# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=131

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**Page:** 132

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## [How to copy array back from GPU do CPU?](https://discourse.julialang.org/t/how-to-copy-array-back-from-gpu-do-cpu/110802)

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**Author:** [@Gregstrq](https://discourse.julialang.org/u/Gregstrq)\
**Replies:** 2\
**Last updated:** [February 26, 2024, 8:59pm UTC](https://discourse.julialang.org/t/how-to-copy-array-back-from-gpu-do-cpu/110802 "2024-02-26T20:59:45Z")

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Let’s say I have a done a computation on a GPU. How do I copy this data back to the CPU, so that I can play around with it on CPU (like make the plots) and save it to disk (more important for me)?

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## [Basis and non-basis matrix](https://discourse.julialang.org/t/basis-and-non-basis-matrix/110219)

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**Author:** [@mohammad\_amini](https://discourse.julialang.org/u/mohammad_amini)\
**Replies:** 14\
**Last updated:** [February 26, 2024, 7:35pm UTC](https://discourse.julialang.org/t/basis-and-non-basis-matrix/110219 "2024-02-26T19:35:46Z")

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I am seeking methods to identify the basis and non-basis matrices in HiGHS, or determine the status of variables and columns within the basis and non-basis. Additionally, I am curious about accessing the final simplex ta…

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## [@unpack from Catalyst reaction system and unused variables](https://discourse.julialang.org/t/unpack-from-catalyst-reaction-system-and-unused-variables/110766)

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**Author:** [@johannesnauta](https://discourse.julialang.org/u/johannesnauta)\
**Replies:** 9\
**Last updated:** [February 26, 2024, 3:26pm UTC](https://discourse.julialang.org/t/unpack-from-catalyst-reaction-system-and-unused-variables/110766 "2024-02-26T15:26:27Z")

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Hi all. I have happily been using Catalyst.jl (and of course related packages, such as ModelingToolkit.jl and DifferentialEquations.jl), but when remaking problems while using EnsembleProblem I encountered some odd behav…

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## [Displaying an image from a matrix using Gtk4](https://discourse.julialang.org/t/displaying-an-image-from-a-matrix-using-gtk4/104748)

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**Author:** [@xor0110](https://discourse.julialang.org/u/xor0110)\
**Replies:** 5\
**Last updated:** [February 26, 2024, 2:47pm UTC](https://discourse.julialang.org/t/displaying-an-image-from-a-matrix-using-gtk4/104748 "2024-02-26T14:47:42Z")

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I want to display an image using Gtk, and be able to change the pixels later. I love ImageView and Makie, but I’m trying to do something as simple and low-level as possibel. There are a couple of examples in the forum u…

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## [Warning/Error handling from complex, sparse array on SVD (PROPACK)](https://discourse.julialang.org/t/warning-error-handling-from-complex-sparse-array-on-svd-propack/110779)

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**Author:** [@KSfairopoulos](https://discourse.julialang.org/u/KSfairopoulos)\
**Replies:** 0\
**Last updated:** [February 26, 2024, 2:16pm UTC](https://discourse.julialang.org/t/warning-error-handling-from-complex-sparse-array-on-svd-propack/110779 "2024-02-26T14:16:45Z")

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Let’s assume I have a sparse matrix with complex entries. I want to perform svd on it. So, I use the Propack package (do you have any better suggestions?). I do this with the command: tsvdvals(gs, k=p), where I retain …

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## [Building Julia on a Raspberry Pi](https://discourse.julialang.org/t/building-julia-on-a-raspberry-pi/110632)

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**Author:** [@yakir12](https://discourse.julialang.org/u/yakir12)\
**Replies:** 5\
**Last updated:** [February 26, 2024, 11:33am UTC](https://discourse.julialang.org/t/building-julia-on-a-raspberry-pi/110632 "2024-02-26T11:33:16Z")

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I’m trying to build Julia from source (v1.10.1) on a Raspberry Pi (4 Model B, with OS 64-bit, Lite, Bookworm on it). It’s been a struggle… I’ve installed zram, and that does help with the process, but it does occasionall…

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## [Need access to ImageInpainting.jl](https://discourse.julialang.org/t/need-access-to-imageinpainting-jl/110404)

