# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?page=439

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**Page:** 440

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## [Rational{Int64} variables in JuMP?](https://discourse.julialang.org/t/rational-int64-variables-in-jump/42048)

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**Author:** [@GeneralPoxter](https://discourse.julialang.org/u/GeneralPoxter)\
**Replies:** 7\
**Last updated:** [June 26, 2020, 9:51am UTC](https://discourse.julialang.org/t/rational-int64-variables-in-jump/42048 "2020-06-26T09:51:36Z")

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I’ve been trying to make an array of rationals using the @variable macro in JuMP, but I can’t seem to find out how to constrain the array to only rational values. Does JuMP allow you to build variables with Rational typ…

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## [Deterministic Clustering in Julia?](https://discourse.julialang.org/t/deterministic-clustering-in-julia/42068)

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**Author:** [@mthelm85](https://discourse.julialang.org/u/mthelm85)\
**Replies:** 4\
**Last updated:** [June 26, 2020, 6:54am UTC](https://discourse.julialang.org/t/deterministic-clustering-in-julia/42068 "2020-06-26T06:54:41Z")

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Are there any deterministic clustering methods implemented in Julia? For example: using Clustering using DataFrames df = DataFrame(subject=1:10, height=rand(10), weight=rand(10)) julia\> groups = kmeans(Matrix(df\[:, 2:…

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## [Adaptive control and online parameter estimation](https://discourse.julialang.org/t/adaptive-control-and-online-parameter-estimation/42054)

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**Author:** [@jonniedie](https://discourse.julialang.org/u/jonniedie)\
**Replies:** 2\
**Last updated:** [June 26, 2020, 2:01am UTC](https://discourse.julialang.org/t/adaptive-control-and-online-parameter-estimation/42054 "2020-06-26T02:01:27Z")

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Since control systems modeling questions tend to pop up on here quite a bit, I figured I’d share the approach I’ve been taking for these kinds of things using ControlSystems.jl to build linear components for nonlinear Di…

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## [Improve CBC solve time](https://discourse.julialang.org/t/improve-cbc-solve-time/42082)

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**Author:** [@GeneralPoxter](https://discourse.julialang.org/u/GeneralPoxter)\
**Replies:** 2\
**Last updated:** [June 26, 2020, 3:00am UTC](https://discourse.julialang.org/t/improve-cbc-solve-time/42082 "2020-06-26T03:00:20Z")

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While watching the output of the CBC optimizer, I noticed that after a while, the optimizer would get “stuck” on a best solution, even though I set the primal tolerance and allowable gap to relatively low values. I also…

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## [Luxor questions](https://discourse.julialang.org/t/luxor-questions/41946)

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**Author:** [@turtle](https://discourse.julialang.org/u/turtle)\
**Replies:** 14\
**Last updated:** [June 25, 2020, 11:00pm UTC](https://discourse.julialang.org/t/luxor-questions/41946 "2020-06-25T23:00:11Z")

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I have started learning Luxor.jl, and I find it great. I would have two questions: Can I reverse the default coordinate system somehow? (i.e. x axis to the right, but y axis upwards) Can I use LaTeX expressions as te…

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## [Normalized laplacian of weighted graphs](https://discourse.julialang.org/t/normalized-laplacian-of-weighted-graphs/42064)

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**Author:** [@Neurovium](https://discourse.julialang.org/u/Neurovium)\
**Replies:** 1\
**Last updated:** [June 25, 2020, 8:55pm UTC](https://discourse.julialang.org/t/normalized-laplacian-of-weighted-graphs/42064 "2020-06-25T20:55:26Z")

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Hi, Is there anyway to calculate normalized laplacian for a weighted graph? See below for an example graph created with SimpleWeightedGraphs (https://github.com/JuliaGraphs/SimpleWeightedGraphs.jl) When I call Normal…

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## [Repartitioning 2TB of csv into parquets](https://discourse.julialang.org/t/repartitioning-2tb-of-csv-into-parquets/27716)

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**Author:** [@gabomgp](https://discourse.julialang.org/u/gabomgp)\
**Replies:** 21\
**Last updated:** [June 25, 2020, 6:09pm UTC](https://discourse.julialang.org/t/repartitioning-2tb-of-csv-into-parquets/27716 "2020-06-25T18:09:31Z")

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Good morning from Colombia. I’m beginner in big data/data science, and i’m trying to do the next task: We have 2 TB of CSV from one table. We want to try to use a SQL Layer to query that data. Currently, the data is s…

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## [How to reduce bar padding in horizontal bar plotting?](https://discourse.julialang.org/t/how-to-reduce-bar-padding-in-horizontal-bar-plotting/42039)

