# \#jet

**URL:** https://discourse.julialang.org/tag/jet/769.md

[Latest](https://discourse.julialang.org/latest.md) · [Categories](https://discourse.julialang.org/categories.md) · [Tags](https://discourse.julialang.org/tags.md)

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## [\[ANN\] DependencyAtlas.jl—Explore Julia codebases as dependency graphs](https://discourse.julialang.org/t/ann-dependencyatlas-jl-explore-julia-codebases-as-dependency-graphs/136317)

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**Author:** [@karei](https://discourse.julialang.org/u/karei)\
**Replies:** 12\
**Last updated:** [May 7, 2026, 10:39am UTC](https://discourse.julialang.org/t/ann-dependencyatlas-jl-explore-julia-codebases-as-dependency-graphs/136317 "2026-05-07T10:39:26Z")

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I’m happy to share DependencyAtlas.jl, a software package for turning Julia codebases into explorable dependency graphs. DependencyAtlas focuses on static and compiler-time source analysis. It builds graph views from th…

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## [JETLS warnings](https://discourse.julialang.org/t/jetls-warnings/134700)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 2\
**Last updated:** [December 23, 2025, 5:55am UTC](https://discourse.julialang.org/t/jetls-warnings/134700 "2025-12-23T05:55:35Z")

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I have the following code: local pos\_B, pos\_C, pos\_D for i in 1:4 particle=particles\[i\] x, y, z = particle\[1\], particle\[2\], particle\[3\] if i==2 pos\_B = SVector(x,y,z) …

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## [\[ANN\] JET v0.11](https://discourse.julialang.org/t/ann-jet-v0-11/133366)

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**Author:** [@aviatesk](https://discourse.julialang.org/u/aviatesk)\
**Replies:** 0\
**Last updated:** [October 22, 2025, 6:30pm UTC](https://discourse.julialang.org/t/ann-jet-v0-11/133366 "2025-10-22T18:30:06Z")

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Hi everyone, Today, I’d like to introduce the new version of JET, v0.11. In JET v0.11.0, the implementation of report\_package has been revamped and switched to a Revise-based implementation. This allows it to work reli…

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## [JET: How to use the function\_filter argument?](https://discourse.julialang.org/t/jet-how-to-use-the-function-filter-argument/122470)

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**Author:** [@matthias314](https://discourse.julialang.org/u/matthias314)\
**Replies:** 1\
**Last updated:** [September 10, 2025, 2:19pm UTC](https://discourse.julialang.org/t/jet-how-to-use-the-function-filter-argument/122470 "2025-09-10T14:19:34Z")

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I’m trying to get the function\_filter argument to the JET macro @report\_opt to work, without success. I guess I’m missing something. Here is an example: f(x::T) where T = x \> 0 ? 1 : error("illegal argument of type $T")…

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## [What to do when packages fail PkgEval because of JET?](https://discourse.julialang.org/t/what-to-do-when-packages-fail-pkgeval-because-of-jet/123525)

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**Author:** [@gdalle](https://discourse.julialang.org/u/gdalle)\
**Replies:** 15\
**Last updated:** [April 16, 2025, 5:23am UTC](https://discourse.julialang.org/t/what-to-do-when-packages-fail-pkgeval-because-of-jet/123525 "2025-04-16T05:23:50Z")

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I love JET.jl. It’s really useful to detect typos, type instabilities and other issues with my code. Unfortunately, it is deeply tied to Julia internals, which means that it often breaks on the nightly version of the lan…

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## [Runtime dispatch for plan\_fft](https://discourse.julialang.org/t/runtime-dispatch-for-plan-fft/126958)

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**Author:** [@henry2004y](https://discourse.julialang.org/u/henry2004y)\
**Replies:** 1\
**Last updated:** [March 14, 2025, 5:24pm UTC](https://discourse.julialang.org/t/runtime-dispatch-for-plan-fft/126958 "2025-03-14T17:24:10Z")

