12
我在玩C＃并希望加快一个程序。我做了改变，并能够这样做。但是，我需要帮助理解为什么变化更快。帮助理解C＃优化
我试图减少代码，以更容易理解的问题。 Score1和Report1是较慢的方法。 Score2和Report2是更快的方法。第一种方法首先在并行结构中存储一个字符串和一个int。接下来，在一个串行循环中，它循环遍历这些结构的数组并将它们的数据写入缓冲区。第二种方法首先将数据并行写入字符串缓冲区。接下来，在串行循环中，它将字符串数据写入缓冲区。下面是一些样品运行时间：
运行1总平均时间= 0.492087秒 运行2总平均时间= 0.273619秒
当我随着早期非水货版的这个工作，时间几乎一样。为什么与平行版本有所不同？
即使我减少Report1中的循环以将单行输出写入缓冲区，它仍然较慢（总时间约为.42秒）。
这里是简化代码：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Diagnostics;
using System.Threading.Tasks;
using System.IO;
namespace OptimizationQuestion
{
class Program
{
struct ValidWord
{
public string word;
public int score;
}
ValidWord[] valid;
StringBuilder output;
int total;
public void Score1(string[] words)
{
valid = new ValidWord[words.Length];
for (int i = 0; i < words.Length; i++)
{
StringBuilder builder = new StringBuilder();
foreach (char c in words[i])
{
if (c != 'U')
builder.Append(c);
}
if (words[i].Length == 3)
{
valid[i] = new ValidWord
{ word = builder.ToString(), score = words[i].Length };
}
}
}
public void Report1(StringBuilder outputBuffer)
{
int total = 0;
foreach (ValidWord wordInfo in valid)
{
if (wordInfo.score > 0)
{
outputBuffer.AppendLine(String.Format("{0} {1}", wordInfo.word.ToString(), wordInfo.score));
total += wordInfo.score;
}
}
outputBuffer.AppendLine(string.Format("Total = {0}", total));
}
public void Score2(string[] words)
{
output = new StringBuilder();
total = 0;
for (int i = 0; i < words.Length; i++)
{
StringBuilder builder = new StringBuilder();
foreach (char c in words[i])
{
if (c != 'U')
builder.Append(c);
}
if (words[i].Length == 3)
{
output.AppendLine(String.Format("{0} {1}", builder.ToString(), words[i].Length));
total += words[i].Length;
}
}
}
public void Report2(StringBuilder outputBuffer)
{
outputBuffer.Append(output.ToString());
outputBuffer.AppendLine(string.Format("Total = {0}", total));
}
static void Main(string[] args)
{
Program[] program = new Program[100];
for (int i = 0; i < program.Length; i++)
program[i] = new Program();
string[] words = File.ReadAllLines("words.txt");
Stopwatch stopwatch = new Stopwatch();
const int TIMING_REPETITIONS = 20;
double averageTime1 = 0.0;
StringBuilder output = new StringBuilder();
for (int i = 0; i < TIMING_REPETITIONS; ++i)
{
stopwatch.Reset();
stopwatch.Start();
output.Clear();
Parallel.ForEach<Program>(program, p =>
{
p.Score1(words);
});
for (int k = 0; k < program.Length; k++)
program[k].Report1(output);
stopwatch.Stop();
averageTime1 += stopwatch.Elapsed.TotalSeconds;
GC.Collect();
}
averageTime1 /= (double)TIMING_REPETITIONS;
Console.WriteLine(string.Format("Run 1 Total Average Time = {0:0.000000} sec", averageTime1));
double averageTime2 = 0.0;
for (int i = 0; i < TIMING_REPETITIONS; ++i)
{
stopwatch.Reset();
stopwatch.Start();
output.Clear();
Parallel.ForEach<Program>(program, p =>
{
p.Score2(words);
});
for (int k = 0; k < program.Length; k++)
program[k].Report2(output);
stopwatch.Stop();
averageTime2 += stopwatch.Elapsed.TotalSeconds;
GC.Collect();
}
averageTime2 /= (double)TIMING_REPETITIONS;
Console.WriteLine(string.Format("Run 2 Total Average Time = {0:0.000000} sec", averageTime2));
Console.ReadLine();
}
}
}
为什么你试图排名这样不同的代码为报表和报告2？ Report1包含一个循环，Report2不包含。也许在非并行版本中，C＃编译器展开了循环或其他魔法？ – Earlz 2011-02-09 05:32:27
将Report1循环减少为一次迭代有一点帮助（.42秒），但发布后，我认为它是Score1中的数组分配。 – jlim 2011-02-09 05:35:52
注意：单词列表大约是14,000行字符串。因此，每次调用score1分配14,000个结构。 – jlim 2011-02-09 06:02:11