# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=180

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

**Page:** 181

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## [Solving PDE + DAE using method of lines?](https://discourse.julialang.org/t/solving-pde-dae-using-method-of-lines/101370)

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**Author:** [@KevinModica](https://discourse.julialang.org/u/KevinModica)\
**Replies:** 3\
**Last updated:** [July 9, 2023, 2:03pm UTC](https://discourse.julialang.org/t/solving-pde-dae-using-method-of-lines/101370 "2023-07-09T14:03:17Z")

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Hello All, I am new to Julia, and I have a lot of difficulty navigating the documentation (especially with functions being imported all at once with “using …”, so I can never tell what function belongs to what). I’m tr…

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## [How to linearize a model](https://discourse.julialang.org/t/how-to-linearize-a-model/99886)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 14\
**Last updated:** [July 9, 2023, 8:07am UTC](https://discourse.julialang.org/t/how-to-linearize-a-model/99886 "2023-07-09T08:07:54Z")

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What I did so far: I can define a model using ModelingToolkit.jl I can simplify the system of equations I can simulate the step response of the model Now I would like to linearize the model. In theory very easy, just …

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## [Best approach to solving this coupled nonlinear PDE system (incompressible convection)?](https://discourse.julialang.org/t/best-approach-to-solving-this-coupled-nonlinear-pde-system-incompressible-convection/101290)

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**Author:** [@PeX](https://discourse.julialang.org/u/PeX)\
**Replies:** 3\
**Last updated:** [July 8, 2023, 9:17pm UTC](https://discourse.julialang.org/t/best-approach-to-solving-this-coupled-nonlinear-pde-system-incompressible-convection/101290 "2023-07-08T21:17:44Z")

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Hello everyone! I’m new to solving PDEs with Julia, only done ODEs so far. My problem looks like this: -\\nabla P+\\nabla \\cdot \\sigma+\\rho \\vec{g}=0 \\nabla \\cdot \\vec{u}=0 \\dot{\\varepsilon}=\\frac{1}{2}\\left(\\nabla …

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## [SOS Julia Newton Polytopes](https://discourse.julialang.org/t/sos-julia-newton-polytopes/101369)

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**Author:** [@ilovemath](https://discourse.julialang.org/u/ilovemath)\
**Replies:** 0\
**Last updated:** [July 8, 2023, 9:08pm UTC](https://discourse.julialang.org/t/sos-julia-newton-polytopes/101369 "2023-07-08T21:08:58Z")

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I am trying to investigate the details in which Newton polytope reduction is being incorporated in the sum of squares constraints for SumOfSquares/JuMP. Firstly, is the Newton polytope reduction being exploited automati…

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## [JuMP Objective coefficient writing](https://discourse.julialang.org/t/jump-objective-coefficient-writing/101286)

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**Author:** [@Luiz\_Monteiro](https://discourse.julialang.org/u/Luiz_Monteiro)\
**Replies:** 4\
**Last updated:** [July 8, 2023, 7:03pm UTC](https://discourse.julialang.org/t/jump-objective-coefficient-writing/101286 "2023-07-08T19:03:54Z")

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Hi, I am trying to write an objective using index for each element of an expression, just like a simple constraint (example: i, h, k in @constraint(model1, con19B\[i in V0\_customer, h in Vstation, j in V0\_customer, k in …

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## [Choice of Kernel Function (MultiOutput Gaussian Process)](https://discourse.julialang.org/t/choice-of-kernel-function-multioutput-gaussian-process/101359)

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**Author:** [@lsablon](https://discourse.julialang.org/u/lsablon)\
**Replies:** 0\
**Last updated:** [July 8, 2023, 6:55pm UTC](https://discourse.julialang.org/t/choice-of-kernel-function-multioutput-gaussian-process/101359 "2023-07-08T18:55:35Z")

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Hi ! I am using Gaussian Processes in my research, but I lack some theoretical knowledge about multioutput kernels. For the moment, I am using the JuliaGaussianProcesses ecosystem. My training data are maps associated…