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**Author:** [@sylvaticus](https://discourse.julialang.org/u/sylvaticus)\
**Replies:** 2\
**Last updated:** [June 25, 2020, 3:40pm UTC](https://discourse.julialang.org/t/how-to-reduce-bar-padding-in-horizontal-bar-plotting/42039 "2020-06-25T15:40:22Z")

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How can I set the bar padding in bar ? using Plots kDiff = \[-0.4665307712613753, 1.3988034802362372, 0.26964352271121106, 1.9321483556515853, 0.027055373158908935, -0.2508916681408131\] sentences = \["Industrie", "Noeffec…

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## [FreeBSD GR download link missing](https://discourse.julialang.org/t/freebsd-gr-download-link-missing/24241)

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**Author:** [@Rob\_van\_Weelderen](https://discourse.julialang.org/u/Rob_van_Weelderen)\
**Replies:** 2\
**Last updated:** [June 25, 2020, 2:10pm UTC](https://discourse.julialang.org/t/freebsd-gr-download-link-missing/24241 "2020-06-25T14:10:41Z")

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Hi there, I’m trying to install the GR plotting library on FreeBSD 12.0 (stable), but the build fails with the message (see below), of which the main complaint is: Error opening archive: Failed to open 'downloads/gr-0.…

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## [A question about sort](https://discourse.julialang.org/t/a-question-about-sort/42035)

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**Author:** [@abcde](https://discourse.julialang.org/u/abcde)\
**Replies:** 4\
**Last updated:** [June 25, 2020, 1:24pm UTC](https://discourse.julialang.org/t/a-question-about-sort/42035 "2020-06-25T13:24:20Z")

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How do I sort by the imaginary part of a complex matrix?what function? thanks!

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## [A question about fft function](https://discourse.julialang.org/t/a-question-about-fft-function/42026)

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**Author:** [@abcde](https://discourse.julialang.org/u/abcde)\
**Replies:** 1\
**Last updated:** [June 25, 2020, 7:24am UTC](https://discourse.julialang.org/t/a-question-about-fft-function/42026 "2020-06-25T07:24:25Z")

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it does not work ,why? a=\[1 ,2 ,3 ,4\] b=\[7 8 9 5\] foo=x-\>fft(x,2) foo.(b) #print(fft(b,2))

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## [Getting started with mixed models](https://discourse.julialang.org/t/getting-started-with-mixed-models/41998)

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**Author:** [@pdeffebach](https://discourse.julialang.org/u/pdeffebach)\
**Replies:** 4\
**Last updated:** [June 24, 2020, 10:36pm UTC](https://discourse.julialang.org/t/getting-started-with-mixed-models/41998 "2020-06-24T22:36:18Z")

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I think I’m missing something very basic with MixedModels… julia\> using MixedModels, StatsBase julia\> t = (y = rand(100), x = rand(100)); julia\> fit(MixedModel, @formula(y ~ x), t) ERROR: MethodError: no method matchi…

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## [Mixed multi-membership models in Julia](https://discourse.julialang.org/t/mixed-multi-membership-models-in-julia/42005)

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**Author:** [@dhalpern](https://discourse.julialang.org/u/dhalpern)\
**Replies:** 4\
**Last updated:** [June 24, 2020, 10:23pm UTC](https://discourse.julialang.org/t/mixed-multi-membership-models-in-julia/42005 "2020-06-24T22:23:27Z")

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I was wondering if it was possible to fit a multi-membership model with MixedModels in Julia, as described by Ben Bolker for lme4 here. It seems like it should be in principle possible by editing the random effects matri…

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## [How to add weights parameter to Generalized Mixed Model](https://discourse.julialang.org/t/how-to-add-weights-parameter-to-generalized-mixed-model/41984)

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**Author:** [@laut](https://discourse.julialang.org/u/laut)\
**Replies:** 33\
**Last updated:** [June 24, 2020, 8:51pm UTC](https://discourse.julialang.org/t/how-to-add-weights-parameter-to-generalized-mixed-model/41984 "2020-06-24T20:51:48Z")

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How do you add the weight of an observation to a Mixed Model? I thought I could add the Freq column to wt argument, but apparently not. using RDatasets MixedModels titanic = RDatasets.dataset("datasets", "Titanic") tita…

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## [PIC (particle-in-cell), space charge tracking simulation?](https://discourse.julialang.org/t/pic-particle-in-cell-space-charge-tracking-simulation/26077)

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**Author:** [@jling](https://discourse.julialang.org/u/jling)\
**Replies:** 32\
**Last updated:** [June 24, 2020, 2:29pm UTC](https://discourse.julialang.org/t/pic-particle-in-cell-space-charge-tracking-simulation/26077 "2020-06-24T14:29:44Z")

