Job System & Burst

using Unity.Jobs;
using Unity.Collections;
using Unity.Burst;
using Unity.Mathematics;
using UnityEngine;

// [BurstCompile] → compile sang SIMD native code
[BurstCompile]
struct CalculatePositionsJob : IJobParallelFor
{
  [ReadOnly] public NativeArray<float3> velocities;
  public NativeArray<float3> positions; // Ghi kết quả vào đây
  public float deltaTime;

  // Execute chạy song song cho từng index
  public void Execute(int index)
  {
      positions[index] += velocities[index] * deltaTime;
  }
}

public class FlockSimulation : MonoBehaviour
{
  const int COUNT = 10000;
  NativeArray<float3> positions, velocities;
  JobHandle jobHandle;

  void Awake()
  {
      positions  = new NativeArray<float3>(COUNT, Allocator.Persistent);
      velocities = new NativeArray<float3>(COUNT, Allocator.Persistent);
  }

  void Update()
  {
      jobHandle.Complete(); // Chờ job frame trước xong
      jobHandle = new CalculatePositionsJob
      {
          velocities = velocities,
          positions  = positions,
          deltaTime  = Time.deltaTime
      }.Schedule(COUNT, 64); // 64 = batch size per thread
  }

  void OnDestroy()
  {
      jobHandle.Complete();
      positions.Dispose();
      velocities.Dispose();
  }
}

using Unity.Jobs;
using Unity.Collections;
using Unity.Burst;

// Hai job chạy nối tiếp qua dependency — không block main thread giữa chừng
void ScheduleChain(NativeArray<float> data)
{
  // Job 1: tính bình phương
  var squareJob = new SquareJob { data = data };
  JobHandle squareHandle = squareJob.Schedule(data.Length, 32);

  // Job 2: cần job 1 xong mới chạy → truyền handle làm dependency
  var sumJob = new SumJob { data = data };
  JobHandle sumHandle = sumJob.Schedule(squareHandle); // dependency!

  // Main thread không bị block. Cả chain chạy parallel với render...
  // ...đến LateUpdate mới cần kết quả:
  sumHandle.Complete();
  Debug.Log($"Sum of squares: {sumJob.result[0]}");
}

// Nhiều job song song rồi merge:
void ScheduleParallel()
{
  var jobA = new JobA().Schedule();
  var jobB = new JobB().Schedule();
  // CombineDependencies: chờ CẢ HAI xong mới chạy jobC
  var combined = JobHandle.CombineDependencies(jobA, jobB);
  var jobC = new JobC().Schedule(combined);
  jobC.Complete();
}