Job.cs

using System;
using System.Diagnostics;
using Unity.Collections;
using Unity.Jobs;
using Unity.Burst;
using UnityEngine;
using Debug = UnityEngine.Debug;
using static Unity.Mathematics.math;

using Unity.Mathematics;

[BurstCompile]
public struct FindPolygonContainingPoint : IJobParallelFor
{
  [ReadOnly]
  public NativeArray<float4> polygons;

  [ReadOnly]
  public float4 point;

  [WriteOnly]
  public NativeArray<int> result;

  bool done;

  // The code actually running on the job
  public void Execute(int i)
  {
    if(done) return;

    var p0 = polygons[i * 3 ];
    var p1 = polygons[i * 3 + 1];
    var p2 = polygons[i * 3 + 2];
    var s = p0.y * p2.x - p0.x * p2.y + (p2.y - p0.y) * point.x + (p0.x - p2.x) * point.y;
    var t = p0.x * p1.y - p0.y * p1.x + (p0.y - p1.y) * point.x + (p1.x - p0.x) * point.y;

    if ((s < 0) == (t < 0))
    {
      var a = -p1.y * p2.x + p0.y * (p2.x - p1.x) + p0.x * (p1.y - p2.y) + p1.x * p2.y;

      if(a < 0 ?
        (s <= 0 && s + t >= a) :
        (s >= 0 && s + t <= a))
      {
        result[0] = i;
        done = true;
      }
    }
  }
}