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How to calculate EntityCommandBuffer.Concurrent jobIndex with IJobChunk?

Discussion in 'Data Oriented Technology Stack' started by Jay-Pavlina, Jan 26, 2019.

  1. Jay-Pavlina

    Jay-Pavlina

    Joined:
    Feb 19, 2012
    Posts:
    195
    I am unsure of how to calculate the jobIndex needed for EntityCommandBuffer.Concurrent when using an IJobChunk. Does anyone know?

    Code (CSharp):
    1. struct Job : IJobChunk {
    2.     public EntityCommandBuffer.Concurrent commandBuffer;
    3.  
    4.     public void Execute(ArchetypeChunk chunk, int chunkIndex, int firstEntityIndex) {
    5.        var entities = chunk.GetNativeArray(entityType);
    6.        for (var i = 0; i < chunk.Count; i++) {
    7.            var entity = entities[i];
    8.            var jobIndex = ?
    9.            commandBuffer.AddComponent(jobIndex, entity, new Whatever());
    10.        }
    11.     }
    12. }
     
  2. tertle

    tertle

    Joined:
    Jan 25, 2011
    Posts:
    2,967
    You can just use the chunkIndex.

    Alternatively you can always inject the thread index.

    Code (CSharp):
    1. [NativeSetThreadIndex]
    2. private int ThreadIndex;
    But yeah, just use chunkIndex.
     
    tango209 likes this.
  3. Jay-Pavlina

    Jay-Pavlina

    Joined:
    Feb 19, 2012
    Posts:
    195
    Thanks. Do you know why they provide firstEntityIndex? What is that useful for?
     
  4. tertle

    tertle

    Joined:
    Jan 25, 2011
    Posts:
    2,967
    Not sure, it was a new addition to IJobChunk in p23 so I'm sure they have some type of pattern in mind.
     
  5. eizenhorn

    eizenhorn

    Joined:
    Oct 17, 2016
    Posts:
    2,266
    May be It like chunk.StartIndex which was removed in past I think :)
     
    GilCat likes this.
  6. Joachim_Ante

    Joachim_Ante

    Unity Technologies

    Joined:
    Mar 16, 2005
    Posts:
    5,158
    chunkIndex is enough to achieve deterministic playback.
     
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