When the article mentioned “more efficient”, I was expecting some actual measurements.
Instead, it seems to just assert that allocating (dense) matrices in a big block is better than the usual array of pointers that you would get in older C/C++.
FWIW it definitely is and that's why you'd really probably just get a function or macro converting coordinates into a single-dimension offset in older C/C++.
It depends on hardware but I've seen improvements of 100 times faster. There's data available for a number of examples if you search.
Instead, it seems to just assert that allocating (dense) matrices in a big block is better than the usual array of pointers that you would get in older C/C++.