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## [Gather Optimal Tableau Information using CPLEX.jl](https://discourse.julialang.org/t/gather-optimal-tableau-information-using-cplex-jl/101331)

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**Author:** [@afazevedo](https://discourse.julialang.org/u/afazevedo)\
**Replies:** 3\
**Last updated:** [July 8, 2023, 2:56pm UTC](https://discourse.julialang.org/t/gather-optimal-tableau-information-using-cplex-jl/101331 "2023-07-08T14:56:24Z")

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Hey! I’m currently working on implementing fractional Gomory cuts, and I need to know the optimal simplex tableau in order to obtain these constraints. In this post on Simplex tableau, they suggested using ccall and men…

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## [Largest number of variables that SCS.jl can handle](https://discourse.julialang.org/t/largest-number-of-variables-that-scs-jl-can-handle/100929)

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**Author:** [@WellWellww](https://discourse.julialang.org/u/WellWellww)\
**Replies:** 11\
**Last updated:** [July 8, 2023, 2:50pm UTC](https://discourse.julialang.org/t/largest-number-of-variables-that-scs-jl-can-handle/100929 "2023-07-08T14:50:10Z")

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I was using JuMP.jl and SCS.jl to code and solve an optimization problem. The problem involved 234,932 optimization variables and 251,088 constraints. However, I encountered the following error: \[113945\] signal (11.1): …

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## [Calligraphic LaTeX fonts in Makie](https://discourse.julialang.org/t/calligraphic-latex-fonts-in-makie/101209)

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**Author:** [@Pablo\_Marchant](https://discourse.julialang.org/u/Pablo_Marchant)\
**Replies:** 10\
**Last updated:** [July 8, 2023, 11:08am UTC](https://discourse.julialang.org/t/calligraphic-latex-fonts-in-makie/101209 "2023-07-08T11:08:40Z")

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Hi all, I’ve run into a small problem regarding mismatch of LaTeX fonts between Makie and the LaTeX documents where I am placing such figures. This is really a problem with the calligraphic fonts that are used in math m…

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## [Benchmarking the Parallel 1D Heat Equation Solver in Chapel, Charm++, C++, HPX, Go, Julia, Python, Rust, Swift, and Java](https://discourse.julialang.org/t/benchmarking-the-parallel-1d-heat-equation-solver-in-chapel-charm-c-hpx-go-julia-python-rust-swift-and-java/101330)

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**Author:** [@Perrin\_Meyer](https://discourse.julialang.org/u/Perrin_Meyer)\
**Replies:** 7\
**Last updated:** [July 8, 2023, 10:11am UTC](https://discourse.julialang.org/t/benchmarking-the-parallel-1d-heat-equation-solver-in-chapel-charm-c-hpx-go-julia-python-rust-swift-and-java/101330 "2023-07-08T10:11:45Z")

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Interesting arXiv preprint… TLDNR: (Julia crushes Numpy…)

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## [Hyperthreading in HPC](https://discourse.julialang.org/t/hyperthreading-in-hpc/101316)

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**Author:** [@fgerick](https://discourse.julialang.org/u/fgerick)\
**Replies:** 16\
**Last updated:** [July 8, 2023, 7:04am UTC](https://discourse.julialang.org/t/hyperthreading-in-hpc/101316 "2023-07-08T07:04:18Z")

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Hi everyone, I have a question regarding the use of hyperthreading/SMT on HPC systems. HPC hyperthreading on off - Google Search reveals some vague hints that in the past it has been accepted that enabling hyperthreadin…

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## [CAN bus library for Julia?](https://discourse.julialang.org/t/can-bus-library-for-julia/35292)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 4\
**Last updated:** [July 8, 2023, 6:39am UTC](https://discourse.julialang.org/t/can-bus-library-for-julia/35292 "2023-07-08T06:39:38Z")

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Good evening, Is there any package that supports to send and receive CAN bus messages for Julia? If not, would you suggest to use a Python library or a C/C++ library? There is a Python package: https://python-can.rea…

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## [Running OOM trying to load data to GPU](https://discourse.julialang.org/t/running-oom-trying-to-load-data-to-gpu/100480)

