Adding support for components/broadcasting/views with StructArrays of StaticArrays

[jlchan]

Enables both StructArrays.components and broadcasting with StaticArray types. Fixes #179.

[piever]

Thank you for the PR! It mostly looks good, I've added a few nitpicking in the comments.

[jlchan]

added @inline in e982f1a so that Base.view is non-allocating for StructArrays with tuple and StaticArray element types

Improves performance for tuples

julia> x = StructArray((rand(2,2),rand(2,2)));

julia> function Base.view(s::StructArray{T, N, C}, I...) where {T, N, C}
           StructArray{T}(map(v -> view(v, I...), StructArrays.components(s)))
       end

julia> @btime view($x,$:,$1);
  935.464 ns (11 allocations: 416 bytes)

julia> @inline function Base.view(s::StructArray{T, N, C}, I...) where {T, N, C}
           StructArray{T}(map(v -> view(v, I...), StructArrays.components(s)))
       end

julia> @btime view($x,$:,$1);
  3.906 ns (0 allocations: 0 bytes)

Improves performance for StaticArrays

julia> x = StructArray(SVector{2}.(rand(2,2), rand(2,2)));

julia> function Base.view(s::StructArray{T, N, C}, I...) where {T, N, C}
           StructArray{T}(map(v -> view(v, I...), StructArrays.components(s)))
       end

julia> @btime view($x,$:,$1);
  932.808 ns (11 allocations: 416 bytes)

julia> @inline function Base.view(s::StructArray{T, N, C}, I...) where {T, N, C}
           StructArray{T}(map(v -> view(v, I...), StructArrays.components(s)))
       end

julia> @btime view($x,$:,$1);
  4.092 ns (0 allocations: 0 bytes)

Doesn't seem to really impact NamedTuples.

julia> x = StructArray((a=rand(2,2),b=rand(2,2)));

julia> function Base.view(s::StructArray{T, N, C}, I...) where {T, N, C}
           StructArray{T}(map(v -> view(v, I...), StructArrays.components(s)))
       end

julia> @btime view($x,$:,$1);
  201.029 ns (5 allocations: 304 bytes)

julia> @inline function Base.view(s::StructArray{T, N, C}, I...) where {T, N, C}
           StructArray{T}(map(v -> view(v, I...), StructArrays.components(s)))
       end

julia> @btime view($x,$:,$1);
  200.084 ns (5 allocations: 304 bytes)

[piever]

LGTM! I've suggested some minor changes of wording and formatting. If you are happy with those, you can just accept the changes and this should be good to go. I will just wait a little bit before merging because it is a breaking change, so that gives a chance to people relying on the old behavior to look at it.

[jlchan]

Sounds great. Thanks for the guidance throughout this PR!

[piever]

Thanks again for the very nice contribution!

[jlchan]

Thank you for taking the time to review my code and walk me through my first PR!

[jlchan]

@piever do have a timeline for releasing a new version with this PR? We're using the StaticArrays functionality in https://github.com/trixi-framework/Trixi.jl/, but the CI is somewhat involved and is having issues with rev="master".

[piever]

I was hoping to clump more breaking changes (from https://github.com/JuliaArrays/StructArrays.jl/milestone/2) with this one, but I clearly don't have the bandwidth to work on those at the moment. Even though this is the only breaking change, I guess it is not too bad to just tag 0.6 now (the updating should be almost automated for most dependent packages).

[jlchan]

No pressure either way - we can work on the CI on our end too. However, a 0.6 tag would certainly be nice for our CI setup :)

[piever]

In the end, it's probably best to tag now to see if overall users are happy with the new StaticArrays support. I'll just wait a little bit to see if there is an easy solution to JuliaData/WeakRefStrings.jl#72 (to keep supporting julia 1.0), otherwise I'll just require julia 1.3 and tag.

[piever]

@jlchan the 0.6 tag was just merged in the General Registry.

[jlchan]

Thank you! Much appreciated.