nvim-treesitter / nvim-treesitter/nvim-treesitter-textobjects

The `move` function is very slow on some large cpp files

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#560 2 comments 0 reactions 0 assignees View on GitHub

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bug
Dominant language
Tree-sitter Query
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Forks
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Avg merge
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Merged PRs (30d)
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Description

Describe the bug
The move function is very slow on some large cpp files. Not sure if it's a bug, but it should be an optimization option.

To Reproduce
Steps to reproduce the behavior:

  1. Prepare a large cpp file. In my case it's a file of over 1k lines
  2. call goto_* function

Output of :checkhealth nvim-treesitter

nvim-treesitter: require("nvim-treesitter.health").check()

Installation ~

  • WARNING tree-sitter executable not found (parser generator, only needed for :TSInstallFromGrammar, not required for :TSInstall)
  • OK node found v20.11.0 (only needed for :TSInstallFromGrammar)
  • OK git executable found.
  • OK cc executable found. Selected from { vim.NIL, "cc", "gcc", "clang", "cl", "zig" }
    Version: cc (Ubuntu 11.4.0-1ubuntu1~22.04) 11.4.0
  • OK Neovim was compiled with tree-sitter runtime ABI version 14 (required >=13). Parsers must be compatible with runtime ABI.

OS Info:
{
machine = "x86_64",
release = "5.15.133.1-microsoft-standard-WSL2",
sysname = "Linux",
version = "#1 SMP Thu Oct 5 21:02:42 UTC 2023"
} ~

Parser/Features H L F I J

  • bash ✓ ✓ ✓ . ✓
  • c ✓ ✓ ✓ ✓ ✓
  • cmake ✓ . ✓ ✓ .
  • cpp ✓ ✓ ✓ ✓ ✓
  • json ✓ ✓ ✓ ✓ .
  • lua ✓ ✓ ✓ ✓ ✓
  • markdown ✓ . ✓ ✓ ✓
  • markdown_inline ✓ . . . ✓
  • python ✓ ✓ ✓ ✓ ✓
  • query ✓ ✓ ✓ ✓ ✓
  • regex ✓ . . . .
  • sql ✓ . . ✓ ✓
  • vim ✓ ✓ ✓ . ✓
  • vimdoc ✓ . . . ✓

Legend: H[ighlight], L[ocals], F[olds], I[ndents], In[j]ections
+) multiple parsers found, only one will be used
x) errors found in the query, try to run :TSUpdate {lang} ~

Paste the output here

Output of nvim --version

NVIM v0.10.0-dev
Build type: RelWithDebInfo
LuaJIT 2.1.0-beta3

Additional context

Below is the result captured by the profiler, you can see that a single query takes close to 3s, which makes neovim appear unresponsive for 3s.

1707037303769

After more digging, I found that nvim-treesitter.query.find_best_match loops at least 2w+ times per execution, which I think may be the culprit for this issue.

Contributor guide

Open the contributing guide

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 profiler result and inspect nvim-treesitter.query.find_best_match, which the issue identifies as looping at least 2w+ times per execution. Reproduce the delay by calling a goto_* function on a large C++ file, then verify that the query no longer makes Neovim unresponsive for several seconds.

Written by the indexing model from the issue text.

Assessment

Tech stack
cpp, lua
Domain
devtools, performance
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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