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Hi, I am learning about JET.jl while optimizing a function that involves FFT. I happened to find that JET.jl detected a runtime dispatch for plan\_fft or plan\_fft!: using JET using FFTW julia\> @report\_opt plan\_fft!(zer…

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## [Isolating a test case from JET.@report\_opt](https://discourse.julialang.org/t/isolating-a-test-case-from-jet-report-opt/125018)

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**Author:** [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Replies:** 0\
**Last updated:** [January 21, 2025, 1:38pm UTC](https://discourse.julialang.org/t/isolating-a-test-case-from-jet-report-opt/125018 "2025-01-21T13:38:35Z")

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I am trying to find a type instability using JET.jl. The top-level code is inferred, but JET.@report\_opt reports a couple of instabilities that do not appear to affect the final type, yet cause allocations and runtime di…

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## [Testing type stability across Julia and JET versions](https://discourse.julialang.org/t/testing-type-stability-across-julia-and-jet-versions/116289)

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**Author:** [@gdalle](https://discourse.julialang.org/u/gdalle)\
**Replies:** 7\
**Last updated:** [December 22, 2024, 1:24am UTC](https://discourse.julialang.org/t/testing-type-stability-across-julia-and-jet-versions/116289 "2024-12-22T01:24:36Z")

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In my package DifferentiationInterface.jl, the test suite includes type-stability checks for some differentiation operators. I perform these checks with JET.jl and the @test\_opt macro, which actually verifies a stronger …

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## [Type-instability of mapreduce vs. map + reduce](https://discourse.julialang.org/t/type-instability-of-mapreduce-vs-map-reduce/121136)

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**Author:** [@gdalle](https://discourse.julialang.org/u/gdalle)\
**Replies:** 18\
**Last updated:** [October 10, 2024, 4:43pm UTC](https://discourse.julialang.org/t/type-instability-of-mapreduce-vs-map-reduce/121136 "2024-10-10T16:43:03Z")

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I’m a bit surprised that in this simple example, f is type-stable but g is not. Is this a JET.jl issue (@aviatesk) or a Julia issue? using JET function f(m, n) blocks = map(1:n) do i ones(m) end ret…

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## [Different test results of @test\_opt inside and outside the @testitem block](https://discourse.julialang.org/t/different-test-results-of-test-opt-inside-and-outside-the-testitem-block/119564)

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**Author:** [@aaoo](https://discourse.julialang.org/u/aaoo)\
**Replies:** 0\
**Last updated:** [September 18, 2024, 4:45pm UTC](https://discourse.julialang.org/t/different-test-results-of-test-opt-inside-and-outside-the-testitem-block/119564 "2024-09-18T16:45:58Z")

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I found that when the function contains @warn, the testing results of @test\_opt inside the @testitem block differ from those outside, i.e. in the REPL. Please see the code below. Could someone explain why this happens …

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## [RFC: @jet\_ignore to let JET.jl ignore specific functions](https://discourse.julialang.org/t/rfc-jet-ignore-to-let-jet-jl-ignore-specific-functions/119258)

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**Author:** [@nielsls](https://discourse.julialang.org/u/nielsls)\
**Replies:** 0\
**Last updated:** [September 10, 2024, 7:45pm UTC](https://discourse.julialang.org/t/rfc-jet-ignore-to-let-jet-jl-ignore-specific-functions/119258 "2024-09-10T19:45:57Z")

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Unleashing JET.jl on my codebase tends to flood the prompt with errors due to the use of IO, DataFrames, etc… A lot of these runtime-dispatches are okay, but some are not. As an example, assume that I’m okay with the p…

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## [\[ANN\] JET/Cthulhu integration](https://discourse.julialang.org/t/ann-jet-cthulhu-integration/118430)

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**Author:** [@tim.holy](https://discourse.julialang.org/u/tim.holy)\
**Replies:** 0\
**Last updated:** [August 20, 2024, 8:17pm UTC](https://discourse.julialang.org/t/ann-jet-cthulhu-integration/118430 "2024-08-20T20:17:12Z")

