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Using query.IsEmpty to reduce scheduling cost?

Discussion in 'Data Oriented Technology Stack' started by Timboc, Mar 20, 2021.

  1. Timboc


    Jun 22, 2015
    Given a chain of jobs within a system:
    Code (CSharp):
    1. systemState.Dependency = someIJC1.ScheduleParallel(query1, systemState.Dependency);
    2. systemState.Dependency = someIJC2.ScheduleParallel(query2, systemState.Dependency);
    3. systemState.Dependency = someIJC3.ScheduleParallel(query3, systemState.Dependency);
    4. systemState.Dependency = someIJC4.ScheduleParallel(query4, systemState.Dependency);
    I have a large system with a chain of 20 such jobs and I was investigating what I could do about the main thread cost (~0.4ms in a build for just the scheduling overhead).
    I found that wrapping them each with a
    was hugely helpful.
    Code (CSharp):
    1. if(!query1.IsEmptyIgnoreFilter) systemState.Dependency = someIJC1.ScheduleParallel(query1, systemState.Dependency);
    2. if(!query2.IsEmptyIgnoreFilter) systemState.Dependency = someIJC2.ScheduleParallel(query2, systemState.Dependency);
    3. if(!query3.IsEmptyIgnoreFilter) systemState.Dependency = someIJC3.ScheduleParallel(query3, systemState.Dependency);
    4. if(!query4.IsEmptyIgnoreFilter) systemState.Dependency = someIJC4.ScheduleParallel(query4, systemState.Dependency);
    I was quite surprised by the difference this made. Is this an optimisation that could be built-in to Schedule/ScheduleParallel or am I somehow shooting myself in the foot by doing this?

    *My test was in a fully bursted ISystemBase (hence IJC not batch entity) but I believe this applies to SystemBase too
    **I also tried JobHandle.CombineDependencies(NativeArray<>) - but perhaps as a lot of my jobs depend on the jobhandle of the previous - this was no better. Behaviour was also still the same.
    Last edited: Mar 20, 2021