a-b-street/abstreet

Optimize scheduler

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#54 opened on Apr 30, 2020

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 (12 comments) (0 reactions) (0 assignees)Rust (256 forks)batch import
good first issue

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Description

Profiling reveals https://github.com/dabreegster/abstreet/blob/master/sim/src/scheduler.rs as a hot spot, which makes sense. Anybody have ideas to speed it up? It's a priority queue with updateable priorities. There are lots of alternatives to std::collections::BinaryHeap, but I think I had trouble finding one that was deterministic (given the same inputs, simulations must run exactly the same).

I squeezed running a huge scenario from 71s to 63s using 7a0b9cd09a96e155a26f3304029d7c3ae753a9dc. I bet there's more possible.

Contributor guide

Research direction
Profile the scheduler to identify specific bottlenecks, then explore alternative priority queue implementations that maintain determinism. Benchmark and compare performance.
Tech stack
rust
Domain
backend
Issue type
Performance
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.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Rustprofiling tools
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50