Unity Job.Run vs Function Pointer, both bursted

BurstTest.cs

    class BurstTest
    {
        [BurstCompile]
        public struct MultJob : IJob
        {
            [ReadOnly]
            public NativeArray<float> a;
            [ReadOnly]
            public NativeArray<float> b;
            [WriteOnly]
            public NativeArray<float> result;

            public void Execute()
            {
                for (int i = 0; i < a.Length; i++)
                {
                    result[i] = a[i] * b[i];
                }
            }
        }

        [BurstCompile]
        class Funcs
        {
            public delegate void MultArraysDel(ref NativeArray<float> a, ref NativeArray<float> b, ref NativeArray<float> result);

            [BurstCompile]
            public static void MultArrays(ref NativeArray<float> a, ref NativeArray<float> b, ref NativeArray<float> result)
            {
                for (int i = 0; i < a.Length; i++)
                {
                    result[i] = a[i] * b[i];
                }
            }
        }

        [Test]
        public void BurstFuncPointerTest()
        {
            var a = new NativeArray<float>(500, Allocator.TempJob);
            var b = new NativeArray<float>(500, Allocator.TempJob);
            var r = new NativeArray<float>(500, Allocator.TempJob);

            var funcPointer = BurstCompiler.CompileFunctionPointer<Funcs.MultArraysDel>(Funcs.MultArrays);
            funcPointer.Invoke(ref a, ref b, ref r);

            var s = Stopwatch.StartNew();
            for (int i = 0; i < 500; i++)
            {
                funcPointer.Invoke(ref a, ref b, ref r);
            }
            Debug.Log("func pointer: " + s.Elapsed.TotalMilliseconds);

            new MultJob { a = a, b = b, result = r }.Run();

            s.Restart();
            for (int i = 0; i < 500; i++)
            {
                new MultJob { a = a, b = b, result = r }.Run();
            }
            Debug.Log("job run: " + s.Elapsed.TotalMilliseconds);

            a.Dispose();
            b.Dispose();
            r.Dispose();
        }
    }

Thanks for sharing this gist. I was curious about the timings too

    static void BurstFuncPointerTest()
    {
        var a = new NativeArray<float>(5000, Allocator.TempJob);
        var b = new NativeArray<float>(5000, Allocator.TempJob);
        var r = new NativeArray<float>(5000, Allocator.TempJob);

        var funcPointer = BurstCompiler.CompileFunctionPointer<Funcs.MultArraysDel>(Funcs.MultArrays);
        var fp = funcPointer.Invoke;
        fp(ref a, ref b, ref r);

        for (var x = 0; x < 10; x++)
        {
            var s = Stopwatch.StartNew();
            for (var i = 0; i < 5000; i++)
            {
                fp(ref a, ref b, ref r);
            }
            Debug.Log("func pointer: " + s.Elapsed.TotalMilliseconds);

            new MultJob { a = a, b = b, result = r }.Run();

            s.Restart();
            for (var i = 0; i < 5000; i++)
            {
                new MultJob { a = a, b = b, result = r }.Run();
            }
            Debug.Log("job run: " + s.Elapsed.TotalMilliseconds);
        }

        a.Dispose();
        b.Dispose();
        r.Dispose();
    }

tweaked for more iterations and to cache the invoke method. For me this made the function-pointer approach faster than the IJob.Run approach (when in the original version IJob.Run was faster on my machine)