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**Author:** [@lepton01](https://discourse.julialang.org/u/lepton01)\
**Replies:** 2\
**Last updated:** [July 8, 2023, 6:26am UTC](https://discourse.julialang.org/t/running-oom-trying-to-load-data-to-gpu/100480 "2023-07-08T06:26:11Z")

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Hello there. After training the CNN, I wrote a function to estimate the accuracy of it. function accuracy(A, B, name) BSON.@load name \* ".bson" model model = model |\> gpu X1, Y1 = A X2, Y2 = B Y\_tr\_…

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## [How to implement a Bessel filter with ModelingToolkit?](https://discourse.julialang.org/t/how-to-implement-a-bessel-filter-with-modelingtoolkit/101220)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 13\
**Last updated:** [July 8, 2023, 3:47am UTC](https://discourse.julialang.org/t/how-to-implement-a-bessel-filter-with-modelingtoolkit/101220 "2023-07-08T03:47:46Z")

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How can I implement the following Bessel filter with ModelingToolkit? \\frac{w\_1²}{0.618 s²~+~1.3617 w\_1 s~+~w\_1²} I know there is this filter component in the standard library: Basic Blocks · ModelingToolkitStandardLib…

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## [Cannot multiply a quadratic expression by an affine expression](https://discourse.julialang.org/t/cannot-multiply-a-quadratic-expression-by-an-affine-expression/101240)

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**Author:** [@horvetz](https://discourse.julialang.org/u/horvetz)\
**Replies:** 6\
**Last updated:** [July 7, 2023, 11:57pm UTC](https://discourse.julialang.org/t/cannot-multiply-a-quadratic-expression-by-an-affine-expression/101240 "2023-07-07T23:57:01Z")

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I am trying to define an expression P = Q’ \* R \* Q using @expression but it is not cooperating. I tried to split the matrix product and even use @NLexpression macro but no luck. Can someone suggest a way to define P? u…

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## [Include fixed point in JuMP](https://discourse.julialang.org/t/include-fixed-point-in-jump/101236)

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**Author:** [@leima0521](https://discourse.julialang.org/u/leima0521)\
**Replies:** 10\
**Last updated:** [July 7, 2023, 8:30pm UTC](https://discourse.julialang.org/t/include-fixed-point-in-jump/101236 "2023-07-07T20:30:41Z")

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Hi, I am using JuMP to maximize a nonlinear function. The function takes two vector inputs: d and p. The dimension of p is much smaller than the dimension of d. The trick is that the value of d is determined by p. Give…

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## [VSCode, conda environments, and Stan.jl](https://discourse.julialang.org/t/vscode-conda-environments-and-stan-jl/101271)

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**Author:** [@opera\_malenky](https://discourse.julialang.org/u/opera_malenky)\
**Replies:** 6\
**Last updated:** [July 7, 2023, 7:56pm UTC](https://discourse.julialang.org/t/vscode-conda-environments-and-stan-jl/101271 "2023-07-07T19:56:51Z")

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I have spent the last couple of days trying to get Stan.jl to run with VSCode. Stan.jl requires cmdstan, which (on my platform, Windows) is most easily installed via conda. However, the conda environments seem to be giv…

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## [JuMP summation constraint error](https://discourse.julialang.org/t/jump-summation-constraint-error/101181)

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**Author:** [@Stuart\_Rogers](https://discourse.julialang.org/u/Stuart_Rogers)\
**Replies:** 5\
**Last updated:** [July 7, 2023, 2:10am UTC](https://discourse.julialang.org/t/jump-summation-constraint-error/101181 "2023-07-07T02:10:40Z")

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I’m trying to add a constraint to a JuMP model that sums the elements of a constant matrix c times binary variables x. For i=1:I, x\[i,j\] is a binary variable for j=1:len\_J\_i\[i\]. That is for each i=1:I, x\[i,:\] is a vecto…

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## [Ipopt solves large-scale nonlinear problems](https://discourse.julialang.org/t/ipopt-solves-large-scale-nonlinear-problems/98831)

