# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=346

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**Page:** 347

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## [LoadError: UndefVarError: @defVar not defined](https://discourse.julialang.org/t/loaderror-undefvarerror-defvar-not-defined/66022)

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**Author:** [@zhangsanle](https://discourse.julialang.org/u/zhangsanle)\
**Replies:** 4\
**Last updated:** [August 9, 2021, 10:50am UTC](https://discourse.julialang.org/t/loaderror-undefvarerror-defvar-not-defined/66022 "2021-08-09T10:50:21Z")

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I have a piece of code about JuMP. When I run it ,it says that LoadError: UndefVarError: @defVar not defined. I have tried using global forward or backward but both fails. See: function T1(w\_func,grid\_b,β,u,z) …

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## [Multiple GPUs with Julia](https://discourse.julialang.org/t/multiple-gpus-with-julia/11248)

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**Author:** [@jacobcvt12](https://discourse.julialang.org/u/jacobcvt12)\
**Replies:** 8\
**Last updated:** [August 9, 2021, 9:49am UTC](https://discourse.julialang.org/t/multiple-gpus-with-julia/11248 "2021-08-09T09:49:25Z")

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Has anyone every used multiple GPUs with Flux? If so, did you have to modify your code to run on multiple GPUs?

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## [Getting Started with High Frequency Finance using Crypto Data and Julia](https://discourse.julialang.org/t/getting-started-with-high-frequency-finance-using-crypto-data-and-julia/63730)

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**Author:** [@dm13450](https://discourse.julialang.org/u/dm13450)\
**Replies:** 11\
**Last updated:** [August 9, 2021, 12:03am UTC](https://discourse.julialang.org/t/getting-started-with-high-frequency-finance-using-crypto-data-and-julia/63730 "2021-08-09T00:03:08Z")

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I’ve written about how to use my CoinbasePro.jl package in Julia to get started with some concepts in high frequency finance. Happy to answer any questions around the subject for anyone interested!

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## [Q: The scope for development of a flexible framework for coupled stiff integro-differential equations](https://discourse.julialang.org/t/q-the-scope-for-development-of-a-flexible-framework-for-coupled-stiff-integro-differential-equations/65935)

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**Author:** [@SMijin](https://discourse.julialang.org/u/SMijin)\
**Replies:** 7\
**Last updated:** [August 8, 2021, 10:28pm UTC](https://discourse.julialang.org/t/q-the-scope-for-development-of-a-flexible-framework-for-coupled-stiff-integro-differential-equations/65935 "2021-08-08T22:28:27Z")

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Hello, New user here, quite eager to get involved with the community, so my apologies for the long post! I work in fusion research, and am interested in testing modelling approaches for systems of coupled stiff integro…

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## [EnsembleProblem: data saving and logging](https://discourse.julialang.org/t/ensembleproblem-data-saving-and-logging/66025)

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**Author:** [@Gregstrq](https://discourse.julialang.org/u/Gregstrq)\
**Replies:** 0\
**Last updated:** [August 8, 2021, 3:49pm UTC](https://discourse.julialang.org/t/ensembleproblem-data-saving-and-logging/66025 "2021-08-08T15:49:20Z")

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Great job with the facilities for Monte Carlo Simulations. I have a couple of question about EnsembleProblem. From the docs, it follows that the data from all the trajectories is saved. Is it possible to use Welford’s o…

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## [Why for loop doesn't work in my code](https://discourse.julialang.org/t/why-for-loop-doesnt-work-in-my-code/65567)

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**Author:** [@sajad\_ghassemi](https://discourse.julialang.org/u/sajad_ghassemi)\
**Replies:** 24\
**Last updated:** [August 8, 2021, 2:59pm UTC](https://discourse.julialang.org/t/why-for-loop-doesnt-work-in-my-code/65567 "2021-08-08T14:59:31Z")

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Hi dear friends, I have problem with for loop. I don’t know my code doesn’t enter and repeat in loop. using Plots plotly() Plots.PlotlyBackend() currentcap=zeros(1,250001); voltagecap=zeros(1,250001); currentind=zeros(…

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## [Turning a function into distrubution for turing](https://discourse.julialang.org/t/turning-a-function-into-distrubution-for-turing/66016)

