RoaringBitmap / RoaringBitmap/roaring-rs

Optimization: Galloping Array-Array operations

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Dominant language
Rust
Stars
957
Forks
119
Avg merge
3d 3h
Merged PRs (30d)
1

Description

Most of the Array-Array operations use a two pointer walk. I think there may be gains to be had from "galloping" while merging.

To my knowledge this is a novel optimization. CRoaring vectorized Array-Array intersection is galloping (according to the paper) however AFAICT none of the scalar Array-Array ops perform galloping.

Links
https://en.wikipedia.org/wiki/Timsort#Galloping_mode_during_merge
http://hg.openjdk.java.net/jdk8/jdk8/jdk/file/687fd7c7986d/src/share/classes/java/util/TimSort.java#l701

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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 by locating the scalar Array-Array operations that currently use a two-pointer walk. Read the linked Timsort and CRoaring references to understand galloping during merges, then determine which operations could benefit and how to measure the change. Done means a validated optimization with evidence that it improves the relevant operations without changing their results.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
performance
Issue type
Refactor
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
25/100

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