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There’s a lot of demand in plasma/accelerator science to simulate space charge through so-called particle-in-cell model (which is somewhat like finite element analysis in structural dynamics etc) Many of them, for examp…

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## [Is there a way to set Ipopt's intemediate callback from JuMP?](https://discourse.julialang.org/t/is-there-a-way-to-set-ipopts-intemediate-callback-from-jump/41976)

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**Author:** [@pjssilva](https://discourse.julialang.org/u/pjssilva)\
**Replies:** 3\
**Last updated:** [June 24, 2020, 1:03pm UTC](https://discourse.julialang.org/t/is-there-a-way-to-set-ipopts-intemediate-callback-from-jump/41976 "2020-06-24T13:03:11Z")

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Hello, I was looking at the Ipopt.jl MOI interface and I could not find an easy way to set the intermediate callback (to stop iteration if needed). Is there any workaround? Maybe grab the Ipopt Optimizer struct directly…

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## [Error with ForwardDiff no method matching Float64](https://discourse.julialang.org/t/error-with-forwarddiff-no-method-matching-float64/41905)

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**Author:** [@smickus](https://discourse.julialang.org/u/smickus)\
**Replies:** 4\
**Last updated:** [June 23, 2020, 8:07pm UTC](https://discourse.julialang.org/t/error-with-forwarddiff-no-method-matching-float64/41905 "2020-06-23T20:07:29Z")

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I am trying to use forwardDiff to compute the gradient of a function in which I am solving an ODE, but I am getting an error that there is no method matching Float64. I have been stumped with this error for awile and wo…

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## [How to plot a matrix of colors](https://discourse.julialang.org/t/how-to-plot-a-matrix-of-colors/41920)

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**Author:** [@Torkel](https://discourse.julialang.org/u/Torkel)\
**Replies:** 6\
**Last updated:** [June 23, 2020, 4:22pm UTC](https://discourse.julialang.org/t/how-to-plot-a-matrix-of-colors/41920 "2020-06-23T16:22:50Z")

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If I have a matrix with colors: color\_matrix = \[:red :red; :red :blue\] how do I do to plot this in a 2d plot, showing the corresponding colors? E.g., if I had color\_matrix = \[:blue :white :red; :blue :white :red\] I …

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## [Reading outlook .msg extension file through Julia](https://discourse.julialang.org/t/reading-outlook-msg-extension-file-through-julia/41930)

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**Author:** [@akscse](https://discourse.julialang.org/u/akscse)\
**Replies:** 1\
**Last updated:** [June 23, 2020, 2:20pm UTC](https://discourse.julialang.org/t/reading-outlook-msg-extension-file-through-julia/41930 "2020-06-23T14:20:02Z")

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I need to do text analysis on an email dump. This dump contains outlook messages in .msg extension. Could you please suggest if there is some standard library to read .msg extensions. Thanks

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## [Threading two consecutive double loops](https://discourse.julialang.org/t/threading-two-consecutive-double-loops/41931)

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**Author:** [@jcook](https://discourse.julialang.org/u/jcook)\
**Replies:** 0\
**Last updated:** [June 23, 2020, 11:35am UTC](https://discourse.julialang.org/t/threading-two-consecutive-double-loops/41931 "2020-06-23T11:35:08Z")

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Hi All, I’m trying to improve the threaded performance of some code: I’ve written up the associated MWE. Essentially we have a matrix m, which is mutated in two consecutive double for loops. The first loop: The fir…

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## [Plotting lines from Contours.jl](https://discourse.julialang.org/t/plotting-lines-from-contours-jl/41923)

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**Author:** [@misha\_mikhasenko](https://discourse.julialang.org/u/misha_mikhasenko)\
**Replies:** 0\
**Last updated:** [June 23, 2020, 9:37am UTC](https://discourse.julialang.org/t/plotting-lines-from-contours-jl/41923 "2020-06-23T09:37:11Z")

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x = range(-50,50,length=1000) y = range(0,30,length=1000) f(x,y) = x/3+log(1000+((x-10)^2+(2y)^2-15^2)^2); z = f.(transpose(x), y) contour(x, y, z, levels=0:2.5:40, fill=(true, cgrad(:matter, categorical = true)), cl…

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## [Stiff system (of \>100 equations) - Rodas5 - multiple runs - instability or not](https://discourse.julialang.org/t/stiff-system-of-100-equations-rodas5-multiple-runs-instability-or-not/41868)

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**Author:** [@Polina](https://discourse.julialang.org/u/Polina)\
**Replies:** 7\
**Last updated:** [June 23, 2020, 4:30am UTC](https://discourse.julialang.org/t/stiff-system-of-100-equations-rodas5-multiple-runs-instability-or-not/41868 "2020-06-23T04:30:38Z")