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**Author:** [@marouane](https://discourse.julialang.org/u/marouane)\
**Replies:** 0\
**Last updated:** [August 8, 2021, 11:54am UTC](https://discourse.julialang.org/t/turning-a-function-into-distrubution-for-turing/66016 "2021-08-08T11:54:39Z")

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I have a target function that I want to transform into distribution in order to use Turing, let’s suppose that the target function is written on this form: logtarget(x::Vector)= log(prod(x))^2 how can I turn it into d…

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## [Error (optimize! not defined) using JuMP optimizing routines](https://discourse.julialang.org/t/error-optimize-not-defined-using-jump-optimizing-routines/65975)

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**Author:** [@Peter-Jolly](https://discourse.julialang.org/u/Peter-Jolly)\
**Replies:** 2\
**Last updated:** [August 8, 2021, 4:30am UTC](https://discourse.julialang.org/t/error-optimize-not-defined-using-jump-optimizing-routines/65975 "2021-08-08T04:30:11Z")

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Hi, I am trying out the examples in Julia documentation concerning JuMP. I get the same error no matter whether I use the linear or non linear examples(below is the linear example taken from the documentation: The error…

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## [StatsModels R-like formula for a general quadratic model](https://discourse.julialang.org/t/statsmodels-r-like-formula-for-a-general-quadratic-model/64441)

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**Author:** [@joergbuchwald](https://discourse.julialang.org/u/joergbuchwald)\
**Replies:** 7\
**Last updated:** [August 7, 2021, 10:46pm UTC](https://discourse.julialang.org/t/statsmodels-r-like-formula-for-a-general-quadratic-model/64441 "2021-08-07T22:46:22Z")

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Hi! I want to construct a regression formula for a general quadratic model without writing out each interaction term separately. I remember that for the python Statsmodels package I could do something like: y~np.power(…

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## [OMJulia simulate command returns error](https://discourse.julialang.org/t/omjulia-simulate-command-returns-error/65612)

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**Author:** [@cubakija](https://discourse.julialang.org/u/cubakija)\
**Replies:** 18\
**Last updated:** [August 7, 2021, 6:10pm UTC](https://discourse.julialang.org/t/omjulia-simulate-command-returns-error/65612 "2021-08-07T18:10:38Z")

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Hi everyone, Someone can help me to fix below error, when trying to simulate model: ERROR: failed process: Process(C:/Users/USUARIO/AppData/Local/Temp/jl\_gGQfHg/RLC.exe, ProcessExited(3221225785)) \[3221225785\] Stacktr…

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## [\[Symbolics.jl\] How to select between simplifier backends?](https://discourse.julialang.org/t/symbolics-jl-how-to-select-between-simplifier-backends/65973)

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**Author:** [@Samuel\_Ainsworth](https://discourse.julialang.org/u/Samuel_Ainsworth)\
**Replies:** 1\
**Last updated:** [August 7, 2021, 1:58pm UTC](https://discourse.julialang.org/t/symbolics-jl-how-to-select-between-simplifier-backends/65973 "2021-08-07T13:58:13Z")

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My understanding is that Symbolics.jl has multiple different simplifier backends (ref Symbolics.jl - High performance symbolic numerics via multiple dispatch, Julia Computer Algebra - YouTube). But I haven’t been able to…

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## [How to do multiple cameras in subplots with plot3d()](https://discourse.julialang.org/t/how-to-do-multiple-cameras-in-subplots-with-plot3d/65940)

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**Author:** [@DoctorDalek1963](https://discourse.julialang.org/u/DoctorDalek1963)\
**Replies:** 1\
**Last updated:** [August 6, 2021, 4:16pm UTC](https://discourse.julialang.org/t/how-to-do-multiple-cameras-in-subplots-with-plot3d/65940 "2021-08-06T16:16:51Z")

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I’m using the Plots library to visualise some randomly generated gravitational motion in a gif. I generate a Vector{Vector{Vector{Float64}}}, which can be thought of as a list of frames, where each frame has a list of bo…

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## [Why won't Symbolics.jl simplify \`sqrt(1)\` to \`1\`?](https://discourse.julialang.org/t/why-wont-symbolics-jl-simplify-sqrt-1-to-1/65921)

