Exercise 5

Exercise 5

Distribute a global square NxN matrix (with N fixed) over P processors, so that each task has a local portion of it in its memory. Initialize such portion with the task's rank.
NOTE: the exercise does not state that P has to be a divisor of N. How to deal with the matrix distribution if the number of rows/columns isn't the same for all tasks?

Each task sends its first and last columns (if Fortran) or rows (if C) to its neighbours (i.e.: the first column/row to the left processor, the last column/row to the right processor). Note that each task has to actually allocate a larger portion of its submatrix (ghost cells), with two extra columns/rows at the extremities to hold the received values.