Hello! I think this should be fairly simple, suppose I have: b = collect(1:999) Where x,y, and z are given as: x = b[1:3:end] y = b[2:3:end] z = b[3:3:end] How would I then convert / parse this into a Vector of StaticArrays with 333 elements? Is there a simple way to do it without for loops? K…

You can try using reinterpret if you want to avoid allocations: reinterpret(SVector{3, eltype(b)}, b)

Are you looking for something like this? [b[3*(i-1)+1:3i] for i = 1:333] You can use StaticArrays if you want. I would suspect if this for loop can be avoided.

[image] vavrines: [b[3*(i-1)+1:3i] for i = 1:333] Yep, that does what I want and is a one liner. I did a small benchmark using BenchmarkTools: @btime [b[3*(i-1)+1:3i] for i = 1:333] 16.299 μs (669 allocations: 49.64 KiB) And just for fun reshape @btime reshape(b,(333,3)) 52.990 ns (2 a…

That worked too, giving this performance: @btime reinterpret(SVector{3, eltype(b)}, b) 936.667 ns (10 allocations: 608 bytes) So a lot better. Do you know though if the type of the reinterpret could become a “headache”? Now it is given as: Base.ReinterpretArray{SArray{Tuple{3},Int64,1,3},1,Int…

Your benchmark results are skewed due to the fact that b is a non-const global variable (see Manual · BenchmarkTools.jl ). If you fix that, you’ll get more realistic results: julia> b = collect(1:999); julia> f_comprehension(b) = [b[3*(i-1)+1:3i] for i = 1:333] f_comprehension (generic function wi…

I see thanks, marked reinterpret as the answer :slight_smile: And thanks for the hints regarding using AbstractArrays etc., I did not think of that usually I would define numeric type too. Kind regards

[image] Ahmed_Salih: Seems like this is the best approach though, other than the return type or am I overthinking? It is just ugly :slight_smile: But apparently there is no “solution” to the aesthetic problem. [image] Simplify type information when reinterpreting/reshaping G…

I would like to add, because I just faced this, that for the reinterpretation of a 2D array to a vector of static vectors to actually work in function accepting AbstractVectors, one need to add a vec to the conversion: julia> f(x::AbstractVector{<:AbstractVector}) = "this is a vector of vectors" f …

What is the purpose of the ‘ugly’ type signatures for reshape and ‘reinterpret’? Is there any difference in layout between [image] Ahmed_Salih: Base.ReinterpretArray{SArray{Tuple{3},Int64,1,3},1,Int64,Array{Int64,1}} and Array{SVector{3, Int64},1}? I thought that the only thing that reshape …

[image] lmiq: y = vec(reinterpret(SVector{3,Float64},x)) Is that better than: x = rand(3,5) y = SVector{5}(reinterpret(SVector{3,Float64},x)) ?

In my MWE I didn’t mean to imply that 5 was typical (small) dimension. Usually I’m talking about particle simulations, and this dimension is on the tenths-of-thousands. So making that a static array is not possible.

Convert 1D Array to 1D Array of StaticArrays?

General Usage

lmiq September 3, 2021, 7:33pm 8

It is just ugly But apparently there is no “solution” to the aesthetic problem.

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Convert 1D Array to 1D Array of StaticArrays?

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