linux计时函数

#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <sys/time.h>struct timeval tpstart,tpend;double timeuse;void timebegin(){  gettimeofday(&tpstart,NULL);//记录开始计时时间tpstart}void timeend(const char *str){  gettimeofday(&tpend,NULL);//记录计时结束时间tpend  timeuse=1000000*(tpend.tv_sec-tpstart.tv_sec)+tpend.tv_usec-tpstart.tv_usec;  timeuse/=1000000;  printf("%s %lf s\n",str, timeuse);} int main() {    int count = 4000 * 3000;    float  *array = (float *) calloc(4000,3000 * sizeof(float));    timebegin();    int i=0;    for (i = 0; i < count; ++i)    {        array[i] = 12.56*123.6 + 12.3;    }    timeend("time use ");    free(array);    array = NULL;    return 0;}