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

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Merged
xezon merged 2 commits into from
Sep 9, 2025
Merged

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

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c5b75d8
bugfix(network): fix runahead update logic so the runahead always fol…
Mauller Aug 23, 2025
070e3f6
Change Maxlat variable to camelCase
xezon Sep 9, 2025
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2 changes: 1 addition & 1 deletion Generals/Code/GameEngine/Include/GameNetwork/ConnectionManager.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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.

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1 change: 1 addition & 0 deletions Generals/Code/GameEngine/Include/GameNetwork/NetworkDefs.h
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Expand Up @@ -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;

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43 changes: 16 additions & 27 deletions Generals/Code/GameEngine/Source/GameNetwork/ConnectionManager.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -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);
Expand Down Expand Up @@ -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) {
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1 change: 1 addition & 0 deletions Generals/Code/GameEngine/Source/GameNetwork/NetworkUtil.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -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;
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2 changes: 1 addition & 1 deletion GeneralsMD/Code/GameEngine/Include/GameNetwork/ConnectionManager.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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.

Expand Down
1 change: 1 addition & 0 deletions GeneralsMD/Code/GameEngine/Include/GameNetwork/NetworkDefs.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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;

Expand Down
43 changes: 16 additions & 27 deletions GeneralsMD/Code/GameEngine/Source/GameNetwork/ConnectionManager.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -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);
Expand Down Expand Up @@ -1361,24 +1359,15 @@ void ConnectionManager::updateRunAhead(Int oldRunAhead, Int frameRate, Bool didS
}

Real ConnectionManager::getMaximumLatency() {
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// 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) {
Expand Down
1 change: 1 addition & 0 deletions GeneralsMD/Code/GameEngine/Source/GameNetwork/NetworkUtil.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down
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