# General Usage

**URL:** https://discourse.julialang.org/c/usage/6.md?page=23

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**Page:** 24

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## [In-place mul! much slower than \* for real-complex matrix multiplication](https://discourse.julialang.org/t/in-place-mul-much-slower-than-for-real-complex-matrix-multiplication/134938)

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**Author:** [@chrisbrahms](https://discourse.julialang.org/u/chrisbrahms)\
**Replies:** 9\
**Last updated:** [January 8, 2026, 6:23am UTC](https://discourse.julialang.org/t/in-place-mul-much-slower-than-for-real-complex-matrix-multiplication/134938 "2026-01-08T06:23:12Z")

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In some use cases of Luna.jl, the runtime is dominated by large matrix-matrix multiplications inside Hankel.jl. I see a dramatic performance drop when using complex-valued matrices, which I’ve traced to the mul! operatio…

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## [Plot every columns of a DataFrame](https://discourse.julialang.org/t/plot-every-columns-of-a-dataframe/134808)

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**Author:** [@Ju\_ska](https://discourse.julialang.org/u/Ju_ska)\
**Replies:** 5\
**Last updated:** [January 7, 2026, 6:58pm UTC](https://discourse.julialang.org/t/plot-every-columns-of-a-dataframe/134808 "2026-01-07T18:58:41Z")

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Hi, I would like to stack plots on top of each other without having to manage columns. Like separating the x axis from every other columns, then plot. using DataFrames using Plots df = DataFrame(x = \[1,2,3,4\], y1 = \[…

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## [How to implement promotion for functions like \`collect\` and \`map\`?](https://discourse.julialang.org/t/how-to-implement-promotion-for-functions-like-collect-and-map/134912)

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**Author:** [@Deduction42](https://discourse.julialang.org/u/Deduction42)\
**Replies:** 7\
**Last updated:** [January 7, 2026, 6:27pm UTC](https://discourse.julialang.org/t/how-to-implement-promotion-for-functions-like-collect-and-map/134912 "2026-01-07T18:27:49Z")

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I’m implementing more advanced promotion rules in FlexUnits.jl but I’m getting stuck with functions like collect and map. If I put quantities in a vector with missing values, promotion rules I made give me a fully inferr…

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## [NetworkDynamics.jl with Neural Networks](https://discourse.julialang.org/t/networkdynamics-jl-with-neural-networks/134918)

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**Author:** [@lear](https://discourse.julialang.org/u/lear)\
**Replies:** 2\
**Last updated:** [January 6, 2026, 10:56pm UTC](https://discourse.julialang.org/t/networkdynamics-jl-with-neural-networks/134918 "2026-01-06T22:56:05Z")

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Hi, I am working on integrating Neural ODEs into network simulations using NetworkDynamics.jl and ModelingToolkitNeuralNets.jl. The Problem is NetworkDynamics.jl appears to generate duplicate symbol names when processing…

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## [SunCalc returning times for wrong day](https://discourse.julialang.org/t/suncalc-returning-times-for-wrong-day/134733)

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**Author:** [@healyp](https://discourse.julialang.org/u/healyp)\
**Replies:** 3\
**Last updated:** [January 6, 2026, 8:46am UTC](https://discourse.julialang.org/t/suncalc-returning-times-for-wrong-day/134733 "2026-01-06T08:46:50Z")

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Is my use of SunCalc below correct? It’s reporting sunrise/sunset for the day before I specified. Is it a timezone issue? Many thanks. julia\> s=Date(2025,1,5) 2025-01-05 julia\> lat,lon = (52.9335, -9.3441) (52.9335,…

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## [Broadcast StepRange](https://discourse.julialang.org/t/broadcast-steprange/134867)

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**Author:** [@freeman](https://discourse.julialang.org/u/freeman)\
**Replies:** 3\
**Last updated:** [January 5, 2026, 12:23am UTC](https://discourse.julialang.org/t/broadcast-steprange/134867 "2026-01-05T00:23:01Z")

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Consider times\_dt = DateTime("2025-12-29T00:18:00"):Minute(1):DateTime("2025-12-29T22:21:00") typeof(times\_dt) # StepRange{DateTime, Minute} Consider broading on this. DateTime.(times\_dt) |\> typeof # Vector{DateTim…

