricted > 0 ?
-				this->shares.upper_bound(RandomRange(this->unrestricted))->second :
+				this->upper_bound(RandomRange(this->unrestricted))->second :
 				INVALID_STATION;
 	}
 
@@ -161,11 +275,36 @@ public:
 	}
 
 private:
-	SharesMap shares;  ///< Shares of flow to be sent via specified station (or consumed locally).
+	uint32 GetLastKey() const
+	{
+		return this->data()[this->count - 1].first;
+	}
+
+	struct ptr_buffer {
+		ShareEntry *buffer;
+		uint16 elem_capacity;
+	}
+#if OTTD_ALIGNMENT == 0 && (defined(__GNUC__) || defined(__clang__))
+	__attribute__((packed, aligned(4)))
+#endif
+	;
+	union storage_union {
+		ShareEntry inline_shares[2]; ///< Small buffer optimisation: size = 1 is ~90%, size = 2 is ~9%, size >= 3 is ~1%
+		ptr_buffer ptr_shares;
+
+		// Actual construction/destruction done by class FlowStat
+		storage_union() {}
+		~storage_union() {}
+	};
+	storage_union storage; ///< Shares of flow to be sent via specified station (or consumed locally).
 	uint unrestricted; ///< Limit for unrestricted shares.
+	uint16 count;
 	StationID origin;
 };
 static_assert(std::is_nothrow_move_constructible<FlowStat>::value, "FlowStat must be nothrow move constructible");
+#if OTTD_ALIGNMENT == 0 && (defined(__GNUC__) || defined(__clang__))
+static_assert(sizeof(FlowStat) == 20, "");
+#endif
 
 template<typename cv_value, typename cv_container, typename cv_index_iter>
 class FlowStatMapIterator
@@ -224,7 +363,6 @@ public:
 	void PassOnFlow(StationID origin, StationID via, uint amount);
 	StationIDStack DeleteFlows(StationID via);
 	void RestrictFlows(StationID via);
-	void ReleaseFlows(StationID via);
 	void FinalizeLocalConsumption(StationID self);
 
 private:

src/station_cmd.cpp

@@ -63,13 +63,6 @@
 
 #include "safeguards.h"
 
-/**
- * Static instance of FlowStat::SharesMap.
- * Note: This instance is created on task start.
- *       Lazy creation on first usage results in a data race between the CDist threads.
- */
-/* static */ const FlowStat::SharesMap FlowStat::empty_sharesmap;
-
 /**
  * Check whether the given tile is a hangar.
  * @param t the tile to of whether it is a hangar.
@@ -4629,6 +4622,25 @@ static CommandCost TerraformTile_Station(TileIndex tile, DoCommandFlag flags, in
 	return DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
 }
 
+FlowStat::iterator FlowStat::erase_item(FlowStat::iterator iter, uint flow_reduction)
+{
+	assert(!this->empty());
+	const uint offset = iter - this->begin();
+	const iterator last = this->end() - 1;
+	for (; iter < last; ++iter) {
+		*iter = { (iter + 1)->first - flow_reduction, (iter + 1)->second };
+	}
+	--this->count;
+	if (this->count == 2) {
+		// transition from external to internal storage
+		ShareEntry *ptr = this->storage.ptr_shares.buffer;
+		this->storage.inline_shares[0] = ptr[0];
+		this->storage.inline_shares[1] = ptr[1];
+		free(ptr);
+	}
+	return this->begin() + offset;
+}
+
 /**
  * Get flow for a station.
  * @param st Station to get flow for.
@@ -4637,7 +4649,7 @@ static CommandCost TerraformTile_Station(TileIndex tile, DoCommandFlag flags, in
 uint FlowStat::GetShare(StationID st) const
 {
 	uint32 prev = 0;
-	for (SharesMap::const_iterator it = this->shares.begin(); it != this->shares.end(); ++it) {
+	for (const_iterator it = this->begin(); it != this->end(); ++it) {
 		if (it->second == st) {
 			return it->first - prev;
 		} else {
@@ -4656,30 +4668,30 @@ uint FlowStat::GetShare(StationID st) const
 StationID FlowStat::GetVia(StationID excluded, StationID excluded2) const
 {
 	if (this->unrestricted == 0) return INVALID_STATION;
-	assert(!this->shares.empty());
-	SharesMap::const_iterator it = this->shares.upper_bound(RandomRange(this->unrestricted));
-	assert(it != this->shares.end() && it->first <= this->unrestricted);
+	assert(!this->empty());
+	const_iterator it = std::upper_bound(this->data(), this->data() + this->count, RandomRange(this->unrestricted));
+	assert(it != this->end() && it->first <= this->unrestricted);
 	if (it->second != excluded && it->second != excluded2) return it->second;
 
