JuliaArrays / JuliaArrays/AxisArrays.jl
Axes are copied when taking a view
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- Dominant language
- Julia
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Description
Having looked at the source code it is clear that when taking a view of an AxisArray, the indexed axes might be copied if _new_axes is called (https://github.com/JuliaArrays/AxisArrays.jl/blob/master/src/indexing.jl#L80). Is this the intended behaviour? It would make more sense to me for views to be taken of the original axes as well, to aid performance.
Example below (there is 16KB of allocation - i.e. the index copy)
using Dates
using AxisArrays
using BenchmarkTools
index = collect(DateTime(2018, 1, 1):Minute(1):DateTime(2018, 1, 10))
B = AxisArray(randn(Float64, (length(index), 10)), index)
@btime view(B, 1000:3000, :)
# 994.800 ns (6 allocations: 15.98 KiB)
If this should be fixed / changed, I'm happy to give a PR a go.
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First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start with src/indexing.jl around line 80 and reproduce the allocation shown in the issue using the DateTime AxisArray example. Determine whether view should preserve the original axes, then verify the intended behavior and allocation impact with the provided BenchmarkTools expression.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- julia
- Domain
- data
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100