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## [\`logsumexp\` using Accessors?](https://discourse.julialang.org/t/logsumexp-using-accessors/134835)

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**Author:** [@jar1](https://discourse.julialang.org/u/jar1)\
**Replies:** 6\
**Last updated:** [January 4, 2026, 1:46pm UTC](https://discourse.julialang.org/t/logsumexp-using-accessors/134835 "2026-01-04T13:46:42Z")

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Is it possible to do logsumexp in a cool way using Accessors? using Accessors julia\> @modify(log, 1:1.0:9 |\> sum(\_\[∗\])) ERROR: This should be unreachable. You probably need to overload \`Accessors.set(obj::Float64, ::typ…

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## [Julia in docker could not find packages in \`$JULIA\_LOAD\_PATH\`](https://discourse.julialang.org/t/julia-in-docker-could-not-find-packages-in-julia-load-path/134865)

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**Author:** [@Chrysoberyl](https://discourse.julialang.org/u/Chrysoberyl)\
**Replies:** 2\
**Last updated:** [January 4, 2026, 10:29am UTC](https://discourse.julialang.org/t/julia-in-docker-could-not-find-packages-in-julia-load-path/134865 "2026-01-04T10:29:24Z")

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I’m using Julia inside a docker container. I set $JULIA\_LOAD\_PATH to $load\_path:, where $load\_path contains $ ls $load\_path ... Compat ... NNlib ... $ cat $load\_path/Compat/Project.toml ... \[extensions\] CompatLinearAlg…

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## [Parsing one or more networks in ConfParser](https://discourse.julialang.org/t/parsing-one-or-more-networks-in-confparser/134838)

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**Author:** [@phma](https://discourse.julialang.org/u/phma)\
**Replies:** 1\
**Last updated:** [January 4, 2026, 7:28am UTC](https://discourse.julialang.org/t/parsing-one-or-more-networks-in-confparser/134838 "2026-01-04T07:28:32Z")

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I’m writing a config file parser using ConfParser for a config file which includes, among other things, the latitude, longitude, and networks from which clients may connect. The file looks like this: Latitude 35.snip Lo…

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## [Adopt the SciML Style Guide for Julia Base and Standard Library?](https://discourse.julialang.org/t/adopt-the-sciml-style-guide-for-julia-base-and-standard-library/134845)

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**Author:** [@mkitti](https://discourse.julialang.org/u/mkitti)\
**Replies:** 10\
**Last updated:** [January 3, 2026, 11:51pm UTC](https://discourse.julialang.org/t/adopt-the-sciml-style-guide-for-julia-base-and-standard-library/134845 "2026-01-03T23:51:09Z")

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After thinking about docstrings from another post, I was wondering if the Julia Style Guide, particularly for Core, Base, and the standard libraries should be further specified, particularly for docstrings. Perhaps a …

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## [The is "Expando objects" in Julia?](https://discourse.julialang.org/t/the-is-expando-objects-in-julia/5957)

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**Author:** [@gabomgp](https://discourse.julialang.org/u/gabomgp)\
**Replies:** 5\
**Last updated:** [January 3, 2026, 1:14pm UTC](https://discourse.julialang.org/t/the-is-expando-objects-in-julia/5957 "2026-01-03T13:14:39Z")

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In C# is possible to have a dynamic object with fields defined at runtime using expando objects. Example: dynamic contact = new ExpandoObject(); contact.Name = “Patrick Hines”; contact.Phone = “206-555-0144”; As you ca…

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## [Should \`esc\` work for the macro name of a \`macrocall\` expression?](https://discourse.julialang.org/t/should-esc-work-for-the-macro-name-of-a-macrocall-expression/134817)

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**Author:** [@matthias314](https://discourse.julialang.org/u/matthias314)\
**Replies:** 4\
**Last updated:** [January 3, 2026, 5:59am UTC](https://discourse.julialang.org/t/should-esc-work-for-the-macro-name-of-a-macrocall-expression/134817 "2026-01-03T05:59:46Z")

