stabilize packet throttle when RTT variance is low

include/enet/utility.h

@@ -7,6 +7,7 @@
 
 #define ENET_MAX(x, y) ((x) > (y) ? (x) : (y))
 #define ENET_MIN(x, y) ((x) < (y) ? (x) : (y))
+#define ENET_DIFFERENCE(x, y) ((x) < (y) ? (y) - (x) : (x) - (y))
 
 #endif /* __ENET_UTILITY_H__ */
 

peer.c

@@ -66,7 +66,7 @@ enet_peer_throttle (ENetPeer * peer, enet_uint32 rtt)
         peer -> packetThrottle = peer -> packetThrottleLimit;
     }
     else
-    if (rtt < peer -> lastRoundTripTime)
+    if (rtt <= peer -> lastRoundTripTime)
     {
         peer -> packetThrottle += peer -> packetThrottleAcceleration;
 
@@ -76,7 +76,7 @@ enet_peer_throttle (ENetPeer * peer, enet_uint32 rtt)
         return 1;
     }
     else
-    if (rtt > peer -> lastRoundTripTime + 2 * peer -> lastRoundTripTimeVariance)
+    if (rtt >= peer -> lastRoundTripTime + 2 * peer -> lastRoundTripTimeVariance)
     {
         if (peer -> packetThrottle > peer -> packetThrottleDeceleration)
           peer -> packetThrottle -= peer -> packetThrottleDeceleration;

protocol.c

@@ -862,28 +862,9 @@ enet_protocol_handle_acknowledge (ENetHost * host, ENetEvent * event, ENetPeer *
        enet_peer_throttle (peer, roundTripTime);
 
        roundTripTime <<= 8;
-       if (roundTripTime >= accumRoundTripTime)
-       {
-          enet_uint32 diff = roundTripTime - accumRoundTripTime;
-          accumRoundTripTimeVariance -= accumRoundTripTimeVariance / 4;
-          accumRoundTripTimeVariance += diff / 4;
-          accumRoundTripTime += diff / 8;
-       }
-       else
-       {
-          enet_uint32 diff = accumRoundTripTime - roundTripTime;
-          if (diff <= accumRoundTripTimeVariance)
-          {
-             accumRoundTripTimeVariance -= accumRoundTripTimeVariance / 4;
-             accumRoundTripTimeVariance += diff / 4;
-          }
-          else
-          {
-             accumRoundTripTimeVariance -= accumRoundTripTimeVariance / 32;
-             accumRoundTripTimeVariance += diff / 32;
-          }
-          accumRoundTripTime -= diff / 8;
-       }
+       accumRoundTripTimeVariance = (accumRoundTripTimeVariance * 3 + ENET_DIFFERENCE (roundTripTime, accumRoundTripTime)) / 4;
+       accumRoundTripTime = (accumRoundTripTime * 7 + roundTripTime) / 8;
+
        peer -> roundTripTime = accumRoundTripTime >> 8;
        peer -> roundTripTimeRemainder = accumRoundTripTime & 0xFF;
        peer -> roundTripTimeVariance = accumRoundTripTimeVariance >> 8;
@@ -892,7 +873,7 @@ enet_protocol_handle_acknowledge (ENetHost * host, ENetEvent * event, ENetPeer *
     else
     {
        peer -> roundTripTime = roundTripTime;
-       peer -> roundTripTimeVariance = roundTripTime / 2;
+       peer -> roundTripTimeVariance = (roundTripTime + 1) / 2;
     }
 
     if (peer -> roundTripTime < peer -> lowestRoundTripTime)
@@ -905,7 +886,7 @@ enet_protocol_handle_acknowledge (ENetHost * host, ENetEvent * event, ENetPeer *
         ENET_TIME_DIFFERENCE (host -> serviceTime, peer -> packetThrottleEpoch) >= peer -> packetThrottleInterval)
     {
         peer -> lastRoundTripTime = peer -> lowestRoundTripTime;
-        peer -> lastRoundTripTimeVariance = peer -> highestRoundTripTimeVariance;
+        peer -> lastRoundTripTimeVariance = ENET_MAX (peer -> highestRoundTripTimeVariance, 2);
         peer -> lowestRoundTripTime = peer -> roundTripTime;
         peer -> highestRoundTripTimeVariance = peer -> roundTripTimeVariance;
         peer -> packetThrottleEpoch = host -> serviceTime;
@@ -1691,19 +1672,9 @@ enet_protocol_send_outgoing_commands (ENetHost * host, ENetEvent * event, int ch
 #ifdef ENET_DEBUG
            printf ("peer %u: %f%%+-%f%% packet loss, %u+-%u ms round trip time, %f%% throttle, %u/%u outgoing, %u/%u incoming\n", currentPeer -> incomingPeerID, currentPeer -> packetLoss / (float) ENET_PEER_PACKET_LOSS_SCALE, currentPeer -> packetLossVariance / (float) ENET_PEER_PACKET_LOSS_SCALE, currentPeer -> roundTripTime, currentPeer -> roundTripTimeVariance, currentPeer -> packetThrottle / (float) ENET_PEER_PACKET_THROTTLE_SCALE, enet_list_size (& currentPeer -> outgoingReliableCommands), enet_list_size (& currentPeer -> outgoingUnreliableCommands), currentPeer -> channels != NULL ? enet_list_size (& currentPeer -> channels -> incomingReliableCommands) : 0, currentPeer -> channels != NULL ? enet_list_size (& currentPeer -> channels -> incomingUnreliableCommands) : 0);
 #endif
-          
-           currentPeer -> packetLossVariance -= currentPeer -> packetLossVariance / 4;
 
-           if (packetLoss >= currentPeer -> packetLoss)
-           {
-              currentPeer -> packetLoss += (packetLoss - currentPeer -> packetLoss) / 8;
-              currentPeer -> packetLossVariance += (packetLoss - currentPeer -> packetLoss) / 4;
-           }
-           else
-           {
-              currentPeer -> packetLoss -= (currentPeer -> packetLoss - packetLoss) / 8;
-              currentPeer -> packetLossVariance += (currentPeer -> packetLoss - packetLoss) / 4;
-           }
+           currentPeer -> packetLossVariance = (currentPeer -> packetLossVariance * 3 + ENET_DIFFERENCE (packetLoss, currentPeer -> packetLoss)) / 4;
+           currentPeer -> packetLoss = (currentPeer -> packetLoss * 7 + packetLoss) / 8;
 
            currentPeer -> packetLossEpoch = host -> serviceTime;
            currentPeer -> packetsSent = 0;