Best way to allocate memory to a two-dimensional array in C?

Question

What is the best way to allocate memory to a two-d array in C,from both the perspectives : memory-management and speed ?

Answer 1

data_type (*mat)[size_2] = malloc(size_1 * size_2 * sizeof(data_type));

That will allocate contiguous memory for an array of arrays ("2d array"). If you don't require ridiculous¹ amounts of space, this is the way to go. You'll decrease memory fragmentation, increase cache friendliness and avoid too much overhead due to the use of malloc.

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¹ _{For some (application specific) definition of ridiculous}