(In practice the cache architecture is now quite complicated with as many as 3 or 4 levels of cache memory, but the basic idea can be explained with a one-level cache of the sort that computers had in my younger days.) These chunks of data are temporarily stored in a fast memory cache and written back out as needed. The second important thing that you need to understand is that modern processors don't access memory one location at a time, but rather load and store "cache lines" of 64 or even 128 contiguous bytes (8 or 16 double precision floating point numbers) at a time from memory. This choice of column major order is arbitrary- we could just easily adopt a "row major order" convention, and in fact that's what is done in C and some other programming languages. if A is a 2 by 3 by 10 matrix, then the entries will be stored in memory in the order
There are two key things that you need to understand.įirst, MATLAB (and Fortran, but not C and most other programming languages) stores arrays in memory in "column major order." e.g. A somewhat longer answer that explains why it's more efficient to have the left most index varying most rapidly.
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