Ubuntu 9.10下C语言函数运行时间测试

最近突然有必要测试C语言中各个函数的运行时间，于是就搜索了一下，发现有4种方法可以达成测算程序运行时间的目的。
它们分别是使用clock, times, gettimeofday, getrusage来实现的。下面就来逐一介绍，并比较它们的优劣点。

系统测试环境：
VirtualBox (Ubuntu 9.10)
gcc version 4.4.1
libc6 2.10.1-0ubuntu16
Core Duo T2500 2GMHz

首先先贴出我测试用的程序吧。
程序做的处理很简单，就是填写一个1024*1024的矩阵。
只要修改第11行的定义值，就可以使用不同的测量方法了。

#include <sys/time.h>
#include <sys/resource.h>
#include <unistd.h>
#include <stdio.h>
#include <time.h>

#define TEST_BY_CLOCK   (char)(0x00)
#define TEST_BY_TIMES   (char)(0x01)
#define TEST_BY_GETTIMEOFDAY (char)(0x02)
#define TEST_BY_GETRUSAGE  (char)(0x03)
#define TEST_METHOD    (TEST_BY_GETTIMEOFDAY)

#define COORDINATION_X   (int)(1024)
#define COORDINATION_Y   (int)(1024)

static int g_Matrix[COORDINATION_X][COORDINATION_Y];

double getTimeval()
{
 struct rusage stRusage;
 struct timeval stTimeval;
 if (TEST_METHOD == TEST_BY_GETTIMEOFDAY) {
  gettimeofday(&stTimeval, NULL);
 } else if (TEST_METHOD == TEST_BY_GETRUSAGE) {
  getrusage(RUSAGE_SELF, &stRusage);
  stTimeval = stRusage.ru_utime;
 }
 return stTimeval.tv_sec + (double)stTimeval.tv_usec*1E-6;
}

int main()
{
 int i, j;
 int n = 0;
 clock_t clockT1, clockT2;
 double doubleT1, doubleT2;

if (TEST_METHOD == TEST_BY_CLOCK) {
  clockT1 = clock();
 } else if (TEST_METHOD == TEST_BY_TIMES) {
  times(&clockT1);
 } else if (TEST_METHOD == TEST_BY_GETTIMEOFDAY) {
  doubleT1 = getTimeval();
 } else if (TEST_METHOD == TEST_BY_GETRUSAGE) {
  doubleT1 = getTimeval();
 }

for (i = 0; i < COORDINATION_X; i++) {
  for (j = 0; j < COORDINATION_Y; j++) {
   g_Matrix[i][j] = i * j;
  }
 }

if (TEST_METHOD == TEST_BY_CLOCK) {
  clockT2 = clock();
  printf("Time result tested by clock = %10.30f\n",
    (double)(clockT2 - clockT1)/CLOCKS_PER_SEC);
 } else if (TEST_METHOD == TEST_BY_TIMES) {
  times(&clockT2);
  printf("Time result tested by times = %10.30f\n",
    (double)(clockT2 - clockT1)/sysconf(_SC_CLK_TCK));
 } else if (TEST_METHOD == TEST_BY_GETTIMEOFDAY) {
  doubleT2 = getTimeval();
  printf("Time result tested by gettimeofday = %10.30f\n",
    (double)(doubleT2 - doubleT1));
 } else if (TEST_METHOD == TEST_BY_GETRUSAGE) {
  doubleT2 = getTimeval();
  printf("Time result tested by getrusage = %10.70f\n",
    (double)(doubleT2 - doubleT1));
 }

return 0;
}