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**Author:** [@juliohm](https://discourse.julialang.org/u/juliohm)\
**Replies:** 3\
**Last updated:** [February 26, 2024, 11:10am UTC](https://discourse.julialang.org/t/need-access-to-imageinpainting-jl/110404 "2024-02-26T11:10:54Z")

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I wrote this package a long time ago, when I co-founded JuliaImages. I am not an org owner anymore, and can’t access the repository settings to fix TAGBOT keys. Can an owner of JuliaImages please help fix this? I want t…

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## [Can I recover variable names to PATH labels? JuMP-\>MOI-\>PATHSolver-\>PATH-\>JuMP](https://discourse.julialang.org/t/can-i-recover-variable-names-to-path-labels-jump-moi-pathsolver-path-jump/110703)

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**Author:** [@EliLazarus](https://discourse.julialang.org/u/EliLazarus)\
**Replies:** 2\
**Last updated:** [February 26, 2024, 2:19am UTC](https://discourse.julialang.org/t/can-i-recover-variable-names-to-path-labels-jump-moi-pathsolver-path-jump/110703 "2024-02-26T02:19:17Z")

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I am passing named variable/constraints to JuMP. Is there a way to track the variable/constraint name linked to the row f\[ #\] which is what is reported by PATH (looks like unnamed rows as in this example without names)? …

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## [Understanding stride loop](https://discourse.julialang.org/t/understanding-stride-loop/110721)

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**Author:** [@PharmCat](https://discourse.julialang.org/u/PharmCat)\
**Replies:** 7\
**Last updated:** [February 25, 2024, 7:38pm UTC](https://discourse.julialang.org/t/understanding-stride-loop/110721 "2024-02-25T19:38:56Z")

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I try to read performance tips :sweat\_smile:) (Performance Tips · CUDA.jl) and can’t understand what is the point of this example, because seems while executed only once. function gpu\_add5!(y, x) index = (blockIdx…

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## [Differentiating optimization problem solutions in Julia](https://discourse.julialang.org/t/differentiating-optimization-problem-solutions-in-julia/75988)

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**Author:** [@mtfishman](https://discourse.julialang.org/u/mtfishman)\
**Replies:** 9\
**Last updated:** [February 25, 2024, 2:10pm UTC](https://discourse.julialang.org/t/differentiating-optimization-problem-solutions-in-julia/75988 "2024-02-25T14:10:32Z")

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Hello, I was recently made aware of the paper “Efficient and Modular Implicit Differentiation”: which is implemented in Jax here: It is about automatically generating differentiation rules for optimization problem…

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## [Solve MCP problems with nonlinear constraints](https://discourse.julialang.org/t/solve-mcp-problems-with-nonlinear-constraints/110061)

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**Author:** [@vicentemunozlh](https://discourse.julialang.org/u/vicentemunozlh)\
**Replies:** 8\
**Last updated:** [February 25, 2024, 10:44am UTC](https://discourse.julialang.org/t/solve-mcp-problems-with-nonlinear-constraints/110061 "2024-02-25T10:44:00Z")

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Hello ! Ive been trying to solve an MCP problem with JuMP and non linear constraints/optimality condition but have not been able to do so. Is there a way around this? or other package that might do the trick? Thank you…

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## [Load graphml with LightGraphs](https://discourse.julialang.org/t/load-graphml-with-lightgraphs/110590)

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**Author:** [@Andromeda258](https://discourse.julialang.org/u/Andromeda258)\
**Replies:** 4\
**Last updated:** [February 25, 2024, 6:15am UTC](https://discourse.julialang.org/t/load-graphml-with-lightgraphs/110590 "2024-02-25T06:15:02Z")

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I want to load a graphml graph as LightGraphs SimpleGraphs. This is the code I am using: \` using LightGraphs using GraphIO g = loadgraph(“graph.graphml”, GraphMLFormat()) ’ But I got this error: · ERROR: UndefVar…

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## [Choice variable doesn't optimize the objective function](https://discourse.julialang.org/t/choice-variable-doesnt-optimize-the-objective-function/110633)

