double在输出为字符串的几种方法效率测试

测试结果：

double->none 366ms
double->long 161ms
double->long2 188ms
double->format 564ms
double->Round 393ms

代码：

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace testStringbuilder
{
    class Program
    {
        static void Main(string[] args)
        {
            const int count = 1000000;

            RunTest("double->none",()=>
            {
                StringBuilder sb = new StringBuilder(1000*1024*32);
                double a = 3.1415926;
                for (int i = 0; i < count; i++)
                {
                    sb.Append(a);
                    sb.Append(',');
                }
            });

            RunTest("double->long", () =>
            {
                StringBuilder sb = new StringBuilder(1000 * 1024 * 32);
                double a = 3.1415926;
                for (int i = 0; i < count; i++)
                {
                    sb.Append((long)a);
                    sb.Append(',');
                }
            });

            RunTest("double->long2", () =>
            {
                StringBuilder sb = new StringBuilder(1000 * 1024 * 32);
                double a = 3.1415926;
                for (int i = 0; i < count; i++)
                {
                    sb.Append((long)(a * 100));
                    sb.Append(',');
                }
            });

            RunTest("double->format", () =>
            {
                StringBuilder sb = new StringBuilder(1000 * 1024 * 32);
                double a = 3.1415926;
                for (int i = 0; i < count; i++)
                {
                    sb.AppendFormat("{0:f3}",a);
                    sb.Append(',');
                }
            });

            RunTest("double->Round", () =>
            {
                StringBuilder sb = new StringBuilder(1000 * 1024 * 32);
                double a = 3.1415926;
                for (int i = 0; i < count; i++)
                {
                    sb.Append(Math.Round(a, 3));
                    sb.Append(',');
                }
            });
        }

        private static void RunTest(string key, Action action)
        {
            double milli = 0;
            for (int i = 0; i < 3; i++)
            {
                Stopwatch watch = Stopwatch.StartNew();

                try
                {
                    action();
                }
                catch (Exception ex)
                {
                    Console.WriteLine(ex);
                }

                watch.Stop();
                milli += watch.ElapsedMilliseconds;
            }

            Console.WriteLine("{0}\t{1}ms", key, (long) (milli/3));
        }
    }
}