use StructArrays.jl

[MasonProtter]

Your currently just have

aos_to_soa(x) = x

I feel like it might be worth it to just add a dependancy on StructArrays.jl, which imo should really be a baked in part of Julia's array interface.

[ChrisRackauckas]

Does that work with Tracker?

[MasonProtter]

Hm, no it appears to not work with it at least out of the box:

julia> using Tracker

julia> v = rand(10) |> param
Tracked 10-element Array{Float64,1}:
 0.19747042290556305
 0.3577805915969372
 0.41164333584420354
 0.07956973618070462
 0.3882813140794923
 0.030429901869670095
 0.13329838162061325
 0.3263069803112133
 0.32484677886198
 0.37871805455668994

julia> using StructArrays

julia> StructArray(v)
0-element StructArray() with eltype Float64 with indices 1:0

I wonder if we just need to pirate in the right constructor though. I don't really know anything about Tracker.

Alternatively, we could just define the default to be aos_to_soa(x) = StructArray(x) and then use some custom implementation that doesn't use StructArray for Tracker.

I don't have any stakes in this, just a random thought, so feel free to ignore if this isn't the direction you're interested.

[ChrisRackauckas]

Yeah maybe it's a better default than doing nothing. But I'd like to keep this pretty much dependency free. StructArrays seems to leak to some weird data stuff...