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**Author:** [@Samuel\_Ainsworth](https://discourse.julialang.org/u/Samuel_Ainsworth)\
**Replies:** 5\
**Last updated:** [August 6, 2021, 8:42pm UTC](https://discourse.julialang.org/t/why-wont-symbolics-jl-simplify-sqrt-1-to-1/65921 "2021-08-06T20:42:09Z")

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@variables x sqrt(cos(x)^2 + sin(x)^2) |\> simplify gives me sqrt(1). Why isn’t this reduced to simply 1? OTOH sqrt(0\*x+1) |\> simplify reduces to 1, no problem.

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## [DataFrames: ByRow fails in transform with PooledArrays after CSV.read](https://discourse.julialang.org/t/dataframes-byrow-fails-in-transform-with-pooledarrays-after-csv-read/65957)

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**Author:** [@hdavid16](https://discourse.julialang.org/u/hdavid16)\
**Replies:** 6\
**Last updated:** [August 6, 2021, 7:57pm UTC](https://discourse.julialang.org/t/dataframes-byrow-fails-in-transform-with-pooledarrays-after-csv-read/65957 "2021-08-06T19:57:54Z")

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I am having an issue with a transform operation on a DataFrame that is read from a .csv using CSV. I don’t have the following issue when my dataframe has few rows because the importing from the .csv file uses SentinelArr…

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## [Quality of life improvements for ModelingToolkit/DiffEq/SciML ecosystem](https://discourse.julialang.org/t/quality-of-life-improvements-for-modelingtoolkit-diffeq-sciml-ecosystem/65939)

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**Author:** [@dawbarton](https://discourse.julialang.org/u/dawbarton)\
**Replies:** 1\
**Last updated:** [August 6, 2021, 12:14pm UTC](https://discourse.julialang.org/t/quality-of-life-improvements-for-modelingtoolkit-diffeq-sciml-ecosystem/65939 "2021-08-06T12:14:40Z")

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I’m applying for funding for a research software engineer to do some quality-of-life improvements for the ModelingToolkit/DiffEq/SciML ecosystem from one of the research councils in the UK (specifically the EPSRC Softwar…

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## [ModelingToolkit performance issue with repeated evaluations of variables in system of equations](https://discourse.julialang.org/t/modelingtoolkit-performance-issue-with-repeated-evaluations-of-variables-in-system-of-equations/64890)

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**Author:** [@ograsdijk](https://discourse.julialang.org/u/ograsdijk)\
**Replies:** 3\
**Last updated:** [August 6, 2021, 10:21am UTC](https://discourse.julialang.org/t/modelingtoolkit-performance-issue-with-repeated-evaluations-of-variables-in-system-of-equations/64890 "2021-08-06T10:21:20Z")

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Solving an ODEProblem created from an ODESystem with ModelingToolkit is slow when a simple time dependent variable (e.g. sin(t)) is added to the system of equations. For example: using ModelingToolkit using Differentia…

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## [Any implementation of 'Fixed smooth convolutional layer for avoiding checkerboard artifacts in CNNs'?](https://discourse.julialang.org/t/any-implementation-of-fixed-smooth-convolutional-layer-for-avoiding-checkerboard-artifacts-in-cnns/65881)

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**Author:** [@czexana](https://discourse.julialang.org/u/czexana)\
**Replies:** 2\
**Last updated:** [August 6, 2021, 9:10am UTC](https://discourse.julialang.org/t/any-implementation-of-fixed-smooth-convolutional-layer-for-avoiding-checkerboard-artifacts-in-cnns/65881 "2021-08-06T09:10:54Z")

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Hello, I’m wondering if anyone has implemented the above paper, found at \[2002.02117\] Fixed smooth convolutional layer for avoiding checkerboard artifacts in CNNs that purports to fix checkerboard artifacts in conv and …

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## [Is there a package for creating custom world](https://discourse.julialang.org/t/is-there-a-package-for-creating-custom-world/65883)

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**Author:** [@development\_mentor](https://discourse.julialang.org/u/development_mentor)\
**Replies:** 8\
**Last updated:** [August 6, 2021, 6:35am UTC](https://discourse.julialang.org/t/is-there-a-package-for-creating-custom-world/65883 "2021-08-06T06:35:36Z")

