``` Step1 All time:226.000000 Step2 All time:73.000000 Step4 All time:39.000000 Step8 All time:25.000000 Step16 All time:23.000000 Step20 All time:21.000000 Step32 All time:23.000000 Step40 All time:23.000000 Step64 All time:13.000000 Step128 All time:7.000000 ``` ``` #include <stdio.h> #include <stdlib.h> #include <time.h> //引入时间统计 clock_t start, end; double n; //统计各个步骤的时间 int main() { int len = 64*1024*1024; int *a; a = (int *)malloc(len*sizeof(int)); int i,j; start=clock(); //开始统计时间 // Loop 1 for(i=0; i<len; i++) { a[i] *= 3; } end=clock(); //结束统计时间 n = difftime(end,start); printf("Step%d All time:%f\n",1, n); start=clock(); //开始统计时间 // Loop 1 for(i=0; i<len; i+=2) { a[i] *= 3; } end=clock(); //结束统计时间 n = difftime(end,start); printf("Step%d All time:%f\n",2, n); start=clock(); //开始统计时间 // Loop 1 for(i=0; i<len; i+=4) { a[i] *= 3; } end=clock(); //结束统计时间 n = difftime(end,start); printf("Step%d All time:%f\n",4, n); start=clock(); //开始统计时间 // Loop 1 for(i=0; i<len; i+=8) { a[i] *= 3; } end=clock(); //结束统计时间 n = difftime(end,start); printf("Step%d All time:%f\n",8, n); start=clock(); //开始统计时间 // Loop 1 for(i=0; i<len; i+=16) { a[i] *= 3; } end=clock(); //结束统计时间 n = difftime(end,start); printf("Step%d All time:%f\n",16, n); start=clock(); //开始统计时间 // Loop 1 for(i=0; i<len; i+=20) { a[i] *= 3; } end=clock(); //结束统计时间 n = difftime(end,start); printf("Step%d All time:%f\n",20, n); start=clock(); //开始统计时间 // Loop 1 for(i=0; i<len; i+=32) { a[i] *= 3; } end=clock(); //结束统计时间 n = difftime(end,start); printf("Step%d All time:%f\n",32, n); start=clock(); //开始统计时间 // Loop 1 for(i=0; i<len; i+=40) { a[i] *= 3; } end=clock(); //结束统计时间 n = difftime(end,start); printf("Step%d All time:%f\n",40, n); start=clock(); //开始统计时间 // Loop 1 for(i=0; i<len; i+=64) { a[i] *= 3; } end=clock(); //结束统计时间 n = difftime(end,start); printf("Step%d All time:%f\n",64, n); start=clock(); //开始统计时间 // Loop 1 for(i=0; i<len; i+=128) { a[i] *= 3; } end=clock(); //结束统计时间 n = difftime(end,start); printf("Step%d All time:%f\n",128, n); return 0; } ```