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JET, a package which can systematically analyze your code to detect runtime dispatch, now integrates conveniently with Cthulhu, a package for gaining insights about the source of runtime dispatch and other failures of in…

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## [Does JET not detect the UndefRefError in this code?](https://discourse.julialang.org/t/does-jet-not-detect-the-undefreferror-in-this-code/117676)

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**Author:** [@jishnub](https://discourse.julialang.org/u/jishnub)\
**Replies:** 3\
**Last updated:** [August 1, 2024, 12:13pm UTC](https://discourse.julialang.org/t/does-jet-not-detect-the-undefreferror-in-this-code/117676 "2024-08-01T12:13:05Z")

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julia\> using StaticArrays, LinearAlgebra, JET julia\> M = Matrix{BigInt}(undef, 2, 2); M\[1,1\] = M\[2,2\] = M\[1,2\] = 3; M 2×2 Matrix{BigInt}: 3 3 #undef 3 julia\> S = SizedMatrix{2,2}(M) 2×2 SizedMatrix{2, 2, BigIn…

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## [Help understanding JET.jl output](https://discourse.julialang.org/t/help-understanding-jet-jl-output/116788)

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**Author:** [@james3](https://discourse.julialang.org/u/james3)\
**Replies:** 1\
**Last updated:** [July 9, 2024, 2:47pm UTC](https://discourse.julialang.org/t/help-understanding-jet-jl-output/116788 "2024-07-09T14:47:57Z")

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I’m using JET.jl with my code. It is giving me an error with a function, but I don’t really understand why. For a vector x (e.g. x = -.3 .+ rand(10)), I have a simple one-liner, vmapreduce(abs, max, x), which calculates …

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## [JET: are union incurred runtime dispatches really happening?](https://discourse.julialang.org/t/jet-are-union-incurred-runtime-dispatches-really-happening/116635)

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**Author:** [@filchristou](https://discourse.julialang.org/u/filchristou)\
**Replies:** 10\
**Last updated:** [July 5, 2024, 11:01am UTC](https://discourse.julialang.org/t/jet-are-union-incurred-runtime-dispatches-really-happening/116635 "2024-07-05T11:01:46Z")

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I tend to think that the compiler is pretty smart and staff like union-splitting are handled gracefully under the hood. However, I was currently using JET.@code\_opt and I saw some dynamic dispatch where I thought there …

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## [Understanding @report\_code output](https://discourse.julialang.org/t/understanding-report-code-output/116000)

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**Author:** [@miguelborrero](https://discourse.julialang.org/u/miguelborrero)\
**Replies:** 3\
**Last updated:** [June 23, 2024, 6:56pm UTC](https://discourse.julialang.org/t/understanding-report-code-output/116000 "2024-06-23T18:56:25Z")

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Hi there, This is my first time using JET.jl to fix the type-instability issues of my code. I am aware that maybe asking without a reproducible example might be a stretch but I will try anyways. My function takes as an…

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## [Why does JET seemingly not flag dynamic dispatch in this string interpolation?](https://discourse.julialang.org/t/why-does-jet-seemingly-not-flag-dynamic-dispatch-in-this-string-interpolation/112603)

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**Author:** [@jishnub](https://discourse.julialang.org/u/jishnub)\
**Replies:** 4\
**Last updated:** [April 23, 2024, 1:13pm UTC](https://discourse.julialang.org/t/why-does-jet-seemingly-not-flag-dynamic-dispatch-in-this-string-interpolation/112603 "2024-04-23T13:13:54Z")

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julia\> using LinearAlgebra, Cthulhu, JET julia\> D = Diagonal(rand(2)); julia\> @descend setindex!(D, 2, 1, 2) # Cthulhu setindex!(D::Diagonal, v, i::Int64, j::Int64) @ LinearAlgebra ~/.julia/juliaup/julia-1.11.0-alpha2+…

