[No0000B7]If else 与 三元表达式? : 效率对比 |
您所在的位置：网站首页 › if和三元判定的效率 › [No0000B7]If else 与 三元表达式? : 效率对比 |
[No0000B7]If else 与 三元表达式? : 效率对比
|
先看 if else 一段代码 using System; class Program { private static void Main() { int i = 0; if (i == 0) i = -1; else i = -2; Console.WriteLine(i); } }输出 -1
用IL DASM （"C:\Program Files (x86)\Microsoft SDKs\Windows\v10.0A\bin\NETFX 4.6.1 Tools\ildasm.exe"vs2015 up3，项目框架.NET Framework 4.5.2）打开 .method private hidebysig static void Main() cil managed { .entrypoint // 代码大小 26 (0x1a) .maxstack 2 .locals init ([0] int32 i, [1] bool V_1) IL_0000: nop IL_0001: ldc.i4.0 IL_0002: stloc.0 IL_0003: ldloc.0 IL_0004: ldc.i4.0 IL_0005: ceq IL_0007: stloc.1 IL_0008: ldloc.1 IL_0009: brfalse.s IL_000f IL_000b: ldc.i4.m1 IL_000c: stloc.0 IL_000d: br.s IL_0012 IL_000f: ldc.i4.s -2 IL_0011: stloc.0 IL_0012: ldloc.0 IL_0013: call void [mscorlib]System.Console::WriteLine(int32) IL_0018: nop IL_0019: ret } // end of method Program::Main在看三元表达式? :一段代码 using System; class Program { private static void Main() { int i = 0; i = i == 0 ? -1 : -2; Console.WriteLine(i); } }输出 -1
明显，执行效率不一样。三元表达式? :执行效率更高。 using System; using System.Diagnostics; class Program { private static void Main() { int i = 0; Stopwatch stopwatch = new Stopwatch(); stopwatch.Start(); for (int j = 0; j < 100000000; j++) { if (i == 0) i = -1; else i = -2; } stopwatch.Stop(); Console.WriteLine(stopwatch.ElapsedMilliseconds); stopwatch.Reset(); stopwatch.Start(); for (int j = 0; j < 100000000; j++) { i = i == 0 ? -1 : -2; } stopwatch.Stop(); Console.WriteLine(stopwatch.ElapsedMilliseconds); } }
|
【本文地址】
今日新闻 |
推荐新闻 |