Interoperability of indexing-based SIMD interface

[tkf]

In my small sparse array package https://github.com/tkf/SparseXX.jl, I want to use indexing-based SIMD interface with different "non-standard" arrays like the ones from MappedArrays.jl and FillArrays.jl. It may even make sense to support SIMD-indexing Broadcasted object so that it works with LazyArrays.jl. At first, I was rather hoping that I can do it by some duck typing so that array libraries do not need to know about SIMD.jl. However, as pointed out by @timholy and @mbauman in JuliaArrays/MappedArrays.jl#24, it looks we need some code importing both SIMD.jl and the array libraries and define getindex etc. that are aware of those libraries.

The question is who distribute/maintain the code. As I'm the only one using this feature now, I think it's probably better if I create a package that does it (here is the proof-of-concept: https://github.com/tkf/SIMDIndexing.jl). But then it becomes technically a type piracy since I don't "own" those types or functions. So, I thought it's better to get the "permission" of doing the type piracy in a friendly fashion.

Of course, if you want to add the code in SIMD.jl by including the array packages as "soft" dependencies using @require, I will happily create a PR.

cc: @dlfivefifty, as you seems to be maintaining FillArrays.jl

[dlfivefifty]

SIMD.jl is a very lightweight package, why not just have FillArrays.jl depend on SIMD.jl?

[timholy]

16 exports and almost 2k LOC isn't lightweight compared to some AbstractArray types. For example, PaddedViews is roughly 10% of the size of SIMD.

[dlfivefifty]

I meant lightweight in terms of it has no dependencies.

[tkf]

FillArrays.jl depend on SIMD.jl?

Yes, this is a possible solution. But that's O(N) work for me where N = the number of array package authors because I have to keep convincing them to have SIMD.jl as a dependency or to use Requires.jl. In practice N is probably 2 (= #{@timholy, @dlfivefifty}) but the possibility that N may grow makes me not wanting to go to this direction...