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**Author:** [@Ayesha](https://discourse.julialang.org/u/Ayesha)\
**Replies:** 3\
**Last updated:** [February 25, 2024, 12:34am UTC](https://discourse.julialang.org/t/choice-variable-doesnt-optimize-the-objective-function/110633 "2024-02-25T00:34:31Z")

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begin # set parameters b = 100.0 r = 0.2 α = 0.85 θ = 2.5 β = 0.9 A = 1.0 s = 1.0 end begin f(b) = b^α Y₂(b,θ) = θ\*f(b) C₂(R₂,b,θ) = Y₂(b,θ) - R₂ R̄(b,r) = (1+r)\*b U₂(R₂, θ, b, α) = A\*log(max(θ \* f(b) - …

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## [Fitted Flux model is "off" by one](https://discourse.julialang.org/t/fitted-flux-model-is-off-by-one/110709)

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**Author:** [@affans](https://discourse.julialang.org/u/affans)\
**Replies:** 2\
**Last updated:** [February 24, 2024, 9:12pm UTC](https://discourse.julialang.org/t/fitted-flux-model-is-off-by-one/110709 "2024-02-24T21:12:09Z")

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I am trying to reproduce a simple NN model in Julia using Lux.jl, originally using the R package forecast which trains an AR(2) model using nnet internally. I am almost able to reproduce it, but my fitted model is off by…

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## [Using structures with JuMP](https://discourse.julialang.org/t/using-structures-with-jump/110663)

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**Author:** [@joaomcostab](https://discourse.julialang.org/u/joaomcostab)\
**Replies:** 5\
**Last updated:** [February 24, 2024, 9:07pm UTC](https://discourse.julialang.org/t/using-structures-with-jump/110663 "2024-02-24T21:07:30Z")

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I am trying to solve a non-linear system re-writing it in a way that I can use optimization (basically the objective function is 1.0 and the constraints are the equations of the system). However, these equations use use…

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## [Nullspace Function Vs QR decomposition](https://discourse.julialang.org/t/nullspace-function-vs-qr-decomposition/110656)

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**Author:** [@fimiller](https://discourse.julialang.org/u/fimiller)\
**Replies:** 8\
**Last updated:** [February 24, 2024, 7:16pm UTC](https://discourse.julialang.org/t/nullspace-function-vs-qr-decomposition/110656 "2024-02-24T19:16:54Z")

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I am attempting to compute a nullspace for a matrix A. I have two potential techniques of doing this. One is to use a permuted QR decomposition, and the other is to use the nullspace function. These two approaches give…

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## [Dumb question: why autodifferentiation is needed in Neural Networks](https://discourse.julialang.org/t/dumb-question-why-autodifferentiation-is-needed-in-neural-networks/110673)

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**Author:** [@sylvaticus](https://discourse.julialang.org/u/sylvaticus)\
**Replies:** 9\
**Last updated:** [February 24, 2024, 6:11pm UTC](https://discourse.julialang.org/t/dumb-question-why-autodifferentiation-is-needed-in-neural-networks/110673 "2024-02-24T18:11:21Z")

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I know little other than the basic NN, but why autodiff is needed for DeepLearning? Using backchain it is fairly easy to get the gradient without autodiff, or at least if standard activation functions are provided. For …

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## [Is JuMP suitable for very big problems?](https://discourse.julialang.org/t/is-jump-suitable-for-very-big-problems/110642)

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**Author:** [@mrys](https://discourse.julialang.org/u/mrys)\
**Replies:** 3\
**Last updated:** [February 23, 2024, 7:24pm UTC](https://discourse.julialang.org/t/is-jump-suitable-for-very-big-problems/110642 "2024-02-23T19:24:41Z")

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This question has certainly been asked, but I couldn’t actually find a clear answer. Having the following problem: n = 10000; k = rand(n, n) ke = 0.5(k + k'); function func(x::T...) where T y = collect(x) retur…

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## [How to connect MTK thermal Heatport?](https://discourse.julialang.org/t/how-to-connect-mtk-thermal-heatport/110586)