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## [JET \`report\_call\` error on array.jl for \`iterate(::DataType)\` using \`typeof\`](https://discourse.julialang.org/t/jet-report-call-error-on-array-jl-for-iterate-datatype-using-typeof/106670)

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**Author:** [@filchristou](https://discourse.julialang.org/u/filchristou)\
**Replies:** 0\
**Last updated:** [November 24, 2023, 9:55am UTC](https://discourse.julialang.org/t/jet-report-call-error-on-array-jl-for-iterate-datatype-using-typeof/106670 "2023-11-24T09:55:57Z")

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I define the following function, which seems pretty robust to me myf(vs::Vector{N}) where {N\<:Number} = \[typeof(v) for v in vs\] But, using JET, I get a possible error julia\> JET.report\_call(myf) ═════ 1 possible erro…

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## [Cannot achieve type stability](https://discourse.julialang.org/t/cannot-achieve-type-stability/106194)

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**Author:** [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Replies:** 17\
**Last updated:** [November 14, 2023, 2:34pm UTC](https://discourse.julialang.org/t/cannot-achieve-type-stability/106194 "2023-11-14T14:34:01Z")

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See the MWE below, inferred as Vector on both 1.9 and 1.10-pre. struct Quadrature{T} x::Vector{T} w::Vector{T} end function cubature(f::F, quadrature::Quadrature, B::NTuple{N}) where {F,N} (; x, w) = quadra…

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## [Static testing with JET vs interfaces](https://discourse.julialang.org/t/static-testing-with-jet-vs-interfaces/97985)

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**Author:** [@gdalle](https://discourse.julialang.org/u/gdalle)\
**Replies:** 5\
**Last updated:** [April 27, 2023, 9:47am UTC](https://discourse.julialang.org/t/static-testing-with-jet-vs-interfaces/97985 "2023-04-27T09:47:51Z")

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Hi there! I’m starting to add JET testing to several packages, but I run into problems when I try to define abstract interfaces. As of right now, interfaces in Julia are mostly methodless functions with explicit documen…

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## [JET.jl only show problems in my script](https://discourse.julialang.org/t/jet-jl-only-show-problems-in-my-script/93018)

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**Author:** [@Impressium](https://discourse.julialang.org/u/Impressium)\
**Replies:** 1\
**Last updated:** [January 16, 2023, 11:59am UTC](https://discourse.julialang.org/t/jet-jl-only-show-problems-in-my-script/93018 "2023-01-16T11:59:38Z")

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Hey all :slight\_smile: Is there a setting in JET.jl so that I only get error reported in my script. I basically want to disable the displaying of error from imported pkgs. Cheers

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## [Time for JET.jl first run?](https://discourse.julialang.org/t/time-for-jet-jl-first-run/75827)

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**Author:** [@TI36XPro](https://discourse.julialang.org/u/TI36XPro)\
**Replies:** 3\
**Last updated:** [July 25, 2022, 7:03pm UTC](https://discourse.julialang.org/t/time-for-jet-jl-first-run/75827 "2022-07-25T19:03:12Z")

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I just updated to Julia v1.7.1 and added Jet.jl to my project environment. I put together a file like this # contents of jet\_test.jl using MyPackage const problem\_size = 2^7 function main(problem\_size) tmp = MyFun…

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## [JET is unhappy with broadcast assigning a matrix to a submatrix, rooted in \`abstractarray.jl\`](https://discourse.julialang.org/t/jet-is-unhappy-with-broadcast-assigning-a-matrix-to-a-submatrix-rooted-in-abstractarray-jl/83750)

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**Author:** [@Krastanov](https://discourse.julialang.org/u/Krastanov)\
**Replies:** 0\
**Last updated:** [July 4, 2022, 4:34pm UTC](https://discourse.julialang.org/t/jet-is-unhappy-with-broadcast-assigning-a-matrix-to-a-submatrix-rooted-in-abstractarray-jl/83750 "2022-07-04T16:34:13Z")

