# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=156

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**Page:** 157

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## [Best Discrete Simulation Learning path](https://discourse.julialang.org/t/best-discrete-simulation-learning-path/105132)

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**Author:** [@ameresv](https://discourse.julialang.org/u/ameresv)\
**Replies:** 3\
**Last updated:** [November 2, 2023, 12:15am UTC](https://discourse.julialang.org/t/best-discrete-simulation-learning-path/105132 "2023-11-02T00:15:50Z")

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Hi folks! I seek suggestions for the best learning path of Discrete Simulation in Julia. Is there any book that you could suggest? I find that there are two packages: DiscreteEvents.jl and Simulate.jl; which is the mo…

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## [What does \`density()\` do when applied to a \`Distribution\` directly?](https://discourse.julialang.org/t/what-does-density-do-when-applied-to-a-distribution-directly/105621)

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**Author:** [@Alseidon](https://discourse.julialang.org/u/Alseidon)\
**Replies:** 6\
**Last updated:** [November 1, 2023, 10:18pm UTC](https://discourse.julialang.org/t/what-does-density-do-when-applied-to-a-distribution-directly/105621 "2023-11-01T22:18:12Z")

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I just started experimenting with Distributions.jl and StatsPlots.jl, and made a basic mistake, writing density(Normal()) instead of density(rand(Normal(), 100\_000)) or plot(Normal()). When executing julia\> plot(Normal(…

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## [Unexpected behavior when using Impute.locf within @by](https://discourse.julialang.org/t/unexpected-behavior-when-using-impute-locf-within-by/105642)

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**Author:** [@BeitianMa](https://discourse.julialang.org/u/BeitianMa)\
**Replies:** 2\
**Last updated:** [November 1, 2023, 3:12pm UTC](https://discourse.julialang.org/t/unexpected-behavior-when-using-impute-locf-within-by/105642 "2023-11-01T15:12:24Z")

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As the following code shows, i want to forward fill missing values use Impute.locf function, but just within the same :id using DataFramesMeta, Impute df = DataFrame(id = repeat(1:3, 2), value = \[1,missing,3,4,missing,…

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## [Using a JuMP \`Bin\` vector to index an array (checkbounds fails with type VariableRef)](https://discourse.julialang.org/t/using-a-jump-bin-vector-to-index-an-array-checkbounds-fails-with-type-variableref/102674)

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**Author:** [@Datseris](https://discourse.julialang.org/u/Datseris)\
**Replies:** 15\
**Last updated:** [November 1, 2023, 3:15pm UTC](https://discourse.julialang.org/t/using-a-jump-bin-vector-to-index-an-array-checkbounds-fails-with-type-variableref/102674 "2023-11-01T15:15:28Z")

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Hi there, I am following up from an earlier post \[ How to "prioritize" choosing some parameters over others in Hyperopt.jl or similar packages \] where I was instructed to use JuMP with decision variables. I have a simpl…

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## [How to Handle Multiple Edges in a Routing Problem Using JuMP?](https://discourse.julialang.org/t/how-to-handle-multiple-edges-in-a-routing-problem-using-jump/104226)

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**Author:** [@F\_A](https://discourse.julialang.org/u/F_A)\
**Replies:** 8\
**Last updated:** [October 30, 2023, 9:44pm UTC](https://discourse.julialang.org/t/how-to-handle-multiple-edges-in-a-routing-problem-using-jump/104226 "2023-10-30T21:44:33Z")

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Hi all, I have a multiple edge graph and I want to solve a routing problem on that. I was wondering how to define a binary variables that accounts for all possible edges that exist between let’s say node i to node j. I…

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## [Compatablity Issue Between Versions of DuckDB](https://discourse.julialang.org/t/compatablity-issue-between-versions-of-duckdb/105624)

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**Author:** [@brett\_knoss](https://discourse.julialang.org/u/brett_knoss)\
**Replies:** 11\
**Last updated:** [November 1, 2023, 1:33pm UTC](https://discourse.julialang.org/t/compatablity-issue-between-versions-of-duckdb/105624 "2023-11-01T13:33:38Z")

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When i try to connect to my DuckDB database, I’m told that the version is wrong. IO Error: Trying to read a database file with version number 64, but we can only read version 51. The database file was created with an n…