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It seems that a macro returning a :macrocall expression with escaped macro name does not work whereas a :call expression with escaped function name is no problem: julia\> macro a(ex::Expr) Expr(ex.head, esc.(ex.args)...)…

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## [Numerical sensitivity of eigvecs for \`≈\` identical (unitful) matrices?](https://discourse.julialang.org/t/numerical-sensitivity-of-eigvecs-for-identical-unitful-matrices/134846)

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**Author:** [@bremez](https://discourse.julialang.org/u/bremez)\
**Replies:** 3\
**Last updated:** [January 3, 2026, 2:11am UTC](https://discourse.julialang.org/t/numerical-sensitivity-of-eigvecs-for-identical-unitful-matrices/134846 "2026-01-03T02:11:09Z")

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I came across the following discrepancy, see MWE: using LinearAlgebra, Unitful GHz = 1u"GHz"; wq = 6.7565\*GHz; wc = 20\*GHz; g = 0.1847\*GHz; Ns = 10; op = diagm(1 =\> sqrt.(1:Ns)); b = kron(op, I(Ns+1)); a = kron(I(Ns+1),…

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## [Visualising datasets on static webpage with DOI](https://discourse.julialang.org/t/visualising-datasets-on-static-webpage-with-doi/134842)

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**Author:** [@danieleavitabile](https://discourse.julialang.org/u/danieleavitabile)\
**Replies:** 2\
**Last updated:** [January 2, 2026, 8:07pm UTC](https://discourse.julialang.org/t/visualising-datasets-on-static-webpage-with-doi/134842 "2026-01-02T20:07:02Z")

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Hi All, I am relatively new to Julia, but I know enough to use Makie.jl to visualise relatively complex datasets. For the first time I am considering making a webpage to offer the readers of an upcoming paper of mine th…

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## [How to structure a julia package which should also contain a REST api?](https://discourse.julialang.org/t/how-to-structure-a-julia-package-which-should-also-contain-a-rest-api/134840)

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**Author:** [@DoktorMike](https://discourse.julialang.org/u/DoktorMike)\
**Replies:** 3\
**Last updated:** [January 2, 2026, 6:14pm UTC](https://discourse.julialang.org/t/how-to-structure-a-julia-package-which-should-also-contain-a-rest-api/134840 "2026-01-02T18:14:35Z")

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So what I want to do: I want to build a julia package Foo.jl which should be used by users writing scripts in julia primarily. There’s also a secondary group of users who will want to use a subset of the package through …

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## [Speeding up trig-heavy code](https://discourse.julialang.org/t/speeding-up-trig-heavy-code/134656)

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**Author:** [@langestefan](https://discourse.julialang.org/u/langestefan)\
**Replies:** 26\
**Last updated:** [January 2, 2026, 4:44pm UTC](https://discourse.julialang.org/t/speeding-up-trig-heavy-code/134656 "2026-01-02T16:44:23Z")

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Hello! I recently released v0.3.2 of SolarPosition.jl. I feel like it is now in a position where I am very happy with the performance, at least I think I covered all the basics like type stability covered in Performance…

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## [Moshi.jl and matching a dictionary as a pattern](https://discourse.julialang.org/t/moshi-jl-and-matching-a-dictionary-as-a-pattern/134677)

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**Author:** [@Pedro](https://discourse.julialang.org/u/Pedro)\
**Replies:** 4\
**Last updated:** [January 1, 2026, 4:41am UTC](https://discourse.julialang.org/t/moshi-jl-and-matching-a-dictionary-as-a-pattern/134677 "2026-01-01T04:41:13Z")

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I am currently porting to Julia some Python code that contains a lot of pattern matching for decoding JSON messages received via network socket, which are represented conveniently in Python as dictionaries. Since Julia …

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## [JETLS warning \`md\` is not concretized](https://discourse.julialang.org/t/jetls-warning-md-is-not-concretized/134820)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 2\
**Last updated:** [January 1, 2026, 1:30am UTC](https://discourse.julialang.org/t/jetls-warning-md-is-not-concretized/134820 "2026-01-01T01:30:37Z")