 	/* We've hit one of the excluded stations.
 	 * Draw another share, from outside its range. */
 
 	uint end = it->first;
-	uint begin = (it == this->shares.begin() ? 0 : (--it)->first);
+	uint begin = (it == this->begin() ? 0 : (--it)->first);
 	uint interval = end - begin;
 	if (interval >= this->unrestricted) return INVALID_STATION; // Only one station in the map.
 	uint new_max = this->unrestricted - interval;
 	uint rand = RandomRange(new_max);
-	SharesMap::const_iterator it2 = (rand < begin) ? this->shares.upper_bound(rand) :
-			this->shares.upper_bound(rand + interval);
-	assert(it2 != this->shares.end() && it2->first <= this->unrestricted);
+	const_iterator it2 = (rand < begin) ? this->upper_bound(rand) :
+			this->upper_bound(rand + interval);
+	assert(it2 != this->end() && it2->first <= this->unrestricted);
 	if (it2->second != excluded && it2->second != excluded2) return it2->second;
 
 	/* We've hit the second excluded station.
 	 * Same as before, only a bit more complicated. */
 
 	uint end2 = it2->first;
-	uint begin2 = (it2 == this->shares.begin() ? 0 : (--it2)->first);
+	uint begin2 = (it2 == this->begin() ? 0 : (--it2)->first);
 	uint interval2 = end2 - begin2;
 	if (interval2 >= new_max) return INVALID_STATION; // Only the two excluded stations in the map.
 	new_max -= interval2;
@@ -4689,15 +4701,15 @@ StationID FlowStat::GetVia(StationID excluded, StationID excluded2) const
 		Swap(interval, interval2);
 	}
 	rand = RandomRange(new_max);
-	SharesMap::const_iterator it3 = this->shares.upper_bound(this->unrestricted);
+	const_iterator it3 = this->upper_bound(this->unrestricted);
 	if (rand < begin) {
-		it3 = this->shares.upper_bound(rand);
+		it3 = this->upper_bound(rand);
 	} else if (rand < begin2 - interval) {
-		it3 = this->shares.upper_bound(rand + interval);
+		it3 = this->upper_bound(rand + interval);
 	} else {
-		it3 = this->shares.upper_bound(rand + interval + interval2);
+		it3 = this->upper_bound(rand + interval + interval2);
 	}
-	assert(it3 != this->shares.end() && it3->first <= this->unrestricted);
+	assert(it3 != this->end() && it3->first <= this->unrestricted);
 	return it3->second;
 }
 
@@ -4708,15 +4720,13 @@ StationID FlowStat::GetVia(StationID excluded, StationID excluded2) const
  */
 void FlowStat::Invalidate()
 {
-	assert(!this->shares.empty());
-	SharesMap new_shares;
+	assert(!this->empty());
 	uint i = 0;
-	for (SharesMap::iterator it(this->shares.begin()); it != this->shares.end(); ++it) {
-		new_shares[++i] = it->second;
-		if (it->first == this->unrestricted) this->unrestricted = i;
+	for (iterator it(this->begin()); it != this->end(); ++it) {
+		if (it->first == this->unrestricted) this->unrestricted = i + 1;
+		it->first = ++i;
 	}
-	this->shares.swap(new_shares);
-	assert(!this->shares.empty() && this->unrestricted <= (--this->shares.end())->first);
+	assert(!this->empty() && this->unrestricted <= (this->end() - 1)->first);
 }
 
