JuliaLang/julia

Make `cumsum(A)` compute a summed-area table

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#26,412 opened on Mar 10, 2018

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 (8 comments) (3 reactions) (0 assignees)Julia (5,773 forks)batch import
arraysgood first issue

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Description

The idea has been discussed in a few places (e.g. https://github.com/JuliaLang/julia/issues/20041#issuecomment-275938676) to make cumsum(A) return a summed-area table for multidimensional arrays.

The 1D case is already a summed-area table, since that's just the cumulative sum along the one dimension.

Happily, the appropriate deprecation for cumsum — deprecating it for AbstractArrays with no dims argument — is already in place, so this is just a tracking issue for the idea.

cc: @simonbyrne

Contributor guide

Research direction
Familiarize with the current cumsum implementation in Julia's base/abstractarray.jl, understand the summed area table algorithm, and modify cumsum to return summed area table for multidimensional arrays when no dims argument is given. Ensure compatibility with existing 1D behavior and follow the deprecation plan.
Tech stack
None
Domain
data
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
JuliaGit
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65