Challenges for arrays of arrays?

[jlchan]

When trying to create a component array made of up (for example, two StructArrays with entries which are SVector), I get the following error:ComponentArrays cannot currently contain arrays of arrays as elements. Are there specific challenges to support for arrays of arrays that I could take a look at?

I am trying to create a linearly indexed array u for use in OrdinaryDiffEq.jl where I can access the individual fields u.field_1,u.field_2.

[jonniedie]

You can do:

u = ComponentArray(field_1 = rand(5), field_2 = rand(5))
u.field_1
u.field_2

or even do something more StructArray-like:

a_b =  [(a=rand(), b=rand()) for _ in 1:100]
u = ComponentArray(fields = a_b)
u.fields[1].a  # returns the `a` field of the first element of `fields`
u.fields.a     # returns an array of the `a` elements of `fields` (like a `StructArray` would)

The only thing you can't do is something like:

u = ComponentArray(fields = [rand(5), rand(5)])
u.fields[1]
u.fields[2]

It's probably possible to support the third version, I just haven't implemented it because the first two versions tend to cover most use cases.

[jonniedie]

ComponentArrays can also have nested structure in the StructArray form:

abc = [(a=rand(), b=rand(), c=(a=rand(), b=rand())) for _ in 1:100]
u = ComponentArray(fields = abc)
u.fields.c.a    # Returns a vector of the `.c.a` properties of all `u.fields`

[jlchan]

Those are nice to know about!

My use case is that I have two existing StructArrays that I wanted to combine and label using ComponentArrays. I think I can use the workarounds you described for most of my use cases. thanks!