Doing a double loop in a job in ecs with Job Entites.forech

Question

I am trying to do a double forech loop in Unity ECS within a JOB, a gravitaional like system. I have done it already succesfully with Unity 2018 with a IJOBParalleForEach, but the code didnt work with Unity 2019 so I tried it now with the new Job Entites.forech and it doesnt work either, I really have no idea why I get the error: error DC0001: Entities.ForEach Lambda expression uses field 'physicsMasses'. Either assign the field to a local outside of the lambda expression and use that instead, or use .WithoutBurst() and .Run().

 using System.Collections; using System.Collections.Generic; using UnityEngine; using Unity.Entities; using Unity.Jobs; using Unity.Transforms; using Unity.Mathematics; using Unity.Physics; using Unity.Collections; 
 public class SwarmSystem : JobComponentSystem {
         public float time;
         public float gravK = 6.674f;
         EntityManager entityManager;
         [DeallocateOnJobCompletion]  NativeArray<Translation> translations;
         [DeallocateOnJobCompletion]  NativeArray<PhysicsMass> physicsMasses;
         protected override void OnCreate()
         {
             var v = GameObject.FindObjectOfType<MyGameManager>();
             entityManager = v.entityManager;
         }
         protected override JobHandle OnUpdate(JobHandle inputDeps)
         {
 
             EntityQuery q = GetEntityQuery(ComponentType.ReadOnly<IsPartOfSwarmTag>(), ComponentType.ReadOnly<Translation>(), ComponentType.ReadOnly<PhysicsMass>());
             time = Time.DeltaTime;
             translations = q.ToComponentDataArray<Translation>(Allocator.TempJob);
             physicsMasses = q.ToComponentDataArray<PhysicsMass>(Allocator.TempJob);
     
             var job = Entities.WithAll<IsPartOfSwarmTag>().ForEach((Entity e, ref ForceData f, in PhysicsMass pm, in Translation t ) => {
     
                 for(int i = 0; i< translations.Length; i++)
                 {
                     float k = physicsMasses[i].InverseMass * pm.InverseMass * gravK;
                     float3 vec = t.Value - translations[i].Value;
                     float length = math.length(vec);
                     float potenz = math.pow(length, 3);
                     f.Value += (k / potenz) * vec;
                 }
     
             }).Schedule(inputDeps);
             return job;
         } }

ForceData is just a float3 IComponentData

Answer 1

Answer by andrew-lukasik · May 29, 2020 at 08:51 PM

It wants you to change it to a local variable

 var physicsMasses = q.ToComponentDataArray<PhysicsMass>(Allocator.TempJob);

or make an local alias variable and use it in your job

 var localPhysicsMasses = physicsMasses;//use localPhysicsMasses from now on

NOTE: if you make your system inherit from SystemBase you will be able to use Job semantics (imo more fitting here)

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GamerLordMat · Aug 14, 2021 at 09:55 AM 0

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thanks for the answer! (old post but I totally missed to reply)

Doing a double loop in a job in ecs with Job Entites.forech

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