using System;
using System.Numerics;

using BenchmarkDotNet.Attributes;

namespace SixLabors.ImageSharp.Benchmarks.General
{
    /// <summary>
    /// Has it any effect on performance to store SIMD constants as static readonly fields? Is it OK to always inline them?
    /// Spoiler: the difference seems to be statistically insignificant!
    /// </summary>
    public class Vector4Constants
    {
        private static readonly Vector4 A = new Vector4(1.2f);
        private static readonly Vector4 B = new Vector4(3.4f);
        private static readonly Vector4 C = new Vector4(5.6f);
        private static readonly Vector4 D = new Vector4(7.8f);

        private Random random;

        private Vector4 parameter;

        [GlobalSetup]
        public void Setup()
        {
            this.random = new Random(42);
            this.parameter = new Vector4(
                this.GetRandomFloat(),
                this.GetRandomFloat(),
                this.GetRandomFloat(),
                this.GetRandomFloat()
                );
        }

        [Benchmark(Baseline = true)]
        public Vector4 Static()
        {
            Vector4 p = this.parameter;

            Vector4 x = p * A / B + p * C / D;
            Vector4 y = p / A * B + p / C * D;
            Vector4 z = Vector4.Min(p, A);
            Vector4 w = Vector4.Max(p, B);
            return x + y + z + w;
        }

        [Benchmark]
        public Vector4 Inlined()
        {
            Vector4 p = this.parameter;

            Vector4 x = p * new Vector4(1.2f) / new Vector4(2.3f) + p * new Vector4(4.5f) / new Vector4(6.7f);
            Vector4 y = p / new Vector4(1.2f) * new Vector4(2.3f) + p / new Vector4(4.5f) * new Vector4(6.7f);
            Vector4 z = Vector4.Min(p, new Vector4(1.2f));
            Vector4 w = Vector4.Max(p, new Vector4(2.3f));
            return x + y + z + w;
        }

        private float GetRandomFloat() => (float)this.random.NextDouble();
    }
}