Fix answer checker

[royderegt]

Hi,
I ran into the following while working with the notebook matrix_matrix.ipynb:

a) O(N²) communication and O(N³) computation
b) O(N²) communication and O(N³/P) computation
c) O(N²) communication and O(N²) computation
d) O(N²/P) communication and O(N³/P) computation

Where D is marked as the correct answer. As far as I'm concerned, B is the correct answer as the communication complexity is in O(N²).

Both the slides and the table below the question say that the communication overhead is N² + 2N²/P, which makes N² the dominant factor.

[fverdugo]

Hi @royderegt,

Thanks for noticing this.

Yes, communication cost is N^2 for algorithm 3 in the matrix-matrix product notebook.