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## [DifferentialEquations: Gaussian error term in one of the equations makes it extremely slow (and error prone)](https://discourse.julialang.org/t/differentialequations-gaussian-error-term-in-one-of-the-equations-makes-it-extremely-slow-and-error-prone/105647)

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**Author:** [@MvanSteenbergen](https://discourse.julialang.org/u/MvanSteenbergen)\
**Replies:** 2\
**Last updated:** [November 1, 2023, 12:02pm UTC](https://discourse.julialang.org/t/differentialequations-gaussian-error-term-in-one-of-the-equations-makes-it-extremely-slow-and-error-prone/105647 "2023-11-01T12:02:45Z")

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Hey! For my thesis, I’m trying to implement this model in Julia, using the DifferentialEquations.jl package. I’ve made a rule based on a set of coupled differential equations to simulate some data. I have no previous k…

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## [PlotlyJS updates](https://discourse.julialang.org/t/plotlyjs-updates/105153)

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**Author:** [@jd-foster](https://discourse.julialang.org/u/jd-foster)\
**Replies:** 5\
**Last updated:** [November 1, 2023, 9:37am UTC](https://discourse.julialang.org/t/plotlyjs-updates/105153 "2023-11-01T09:37:31Z")

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I recommend PlutoPlotly a lot to people here and elsewhere. But maybe you could expand on what the barriers are (technical or otherwise) to maybe integrating the codes of PlutoPlotly and PlotlyBase/PlotlyJS?

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## [MethodError: no method matching zero(::Type{Vector{AffExpr}})](https://discourse.julialang.org/t/methoderror-no-method-matching-zero-type-vector-affexpr/105639)

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**Author:** [@Kaiming\_Zhang](https://discourse.julialang.org/u/Kaiming_Zhang)\
**Replies:** 5\
**Last updated:** [November 1, 2023, 7:47am UTC](https://discourse.julialang.org/t/methoderror-no-method-matching-zero-type-vector-affexpr/105639 "2023-11-01T07:47:19Z")

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I met a method error when running code in Julia 1.9. The code was written in Julia 1.1. How should I modify the code so that it can work? { "name": "MethodError", "message": "MethodError: no method matching zero(::Typ…

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## [Formating decimal separator in xticks when plotting with PlotlyJS](https://discourse.julialang.org/t/formating-decimal-separator-in-xticks-when-plotting-with-plotlyjs/105641)

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**Author:** [@nnguyengiatan](https://discourse.julialang.org/u/nnguyengiatan)\
**Replies:** 1\
**Last updated:** [November 1, 2023, 5:59am UTC](https://discourse.julialang.org/t/formating-decimal-separator-in-xticks-when-plotting-with-plotlyjs/105641 "2023-11-01T05:59:25Z")

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Hi all, I have the dataset as follow: df = DataFrame( kvkt = \[ "Service", "Service", "Service", "Service", "Service", "Manufacturing", "Manufacturing", "Manufacturing", "Manufacturing", "Manufacturin…

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## [Fitting a multiple input Flux.jl model with learning networks in MLJ.jl](https://discourse.julialang.org/t/fitting-a-multiple-input-flux-jl-model-with-learning-networks-in-mlj-jl/105597)

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**Author:** [@boutor2](https://discourse.julialang.org/u/boutor2)\
**Replies:** 4\
**Last updated:** [November 1, 2023, 3:54am UTC](https://discourse.julialang.org/t/fitting-a-multiple-input-flux-jl-model-with-learning-networks-in-mlj-jl/105597 "2023-11-01T03:54:25Z")

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Hey there, I have tried to use MLJ.jl to fit a Flux model that takes in multiple inputs. While Flux.jl documentation demonstrates how to build such a model, I unfortunately cannot make it work within MLJ. Here is a MWE,…

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## [Nonlinear constraints in SDDP](https://discourse.julialang.org/t/nonlinear-constraints-in-sddp/105626)

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**Author:** [@Sorooshsa](https://discourse.julialang.org/u/Sorooshsa)\
**Replies:** 3\
**Last updated:** [October 31, 2023, 8:14pm UTC](https://discourse.julialang.org/t/nonlinear-constraints-in-sddp/105626 "2023-10-31T20:14:53Z")

