Rules

1. Submit the answers to Gradescope.

2. You may do homeworks in teams of 2 students. Create a gradescope team and make one submission with both names.

Question

1. The goal is to measure whether OpenMP actually makes matrix multiplication faster, with and w/o SIMD.

2. You may use anything in /parallel-class/openmp that seems useful.

3. Write a C++ program on parallel.ecse to initialize pseudorandomly and multiply two 100x100 float matrices. One possible initialization:

   a[i][j] = i*3 + (j*j)%5; b[i][j] = i*2 + (j*j)%7;

4. (10 points) Report the elapsed time. Include the program listing.

5. Add an OpenMP pragma to do the work in parallel.

6. (10 points) Report the elapsed time, varying the number of threads thus: 1, 2, 4, 8, 16, 32, 64.

   What do you conclude?

7. (5 points) Repeat that two more times to see how consistent the times are.

8. (10 points) Modify the pragma to use SIMD.

   Report the elapsed time, varying the number of threads thus: 1, 2, 4, 8, 16, 32, 64.

   What do you conclude?

9. (10 points) Compile and run your program with two different levels of compiler optimization: O1 and O3, reporting the elapsed time. Modify your program to prevent the optimizer from optimizing the program away to nothing. E.g., print a few values.

10. (5 points) What do you conclude about everything?

Total: 40 pts.