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**Author:** [@lzq-zbc](https://discourse.julialang.org/u/lzq-zbc)\
**Replies:** 18\
**Last updated:** [July 7, 2023, 2:06am UTC](https://discourse.julialang.org/t/ipopt-solves-large-scale-nonlinear-problems/98831 "2023-07-07T02:06:52Z")

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I’m new to Julia, I’m working on optimal power flow problems in the direction of power systems, and when solving large-scale problems with Julia (there are thousands of variables and constraints, of course, most of them …

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## [Identical diagonal elements](https://discourse.julialang.org/t/identical-diagonal-elements/83969)

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**Author:** [@ivzktch99](https://discourse.julialang.org/u/ivzktch99)\
**Replies:** 6\
**Last updated:** [July 7, 2023, 2:01am UTC](https://discourse.julialang.org/t/identical-diagonal-elements/83969 "2023-07-07T02:01:56Z")

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Suppose you have using JuMP,Ipopt model = Model(Ipopt.Optimizer) n = 5 @variable(model, X\[1:n, 1:n\]) What is the easiest way to impose that the elements of main diagonal of X are identical. No restriction on what they …

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## ["BoundError: attempt to access JuMP containers" when creating a constraint](https://discourse.julialang.org/t/bounderror-attempt-to-access-jump-containers-when-creating-a-constraint/100306)

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**Author:** [@Luiz\_Monteiro](https://discourse.julialang.org/u/Luiz_Monteiro)\
**Replies:** 2\
**Last updated:** [July 7, 2023, 1:37am UTC](https://discourse.julialang.org/t/bounderror-attempt-to-access-jump-containers-when-creating-a-constraint/100306 "2023-07-07T01:37:04Z")

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Hi, I’m trying to create a constraint like specified below, but have this error: “ERROR: BoundsError: attempt to access JuMP.Containers.SparseAxisArray{VariableRef, 3, Tuple{Int64, Int64, Bool}} with 44 entries at index”…

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## [Plots.jl: Creating stacked subplots with common x-axis and no margins (padding) in between](https://discourse.julialang.org/t/plots-jl-creating-stacked-subplots-with-common-x-axis-and-no-margins-padding-in-between/101233)

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**Author:** [@ykh-1992](https://discourse.julialang.org/u/ykh-1992)\
**Replies:** 1\
**Last updated:** [July 6, 2023, 7:25pm UTC](https://discourse.julialang.org/t/plots-jl-creating-stacked-subplots-with-common-x-axis-and-no-margins-padding-in-between/101233 "2023-07-06T19:25:56Z")

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Hello! I would like to know if it is possible to create a plot with stacked subplots sharing a common x-axis. I’m looking to have no margins, gaps, spaces, or paddings in between the subplots. Is it possible to do it …

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## [Rodas4 vs Rodas4P vs Rodas4P2 solvers](https://discourse.julialang.org/t/rodas4-vs-rodas4p-vs-rodas4p2-solvers/101261)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 6\
**Last updated:** [July 6, 2023, 7:59pm UTC](https://discourse.julialang.org/t/rodas4-vs-rodas4p-vs-rodas4p2-solvers/101261 "2023-07-06T19:59:11Z")

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Today I found that the solver Rodas4P2 is working best for my model. For an tolerance of 1e-7 it is 4 times faster than Simulink, operating at a tolerance of 1e-3. But what is the difference between Rodas4, Rodas4P and …

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## [Filtering/joining multiple data frames with respect to selected keys](https://discourse.julialang.org/t/filtering-joining-multiple-data-frames-with-respect-to-selected-keys/101108)

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**Author:** [@johnbb](https://discourse.julialang.org/u/johnbb)\
**Replies:** 9\
**Last updated:** [July 6, 2023, 4:52pm UTC](https://discourse.julialang.org/t/filtering-joining-multiple-data-frames-with-respect-to-selected-keys/101108 "2023-07-06T16:52:46Z")

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I have an array/vector of data frames where each data frame has columns site and time and some others with common names. How can I filter the data frames such that each data frame has exactly the same rows for site and t…

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## [Is there a way to parallelize portions of code in Flux?](https://discourse.julialang.org/t/is-there-a-way-to-parallelize-portions-of-code-in-flux/101096)