 /**
@@ -4729,45 +4739,38 @@ void FlowStat::ChangeShare(StationID st, int flow)
 {
 	/* We assert only before changing as afterwards the shares can actually
 	 * be empty. In that case the whole flow stat must be deleted then. */
-	assert(!this->shares.empty());
+	assert(!this->empty());
 
-	uint removed_shares = 0;
-	uint added_shares = 0;
 	uint last_share = 0;
-	SharesMap new_shares;
-	for (SharesMap::iterator it(this->shares.begin()); it != this->shares.end(); ++it) {
+	for (iterator it(this->begin()); it != this->end(); ++it) {
 		if (it->second == st) {
-			if (flow < 0) {
-				uint share = it->first - last_share;
-				if (flow == INT_MIN || (uint)(-flow) >= share) {
-					removed_shares += share;
-					if (it->first <= this->unrestricted) this->unrestricted -= share;
-					if (flow != INT_MIN) flow += share;
-					last_share = it->first;
-					continue; // remove the whole share
-				}
-				removed_shares += (uint)(-flow);
-			} else {
-				added_shares += (uint)(flow);
+			uint share = it->first - last_share;
+			if (flow < 0 && (flow == INT_MIN || (uint)(-flow) >= share)) {
+				if (it->first <= this->unrestricted) this->unrestricted -= share;
+				this->erase_item(it, share);
+				break; // remove the whole share
 			}
 			if (it->first <= this->unrestricted) this->unrestricted += flow;
-
-			/* If we don't continue above the whole flow has been added or
-			 * removed. */
+			for (; it != this->end(); ++it) {
+				it->first += flow;
+			}
 			flow = 0;
+			break;
 		}
-		new_shares[it->first + added_shares - removed_shares] = it->second;
 		last_share = it->first;
 	}
 	if (flow > 0) {
-		new_shares[last_share + (uint)flow] = st;
+		// must be non-empty here
+		last_share = (this->end() - 1)->first;
+		this->AppendShare(st, (uint)flow, true); // true to avoid changing this->unrestricted, which we fixup below
 		if (this->unrestricted < last_share) {
+			// Move to front to unrestrict
 			this->ReleaseShare(st);
 		} else {
+			// First restricted item, so bump unrestricted count
 			this->unrestricted += flow;
 		}
 	}
-	this->shares.swap(new_shares);
 }
 
 /**
@@ -4777,28 +4780,25 @@ void FlowStat::ChangeShare(StationID st, int flow)
  */
 void FlowStat::RestrictShare(StationID st)
 {
-	assert(!this->shares.empty());
-	uint flow = 0;
+	assert(!this->empty());
+	iterator it = this->begin();
+	const iterator end = this->end();
 	uint last_share = 0;
-	SharesMap new_shares;
-	for (SharesMap::iterator it(this->shares.begin()); it != this->shares.end(); ++it) {
-		if (flow == 0) {
-			if (it->first > this->unrestricted) return; // Not present or already restricted.
-			if (it->second == st) {
-				flow = it->first - last_share;
-				this->unrestricted -= flow;
-			} else {
-				new_shares[it->first] = it->second;
+	for (; it != end; ++it) {
+		if (it->first > this->unrestricted) return; // Not present or already restricted.
+		if (it->second == st) {
+			uint flow = it->first - last_share;
+			this->unrestricted -= flow;
+			if (this->unrestricted == last_share) return; // No further action required
+			const iterator last = end - 1;
+			for (iterator jt = it; jt != last; ++jt) {
+				*jt = { (jt + 1)->first - flow, (jt + 1)->second };
 			}
-		} else {
-			new_shares[it->first - flow] = it->second;
+			*last = { flow + (last - 1)->first, st };
+			return;
 		}
 		last_share = it->first;
 	}
-	if (flow == 0) return;
-	new_shares[last_share + flow] = st;
-	this->shares.swap(new_shares);
-	assert(!this->shares.empty());
 }
 
