Answer:
Check the explanation
Explanation:
#include <iostream> #include <chrono> using namespace std::chrono; using namespace std; struct X{ int a,b,c,d,e,f,g,h; }; int main(){ // 3D Array of integers 1000 x 1000 x 1000 int data1[10][10][10]; //Array of struct X struct X data2[10000] ; auto start = high_resolution_clock::now(); //stride 1 access data 1 Loop order 1: for(int i=0;i<1000;i++){ for(int j=0;j<1000;j++){ for(int k=0;k<1000;k++){ data1[i][j][k]; } } } auto stop = high_resolution_clock::now(); auto duration = duration_cast<microseconds>(stop - start); cout<<"3D array Stride 1 Loop Order 1"<<duration.count()<<endl; start = high_resolution_clock::now(); //stride 2 access data 1 Loop order 1: for(int i=0;i<1000;i+=2){ for(int j=0;j<1000;j+=2){ for(int k=0;k<1000;k+=2){ data1[i][j][k]; } } } stop = high_resolution_clock::now(); duration = duration_cast<microseconds>(stop - start); cout<<"3D array Stride 2 Loop Order 1"<<duration.count()<<endl; start = high_resolution_clock::now(); //stride 1 access data 1 Loop order 2: for(int i=0;i<1000;i++){ for(int j=0;j<1000;j++){ for(int k=0;k<1000;k++){ data1[j][i][k]; } } } stop = high_resolution_clock::now(); duration = duration_cast<microseconds>(stop - start); cout<<"3D array Stride 1 Loop Order 2"<<duration.count()<<endl; start = high_resolution_clock::now(); for(int i=0;i<10000;i++){ data2[i]; } stop = high_resolution_clock::now(); duration = duration_cast<microseconds>(stop - start); cout<<"Struct Array "<<duration.count()<<endl; }
Some Observations on the order:
<em><u>Stride 1 goes over all the elements of the array Hence takes more time than stride 2 which goes over alternate elements. </u></em>
<em><u>Loop order in the row major form takes leads time than column major form! </u></em>
<em><u>Struct array takes no time to execute because the structs are not being accessed.</u></em>
Check the code screenshot and code output in the attached image below.