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**Author:** [@josemanuel22](https://discourse.julialang.org/u/josemanuel22)\
**Replies:** 7\
**Last updated:** [July 6, 2023, 4:17pm UTC](https://discourse.julialang.org/t/is-there-a-way-to-parallelize-portions-of-code-in-flux/101096 "2023-07-06T16:17:35Z")

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Hello, I have a code where I want to execute a parallel loop within the code portion responsible for automatic differentiation. This is because the cost function I want to compute relies on certain properties of the esti…

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## [Batch trainning with Lux and multiple optimizers](https://discourse.julialang.org/t/batch-trainning-with-lux-and-multiple-optimizers/100571)

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**Author:** [@James\_Fernandez](https://discourse.julialang.org/u/James_Fernandez)\
**Replies:** 14\
**Last updated:** [July 6, 2023, 3:35pm UTC](https://discourse.julialang.org/t/batch-trainning-with-lux-and-multiple-optimizers/100571 "2023-07-06T15:35:40Z")

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Hello to all, Following the description of batching in Flux in here. I have created a script with Lux: using Lux, Optimization, OptimizationOptimisers, OptimizationOptimJL, OrdinaryDiffEq, SciMLSensitivity, ComponentA…

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## [Training universal differential equations](https://discourse.julialang.org/t/training-universal-differential-equations/100787)

<div class="topic-metadata">

**Author:** [@T\_J](https://discourse.julialang.org/u/T_J)\
**Replies:** 7\
**Last updated:** [July 6, 2023, 3:09pm UTC](https://discourse.julialang.org/t/training-universal-differential-equations/100787 "2023-07-06T15:09:22Z")

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Hello, In a universal differential equation where the ODE + NN is not able to finish the integration routine, Is there a procedure (best practices) to execute in order to train the ODE? If the integration procedure is …

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## [Visualize 3D polygon of brain regions given points representing exterior border](https://discourse.julialang.org/t/visualize-3d-polygon-of-brain-regions-given-points-representing-exterior-border/101247)

<div class="topic-metadata">

**Author:** [@vandenman](https://discourse.julialang.org/u/vandenman)\
**Replies:** 3\
**Last updated:** [July 6, 2023, 11:25am UTC](https://discourse.julialang.org/t/visualize-3d-polygon-of-brain-regions-given-points-representing-exterior-border/101247 "2023-07-06T11:25:19Z")

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I’m trying to create a 3d plot of some brain regions. However, the data I have is not a mesh but a series of 3d points that indicate the exterior border of the regions. How can I plot this with GLMakie? Below is the cod…

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## [Fixing some regions of a Variable array in convex.jl](https://discourse.julialang.org/t/fixing-some-regions-of-a-variable-array-in-convex-jl/101246)

<div class="topic-metadata">

**Author:** [@UgeB](https://discourse.julialang.org/u/UgeB)\
**Replies:** 2\
**Last updated:** [July 6, 2023, 9:11am UTC](https://discourse.julialang.org/t/fixing-some-regions-of-a-variable-array-in-convex-jl/101246 "2023-07-06T09:11:38Z")

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The fix! function in the Convex.jl packages allows to fix the value of a variable to a constant during the optimization. I was wondering how I can get the same result with a multi-dimensional variable for which I want t…

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## [Big PDESystem exceeds maximal parameter space of CUDA kernels](https://discourse.julialang.org/t/big-pdesystem-exceeds-maximal-parameter-space-of-cuda-kernels/101047)

<div class="topic-metadata">

**Author:** [@drsk](https://discourse.julialang.org/u/drsk)\
**Replies:** 7\
**Last updated:** [July 6, 2023, 6:48am UTC](https://discourse.julialang.org/t/big-pdesystem-exceeds-maximal-parameter-space-of-cuda-kernels/101047 "2023-07-06T06:48:06Z")

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I’m using NeuralPDE.jl to find critical points of a geometric flow equation on the four-torus. This ends up being a fairly big system, with 18 variables in total. I think the size of the system makes the CUDA compiler ge…

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