# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=95

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**Page:** 96

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## [Parquet: writing data as row groups](https://discourse.julialang.org/t/parquet-writing-data-as-row-groups/117247)

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**Author:** [@kmiernik](https://discourse.julialang.org/u/kmiernik)\
**Replies:** 1\
**Last updated:** [July 22, 2024, 11:38am UTC](https://discourse.julialang.org/t/parquet-writing-data-as-row-groups/117247 "2024-07-22T11:38:52Z")

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I would appreciate help with my problem. I have data that come in series. After processing raw input I have about 100 columns and about 10^8 rows per series (and about 100 series in total). So far I have been using HDF5 …

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## [Universal differential equations with MTK](https://discourse.julialang.org/t/universal-differential-equations-with-mtk/103225)

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**Author:** [@martincornejo](https://discourse.julialang.org/u/martincornejo)\
**Replies:** 6\
**Last updated:** [July 22, 2024, 8:26am UTC](https://discourse.julialang.org/t/universal-differential-equations-with-mtk/103225 "2024-07-22T08:26:06Z")

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The SciML documentation has this great tutorial on Automatically Discover Missing Physics by Embedding Machine Learning into Differential Equations In the tutorial the universal differential equation is defined as foll…

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## [Understanding @connector in MTK](https://discourse.julialang.org/t/understanding-connector-in-mtk/117223)

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**Author:** [@hexaeder](https://discourse.julialang.org/u/hexaeder)\
**Replies:** 2\
**Last updated:** [July 22, 2024, 8:09am UTC](https://discourse.julialang.org/t/understanding-connector-in-mtk/117223 "2024-07-22T08:09:38Z")

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Hello, I have trouble understanding the modeling scheme of modern MTK with pins /connectors and so on. As a toy example, I try to implement this simple system of two coupled oscillators: I tried to model it using th…

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## [UDE pre-fitting with collocation](https://discourse.julialang.org/t/ude-pre-fitting-with-collocation/117326)

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**Author:** [@martincornejo](https://discourse.julialang.org/u/martincornejo)\
**Replies:** 0\
**Last updated:** [July 22, 2024, 7:58am UTC](https://discourse.julialang.org/t/ude-pre-fitting-with-collocation/117326 "2024-07-22T07:58:08Z")

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Hi, I’d like to pre-train a UDE model using the collocation method from DiffEqFlux.jl: Smoothed Collocation · DiffEqFlux.jl My dataset is 10 days worth of temperature measurements and has around 45,000 points which are …

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## [Question about when MiniZinc will return feasible solutions](https://discourse.julialang.org/t/question-about-when-minizinc-will-return-feasible-solutions/116595)

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**Author:** [@slwu89](https://discourse.julialang.org/u/slwu89)\
**Replies:** 12\
**Last updated:** [July 22, 2024, 6:06am UTC](https://discourse.julialang.org/t/question-about-when-minizinc-will-return-feasible-solutions/116595 "2024-07-22T06:06:17Z")

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Hi all. I have a question about the following MiniZinc model. I am able to give a feasible solution with primal\_feasibility\_report but nothing is found by the solver. I’m aware of the silliness of the presented model, t…

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## [\[Makie\] \\widehat and \\widetilde in xlabel](https://discourse.julialang.org/t/makie-widehat-and-widetilde-in-xlabel/117277)

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**Author:** [@Jeonghun\_Lee](https://discourse.julialang.org/u/Jeonghun_Lee)\
**Replies:** 2\
**Last updated:** [July 22, 2024, 3:26am UTC](https://discourse.julialang.org/t/makie-widehat-and-widetilde-in-xlabel/117277 "2024-07-22T03:26:24Z")

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Here’s my code. using CairoMakie using LaTeXStrings fig = Figure() ax = Axis(fig\[1,1\], xlabel=L"\\widehat{EE}") fig I got the following error message. { "name": "MathTeXEngine.TeXParseError", "message": "TeXParseE…

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## [Primal-Dual Hybrid Gradient for L1 regularization](https://discourse.julialang.org/t/primal-dual-hybrid-gradient-for-l1-regularization/117201)

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**Author:** [@aris](https://discourse.julialang.org/u/aris)\
**Replies:** 23\
**Last updated:** [July 21, 2024, 5:34pm UTC](https://discourse.julialang.org/t/primal-dual-hybrid-gradient-for-l1-regularization/117201 "2024-07-21T17:34:33Z")