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I’m searching for a package that could create a 3D or 2D costume world. Something like the game world, in which you or artificial agent could interact with the environment. Which would follow rules specified by the creat…

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## [Any packages for polychoric correlation?](https://discourse.julialang.org/t/any-packages-for-polychoric-correlation/36515)

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**Author:** [@brett\_knoss](https://discourse.julialang.org/u/brett_knoss)\
**Replies:** 2\
**Last updated:** [August 6, 2021, 2:49am UTC](https://discourse.julialang.org/t/any-packages-for-polychoric-correlation/36515 "2021-08-06T02:49:21Z")

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I’m analyzing a survey that has a lot of ratings scales. Is there a package to do polychoric correlations? If not would anyone be willing to take a crack at creating such a thing?

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## [How do I create a Quantum Time Operator with DifferentialEquations?](https://discourse.julialang.org/t/how-do-i-create-a-quantum-time-operator-with-differentialequations/65766)

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**Author:** [@Noel\_Araujo](https://discourse.julialang.org/u/Noel_Araujo)\
**Replies:** 3\
**Last updated:** [August 5, 2021, 12:20pm UTC](https://discourse.julialang.org/t/how-do-i-create-a-quantum-time-operator-with-differentialequations/65766 "2021-08-05T12:20:21Z")

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For the special case of unitary matrices, my quantum mechanics books tells me to use Time Evolution Operators. β(t) = exp(-im\*H\*t/h)\*β(0) As far I know, I just need to use Matrix Exponential. First, decompose H = ψ\*λ\*…

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## [CUDA memory error while using DifferentialEquations.jl](https://discourse.julialang.org/t/cuda-memory-error-while-using-differentialequations-jl/65855)

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**Author:** [@wsshin](https://discourse.julialang.org/u/wsshin)\
**Replies:** 2\
**Last updated:** [August 5, 2021, 7:40pm UTC](https://discourse.julialang.org/t/cuda-memory-error-while-using-differentialequations-jl/65855 "2021-08-05T19:40:39Z")

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Not sure if I could get an answer to this kind of question here, but hopefully someone has an insight. I am solving a differential equation whose solution is in the form of f(z,ω). For each z, f(z,ω) is some sort of di…

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## [Debugging NLopt :FORCED\_STOP](https://discourse.julialang.org/t/debugging-nlopt-forced-stop/65840)

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**Author:** [@cricci](https://discourse.julialang.org/u/cricci)\
**Replies:** 6\
**Last updated:** [August 5, 2021, 5:39pm UTC](https://discourse.julialang.org/t/debugging-nlopt-forced-stop/65840 "2021-08-05T17:39:06Z")

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Hello, I have some issue when using NLopt.jl to perform constrained minimization. I have a function that I am trying to maximize, whose value depend from the solution of a system of ODE. However the optimizer suddenly t…

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## [(Jump, Gurobi)Binary Variables end up with values no equal 1 or 0](https://discourse.julialang.org/t/jump-gurobi-binary-variables-end-up-with-values-no-equal-1-or-0/65610)

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**Author:** [@Hirnfolter](https://discourse.julialang.org/u/Hirnfolter)\
**Replies:** 8\
**Last updated:** [August 5, 2021, 3:01pm UTC](https://discourse.julialang.org/t/jump-gurobi-binary-variables-end-up-with-values-no-equal-1-or-0/65610 "2021-08-05T15:01:44Z")

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Hello, i try to opimise something and have the variable @variable(m, Taskstartstation\[1:Stationnumber, 1:Ordernumber, 1:Tasknumbertotal\], binary=true); or @variable(m, Taskstartstation\[1:Stationnumber, 1:Ordernum…

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## [Gnuplot.jl: Datetime in xtics](https://discourse.julialang.org/t/gnuplot-jl-datetime-in-xtics/65281)

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**Author:** [@Inna](https://discourse.julialang.org/u/Inna)\
**Replies:** 2\
**Last updated:** [August 5, 2021, 2:35pm UTC](https://discourse.julialang.org/t/gnuplot-jl-datetime-in-xtics/65281 "2021-08-05T14:35:57Z")