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This seems like a pretty innocent piece of code but JET reports a possible issue. julia\> function f1(n) # Vectors work fine m = zeros(2n) sub = zeros(n) m\[n+1:2n\] .= sub m …

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## [Interpreting \`JET\` warnings on a simple \`Polyester\` multithreaded loop](https://discourse.julialang.org/t/interpreting-jet-warnings-on-a-simple-polyester-multithreaded-loop/83681)

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**Author:** [@Krastanov](https://discourse.julialang.org/u/Krastanov)\
**Replies:** 7\
**Last updated:** [July 4, 2022, 3:12am UTC](https://discourse.julialang.org/t/interpreting-jet-warnings-on-a-simple-polyester-multithreaded-loop/83681 "2022-07-04T03:12:23Z")

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Polyester seems to be one of the bigger sources of TTFX in some of my libraries. It is similarly the main source of warnings when using JET. Below is a very simple multi-threaded loop that causes a large number of JET wa…

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## [Are "inline assignments" inside loop predicates bad for type inference?](https://discourse.julialang.org/t/are-inline-assignments-inside-loop-predicates-bad-for-type-inference/81855)

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**Author:** [@Krastanov](https://discourse.julialang.org/u/Krastanov)\
**Replies:** 4\
**Last updated:** [June 2, 2022, 12:55am UTC](https://discourse.julialang.org/t/are-inline-assignments-inside-loop-predicates-bad-for-type-inference/81855 "2022-06-02T00:55:36Z")

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I was playing with JET and noticed that it does not like notation like while (i=f())!==nothing ... while it is perfectly happy with i=f(); while i!==nothing .... f is a function that returns Union{Int,Nothing}. It seems …

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## [Why does JET give these "runtime dispatch detected" lines for some LDLFactorizations calls in Tulip](https://discourse.julialang.org/t/why-does-jet-give-these-runtime-dispatch-detected-lines-for-some-ldlfactorizations-calls-in-tulip/79583)

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**Author:** [@nsajko](https://discourse.julialang.org/u/nsajko)\
**Replies:** 4\
**Last updated:** [April 18, 2022, 12:57pm UTC](https://discourse.julialang.org/t/why-does-jet-give-these-runtime-dispatch-detected-lines-for-some-ldlfactorizations-calls-in-tulip/79583 "2022-04-18T12:57:07Z")

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I’m playing around with linear programming using Tulip.jl and BigFloat, and I wanted to decrease the time necessary for finding each LP solution, so it seemed like JET.jl might be helpful to investigate possible performa…

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## [JET.jl type checker does not update module (can Revise.jl help?)](https://discourse.julialang.org/t/jet-jl-type-checker-does-not-update-module-can-revise-jl-help/68929)

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**Author:** [@greatpet](https://discourse.julialang.org/u/greatpet)\
**Replies:** 0\
**Last updated:** [September 29, 2021, 12:57pm UTC](https://discourse.julialang.org/t/jet-jl-type-checker-does-not-update-module-can-revise-jl-help/68929 "2021-09-29T12:57:45Z")

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Suppose I have a file test.jl which contains using MyModule. I use the type checker JET.jl with report\_file("test.jl"). The main purpose is to perform type checking of the code in MyModule. However, when I update the cod…

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## [JET.jl Invalid Type Signature](https://discourse.julialang.org/t/jet-jl-invalid-type-signature/66719)

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**Author:** [@jekyllstein](https://discourse.julialang.org/u/jekyllstein)\
**Replies:** 1\
**Last updated:** [August 22, 2021, 8:07am UTC](https://discourse.julialang.org/t/jet-jl-invalid-type-signature/66719 "2021-08-22T08:07:23Z")

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I was trying to use JET.jl to analyze a package and I ran into a type signature error. I have a toy example that reproduces the same issue. module Test ParamType = Union{Tuple{Real, Vararg{Real, N} where N}, Tuple{Rea…