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Hi, I have read the similar topics here: But my case is a bit different. I have a constraint with this formula: gen \<= efficiency\*water\_discharged gen is a continuous control variable, efficiency is a continuous s…

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## [DataViewer.jl supported data file formats](https://discourse.julialang.org/t/dataviewer-jl-supported-data-file-formats/105569)

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**Author:** [@rajmac](https://discourse.julialang.org/u/rajmac)\
**Replies:** 15\
**Last updated:** [October 31, 2023, 6:00pm UTC](https://discourse.julialang.org/t/dataviewer-jl-supported-data-file-formats/105569 "2023-10-31T18:00:56Z")

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I was interested in the recent post on DataViewer.jl and wondered if it could be used with csv files or whether it requires hf5/jdl2/json datafiles?

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## [How do I retain model parameters while freezing layers with Lux.jl](https://discourse.julialang.org/t/how-do-i-retain-model-parameters-while-freezing-layers-with-lux-jl/105558)

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**Author:** [@liuyxpp](https://discourse.julialang.org/u/liuyxpp)\
**Replies:** 3\
**Last updated:** [October 31, 2023, 1:52pm UTC](https://discourse.julialang.org/t/how-do-i-retain-model-parameters-while-freezing-layers-with-lux-jl/105558 "2023-10-31T13:52:28Z")

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I am very interested in the example given in the doc Freezing Model Parameters | LuxDL Docs. However, in that example, the parameters are obtained from ps, st = Lux.setup(rng, model\_frozen) I find there is no convenien…

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## [Correct implementation of CuArray's slicing operations](https://discourse.julialang.org/t/correct-implementation-of-cuarrays-slicing-operations/90600)

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**Author:** [@FujiwaraTakumiEH](https://discourse.julialang.org/u/FujiwaraTakumiEH)\
**Replies:** 3\
**Last updated:** [October 31, 2023, 10:29am UTC](https://discourse.julialang.org/t/correct-implementation-of-cuarrays-slicing-operations/90600 "2023-10-31T10:29:10Z")

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Hello, sometimes I need slicing operations on CuArray. I would like to know the correct (and efficient) way to achieve this. I made 4 benchmarks: Datasets: using BenchmarkTools using CUDA CUDA.allowscalar(true) # size o…

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## [Missing precision in the solution of combinations of ODE and jump processes using DifferentialEquations.jl and JumpProcesses.jl](https://discourse.julialang.org/t/missing-precision-in-the-solution-of-combinations-of-ode-and-jump-processes-using-differentialequations-jl-and-jumpprocesses-jl/105370)

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**Author:** [@VincentW](https://discourse.julialang.org/u/VincentW)\
**Replies:** 11\
**Last updated:** [October 31, 2023, 8:58am UTC](https://discourse.julialang.org/t/missing-precision-in-the-solution-of-combinations-of-ode-and-jump-processes-using-differentialequations-jl-and-jumpprocesses-jl/105370 "2023-10-31T08:58:48Z")

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Hey everyone, For a toy model, I tried to simulate an ODE together with a jump process, which jump rate at a certain time is dependent on the ODE at that time. (Motivated by the growth of a tumor and a death process, wh…

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## [How to add the drop-shadow effect to contour plots in Julia with Plots.jl (or Makie.jl)](https://discourse.julialang.org/t/how-to-add-the-drop-shadow-effect-to-contour-plots-in-julia-with-plots-jl-or-makie-jl/105604)

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**Author:** [@jondoe297](https://discourse.julialang.org/u/jondoe297)\
**Replies:** 0\
**Last updated:** [October 31, 2023, 1:04am UTC](https://discourse.julialang.org/t/how-to-add-the-drop-shadow-effect-to-contour-plots-in-julia-with-plots-jl-or-makie-jl/105604 "2023-10-31T01:04:27Z")

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I am very new to Julia, coming from python. I am trying to make a contour plot with drop-shadow effect. (From Scientific Visualization Book) import scipy import numpy as np import matplotlib.pyplot as plt from matplotli…

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## [Speed of ApproxFun.jl solution to Screened Poisson in cylindrical coordinates](https://discourse.julialang.org/t/speed-of-approxfun-jl-solution-to-screened-poisson-in-cylindrical-coordinates/105565)