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I have a script that contains the lines: using DataFrames md::DataFrame = DataFrame() ... I get the following JETLS.jl warning: \`md\` is not concretized but JET needs to use its actual value in order to define types or…

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## [Passing all functions on object A to object B](https://discourse.julialang.org/t/passing-all-functions-on-object-a-to-object-b/134654)

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**Author:** [@alequa](https://discourse.julialang.org/u/alequa)\
**Replies:** 9\
**Last updated:** [December 31, 2025, 2:32pm UTC](https://discourse.julialang.org/t/passing-all-functions-on-object-a-to-object-b/134654 "2025-12-31T14:32:48Z")

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Hello, I have the type: struct Car color::String model::String gears::Int end and I have another struct struct CarGroup cars::Vector{Car} end I would like all the functions called on Car to be applied …

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## [Stdio tee (copy without redirection)](https://discourse.julialang.org/t/stdio-tee-copy-without-redirection/134794)

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**Author:** [@hadrien.theveneau](https://discourse.julialang.org/u/hadrien.theveneau)\
**Replies:** 6\
**Last updated:** [December 31, 2025, 8:51am UTC](https://discourse.julialang.org/t/stdio-tee-copy-without-redirection/134794 "2025-12-31T08:51:33Z")

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Dear all, I would like to make something like Base.redirect\_stdio, but which copies elsewhere the stdout and stderr without suppressing them, like the tee command. Would you know how to do this ? Thanks a lot,

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## [Avoiding false sharing in parallel loop without collecting](https://discourse.julialang.org/t/avoiding-false-sharing-in-parallel-loop-without-collecting/134798)

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**Author:** [@oscarvdvelde](https://discourse.julialang.org/u/oscarvdvelde)\
**Replies:** 8\
**Last updated:** [December 30, 2025, 8:59pm UTC](https://discourse.julialang.org/t/avoiding-false-sharing-in-parallel-loop-without-collecting/134798 "2025-12-30T20:59:29Z")

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I have this function with a parallel loop that probably can benefit from elimination of false sharing. function(t,x,y,z) per\_point\_result\_array = ... #preinitialized @tasks for c in eachindex(gridcells) …

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## [Invalid JETLS warning, buggy kwdef macro](https://discourse.julialang.org/t/invalid-jetls-warning-buggy-kwdef-macro/134776)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 17\
**Last updated:** [December 30, 2025, 8:28am UTC](https://discourse.julialang.org/t/invalid-jetls-warning-buggy-kwdef-macro/134776 "2025-12-30T08:28:03Z")

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The following code: Base.@kwdef mutable struct SysState{P} acc::Float64 = 0 "vector of particle positions in x \[m\]" X::MVector{P, Float64} = zeros(P) end gives the warning: \`KiteUtils.P\` is not defined I …

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## [Inferring the return type of an operation on two variables](https://discourse.julialang.org/t/inferring-the-return-type-of-an-operation-on-two-variables/134778)

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**Author:** [@leespen1](https://discourse.julialang.org/u/leespen1)\
**Replies:** 2\
**Last updated:** [December 29, 2025, 4:09pm UTC](https://discourse.julialang.org/t/inferring-the-return-type-of-an-operation-on-two-variables/134778 "2025-12-29T16:09:32Z")

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Suppose I have two vectors: A::Vector{Type1} and B::Vector{Type2}. I want to create a vector C::Vector{Type3} where Type3 is the type of a \* b, where a and b are elements of A and B, respectively. A basic example of thi…

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## [Large ODE Solver for Metal.jl](https://discourse.julialang.org/t/large-ode-solver-for-metal-jl/134769)

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**Author:** [@Gavin-Rockwood](https://discourse.julialang.org/u/Gavin-Rockwood)\
**Replies:** 11\
**Last updated:** [December 29, 2025, 2:49am UTC](https://discourse.julialang.org/t/large-ode-solver-for-metal-jl/134769 "2025-12-29T02:49:29Z")

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Is there any implementation for ODE solving using Metal.jl backends? I know there is DiffEqGPU, but the metal support is only for ensemble problems. I cannot for instance do f(u,p,t) = A\*u tspan = (0.0f0, 1.0f0) prob = …