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**Author:** [@Zhijian](https://discourse.julialang.org/u/Zhijian)\
**Replies:** 4\
**Last updated:** [February 23, 2024, 4:35pm UTC](https://discourse.julialang.org/t/how-to-connect-mtk-thermal-heatport/110586 "2024-02-23T16:35:12Z")

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Hi guys, I am new to Julia and am using ModelingToolkit to try to build a simple heat conduction model (3R2C wall model). So it will look like this… I am trying to create a constant ambient temperature then switch t…

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## [Line caps and joins in Plots](https://discourse.julialang.org/t/line-caps-and-joins-in-plots/39826)

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**Author:** [@sgaure](https://discourse.julialang.org/u/sgaure)\
**Replies:** 2\
**Last updated:** [February 23, 2024, 4:28pm UTC](https://discourse.julialang.org/t/line-caps-and-joins-in-plots/39826 "2024-02-23T16:28:48Z")

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I have looked around in the Plots package and am unable to find out how to set the line cap style, and line join style. A simple example is this: using Plots pyplot() plot(\[0 0.5; 0.5 1\], \[1 1; 1 1\], linewidth=10) That…

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## [Help with Flux.jl, Metal.jl (Apple Silicon) and Conv layers](https://discourse.julialang.org/t/help-with-flux-jl-metal-jl-apple-silicon-and-conv-layers/105632)

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**Author:** [@JakobPeterlin](https://discourse.julialang.org/u/JakobPeterlin)\
**Replies:** 2\
**Last updated:** [February 23, 2024, 4:27pm UTC](https://discourse.julialang.org/t/help-with-flux-jl-metal-jl-apple-silicon-and-conv-layers/105632 "2024-02-23T16:27:15Z")

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Hello, after trying to use Flux.jl to reimplement some PyTorch code (SpinalVGG), I encountered some difficulties when trying to run my code on an M2 Max’s GPU with Metal.jl. The error boils down to the following code, w…

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## [Arrows in plots](https://discourse.julialang.org/t/arrows-in-plots/110629)

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**Author:** [@blob](https://discourse.julialang.org/u/blob)\
**Replies:** 1\
**Last updated:** [February 23, 2024, 3:50pm UTC](https://discourse.julialang.org/t/arrows-in-plots/110629 "2024-02-23T15:50:29Z")

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I want to plot lines with arrows at the end of the lines. Following this thread, I got: obtained from: Using Plots plot(\[0.0 1.0\]',\[0.0 -0.71\]',label="Correct, solid blue with arrow",palette=:imola100,lw=2,arrow=tr…

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## [How to create an HTML questionnaire that is driven by Julia in the background?](https://discourse.julialang.org/t/how-to-create-an-html-questionnaire-that-is-driven-by-julia-in-the-background/110644)

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**Author:** [@WuSiren](https://discourse.julialang.org/u/WuSiren)\
**Replies:** 2\
**Last updated:** [February 23, 2024, 3:41pm UTC](https://discourse.julialang.org/t/how-to-create-an-html-questionnaire-that-is-driven-by-julia-in-the-background/110644 "2024-02-23T15:41:01Z")

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I want to point a site to an HTML file (using Nginx), which is a questionnaire. For example, people who open the page are asked to fill in a number randomly and click Submit button. Julia records the number each person f…

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## [Problems performing 1D-FDTD for dispersive dielectric uisng lorentz model in Julia](https://discourse.julialang.org/t/problems-performing-1d-fdtd-for-dispersive-dielectric-uisng-lorentz-model-in-julia/110617)

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**Author:** [@geoselenicmonkey](https://discourse.julialang.org/u/geoselenicmonkey)\
**Replies:** 0\
**Last updated:** [February 23, 2024, 1:34am UTC](https://discourse.julialang.org/t/problems-performing-1d-fdtd-for-dispersive-dielectric-uisng-lorentz-model-in-julia/110617 "2024-02-23T01:34:15Z")

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So I am trying to model a dispersive dielectric using the Lorentz model in Julia, more specifically I am trying to obtain the frequency-dependent reflectivity of the material. I am ultimately trying to replicate the resu…

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## [Suppress Error message and draw another random numbs during simulation](https://discourse.julialang.org/t/suppress-error-message-and-draw-another-random-numbs-during-simulation/110555)