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**Author:** [@parb](https://discourse.julialang.org/u/parb)\
**Replies:** 2\
**Last updated:** [October 30, 2023, 8:26pm UTC](https://discourse.julialang.org/t/speed-of-approxfun-jl-solution-to-screened-poisson-in-cylindrical-coordinates/105565 "2023-10-30T20:26:28Z")

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The examples of ApproxFun.jl examples solutions are fascinating and powerful, and I’d love to figure out the best performance for solving the homogeneous screened Poisson equation but in cylindrical coordinates (with cir…

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## [Custom environment with continuous state and action spaces](https://discourse.julialang.org/t/custom-environment-with-continuous-state-and-action-spaces/105595)

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**Author:** [@hicham\_henna](https://discourse.julialang.org/u/hicham_henna)\
**Replies:** 0\
**Last updated:** [October 30, 2023, 7:58pm UTC](https://discourse.julialang.org/t/custom-environment-with-continuous-state-and-action-spaces/105595 "2023-10-30T19:58:58Z")

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how to implement a custom environment with continuous state and action spaces in the reinforcement learning framework under Julia? for example, to control the attitude of satellite we need the definition of: (i) markovia…

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## [Status of constraint programming in JuMP](https://discourse.julialang.org/t/status-of-constraint-programming-in-jump/105580)

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**Author:** [@gdalle](https://discourse.julialang.org/u/gdalle)\
**Replies:** 3\
**Last updated:** [October 30, 2023, 7:45pm UTC](https://discourse.julialang.org/t/status-of-constraint-programming-in-jump/105580 "2023-10-30T19:45:03Z")

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Now that MathOptInterface v1 supports constraint programming, what is the status of this modeling paradigm in the JuMP ecosystem? I found this checklist issue but it is a bit hard to parse for outsiders, so I wanted to m…

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## [Block diagonal and sparse matrices](https://discourse.julialang.org/t/block-diagonal-and-sparse-matrices/105551)

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**Author:** [@loisel](https://discourse.julialang.org/u/loisel)\
**Replies:** 13\
**Last updated:** [October 30, 2023, 5:07pm UTC](https://discourse.julialang.org/t/block-diagonal-and-sparse-matrices/105551 "2023-10-30T17:07:23Z")

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I have a code that does something like this: Z = inv(ABCDE) Here, A is a diagonal matrix. B is block diagonal, its diagonal blocks are 2x2. C is block diagonal, its diagonal blocks are 4x4. Subsequent matrices have lar…

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## [Matlab figure replacement](https://discourse.julialang.org/t/matlab-figure-replacement/74942)

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**Author:** [@ohmsweetohm1](https://discourse.julialang.org/u/ohmsweetohm1)\
**Replies:** 24\
**Last updated:** [October 30, 2023, 4:41pm UTC](https://discourse.julialang.org/t/matlab-figure-replacement/74942 "2023-10-30T16:41:04Z")

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In Matlab it is possible to make a figure and save it to disk. If you re-open this figure you can still zoome, have linked axis and so on. Is there a Julia equivalent? I tried PlotlyJS.jl and saving the plot as a html …

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## [How to set a Non-linear function with double summatory](https://discourse.julialang.org/t/how-to-set-a-non-linear-function-with-double-summatory/105542)

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**Author:** [@PatrickeTownsend](https://discourse.julialang.org/u/PatrickeTownsend)\
**Replies:** 4\
**Last updated:** [October 29, 2023, 9:18pm UTC](https://discourse.julialang.org/t/how-to-set-a-non-linear-function-with-double-summatory/105542 "2023-10-29T21:18:54Z")

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Hello Again! I’m trying to solve this optimization problem: But i’m not really sure about how to write down that objective function, I tried doing this: using JuMP using Ipopt model = Model(Ipopt.Optimizer) set\_att…

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## [MethodError: no method matching \*(::ODESystem, ::Float64)](https://discourse.julialang.org/t/methoderror-no-method-matching-odesystem-float64/105532)

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**Author:** [@aoifehealy](https://discourse.julialang.org/u/aoifehealy)\
**Replies:** 1\
**Last updated:** [October 29, 2023, 11:18am UTC](https://discourse.julialang.org/t/methoderror-no-method-matching-odesystem-float64/105532 "2023-10-29T11:18:47Z")

