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Caching Data for Iterative Jobs

Discussion in 'Data Oriented Technology Stack' started by RandyBuchholz, Jan 27, 2020.

  1. RandyBuchholz

    RandyBuchholz

    Joined:
    Sep 23, 2016
    Posts:
    51
    I have some iterative jobs that depend on the results of the previous run. These are things like feedback loops and integrators/accumulators. I know I can create an entity to hold the intermediate result and read that on the next iteration. I'm looking for a way to avoid that overhead and just "pin" a variable that persists across iterations that is directly accessible to the job, so I can read and write to it on each job iteration. Most commonly, I just need to hold a single value (usually a float) for a single (non-parallel) job. Of course, more general approaches that can hold structs for jobs running in parallel would be useful. In parallel cases, each parallel job would only access its own instance of the variable/struct.
     
  2. Razmot

    Razmot

    Joined:
    Apr 27, 2013
    Posts:
    286
    Can't you just have a persistent NativeArray in the system, and pass it to the jobs ?
     
  3. RandyBuchholz

    RandyBuchholz

    Joined:
    Sep 23, 2016
    Posts:
    51
    By "system" I assume you mean the class with the job and not the overall system. I thought about something like that, but wasn't sure how to handle disposal. It seems I would need some way to hold a reference to the array outside of the system so I can dispose it when I know the system will no longer be used. Or, I would need to manage the overall lifecycle of the system. Kind of like a "sticky" system - I would manually instantiate the system and create the array in the constructor. Then I dispose of it in the destructor when I release the system. I'm worried about how that might mess with the internal JCL processes though.

    I was thinking of creating an in-memory cache and defining an attribute like [Persist <key>]. That still doesn't help with disposal, but would help as a general solution. (And, I don't really know to implement something like the cache).
     
  4. Razmot

    Razmot

    Joined:
    Apr 27, 2013
    Posts:
    286
    OnCreate() and onDestroy() are there for that
    Code (CSharp):
    1. protected override void OnCreate()
    2.         {
    3.             _sources = new NativeList<int3>(Allocator.Persistent);
    4.         }
    5.         protected override void OnDestroy()
    6.         {
    7.             _sources.Dispose();
    8.         }
     
  5. RandyBuchholz

    RandyBuchholz

    Joined:
    Sep 23, 2016
    Posts:
    51
    Cool, thanks. And the system gets created and destroyed once per application run? I didn't know if it was recreated on each frame/sim step, loosing the list contents.
     
  6. Razmot

    Razmot

    Joined:
    Apr 27, 2013
    Posts:
    286
    yes, per application run .
     
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