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Greetings everyone, I was looking for a way to solve the following problem using julia: min\_{f\\geq0} \\; ||Kf-s||\_2^2 +\\alpha ||f||\_1 There’s this paper (section 2.2 specifically), where the authors use a Primal-D…

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## [PowerModels.jl multinetwork for Security Constrained AC-OPF](https://discourse.julialang.org/t/powermodels-jl-multinetwork-for-security-constrained-ac-opf/113511)

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**Author:** [@lcharles](https://discourse.julialang.org/u/lcharles)\
**Replies:** 4\
**Last updated:** [July 21, 2024, 4:52pm UTC](https://discourse.julialang.org/t/powermodels-jl-multinetwork-for-security-constrained-ac-opf/113511 "2024-07-21T16:52:10Z")

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Hi, I’m currently working on a project in which I use the PowerModels package. In the first part of my project, I used the ‘solve\_opf’ function with the different models of quadratic relaxations implemented in the pack…

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## [Best way to implement and solve an ODE with a linearized RHS?](https://discourse.julialang.org/t/best-way-to-implement-and-solve-an-ode-with-a-linearized-rhs/117297)

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**Author:** [@homocomputeris](https://discourse.julialang.org/u/homocomputeris)\
**Replies:** 2\
**Last updated:** [July 21, 2024, 4:33pm UTC](https://discourse.julialang.org/t/best-way-to-implement-and-solve-an-ode-with-a-linearized-rhs/117297 "2024-07-21T16:33:22Z")

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Say, I have a system \\dot{u} = f(u(t),t). I want to linearize the RHS at u(t\_{n}) and have \\dot{u} = f(u(t\_n),t\_n) + f\_{u}'(u(t\_n),t\_n)\\cdot(u(t)-u(t\_{n})). In terms of DifferentialEquations.jl I can define f(u,p,t) whe…

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## [Set custom colorbar tick-labels](https://discourse.julialang.org/t/set-custom-colorbar-tick-labels/69806)

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**Author:** [@luraess](https://discourse.julialang.org/u/luraess)\
**Replies:** 6\
**Last updated:** [July 21, 2024, 3:56pm UTC](https://discourse.julialang.org/t/set-custom-colorbar-tick-labels/69806 "2024-07-21T15:56:46Z")

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Hi, using Plots.jl and GR backend, how to set custom (text) colorbar tick-labels for each of the 5 color “bins” from this MWE using Plots.jl heatmap(rand(5,5), color=palette(:inferno, 5)) Thanks !

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## [Trying to use \`GRBreadmodel\`](https://discourse.julialang.org/t/trying-to-use-grbreadmodel/117199)

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**Author:** [@sstroemer](https://discourse.julialang.org/u/sstroemer)\
**Replies:** 4\
**Last updated:** [July 21, 2024, 12:06pm UTC](https://discourse.julialang.org/t/trying-to-use-grbreadmodel/117199 "2024-07-21T12:06:55Z")

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I’m trying something like using JuMP import Gurobi grb\_model = Gurobi.Optimizer() Gurobi.GRBreadmodel( grb\_model.env, "foo.lp", Ptr{Gurobi.GRBmodel}(pointer\_from\_objref(grb\_model)) ) model = direct\_model(g…

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## [Blending colours of overlapping lines with lighten mode](https://discourse.julialang.org/t/blending-colours-of-overlapping-lines-with-lighten-mode/117291)

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**Author:** [@BenCichos](https://discourse.julialang.org/u/BenCichos)\
**Replies:** 0\
**Last updated:** [July 21, 2024, 9:05am UTC](https://discourse.julialang.org/t/blending-colours-of-overlapping-lines-with-lighten-mode/117291 "2024-07-21T09:05:38Z")

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I want to plot Rays with multiple colours in Makie. Sometimes these rays might overlap each other, for example when I want to show light diffraction from a prism, I would want to represent a white ray but made out of mul…

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## [Starting With Julia!](https://discourse.julialang.org/t/starting-with-julia/117285)

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**Author:** [@ZherpiaWhiskers](https://discourse.julialang.org/u/ZherpiaWhiskers)\
**Replies:** 6\
**Last updated:** [July 21, 2024, 7:14am UTC](https://discourse.julialang.org/t/starting-with-julia/117285 "2024-07-21T07:14:28Z")

