bugfix(network): Fix runahead logic update to better follow the maximum network latency and avoid stutters and slow downs (TheSuperHackers#1482)

Mauller · web-flow · commit bc0d447692e9 · 2025-09-09T08:39:51.000+02:00
diff --git a/Generals/Code/GameEngine/Include/GameNetwork/ConnectionManager.h b/Generals/Code/GameEngine/Include/GameNetwork/ConnectionManager.h
@@ -174,7 +174,7 @@ class ConnectionManager
 
 	//	void doPerFrameMetrics(UnsignedInt frame);
 	void getMinimumFps(Int &minFps, Int &minFpsPlayer);			///< Returns the smallest FPS in the m_fpsAverages list.
-	Real getMaximumLatency(); ///< This actually sums the two biggest latencies in the m_latencyAverages list.
+	Real getMaximumLatency(); ///< Returns the highest average latency between players.
 
 	void requestFrameDataResend(Int playerID, UnsignedInt frame); ///< request of this player that he send the specified frame's data.
 
diff --git a/Generals/Code/GameEngine/Include/GameNetwork/NetworkDefs.h b/Generals/Code/GameEngine/Include/GameNetwork/NetworkDefs.h
@@ -36,6 +36,7 @@ static const Int WOL_NAME_LEN = 64;
 /// Max number of commands per frame
 static const Int MAX_COMMANDS = 256;
 
+extern Int MIN_LOGIC_FRAMES;
 extern Int MAX_FRAMES_AHEAD;
 extern Int MIN_RUNAHEAD;
 
diff --git a/Generals/Code/GameEngine/Source/GameNetwork/ConnectionManager.cpp b/Generals/Code/GameEngine/Source/GameNetwork/ConnectionManager.cpp
@@ -1246,22 +1246,20 @@ void ConnectionManager::updateRunAhead(Int oldRunAhead, Int frameRate, Bool didS
 				// if the minimum fps is within 10% of the desired framerate, then keep the current minimum fps.
 				minFps = frameRate;
 			}
-			if (minFps < 5) {
-				minFps = 5; // Absolutely do not run below 5 fps.
-			}
-			if (minFps > TheGlobalData->m_framesPerSecondLimit) {
-				minFps = TheGlobalData->m_framesPerSecondLimit; // Cap to 30 FPS.
-			}
+
+			// TheSuperHackers @info this clamps the logic time scale fps in network games
+			minFps = clamp<Int>(MIN_LOGIC_FRAMES, minFps, TheGlobalData->m_framesPerSecondLimit);
 			DEBUG_LOG_LEVEL(DEBUG_LEVEL_NET, ("ConnectionManager::updateRunAhead - minFps after adjustment is %d", minFps));
-			Int newRunAhead = (Int)((getMaximumLatency() / 2.0) * (Real)minFps);
-			newRunAhead += (newRunAhead * TheGlobalData->m_networkRunAheadSlack) / 100; // Add in 10% of slack to the run ahead in case of network hiccups.
-			if (newRunAhead < MIN_RUNAHEAD) {
-				newRunAhead = MIN_RUNAHEAD; // make sure its at least MIN_RUNAHEAD.
-			}
 
-			if (newRunAhead > (MAX_FRAMES_AHEAD / 2)) {
-				newRunAhead = MAX_FRAMES_AHEAD / 2; // dont let run ahead get out of hand.
-			}
+			// TheSuperHackers @bugfix Mauller 21/08/2025 calculate the runahead so it always follows the latency
+			// The runahead should always be rounded up to the next integer value to prevent variations in latency from causing stutter
+			// The network slack pushes the runahead up to the next value when the latency is within the slack percentage of the current runahead
+			const Real runAheadSlackScale = 1.0f + ( (Real)TheGlobalData->m_networkRunAheadSlack / 100.0f );
+			Int newRunAhead = ceilf( getMaximumLatency() * runAheadSlackScale * (Real)minFps );
+
+			// TheSuperHackers @info if the runahead goes below 3 logic frames it can start to introduce stutter
+			// We also limit the upper range of the runahead to prevent it getting out of hand
+			newRunAhead = clamp<Int>(MIN_RUNAHEAD, newRunAhead, MAX_FRAMES_AHEAD / 2);
 