 /**
@@ -4808,34 +4808,27 @@ void FlowStat::RestrictShare(StationID st)
  */
 void FlowStat::ReleaseShare(StationID st)
 {
-	assert(!this->shares.empty());
-	uint flow = 0;
-	uint next_share = 0;
-	bool found = false;
-	for (SharesMap::reverse_iterator it(this->shares.rbegin()); it != this->shares.rend(); ++it) {
-		if (it->first < this->unrestricted) return; // Note: not <= as the share may hit the limit.
-		if (found) {
-			flow = next_share - it->first;
-			this->unrestricted += flow;
-			break;
-		} else {
-			if (it->first == this->unrestricted) return; // !found -> Limit not hit.
-			if (it->second == st) found = true;
-		}
-		next_share = it->first;
-	}
-	if (flow == 0) return;
-	SharesMap new_shares;
-	new_shares[flow] = st;
-	for (SharesMap::iterator it(this->shares.begin()); it != this->shares.end(); ++it) {
-		if (it->second != st) {
-			new_shares[flow + it->first] = it->second;
-		} else {
-			flow = 0;
+	assert(!this->empty());
+	iterator it = this->end() - 1;
+	const iterator start = this->begin();
+	for (; it >= start; --it) {
+		if (it->first < this->unrestricted) return; // Already unrestricted
+		if (it->second == st) {
+			if (it - 1 >= start) {
+				uint flow = it->first - (it - 1)->first;
+				this->unrestricted += flow;
+				if (it->first == this->unrestricted) return; // No further action required
+				for (iterator jt = it; jt != start; --jt) {
+					*jt = { (jt - 1)->first + flow, (jt - 1)->second };
+				}
+				*start = { flow, st };
+			} else {
+				// already at start
+				this->unrestricted = it->first;
+			}
+			return;
 		}
 	}
-	this->shares.swap(new_shares);
-	assert(!this->shares.empty());
 }
 
 /**
@@ -4846,14 +4839,12 @@ void FlowStat::ReleaseShare(StationID st)
 void FlowStat::ScaleToMonthly(uint runtime)
 {
 	assert(runtime > 0);
-	SharesMap new_shares;
 	uint share = 0;
-	for (SharesMap::iterator i = this->shares.begin(); i != this->shares.end(); ++i) {
+	for (iterator i = this->begin(); i != this->end(); ++i) {
 		share = max(share + 1, i->first * 30 / runtime);
-		new_shares[share] = i->second;
 		if (this->unrestricted == i->first) this->unrestricted = share;
+		i->first = share;
 	}
-	this->shares.swap(new_shares);
 }
 
 /**
@@ -4869,7 +4860,7 @@ void FlowStatMap::AddFlow(StationID origin, StationID via, uint flow)
 		this->insert(FlowStat(origin, via, flow));
 	} else {
 		origin_it->ChangeShare(via, flow);
-		assert(!origin_it->GetShares()->empty());
+		assert(!origin_it->empty());
 	}
 }
 
@@ -4891,7 +4882,7 @@ void FlowStatMap::PassOnFlow(StationID origin, StationID via, uint flow)
 	} else {
 		prev_it->ChangeShare(via, flow);
 		prev_it->ChangeShare(INVALID_STATION, flow);
-		assert(!prev_it->GetShares()->empty());
+		assert(!prev_it->empty());
 	}
 }
 
@@ -4914,7 +4905,7 @@ void FlowStatMap::FinalizeLocalConsumption(StationID self)
 
 		/* If the local share is used up there must be a share for some
 		 * remote station. */
-		assert(!fs.GetShares()->empty());
+		assert(!fs.empty());
 	}
 }
 