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Heya! I’m a bit new to Julia, so, i’ve been studying the language for a couple of days, i already know some of the syntax, i’ve learned various types of data structures and I’m going to learn algorithms by implementing t…

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## [Notebook widgets do not show up](https://discourse.julialang.org/t/notebook-widgets-do-not-show-up/116985)

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**Author:** [@mocalvao](https://discourse.julialang.org/u/mocalvao)\
**Replies:** 1\
**Last updated:** [July 21, 2024, 2:11am UTC](https://discourse.julialang.org/t/notebook-widgets-do-not-show-up/116985 "2024-07-21T02:11:06Z")

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I have Julia version 1.10.4 and the following packages installed in my work environment: \[61744808\] DynamicalSystems v3.3.17 \[7073ff75\] IJulia v1.25.0 \[c601a237\] Interact v0.10.5 \[91a5bcdd\] Plots v1.40.5 \[c3e4b0f8\] …

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## [Rasters: can I select certain time steps of a lazy rasterseries before or while reading it into memory?](https://discourse.julialang.org/t/rasters-can-i-select-certain-time-steps-of-a-lazy-rasterseries-before-or-while-reading-it-into-memory/116328)

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**Author:** [@aasdelat](https://discourse.julialang.org/u/aasdelat)\
**Replies:** 6\
**Last updated:** [July 20, 2024, 8:38pm UTC](https://discourse.julialang.org/t/rasters-can-i-select-certain-time-steps-of-a-lazy-rasterseries-before-or-while-reading-it-into-memory/116328 "2024-07-20T20:38:28Z")

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I have a bunch of grib files, each covering a different time period, but the same spatial extent. I have opened them as a RasterSeries (library Rasters.jl) with lazy=true, so that the data are not loaded into memory. da…

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## [Dense Layers in Attention Don't Train](https://discourse.julialang.org/t/dense-layers-in-attention-dont-train/117190)

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**Author:** [@Helectus](https://discourse.julialang.org/u/Helectus)\
**Replies:** 1\
**Last updated:** [July 20, 2024, 4:19pm UTC](https://discourse.julialang.org/t/dense-layers-in-attention-dont-train/117190 "2024-07-20T16:19:15Z")

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I am trying to create a transformer model using Flux.jl from scratch. I have an encoder struct that has an attention struct, which includes Q, K, V, O dense layers. My problem is that Dense.weights and Dense.bias don’t s…

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## [3D interpolation in Julia](https://discourse.julialang.org/t/3d-interpolation-in-julia/117035)

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**Author:** [@jgr](https://discourse.julialang.org/u/jgr)\
**Replies:** 21\
**Last updated:** [July 20, 2024, 6:25am UTC](https://discourse.julialang.org/t/3d-interpolation-in-julia/117035 "2024-07-20T06:25:02Z")

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I am doing 3D interpolation with the nodes being \[x,y,z\], where x is a 1\*nx vector, y is 1\*ny,1\*nx, the corresponding values to be interpolated is V which is a nx\*ny\*nz matrix. I use Dierckx for 1d/2d interpolation, but …

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## [Symbolics Simplification](https://discourse.julialang.org/t/symbolics-simplification/117232)

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**Author:** [@brombo](https://discourse.julialang.org/u/brombo)\
**Replies:** 1\
**Last updated:** [July 20, 2024, 1:38am UTC](https://discourse.julialang.org/t/symbolics-simplification/117232 "2024-07-20T01:38:28Z")

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I have started to use the Symbolics package. I am familiar with Sympy and wonder how the simplification of expression in Symbolics compares to that in Sympy both in terms of capability and speed? Also how actively is t…

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## [How to set the number of scales output of Wavelets.jl](https://discourse.julialang.org/t/how-to-set-the-number-of-scales-output-of-wavelets-jl/117251)

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**Author:** [@bryaan](https://discourse.julialang.org/u/bryaan)\
**Replies:** 0\
**Last updated:** [July 19, 2024, 6:34pm UTC](https://discourse.julialang.org/t/how-to-set-the-number-of-scales-output-of-wavelets-jl/117251 "2024-07-19T18:34:32Z")