 			NetRunAheadCommandMsg *msg = newInstance(NetRunAheadCommandMsg);
 			msg->setPlayerID(m_localSlot);
@@ -1361,24 +1359,15 @@ void ConnectionManager::updateRunAhead(Int oldRunAhead, Int frameRate, Bool didS
 }
 
 Real ConnectionManager::getMaximumLatency() {
-	// This works for 2 player games because the latency for the packet router is always 0.
-	Real lat1 = 0.0;
-	Real lat2 = 0.0;
+	Real maxLatency = 0.0f;
 
 	for (Int i = 0; i < MAX_SLOTS; ++i) {
-		if (isPlayerConnected(i)) {
-			if (m_latencyAverages[i] != 0.0) {
-				if (m_latencyAverages[i] > lat1) {
-					lat2 = lat1;
-					lat1 = m_latencyAverages[i];
-				} else if (m_latencyAverages[i] > lat2) {
-					lat2 = m_latencyAverages[i];
-				}
-			}
+		if (isPlayerConnected(i) && m_latencyAverages[i] > maxLatency) {
+				maxLatency = m_latencyAverages[i];
 		}
 	}
 
-	return (lat1 + lat2);
+	return maxLatency;
 }
 
 void ConnectionManager::getMinimumFps(Int &minFps, Int &minFpsPlayer) {
diff --git a/Generals/Code/GameEngine/Source/GameNetwork/NetworkUtil.cpp b/Generals/Code/GameEngine/Source/GameNetwork/NetworkUtil.cpp
@@ -29,6 +29,7 @@
 
 // TheSuperHackers @tweak Mauller 26/08/2025 reduce the minimum runahead from 10
 // This lets network games run at latencies down to 133ms when the network conditions allow
+Int MIN_LOGIC_FRAMES = 5;
 Int MAX_FRAMES_AHEAD = 128;
 Int MIN_RUNAHEAD = 4;
 Int FRAME_DATA_LENGTH = (MAX_FRAMES_AHEAD+1)*2;
diff --git a/GeneralsMD/Code/GameEngine/Include/GameNetwork/ConnectionManager.h b/GeneralsMD/Code/GameEngine/Include/GameNetwork/ConnectionManager.h
@@ -174,7 +174,7 @@ class ConnectionManager
 
 	//	void doPerFrameMetrics(UnsignedInt frame);
 	void getMinimumFps(Int &minFps, Int &minFpsPlayer);			///< Returns the smallest FPS in the m_fpsAverages list.
-	Real getMaximumLatency(); ///< This actually sums the two biggest latencies in the m_latencyAverages list.
+	Real getMaximumLatency(); ///< Returns the highest average latency between players.
 
 	void requestFrameDataResend(Int playerID, UnsignedInt frame); ///< request of this player that he send the specified frame's data.
 
diff --git a/GeneralsMD/Code/GameEngine/Include/GameNetwork/NetworkDefs.h b/GeneralsMD/Code/GameEngine/Include/GameNetwork/NetworkDefs.h
@@ -36,6 +36,7 @@ static const Int WOL_NAME_LEN = 64;
 /// Max number of commands per frame
 static const Int MAX_COMMANDS = 256;
 
+extern Int MIN_LOGIC_FRAMES;
 extern Int MAX_FRAMES_AHEAD;
 extern Int MIN_RUNAHEAD;
 
