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magistraleinformaticanetworking:spm:exercise1617spm

# SPM 1617 Exercise and assignments

## Matrix multiplication

Write e program that generates two N by N matrixes A and B and computes C, the result of the multiplication of A by B. The computation has to be performed by M threads, each working on a partition of C. Check the correctness of the result against result computed sequentially. Plot scalability curve for the program.

### Hints

• use
int atoi(char *)

to convert the command line arguments to integers


int main(int argc, char * argv[]) {
int n = atoi(argv[1]);
int m = atoi(argv[2]);
...
}
• use the
std::chrono

library to get time before and after the parallel computation and to compute the elapsed time:

  std::chrono::time_point<std::chrono::system_clock> start, end;
start = std::chrono::system_clock::now();
...
end = std::chrono::system_clock::now();
std::chrono::duration<double> elapsed_seconds = end-start;
• use plain
rand

to generate random numbers in the two matrixes:

  srand(123);
for(....) {
... = ((float) (rand() % MAX)) / ((float) RAND_MAX);

# Average neighbours

Write a program that generates an N by N matrix A and then executed a number Niter of iterations where at each iteration A[i][j] is substituted by the average of A[i][j] and the four neighbours (north, south, east and west). At the borders, the missing elements in the neighbourhood have to be assumed to be 0. All the new A[i][j] values must be computed summing up values at the current iteration for the neighbours. Computation of the single iteration should be parallelized using threads.

magistraleinformaticanetworking/spm/exercise1617spm.txt · Ultima modifica: 12/10/2016 alle 15:36 (3 anni fa) da Marco Danelutto