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By default for my signal Wavelets.jl cwt is giving 28 columns in the output Y matrix. How can I set this to a constant number of columns no matter the signal? using Wavelets Y = Wavelets.cwt(signal, wavelet(WT.dog2))

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## [Parquet2.jl 0.2.25 outputting corrupted files (0.2.26 fix now up)](https://discourse.julialang.org/t/parquet2-jl-0-2-25-outputting-corrupted-files-0-2-26-fix-now-up/117102)

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**Author:** [@ExpandingMan](https://discourse.julialang.org/u/ExpandingMan)\
**Replies:** 5\
**Last updated:** [July 19, 2024, 6:29pm UTC](https://discourse.julialang.org/t/parquet2-jl-0-2-25-outputting-corrupted-files-0-2-26-fix-now-up/117102 "2024-07-19T18:29:10Z")

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Recently there has been a change in the parquet thrift metadata schema which I included in Parquet2.jl as of 0.2.25. Unfortunately it looks like this is now outputting corrupt files in many circumstances (can confirm th…

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## [BoundsError in Zygote RNN gradient](https://discourse.julialang.org/t/boundserror-in-zygote-rnn-gradient/117219)

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**Author:** [@FabriSR15](https://discourse.julialang.org/u/FabriSR15)\
**Replies:** 0\
**Last updated:** [July 19, 2024, 8:06am UTC](https://discourse.julialang.org/t/boundserror-in-zygote-rnn-gradient/117219 "2024-07-19T08:06:43Z")

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Hi everyone, I’ve experienced some problems with Zygote regarding the computation of gradients of a loss function obtained via sampling. An RNN generates samples autoregressively and the loss function is then computed u…

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## [Constraint on count of variables \>0 in JuMP?](https://discourse.julialang.org/t/constraint-on-count-of-variables-0-in-jump/117072)

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**Author:** [@sdwfrost](https://discourse.julialang.org/u/sdwfrost)\
**Replies:** 3\
**Last updated:** [July 18, 2024, 11:46pm UTC](https://discourse.julialang.org/t/constraint-on-count-of-variables-0-in-jump/117072 "2024-07-18T23:46:06Z")

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I have a model with a control variable as follows: @variable(model, 0 ≤ u\[1:(T+1)\] ≤ u\_max) I want to constrain the number of elements in u greater than 0 to be less than a threshold, u\_nonzero\_max. How can I do this …

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## [Problem on solving periodic solution of ODE using orthogonal polynomial pseudo-arclength method](https://discourse.julialang.org/t/problem-on-solving-periodic-solution-of-ode-using-orthogonal-polynomial-pseudo-arclength-method/117177)

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**Author:** [@cc2024](https://discourse.julialang.org/u/cc2024)\
**Replies:** 4\
**Last updated:** [July 18, 2024, 3:33pm UTC](https://discourse.julialang.org/t/problem-on-solving-periodic-solution-of-ode-using-orthogonal-polynomial-pseudo-arclength-method/117177 "2024-07-18T15:33:41Z")

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a simple Duffing equation: dx/dt=xt dxt/dt=F0u-a1x1-a1tx1t-a3x1^3 du/dt=-omegav+u(1-u^2-v^2) dv/dt=omegau+v(1-u^2-v^2) parameters: \[omega;F0;a1t;a3\]=\[2;0.01;1;0.008;0.75\] initial state point: \[x0;xt0;u0;v0\]=\[0;0;1…

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## [CategoricalArrays.jl syntax question: vectorizing string operation](https://discourse.julialang.org/t/categoricalarrays-jl-syntax-question-vectorizing-string-operation/117106)

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**Author:** [@croberts](https://discourse.julialang.org/u/croberts)\
**Replies:** 7\
**Last updated:** [July 18, 2024, 2:53pm UTC](https://discourse.julialang.org/t/categoricalarrays-jl-syntax-question-vectorizing-string-operation/117106 "2024-07-18T14:53:17Z")

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I’m assuming that there exists convenient syntax to performantly vectorize string operations on categorical arrays? Suppose we want to subset a categorical array to the values whose labels satisfy some condition. Consid…

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## [Using lens in Plots.jl with subplots](https://discourse.julialang.org/t/using-lens-in-plots-jl-with-subplots/117162)

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**Author:** [@PeX](https://discourse.julialang.org/u/PeX)\
**Replies:** 1\
**Last updated:** [July 18, 2024, 11:23am UTC](https://discourse.julialang.org/t/using-lens-in-plots-jl-with-subplots/117162 "2024-07-18T11:23:20Z")

