一直以来只知道托管代码的效率要比非托管代码低，至于低多少也没有可参考的数据。今天在csdn看到的英特尔多核平台编程优化大赛的广告，把里面的代码下载回来，分别用非托管c/托管cpp/c#做了个简略的性能测试，不比不知道，一比吓了一跳。且看数据说话。
第一步：原始代码如：
/**//* compute the potential energy of a collection of */
/**//* particles interacting via pairwise potential */
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <windows.h>
#include <time.h>
#define NPARTS 1000
#define NITER 201
#define DIMS 3
int rand( void );
int computePot(void);
void initPositions(void);
void updatePositions(void);
double r[DIMS][NPARTS];
double pot;
double distx, disty, distz, dist;
int main() 
{
int i;
clock_t start, stop;
initPositions();
updatePositions();
start=clock();
for( i=0; i<NITER; i++ ) {
pot = 0.0;
computePot();
if (i%10 == 0) printf("%5d: Potential: %10.3f\n", i, pot);
updatePositions();
}
stop=clock();
printf ("Seconds = %10.9f\n",(double)(stop-start)/ CLOCKS_PER_SEC);
int e;
scanf("%d",&e);
}
void initPositions() {
int i, j;
for( i=0; i<DIMS; i++ )
for( j=0; j<NPARTS; j++ )
r[i][j] = 0.5 + ( (double) rand() / (double) RAND_MAX );
}
void updatePositions() {
int i, j;
for( i=0; i<DIMS; i++ )
for( j=0; j<NPARTS; j++ )
r[i][j] -= 0.5 + ( (double) rand() / (double) RAND_MAX );
}
int computePot() {
int i, j;
for( i=0; i<NPARTS; i++ ) {
for( j=0; j<i-1; j++ ) {
distx = pow( (r[0][j] - r[0][i]), 2 );
disty = pow( (r[1][j] - r[1][i]), 2 );
distz = pow( (r[2][j] - r[2][i]), 2 );
dist = sqrt( distx + disty + distz );
pot += 1.0 / dist;
}
}
return 0;
}
执行结果如下：
执行时间4.609s。
第二步：托管
新建一个 C++ CLR Console Aplication，命名为mcpp。打开mcpp.cpp文件，将原始代码粘贴进来即可（代码太长这里就不贴出来了，可以在全贴下面的下载全部源码）。
执行结果如下：
执行时间：15.1720s。
第二步：c#
笔者将原始代码翻译成CS代码，如下：
using System;
using System.Collections.Generic;
using System.Text;
namespace cs
{
class Program
{
private const int RAND_MAX = 0x7fff;
private const int NPARTS = 1000;
private const int NITER = 201;
private const int DIMS = 3;
private double pot;
private double distx, disty, distz, dist;
private Random random = new Random(Environment.TickCount);
private double[][] r = new double[DIMS][];
public void main()
{
int i;
int start, stop;
for (int ii = 0; ii < DIMS; ii++)
{
r[ii] = new double[NPARTS];
}
initPositions();
updatePositions();
start = Environment.TickCount;
for (i = 0; i < NITER; i++)
{
pot = 0.0;
computePot();
if (i % 10 == 0)
Console.WriteLine("{0}: Potential: {1:##########.###}", i, pot);
updatePositions();
}
stop = Environment.TickCount;
Console.WriteLine("Seconds = {0:##########.#########}", (double)(stop - start)/1000);
}
private void computePot()
{
int i, j;
for (i = 0; i < NPARTS; i++)
{
for (j = 0; j < i - 1; j++)
{
distx = Math.Pow((r[0][j] - r[0][i]), 2);
disty = Math.Pow((r[1][j] - r[1][i]), 2);
distz = Math.Pow((r[2][j] - r[2][i]), 2);
dist = Math.Sqrt(distx + disty + distz);
pot += 1.0 / dist;
}
}
}
private void updatePositions()
{
int i, j;
for (i = 0; i < DIMS; i++)
for (j = 0; j < NPARTS; j++)
r[i][j] -= 0.5 + ((double)random.Next(RAND_MAX)/(double)RAND_MAX);
}
private void initPositions()
{
int i, j;
for (i = 0; i < DIMS; i++)
for (j = 0; j < NPARTS; j++)
r[i][j] = 0.5 + ((double)random.Next(RAND_MAX)/(double)RAND_MAX);
}
static void Main(string[] args)
{
Program p = new Program();
p.main();
Console.ReadLine();
}
}
}
执行结果如下：
全部代码下载