关于Unity C# Mathf.Abs()取绝对值性能测试详解

2020-01-24 00:05:57

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前言

之前有人提到过取绝对值时直接写三目运算符比用Mathf.Abs()效率高没觉得能高太多

今天测了一下真是不测不知道一测吓一跳直接写三目运算符比Mathf.Abs()效率高2-3倍

这性能差距有点不太合理啊！看下源码发现很多Mathf的方法就是多封装了一层Math里的方法把double型转成float型了即便很简单得方法也没有重新实现

官方有点偷懒了所以性能差距才会这么大以后要求性能高的地方要注意老老实实写一遍能提升不少性能

测试代码:

using UnityEngine;using UnityEditor;using System.Diagnostics;/// <summary>/// 执行时间测试/// ZhangYu 2019-04-04/// </summary>public class TimeTest : MonoBehaviour { public int executeTimes = 1; private static Stopwatch watch; private void OnValidate() { times = executeTimes; } private static int times = 1; [MenuItem("CONTEXT/TimeTest/执行")] private static void Execute() { watch = new Stopwatch(); // 数据 float a = 1; // Mathf.Abs watch.Reset(); watch.Start(); for (int i = 0; i < times; i++) { a = Mathf.Abs(a); } watch.Stop(); string msgMathfAbs = string.Format("Mathf.Abs: {0}s", watch.Elapsed); // 自己实现Abs watch.Reset(); watch.Start(); for (int i = 0; i < times; i++) { a = MyAbs(a); } watch.Stop(); string msgMyAbs = string.Format("自定义Abs: {0}s", watch.Elapsed); // 三目运算符Abs watch.Reset(); watch.Start(); for (int i = 0; i < times; i++) { a = a < 0 ? -a : a; } watch.Stop(); string msg3Abs = string.Format("三目运算符Abs: {0}s", watch.Elapsed); print(msgMathfAbs); print(msgMyAbs); print(msg3Abs); } // == 执行次数：10000000 // Mathf.Abs // (1)0.2803558s // (2)0.2837749s // (3)0.2831089s // (4)0.2829929s // (5)0.2839846s // 自定义Abs // (1)0.2162217s // (2)0.2103635s // (3)0.2103390s // (4)0.2092863s // (5)0.2097648s private static float MyAbs(float a) { return a < 0 ? -a : a; } // 三目运算符Abs // (1)0.0893028s // (2)0.1000181s // (3)0.1017959s // (4)0.1001749s // (5)0.1005737s}

Mathf.Abs()源码:

// Returns the absolute value of /f/.public static float Abs(float f) { return (float)Math.Abs(f); }// Returns the absolute value of /value/.public static int Abs(int value) { return Math.Abs(value); }

官方Mathf部分源码: