JuliaLang/julia

objectid takes arbitrarily long

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#43,542 opened on Dec 24, 2021

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Description

In the following code, I construct a large deeply nested DAG and then call objectid on the root node. I'm expecting this to be instant, but instead the call to objectid takes time proportional to the size of the data structure. With the size 100 used below it probably won't return ever.

struct Foo
  x::Any
  y::Any
end
function test()
  foo = Foo(nothing, nothing)
  for i in 1:100
    foo = Foo(foo, foo)
  end
  println(1)
  println(objectid(foo))
  println(2)
end
test()

Version info:

julia> versioninfo()
Julia Version 1.7.0
Commit 3bf9d17731 (2021-11-30 12:12 UTC)
Platform Info:
  OS: Linux (x86_64-pc-linux-gnu)
  CPU: Intel(R) Core(TM) i5-5300U CPU @ 2.30GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-12.0.1 (ORCJIT, broadwell)

Contributor guide

Research direction
Examine the implementation of `objectid` for mutable composite types to see if it unnecessarily traverses sub objects, and consider adding a depth limit or using object identity directly.
Tech stack
julia
Domain
compilersperformance
Issue type
Bug
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.
Half day
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
Julia
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
55