diff --git a/GeneralsMD/Code/GameEngine/Source/GameNetwork/ConnectionManager.cpp b/GeneralsMD/Code/GameEngine/Source/GameNetwork/ConnectionManager.cpp
@@ -1246,22 +1246,20 @@ void ConnectionManager::updateRunAhead(Int oldRunAhead, Int frameRate, Bool didS
 				// if the minimum fps is within 10% of the desired framerate, then keep the current minimum fps.
 				minFps = frameRate;
 			}
-			if (minFps < 5) {
-				minFps = 5; // Absolutely do not run below 5 fps.
-			}
-			if (minFps > TheGlobalData->m_framesPerSecondLimit) {
-				minFps = TheGlobalData->m_framesPerSecondLimit; // Cap to 30 FPS.
-			}
+
+			// TheSuperHackers @info this clamps the logic time scale fps in network games
+			minFps = clamp<Int>(MIN_LOGIC_FRAMES, minFps, TheGlobalData->m_framesPerSecondLimit);
 			DEBUG_LOG_LEVEL(DEBUG_LEVEL_NET, ("ConnectionManager::updateRunAhead - minFps after adjustment is %d", minFps));
-			Int newRunAhead = (Int)((getMaximumLatency() / 2.0) * (Real)minFps);
-			newRunAhead += (newRunAhead * TheGlobalData->m_networkRunAheadSlack) / 100; // Add in 10% of slack to the run ahead in case of network hiccups.
-			if (newRunAhead < MIN_RUNAHEAD) {
-				newRunAhead = MIN_RUNAHEAD; // make sure its at least MIN_RUNAHEAD.
-			}
 
-			if (newRunAhead > (MAX_FRAMES_AHEAD / 2)) {
-				newRunAhead = MAX_FRAMES_AHEAD / 2; // dont let run ahead get out of hand.
-			}
+			// TheSuperHackers @bugfix Mauller 21/08/2025 calculate the runahead so it always follows the latency
+			// The runahead should always be rounded up to the next integer value to prevent variations in latency from causing stutter
+			// The network slack pushes the runahead up to the next value when the latency is within the slack percentage of the current runahead
+			const Real runAheadSlackScale = 1.0f + ( (Real)TheGlobalData->m_networkRunAheadSlack / 100.0f );
+			Int newRunAhead = ceilf( getMaximumLatency() * runAheadSlackScale * (Real)minFps );
+
+			// TheSuperHackers @info if the runahead goes below 3 logic frames it can start to introduce stutter
+			// We also limit the upper range of the runahead to prevent it getting out of hand
+			newRunAhead = clamp<Int>(MIN_RUNAHEAD, newRunAhead, MAX_FRAMES_AHEAD / 2);
 
 			NetRunAheadCommandMsg *msg = newInstance(NetRunAheadCommandMsg);
 			msg->setPlayerID(m_localSlot);
@@ -1361,24 +1359,15 @@ void ConnectionManager::updateRunAhead(Int oldRunAhead, Int frameRate, Bool didS
 }
 
 Real ConnectionManager::getMaximumLatency() {
-	// This works for 2 player games because the latency for the packet router is always 0.
-	Real lat1 = 0.0;
-	Real lat2 = 0.0;
+	Real maxLatency = 0.0f;
 
 	for (Int i = 0; i < MAX_SLOTS; ++i) {
-		if (isPlayerConnected(i)) {
-			if (m_latencyAverages[i] != 0.0) {
-				if (m_latencyAverages[i] > lat1) {
-					lat2 = lat1;
-					lat1 = m_latencyAverages[i];
-				} else if (m_latencyAverages[i] > lat2) {
-					lat2 = m_latencyAverages[i];
-				}
-			}
+		if (isPlayerConnected(i) && m_latencyAverages[i] > maxLatency) {
+				maxLatency = m_latencyAverages[i];
 		}
 	}
 
-	return (lat1 + lat2);
+	return maxLatency;
 }
 
 void ConnectionManager::getMinimumFps(Int &minFps, Int &minFpsPlayer) {
diff --git a/GeneralsMD/Code/GameEngine/Source/GameNetwork/NetworkUtil.cpp b/GeneralsMD/Code/GameEngine/Source/GameNetwork/NetworkUtil.cpp
@@ -29,6 +29,7 @@
 
 // TheSuperHackers @tweak Mauller 26/08/2025 reduce the minimum runahead from 10
 // This lets network games run at latencies down to 133ms when the network conditions allow
+Int MIN_LOGIC_FRAMES = 5;
 Int MAX_FRAMES_AHEAD = 128;
 Int MIN_RUNAHEAD = 4;
 Int FRAME_DATA_LENGTH = (MAX_FRAMES_AHEAD+1)*2;
