rust-lang/rust-clippy

lint long chains of into/float additions/multiplications

Open

#1,243 opened on Sep 25, 2016

View on GitHub
 (13 comments) (0 reactions) (0 assignees)Rust (10,406 stars) (1,391 forks)batch import
A-lintL-perfT-ASTgood first issue

Description

In generall, (a+b+c)+(d+e+f) is faster to compute than a+b+c+d+e+f, because the former reduces data dependencies, allowing the CPU to run additions in parallel. For float arithmetic, the tree-like addition may improve numerical stability. Suggest inserting parenthesis.

Contributor guide

Tech stack
rust
Domain
toolingdeveloper experience
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
Rust programmingclippy internals
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20
Research direction
This issue requests a new lint to suggest inserting parentheses in long chains of float additions/multiplications to improve performance and numerical stability. The implementation would require analyzing the AST for binary operation chains in clippy lints/src/. The discussion in the thread includes some ideas but no concrete design. The issue is stale and may need maintainer input to refine scope and acceptance criteria.