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**Author:** [@Wooheon](https://discourse.julialang.org/u/Wooheon)\
**Replies:** 6\
**Last updated:** [February 23, 2024, 12:08am UTC](https://discourse.julialang.org/t/suppress-error-message-and-draw-another-random-numbs-during-simulation/110555 "2024-02-23T00:08:50Z")

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Hi, I am trying to calculate the bias and mean squared errors, which need repetition of simulations. The problem is my optimize result sometimes gives an error message of AssertionError: isfinite(phi\_c) && isfinite(dp…

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## [Error in dblquad integration with Unitful and MonteCarloMeasurements](https://discourse.julialang.org/t/error-in-dblquad-integration-with-unitful-and-montecarlomeasurements/110420)

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**Author:** [@GSavvidis](https://discourse.julialang.org/u/GSavvidis)\
**Replies:** 5\
**Last updated:** [February 22, 2024, 7:00pm UTC](https://discourse.julialang.org/t/error-in-dblquad-integration-with-unitful-and-montecarlomeasurements/110420 "2024-02-22T19:00:05Z")

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Hello everyone, This is my first post so apologies in advance for any mistakes in the question format. I have been trying to calculate an integral of two variables using dblquad. The function to be integrated contains …

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## [Implementing a model with column generation](https://discourse.julialang.org/t/implementing-a-model-with-column-generation/110595)

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**Author:** [@Carl\_Baier](https://discourse.julialang.org/u/Carl_Baier)\
**Replies:** 1\
**Last updated:** [February 22, 2024, 6:57pm UTC](https://discourse.julialang.org/t/implementing-a-model-with-column-generation/110595 "2024-02-22T18:57:33Z")

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Hello, I have the following model and want to solve it with column generation according to these instructions. Unfortunately, I am a complete coding newbie and wanted to ask if anyone would like to help me implement this…

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## [How can I solve complex-valued ordinary differential equations (ODEs) using neural networks, given limitations with complex data types in libraries like Lux?](https://discourse.julialang.org/t/how-can-i-solve-complex-valued-ordinary-differential-equations-odes-using-neural-networks-given-limitations-with-complex-data-types-in-libraries-like-lux/110581)

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**Author:** [@sahakyan2003](https://discourse.julialang.org/u/sahakyan2003)\
**Replies:** 2\
**Last updated:** [February 22, 2024, 5:56pm UTC](https://discourse.julialang.org/t/how-can-i-solve-complex-valued-ordinary-differential-equations-odes-using-neural-networks-given-limitations-with-complex-data-types-in-libraries-like-lux/110581 "2024-02-22T17:56:50Z")

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Here I describe the code where I want to train the neural network but face the problem Here are the libraries I use. using NeuralPDE using DifferentialEquations using Plots using Lux, Random The function system\_of\_de! …

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## [Colorbar positionning with Makie](https://discourse.julialang.org/t/colorbar-positionning-with-makie/110582)

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**Author:** [@gdestouet](https://discourse.julialang.org/u/gdestouet)\
**Replies:** 3\
**Last updated:** [February 22, 2024, 5:55pm UTC](https://discourse.julialang.org/t/colorbar-positionning-with-makie/110582 "2024-02-22T17:55:36Z")

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Hi everyone, I am currently struggling to make a colorbar stick to the right yaxis of a contour plot whose x axis need to be align with an other line plot just below. fig = Figure() ax1 = Axis(fig\[1,1\]) Box(fig\[1, 1\], …

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## [How to determine the number of elements in RemoteChannel?](https://discourse.julialang.org/t/how-to-determine-the-number-of-elements-in-remotechannel/20143)

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**Author:** [@jamm](https://discourse.julialang.org/u/jamm)\
**Replies:** 4\
**Last updated:** [February 22, 2024, 12:08pm UTC](https://discourse.julialang.org/t/how-to-determine-the-number-of-elements-in-remotechannel/20143 "2024-02-22T12:08:28Z")

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Hi Community! The simple Cannel show the current number of elements directly: B = Channel(2) put!(B,"one") put!(B,"two") B Channel{Any}(sz\_max:2,sz\_curr:2) the sz\_curr is current numbers of elements in channel. In c…

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