memcpy执行效率测试，无效测试

#include <stdio.h> #include<time.h> #include<math.h> #include <unistd.h> clock_t start,stop; //clock_t是clock()函数返回的变量类型 double duration; //记录被测试函数运行时间，以秒为单位#define MAXK 1e7/*被测函数最大重复调用次数*/void computationtime(double start,double stop,int i) {duration = ((double)(stop-start))/CLOCK_TAI/MAXK;/*计算函数单次运行的时间*///计算运行时间//其它不在测试范围的处理写在后面，例如输出duration的值printf("ticks%d = %f\n",i,(double)(stop - start));printf("duration%d = %6.2e\n",i,duration); }void *fq_memcpy(void *__dest, __const void *__src, size_t __n) {int i = 0;unsigned char *d = (unsigned char *)__dest, *s = (unsigned char *)__src;for (i = __n >> 3; i > 0; i--) {*d++ = *s++;*d++ = *s++;*d++ = *s++;*d++ = *s++;*d++ = *s++;*d++ = *s++;*d++ = *s++;*d++ = *s++;}if (__n & 1 << 2) {*d++ = *s++;*d++ = *s++;*d++ = *s++;*d++ = *s++;}if (__n & 1 << 1) {*d++ = *s++;*d++ = *s++;}if (__n & 1)*d++ = *s++;return __dest; }void *fq2_memcpy(void *dest, const void *src, size_t n) {int i;const char *s = src;char *d = dest;for (i = 0; i < n; i++)d[i] = s[i];return dest; }int main(void) {char * a = "0123456789ABCDEFGHJKLMNOPQRSTUVWXYZ,0123456789ABCDEFGHJKLMNOPQRSTUVWXYZ,0123456789ABCDEFGHJKLMNOPQRSTUVWXYZ,0123456789ABCDEFGHJKLMNOPQRSTUVWXYZ,0123456789ABCDEFGHJKLMNOPQRSTUVWXYZ,0123456789ABCDEFGHJKLMNOPQRSTUVWXYZ,0123456789ABCDEFGHJKLMNOPQRSTUVWXYZ,0123456789ABCDEFGHJKLMNOPQRSTUVWXYZ,0123456789ABCDEFGHJKLMNOPQRSTUVWXYZ,0123456789ABCDEFGHJKLMNOPQRSTUVWXYZ,0123456789ABCDEFGHJKLMNOPQRSTUVWXYZ,0123456789ABCDEFGHJKLMNOPQRSTUVWXYZ,0123456789ABCDEFGHJKLMNOPQRSTUVWXYZ,0123456789ABCDEFGHJKLMNOPQRSTUVWXYZ,0123456789ABCDEFGHJKLMNOPQRSTUVWXYZ";char b[1024];char c[1024];unsigned int i = 0;start = clock();//开始计时for(i=0;i<10*1024;i++)fq_memcpy(c,a,1024);stop = clock();//停止计时computationtime(start,stop,1);start = clock();//开始计时for(i=0;i<10*1024;i++)fq2_memcpy(b,a,1024);stop = clock();//停止计时computationtime(start,stop,1);return 0; }

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