@@ -4930,7 +4921,7 @@ StationIDStack FlowStatMap::DeleteFlows(StationID via)
 	for (FlowStatMap::iterator f_it = this->begin(); f_it != this->end();) {
 		FlowStat &s_flows = *f_it;
 		s_flows.ChangeShare(via, INT_MIN);
-		if (s_flows.GetShares()->empty()) {
+		if (s_flows.empty()) {
 			ret.Push(f_it->GetOrigin());
 			f_it = this->erase(f_it);
 		} else {
@@ -4951,17 +4942,6 @@ void FlowStatMap::RestrictFlows(StationID via)
 	}
 }
 
-/**
- * Release all flows at a station for specific cargo and destination.
- * @param via Remote station of flows to be released.
- */
-void FlowStatMap::ReleaseFlows(StationID via)
-{
-	for (FlowStatMap::iterator it = this->begin(); it != this->end(); ++it) {
-		it->ReleaseShare(via);
-	}
-}
-
 /**
  * Get the sum of all flows from this FlowStatMap.
  * @return sum of all flows.
@@ -4970,7 +4950,7 @@ uint FlowStatMap::GetFlow() const
 {
 	uint ret = 0;
 	for (FlowStatMap::const_iterator i = this->begin(); i != this->end(); ++i) {
-		ret += (--(i->GetShares()->end()))->first;
+		ret += (i->end() - 1)->first;
 	}
 	return ret;
 }
@@ -4998,7 +4978,7 @@ uint FlowStatMap::GetFlowFrom(StationID from) const
 {
 	FlowStatMap::const_iterator i = this->find(from);
 	if (i == this->end()) return 0;
-	return (--(i->GetShares()->end()))->first;
+	return (i->end() - 1)->first;
 }
 
 /**

src/station_gui.cpp

@@ -1515,9 +1515,8 @@ struct StationViewWindow : public Window {
 		for (FlowStatMap::const_iterator it = flows.begin(); it != flows.end(); ++it) {
 			StationID from = it->GetOrigin();
 			CargoDataEntry *source_entry = cargo_entry->InsertOrRetrieve(from);
-			const FlowStat::SharesMap *shares = it->GetShares();
 			uint32 prev_count = 0;
-			for (FlowStat::SharesMap::const_iterator flow_it = shares->begin(); flow_it != shares->end(); ++flow_it) {
+			for (FlowStat::const_iterator flow_it = it->begin(); flow_it != it->end(); ++flow_it) {
 				StationID via = flow_it->second;
 				CargoDataEntry *via_entry = source_entry->InsertOrRetrieve(via);
 				if (via == this->window_number) {
@@ -1546,9 +1545,8 @@ struct StationViewWindow : public Window {
 			const FlowStatMap &flowmap = Station::Get(next)->goods[cargo].flows;
 			FlowStatMap::const_iterator map_it = flowmap.find(source);
 			if (map_it != flowmap.end()) {
-				const FlowStat::SharesMap *shares = map_it->GetShares();
 				uint32 prev_count = 0;
-				for (FlowStat::SharesMap::const_iterator i = shares->begin(); i != shares->end(); ++i) {
+				for (FlowStat::const_iterator i = map_it->begin(); i != map_it->end(); ++i) {
 					tmp.InsertOrRetrieve(i->second)->Update(i->first - prev_count);
 					prev_count = i->first;
 				}
@@ -1598,8 +1596,7 @@ struct StationViewWindow : public Window {
 		for (FlowStatMap::const_iterator it = flows.begin(); it != flows.end(); ++it) {
 			StationID from = it->GetOrigin();
 			const CargoDataEntry *source_entry = source_dest->Retrieve(from);
-			const FlowStat::SharesMap *shares = it->GetShares();
-			for (FlowStat::SharesMap::const_iterator flow_it = shares->begin(); flow_it != shares->end(); ++flow_it) {
+			for (FlowStat::const_iterator flow_it = it->begin(); flow_it != it->end(); ++flow_it) {
 				const CargoDataEntry *via_entry = source_entry->Retrieve(flow_it->second);
 				for (CargoDataSet::iterator dest_it = via_entry->Begin(); dest_it != via_entry->End(); ++dest_it) {
 					CargoDataEntry *dest_entry = *dest_it;