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Hi there, I am trying to model a 3 element windkessel circuit (see below) using modelingtoolkit By code is as following: using ModelingToolkit using Plots using DifferentialEquations @variables t D = Differential(t)…

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## [Displaying a 3D scatter with a lot of data crashes](https://discourse.julialang.org/t/displaying-a-3d-scatter-with-a-lot-of-data-crashes/105352)

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**Author:** [@yuvalw](https://discourse.julialang.org/u/yuvalw)\
**Replies:** 3\
**Last updated:** [October 29, 2023, 9:37am UTC](https://discourse.julialang.org/t/displaying-a-3d-scatter-with-a-lot-of-data-crashes/105352 "2023-10-29T09:37:36Z")

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Hello, Is there an efficient way to do this? I’m having crashes with even 1000 data points. I noticed that using different colors for data points (i.e. zcolor) makes the figure 10x heavier upon saving. I would like to …

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## [Question About MKL on Slurm Cluster](https://discourse.julialang.org/t/question-about-mkl-on-slurm-cluster/105527)

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**Author:** [@TI36XPro](https://discourse.julialang.org/u/TI36XPro)\
**Replies:** 1\
**Last updated:** [October 29, 2023, 5:06am UTC](https://discourse.julialang.org/t/question-about-mkl-on-slurm-cluster/105527 "2023-10-29T05:06:03Z")

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Hello, I am using Julia on an HPC that uses Lmod and Slurm. I wanted to try using MKL for some calculations since I have access to nodes with intel CPUs. I followed the instructions here. At the top of my script the fi…

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## [How to get PDE solutions when doing foward time steps](https://discourse.julialang.org/t/how-to-get-pde-solutions-when-doing-foward-time-steps/105419)

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**Author:** [@aplund](https://discourse.julialang.org/u/aplund)\
**Replies:** 2\
**Last updated:** [October 28, 2023, 11:06pm UTC](https://discourse.julialang.org/t/how-to-get-pde-solutions-when-doing-foward-time-steps/105419 "2023-10-28T23:06:38Z")

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I’ve been trying to get the hang of solving DEs in Julia (i.e. new user). As a simple task, I tried to set up a 1-d Schrödinger equation and perform a time evolution. Here’s my effort so far: using ModelingToolkit usi…

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## [Possible to adaptively shrink number of state variables/ODEs?](https://discourse.julialang.org/t/possible-to-adaptively-shrink-number-of-state-variables-odes/105507)

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**Author:** [@differentialoperator](https://discourse.julialang.org/u/differentialoperator)\
**Replies:** 2\
**Last updated:** [October 28, 2023, 10:26pm UTC](https://discourse.julialang.org/t/possible-to-adaptively-shrink-number-of-state-variables-odes/105507 "2023-10-28T22:26:14Z")

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I’m solving an ODE system adaptively in time (eg RK23). At minimum, I’m solving for the evolution of 10 coupled state variables so I have 10 (coupled non-linear) ODEs that are solved from some initial time to final time.…

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## [Solving F(X)=0 using nlsolve](https://discourse.julialang.org/t/solving-f-x-0-using-nlsolve/105516)

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**Author:** [@havana](https://discourse.julialang.org/u/havana)\
**Replies:** 6\
**Last updated:** [October 28, 2023, 9:29pm UTC](https://discourse.julialang.org/t/solving-f-x-0-using-nlsolve/105516 "2023-10-28T21:29:38Z")

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I wanna solve a root finding problem of the form F(X)=0 using NLsolve. However, I do not know the regularity of the function F, for example if it is not differentiable, so the Jacobian does not exists, how do the functi…

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## [Specifying which parameter to solve for in an ODE](https://discourse.julialang.org/t/specifying-which-parameter-to-solve-for-in-an-ode/105518)

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**Author:** [@aoifehealy](https://discourse.julialang.org/u/aoifehealy)\
**Replies:** 1\
**Last updated:** [October 28, 2023, 6:29pm UTC](https://discourse.julialang.org/t/specifying-which-parameter-to-solve-for-in-an-ode/105518 "2023-10-28T18:29:02Z")

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Hi there, I’m new to Julia and modelingtoolkit, and I am trying to use it to implement a 2 element windkessel model consisting of a capacitor and resistor in parallel My code is as follows: using ModelingToolkit using …

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