remove unnecessary allocs in SideChannelMananger

com.unity.ml-agents/CHANGELOG.md

@@ -35,6 +35,9 @@ removed when training with a player. The Editor still requires it to be clamped
 #### com.unity.ml-agents (C#)
 - Fix a compile warning about using an obsolete enum in `GrpcExtensions.cs`. (#4812)
 - CameraSensor now logs an error if the GraphicsDevice is null. (#4880)
+- Removed unnecessary memory allocations in `ActuatorManager.UpdateActionArray()` (#4877)
+- Removed unnecessary memory allocations in `SensorShapeValidator.ValidateSensors()` (#4879)
+- Removed unnecessary memory allocations in `SideChannelManager.GetSideChannelMessage()` (#4886)
 - Removed several memory allocations that happened during inference. On a test scene, this
  reduced the amount of memory allocated by approximately 25%. (#4887)
 

com.unity.ml-agents/Runtime/SideChannels/SideChannelManager.cs

@@ -120,6 +120,13 @@ internal static byte[] GetSideChannelMessage()
  /// <returns></returns>
  internal static byte[] GetSideChannelMessage(Dictionary<Guid, SideChannel> sideChannels)
  {
+ if (!HasOutgoingMessages(sideChannels))
+ {
+ // Early out so that we don't create the MemoryStream or BinaryWriter.
+ // This is the most common case.
+ return Array.Empty<byte>();
+ }
+
  using (var memStream = new MemoryStream())
  {
  using (var binaryWriter = new BinaryWriter(memStream))
@@ -140,6 +147,25 @@ internal static byte[] GetSideChannelMessage(Dictionary<Guid, SideChannel> sideC
  }
  }
 
+ /// <summary>
+ /// Check whether any of the sidechannels have queued messages.
+ /// </summary>
+ /// <param name="sideChannels"></param>
+ /// <returns></returns>
+ static bool HasOutgoingMessages(Dictionary<Guid, SideChannel> sideChannels)
+ {
+ foreach (var sideChannel in sideChannels.Values)
+ {
+ var messageList = sideChannel.MessageQueue;
+ if (messageList.Count > 0)
+ {
+ return true;
+ }
+ }
+
+ return false;
+ }
+
  /// <summary>
  /// Separates the data received from Python into individual messages for each registered side channel.
  /// </summary>