JuliaArrays / JuliaArrays/MappedArrays.jl

Pass more array information

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enhancement
Dominant language
Julia
Stars
88
Forks
15
PR merge metrics
No merged PRs in 30d

Description

Some trivial information queries become time-consuming because currently there's no way to pass this extra information. And it just falls back to apply the function again and again and again and becomes very inefficient.

using TestImages, ImageTransformations
img = testimage("cameraman")

As = mappedarray(θ->imrotate(img, θ, axes(img)), -π/4:π/16:π/4);

@btime size.($As);  # 22.033 ms (136 allocations: 2.26 MiB)
@btime collect($As); # 22.880 ms (127 allocations: 2.26 MiB)

For this very specific case, axes can be known prior.

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the mappedarray API and reproduce the Julia benchmark in the issue, comparing size.($As) with collect($As). Determine how array information could be supplied before mapping; done means the known axes can be reused without repeatedly applying the function for these queries.

Written by the indexing model from the issue text.

Assessment

Tech stack
julia
Domain
data
Issue type
Feature
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
30/100

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