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Hi all, I’m trying to add zoomed insets to a figure that contains four panels. I’m not sure how to configure the lens function to be added to a specific subplot in the layout. My plot function looks like this: #Adjust…

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## [Finding \*all\* the eigenvalues of a sparse matrix?](https://discourse.julialang.org/t/finding-all-the-eigenvalues-of-a-sparse-matrix/116895)

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**Author:** [@rafaelbailo](https://discourse.julialang.org/u/rafaelbailo)\
**Replies:** 24\
**Last updated:** [July 18, 2024, 9:22am UTC](https://discourse.julialang.org/t/finding-all-the-eigenvalues-of-a-sparse-matrix/116895 "2024-07-18T09:22:44Z")

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Seems that LinearAlgebra.jl does not work with sparse matrices, and the libraries that do (e.g. Arpack.jl, ArnoldiMethod.jl, KrylovKit.jl) all use iterative methods, which are not efficient to find all the eigenvalues. S…

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## [Reducing Numerical Diffusion in advection model using ModelingToolkit.jl and MethodOfLines.jl](https://discourse.julialang.org/t/reducing-numerical-diffusion-in-advection-model-using-modelingtoolkit-jl-and-methodoflines-jl/117135)

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**Author:** [@el\_desesperado](https://discourse.julialang.org/u/el_desesperado)\
**Replies:** 7\
**Last updated:** [July 18, 2024, 8:21am UTC](https://discourse.julialang.org/t/reducing-numerical-diffusion-in-advection-model-using-modelingtoolkit-jl-and-methodoflines-jl/117135 "2024-07-18T08:21:04Z")

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Hello, I have been trying to model the advection equation( du(x,t)/dt + du(x,t)/dx = 0) using ModelingToolkit.jl and MethodOfLines.jl. import OrdinaryDiffEq, ModelingToolkit, MethodOfLines, DomainSets ModelingToolkit.…

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## [Can only run Unit Tests with Gurobi locally because of Licence](https://discourse.julialang.org/t/can-only-run-unit-tests-with-gurobi-locally-because-of-licence/117169)

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**Author:** [@K5Julien](https://discourse.julialang.org/u/K5Julien)\
**Replies:** 1\
**Last updated:** [July 18, 2024, 7:10am UTC](https://discourse.julialang.org/t/can-only-run-unit-tests-with-gurobi-locally-because-of-licence/117169 "2024-07-18T07:10:10Z")

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Dear Julia Discourse Optimization, I can not run Unit Tests (Test.jl) with Gurobi, because CI.yml file and GitHub action don’t have a valid Gurobi Licence. @test rspoptimize(pars, 1, optimizer\_with\_attributes(GLPK.Opt…

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## [How to handle an optimizer which doesn't support an attribute of MathOptInterface?](https://discourse.julialang.org/t/how-to-handle-an-optimizer-which-doesnt-support-an-attribute-of-mathoptinterface/117133)

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**Author:** [@K5Julien](https://discourse.julialang.org/u/K5Julien)\
**Replies:** 2\
**Last updated:** [July 17, 2024, 9:59pm UTC](https://discourse.julialang.org/t/how-to-handle-an-optimizer-which-doesnt-support-an-attribute-of-mathoptinterface/117133 "2024-07-17T21:59:12Z")

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Dear Julia Discourse’s optimization community, Because getting Node Count: MOI.get(m, MOI.NodeCount()) is not supported by GLPK.jl, at the end of my optimization model, I tried the following: nodecount = -1 try…

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## [Functions of variables in @mtkmodel](https://discourse.julialang.org/t/functions-of-variables-in-mtkmodel/117159)

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**Author:** [@sdwfrost](https://discourse.julialang.org/u/sdwfrost)\
**Replies:** 1\
**Last updated:** [July 17, 2024, 8:31pm UTC](https://discourse.julialang.org/t/functions-of-variables-in-mtkmodel/117159 "2024-07-17T20:31:17Z")

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I’m playing with the new (at least to me) @mtkmodel syntax. Here’s my standard SIR model. using Symbolics using ModelingToolkit: t\_nounits as t, D\_nounits as D using OrdinaryDiffEq using Plots @mtkmodel SIR begin …

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