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## [Learning more about Dual and Primal as used in Zygote.jl](https://discourse.julialang.org/t/learning-more-about-dual-and-primal-as-used-in-zygote-jl/134739)

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**Author:** [@firebat](https://discourse.julialang.org/u/firebat)\
**Replies:** 2\
**Last updated:** [December 27, 2025, 10:43am UTC](https://discourse.julialang.org/t/learning-more-about-dual-and-primal-as-used-in-zygote-jl/134739 "2025-12-27T10:43:05Z")

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Hi all, I’ve been interested in learning more about Zygote.jl and some ways I can use it in my optimization programs. Frankly, when terminology such as dual and primal are mentioned in the context of Zygotes mechanism, I…

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## [REPLExt not found in 1.11.8](https://discourse.julialang.org/t/replext-not-found-in-1-11-8/134681)

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**Author:** [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Replies:** 5\
**Last updated:** [December 26, 2025, 9:21pm UTC](https://discourse.julialang.org/t/replext-not-found-in-1-11-8/134681 "2025-12-26T21:21:40Z")

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Since I upgraded to 1.11.8 from 1.11.7, I am running into this error when entering the pkg\> mode: % julia +1.11.8 \_ \_ \_ \_(\_)\_ | Documentation: https://docs.julialang.org (\_) | (\_) (\_) …

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## [Has anyone heard of TOON format? Looking for Julia implementation](https://discourse.julialang.org/t/has-anyone-heard-of-toon-format-looking-for-julia-implementation/133908)

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**Author:** [@scelles](https://discourse.julialang.org/u/scelles)\
**Replies:** 12\
**Last updated:** [December 26, 2025, 3:01pm UTC](https://discourse.julialang.org/t/has-anyone-heard-of-toon-format-looking-for-julia-implementation/133908 "2025-12-26T15:01:05Z")

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Hi everyone, I recently came across TOON (Token-Oriented Object Notation), which is described as a data format designed to be more LLM-friendly than JSON. The format aims to reduce token usage while maintaining readabil…

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## [Using Combinatorics: permutations much slower than copied source code](https://discourse.julialang.org/t/using-combinatorics-permutations-much-slower-than-copied-source-code/134407)

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**Author:** [@depial](https://discourse.julialang.org/u/depial)\
**Replies:** 11\
**Last updated:** [December 26, 2025, 2:46am UTC](https://discourse.julialang.org/t/using-combinatorics-permutations-much-slower-than-copied-source-code/134407 "2025-12-26T02:46:06Z")

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When trying to solve an alphametics problem with permutations from Combinatorics.jl, I came across something I don’t understand about the performance. If I introduce permutations to the namespace via using Combinatorics…

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## [High memory usage when training a custom Lux model](https://discourse.julialang.org/t/high-memory-usage-when-training-a-custom-lux-model/134714)

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**Author:** [@HMegh](https://discourse.julialang.org/u/HMegh)\
**Replies:** 8\
**Last updated:** [December 26, 2025, 1:22am UTC](https://discourse.julialang.org/t/high-memory-usage-when-training-a-custom-lux-model/134714 "2025-12-26T01:22:11Z")

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I am trying to implement a custom Lux model, but I keep running out of memory even with small number (~500) of parameters. I have two kinds of layers (called sympnets) which take in and return two vectors. Each layer upd…

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## [XLSX.jl ignores stop\_in\_empty\_row](https://discourse.julialang.org/t/xlsx-jl-ignores-stop-in-empty-row/134712)

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**Author:** [@Eben60](https://discourse.julialang.org/u/Eben60)\
**Replies:** 5\
**Last updated:** [December 24, 2025, 12:39pm UTC](https://discourse.julialang.org/t/xlsx-jl-ignores-stop-in-empty-row/134712 "2025-12-24T12:39:56Z")

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This is my file f3: an excel table, made with LibreOffice : id val1 val2 1 1.5 4.5 2 2.5 7.5 3 3.5 10.5 4 4.5 13.5 And that is what I get when I read it: julia\> DataFrame(XLSX.readtable(f3, "Sheet1"; header=…

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