>>105513212
>That's a problem with the C flat memory model
that's an issue with every single language, including matlab which is allegedly better at handling arbitrary dimension arrays
>It's trivial to optimize on 2D arrrays on languages that actually support them properly, like fortran and go.
never said it was "hard" to solve, just that basic loop unrolling is out of the equation if your function is doing a lot of things and compilers are incapable of deducing the best memory layout based on what you want to do.
basic example are kernels for 2d operations on matrices (images), if you do operations on multiple column and row at the same times then you'll jump all the over the place in memory for each iteration, that's incredibly slow, as far as I know no language has a compiler with good enough heuristics to deduce this by itself, you need to set the data structures and the right loop index yourself but then you usually lose the autovectorization so you'll also have to do it yourself.
there is a reason ffmpeg or vlc are using assembly because every fucking algorithm is of at the very least quadratic complexity so data layout actually matters, A LOT
>>105513240
if you access your element sequentially then yes, if you don't then it's more complex than that.
>>105513243
>I don't know why but the compiler sucks at automatic vectorization.
it all comes down to "context", compilers aren't very good at understanding what you're trying to do, what C and C++ are really lacking is user-made attributes, I want the ability to tell the compiler to unroll the loop 4 by 4 or to shape my 2d static (it's already doable for heap-allocated arrays with a custom allocator) array into various memory configurations (one big array, row-major, split into sub-arrays of smaller size, etc)
this has to change in the era of llm, if these things can understand my broken english and generate code that containt the right micro-optimizations then compilers should be able to do it too.

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