Loading FixedPointNumbers invalidates ~7,700 precompiled method instances (7x slower first mtkcompile)
还没有人认领这个 Issue。
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- 难度
- 5/5
- 预计耗时
- 一周以上
- 新手友好度
- 42/100
- Issue 类型
- 缺陷
- 描述清晰度
- 基本清楚
- 活跃度
- 活跃
- 技术栈
- julia
- 领域
- performance
调研方向
先从 mwe.jl 和 SnoopCompile 的 invalidation 测量开始，然后检查 src/fixed.jl、src/normed.jl 和 src/FixedPointNumbers.jl 中列出的方法。根据 7,708 次 invalidation 和 mtkcompile 计时，对比更窄的签名或其他更改，同时检查 FixedPointNumbers 的行为是否仍然正确；完成的标准是在没有回归的情况下减少加载影响。
由索引模型根据 Issue 内容生成。
描述
Summary
Loading FixedPointNumbers into a session that already has ModelingToolkit loaded invalidates
7,708 precompiled method instances and makes the first mtkcompile call take 23.59 s
instead of 0.04 s — a huge slowdown in a script that never uses a fixed-point number.
Most users meet this indirectly: ColorTypes/Colors depend on FixedPointNumbers, so any
Makie-based plotting next to ModelingToolkit pays this cost on the first model build.
MWE
# mwe.jl
using ModelingToolkit
using ModelingToolkit: t_nounits as t, D_nounits as D
if get(ENV, "LOAD_FPN", "0") == "1"
@eval using FixedPointNumbers # <-- the only difference
end
@variables x(t)=1.0 y(t)=0.0
@named sys = System([D(x) ~ y, D(y) ~ -x], t)
t0 = time(); mtkcompile(sys); println("mtkcompile: ", round(time()-t0, digits=2), " s")
(test) pkg> st
Status `~/test/Project.toml`
[53c48c17] FixedPointNumbers v0.9.1
[961ee093] ModelingToolkit v11.41.0
$ julia --startup-file=no --project=. mwe.jl
mtkcompile: 0,04 s
$ LOAD_FPN=1 julia --startup-file=no --project=. mwe.jl
mtkcompile: 23.59 s
As a control, loading a package of comparable size that does not add methods to Base
generics (using LaTeXStrings) leaves the time unchanged at 0.04 s, so this is not the
general cost of loading a package.
Attribution
using SnoopCompileCore
using ModelingToolkit
invs = @snoop_invalidations using FixedPointNumbers;
using SnoopCompile
length(uinvalidated(invs)) # 7708, from 15 culprit methods
Ranked by countchildren:
| children | method |
|---|---|
| 14312 | promote_rule(::Type{Fixed{T1,f1}}, ::Type{Fixed{T2,f2}}) where {T1,T2,f1,f2} — src/fixed.jl:199 |
| 3556 | length(r::AbstractUnitRange{N}) where {T<:Unsigned, N<:Normed{T}} — src/normed.jl:304 |
| 3089 | ceil(::Type{Ti}, x::Normed) where Ti<:Integer — src/normed.jl:277 |
| 1668 | showarg(io::IO, a::Array{T}, toplevel) where T<:FixedPoint — src/FixedPointNumbers.jl:279 |
| 403 | reduce_first(::typeof(Base.add_sum), x::FixedPoint) — src/FixedPointNumbers.jl:296 |
| 109 | -(x::X) where X<:FixedPoint — src/FixedPointNumbers.jl:233 |
None of these are type piracy — every one is dispatching on a FixedPointNumbers type. The
cost seems to come from adding methods to widely-inferred Base generics (promote_rule,
length, ceil, convert), which discards inference results in already-loaded packages
that call those generics on non-concrete argument types.
Question
Is there room to narrow any of these signatures, or is this something that has to be fixed
on the consuming side (or in Base)? I am mostly filing this for the record, since the
measured impact is large and I could not find an existing issue about it. Happy to run
further measurements if that helps.
Versions
Julia 1.12.7 (Linux, x86_64), FixedPointNumbers 0.8.6, ModelingToolkit 11.17.0,
SnoopCompile 3.2.9.
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环境准备
从这里开始
- 先读完整个 Issue，再读项目的贡献指南。
- 在 Issue 下留言说明你要接手 —— 这能避免两个人做同样的事。
- Fork 仓库，在一个分支上完成修改。
- 提交 Pull Request，并在描述里引用这个 Issue 编号。
JuliaMath/FixedPointNumbers.jl 的其他 Issue
-
难度 2/5 1-3 小时 新手友好度 76/100
JuliaMath/FixedPointNumbers.jl#310 · 1 条评论 ·
-
难度 4/5 3-5 天 新手友好度 35/100
-
needs comments
难度 3/5 1-2 天 新手友好度 68/100
JuliaMath/FixedPointNumbers.jl#318 · 1 条评论 ·
-
add-on enhancement
难度 5/5 一周以上 新手友好度 35/100
JuliaMath/FixedPointNumbers.jl#311 · 4 条评论 ·
-
难度 4/5 3-5 天 新手友好度 35/100
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