It seems that array dimensions is not included in the type definition (which is really reasonable). I was wondering if there was a mechanism in Julia to force method specialisation based on array dimensions.
Typically, the code would be fed with matrices of dimension (n, M) where n can be any number but M is a fixed integer my code is constantly looping over.
I could create my own type (or something similar) but:
Julia is not supporting inheritance and implementing proxy methods myself would be ludicrous (not a fan of introducing boilerplate and checking the Array interface hasn’t changed in each release).
I really don’t want to hardcode things. It would be a bit of a shame to manually create Matrix1D, Matrix2D, Matrix3D, etc. when the JIT can do it itself, especially if it involves manually creating methods with the only difference being the upper range in a single for loop.
The motivation for this is performance: my code involves a lot of looping over 1:M and knowing M from the start allows LLVM to perform more aggressive optimisations.
StaticArrays include the size in their type, so maybe use those? Not that you should not use them for arrays with more than ~ 100 elements. If this does not cut it for you, you could create a wrapper which contains M as type parameter and which is <:AbstractArray.
Wouldn’t it be better for performance to have the columns have a fixed size, instead of the rows? Then the innermost loop would be super fast. A version of this is quite common: to represent a matrix as a vector of StaticArrays.SVector.