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Hello everyone, I have timeseries and i want to have on xtics Datetime format. my data is called array: 1980 1 111.439 1980-01-01 1 …

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## [Parsing Pcap files](https://discourse.julialang.org/t/parsing-pcap-files/65875)

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**Author:** [@SpinolaHours](https://discourse.julialang.org/u/SpinolaHours)\
**Replies:** 0\
**Last updated:** [August 5, 2021, 11:47am UTC](https://discourse.julialang.org/t/parsing-pcap-files/65875 "2021-08-05T11:47:40Z")

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Hi there. I was wondering if anyone has experience in parsing pcap files in julia. There appears to be a very old package: https://github.com/JuliaIO/Pcap.jl but it doesn’t look to be maintained and I’m having trouble…

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## [Linear Matrix Inequality](https://discourse.julialang.org/t/linear-matrix-inequality/65814)

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**Author:** [@jeanluc](https://discourse.julialang.org/u/jeanluc)\
**Replies:** 11\
**Last updated:** [August 5, 2021, 11:32am UTC](https://discourse.julialang.org/t/linear-matrix-inequality/65814 "2021-08-05T11:32:12Z")

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Hello everyone! Here is a code I have tried to solve an LMI But it failed. How can I fix it? Will this code give the solution? using Convex using SCS using LinearAlgebra n = 2 P = Semidefinite(n) Z12=zeros(Int8, 2, 2…

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## [Solving JuMP model async with HTTP routing doesn't work](https://discourse.julialang.org/t/solving-jump-model-async-with-http-routing-doesnt-work/65854)

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**Author:** [@obar](https://discourse.julialang.org/u/obar)\
**Replies:** 3\
**Last updated:** [August 5, 2021, 5:57am UTC](https://discourse.julialang.org/t/solving-jump-model-async-with-http-routing-doesnt-work/65854 "2021-08-05T05:57:38Z")

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I’m in the process of building a web server that solves a mixed-integer program. The solve is triggered when the user hits a specific url. Because the MIP solve takes a while to complete, this causes a timeout in the HTT…

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## [Constructing ODEProblem parameter map from JSON data](https://discourse.julialang.org/t/constructing-odeproblem-parameter-map-from-json-data/65772)

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**Author:** [@juliascrub](https://discourse.julialang.org/u/juliascrub)\
**Replies:** 3\
**Last updated:** [August 5, 2021, 3:43am UTC](https://discourse.julialang.org/t/constructing-odeproblem-parameter-map-from-json-data/65772 "2021-08-05T03:43:06Z")

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I posted before here regarding this when my project was less fleshed out. Now that Ive actually got things mostly working I’m still struggling with this last task. Ive got some JSON that looks something like this: \[ …

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## [Function that converts rgb color to CAM02-UCS coordinates](https://discourse.julialang.org/t/function-that-converts-rgb-color-to-cam02-ucs-coordinates/65822)

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**Author:** [@empet](https://discourse.julialang.org/u/empet)\
**Replies:** 4\
**Last updated:** [August 4, 2021, 5:47pm UTC](https://discourse.julialang.org/t/function-that-converts-rgb-color-to-cam02-ucs-coordinates/65822 "2021-08-04T17:47:03Z")

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The state of the art perceptual uniform colormaps (matplotlib viridis, plasma, magma, inferno, cividis), all sequential cmocean and cmasher colormaps, and a few seaborn ones have linear lightness in the color appearance…

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## [With Dash, how to obtain a directory name from a file browser](https://discourse.julialang.org/t/with-dash-how-to-obtain-a-directory-name-from-a-file-browser/65826)

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**Author:** [@a5vzener](https://discourse.julialang.org/u/a5vzener)\
**Replies:** 0\
**Last updated:** [August 4, 2021, 4:02pm UTC](https://discourse.julialang.org/t/with-dash-how-to-obtain-a-directory-name-from-a-file-browser/65826 "2021-08-04T16:02:23Z")

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I would like users of my Dash app to be able to select a directory on their local machine — not just one file – and obtain the relative path and name of that directory. Ideally I would get the names of files in the direc…

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