Search Unity

Bug [1.0.0-exp.13] Relevancy works incorrect?

Discussion in 'NetCode for ECS' started by asdfgas-dgasdg, Nov 28, 2022.

  1. asdfgas-dgasdg

    asdfgas-dgasdg

    Joined:
    Oct 25, 2012
    Posts:
    7
    The sample code from Asteroid project are configured to use relevancy to incorrect way, It populate
    GhostRelevancySet with irrelevant ghost instead of relevant ghost.
    Code (CSharp):
    1.    ref var ghostRelevancy = ref SystemAPI.GetSingletonRW<GhostRelevancy>().ValueRW;
    2.                 if (settings.RelevancyRadius == 0)
    3.                 {
    4.                     ghostRelevancy.GhostRelevancyMode = GhostRelevancyMode.Disabled;
    5.                     return;
    6.                 }
    7.  
    8.                 [code=CSharp]ghostRelevancy.GhostRelevancyMode = GhostRelevancyMode.
    9. SetIsIrrelevant
    10. ;
    Code (CSharp):
    1. public void Execute(Entity entity, in GhostComponent ghost, in Translation pos)
    2.             {
    3.      
    4.                 for (int i = 0; i < connections.Length; ++i)
    5.                 {
    6.                     if (math.distance(pos.Value, connections[i].Position) > relevancyRadius)
    7.                     {
    8.                         parallelRelevantSet.TryAdd(
    9.                             new RelevantGhostForConnection(connections[i].ConnectionId, ghost.ghostId), 1);
    10.            
    11.                     }
    12.                 }
    13.             }
    With configuration of say 500 clients and 10,000 server owned interpolated ghosts it makes huge cpu usage because of big data set collected of irrelevant ghosts.

    Changing the code to opposite (select only relevant ghosts), gives
    extremely better performance:

    Code (CSharp):
    1.   ghostRelevancy.GhostRelevancyMode = GhostRelevancyMode.SetIsRelevant;

    Code (CSharp):
    1. if (math.distance(pos.Value, connections[i].Position) < relevancyRadius)
    2.                     {
    3.                         parallelRelevantSet.TryAdd(
    4.                             new RelevantGhostForConnection(connections[i].ConnectionId, ghost.ghostId), 1);
    5.            
    6.                     }
    However, this changes completely break physics simulation on the client world, it is looks like physics bodies doesn't update his position.

    UPD:
    Seems main bottleneck is there
    Code (CSharp):
    1.  NativeParallelHashMap<RelevantGhostForConnection, int> GhostRelevancySet;
    int the
    Code (CSharp):
    1.  
    2. public struct GhostRelevancy : IComponentData
    3.  
    I don't know why, but NativeParallelHashMap is really slow , adding 500*10,000 items takes 2700ms on my mac.
    Changing it to other datatype f.e NativeMultiHashMap gives me several times better result.
     
    Last edited: Nov 29, 2022
  2. NikiWalker

    NikiWalker

    Unity Technologies

    Joined:
    May 18, 2021
    Posts:
    314
    Hey asdfgas-dgasdg!

    I agree that this doesn't scale, but this is intentional, because: The sample is designed to be simple, and so, before the ship spawns, we want to show that asteroids are being sent to the client.

    I.e. When you set this `ghostRelevancy.GhostRelevancyMode = GhostRelevancyMode.SetIsRelevant;`, you'll see nothing until you hit the spacebar. This may be confusing.

    Thanks for the report! I'll investigate tomorrow.
     
  3. NikiWalker

    NikiWalker

    Unity Technologies

    Joined:
    May 18, 2021
    Posts:
    314
    Thanks for your update. An update from our side is that we're aware of the perf difference between these two hashmaps. We're not yet sure what a resolution should be, but the performance hole is noted.

    Also note: We only expect performance characteristics to be superb when Burst is enabled. Saying that, this is still far too slow without burst.