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Dear all, I have a stiff system of \>100 equations (which I’m not allowed to post anywhere at the moment). I tried solve(my\_prob, Rodas5(autodiff=false),reltol=1e-8,abstol=1e-8,saveat=1.0) # let's call it method1 and …

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## [How to paste an image from the system clipboard (MS Windows) in a Gtk canvas?](https://discourse.julialang.org/t/how-to-paste-an-image-from-the-system-clipboard-ms-windows-in-a-gtk-canvas/41912)

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**Author:** [@frangonve](https://discourse.julialang.org/u/frangonve)\
**Replies:** 0\
**Last updated:** [June 23, 2020, 3:54am UTC](https://discourse.julialang.org/t/how-to-paste-an-image-from-the-system-clipboard-ms-windows-in-a-gtk-canvas/41912 "2020-06-23T03:54:31Z")

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I want to paste an image from the system clipboard (MS Windows) in a Gtk canvas. As far as I know InteractiveUtils.clipboard only works with text. Cheers.

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## [Engineering a better activation function for best assembly](https://discourse.julialang.org/t/engineering-a-better-activation-function-for-best-assembly/41897)

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**Author:** [@Palli](https://discourse.julialang.org/u/Palli)\
**Replies:** 0\
**Last updated:** [June 22, 2020, 11:14pm UTC](https://discourse.julialang.org/t/engineering-a-better-activation-function-for-best-assembly/41897 "2020-06-22T23:14:19Z")

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I’m checking out how complex an activation function can be before it’s (much) slower than ReLU, the simplest kind and standard before new Mish. Maybe not surprisingly f1 is as fast (while maybe it, f2 and f4 are no good…

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## [From Julia to VR](https://discourse.julialang.org/t/from-julia-to-vr/4950)

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**Author:** [@Loic\_Chappaz](https://discourse.julialang.org/u/Loic_Chappaz)\
**Replies:** 11\
**Last updated:** [June 22, 2020, 9:54pm UTC](https://discourse.julialang.org/t/from-julia-to-vr/4950 "2020-06-22T21:54:15Z")

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Hi all, I am not quite sure this is the best place for this discussion so fee free to let me know and I’ll move that somewhere more appropriate if needed. Put simply, I want to know if there exists already or if some p…

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## [DifferentialEquations: Confusion regarding time points and values in the solution array](https://discourse.julialang.org/t/differentialequations-confusion-regarding-time-points-and-values-in-the-solution-array/41730)

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**Author:** [@Sanji\_Vinsmoke](https://discourse.julialang.org/u/Sanji_Vinsmoke)\
**Replies:** 10\
**Last updated:** [June 19, 2020, 5:54pm UTC](https://discourse.julialang.org/t/differentialequations-confusion-regarding-time-points-and-values-in-the-solution-array/41730 "2020-06-19T17:54:39Z")

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I am a bit confused about the timepoints that the solution array represents. Since the algorithms used to solve are adaptive, the size of solutions might be different. Now, if I say that all my growth rates of species h…

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## [Have you used the IIS/conflict-refiner feature of a solver? How would you like to access it from JuMP?](https://discourse.julialang.org/t/have-you-used-the-iis-conflict-refiner-feature-of-a-solver-how-would-you-like-to-access-it-from-jump/41862)

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**Author:** [@dourouc05](https://discourse.julialang.org/u/dourouc05)\
**Replies:** 0\
**Last updated:** [June 22, 2020, 1:51pm UTC](https://discourse.julialang.org/t/have-you-used-the-iis-conflict-refiner-feature-of-a-solver-how-would-you-like-to-access-it-from-jump/41862 "2020-06-22T13:51:42Z")

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Hi all, Right now, the plumbing work has been performed in the JuMP ecosystem to let you access the IIS/conflict-refiner functionality of your solver. More precisely, there is a low-level interface in MathOptInterface t…

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## [Genetic Algorithms with julia](https://discourse.julialang.org/t/genetic-algorithms-with-julia/41844)

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**Author:** [@mayar](https://discourse.julialang.org/u/mayar)\
**Replies:** 3\
**Last updated:** [June 22, 2020, 12:03pm UTC](https://discourse.julialang.org/t/genetic-algorithms-with-julia/41844 "2020-06-22T12:03:12Z")

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hello all, I wish to solve a multi objective optimization problem with GA also I have never worked with GA before and I want to learn more about what are the packages that I can find useful? What are the pros of cons of…

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## [Can't load CuArrays](https://discourse.julialang.org/t/cant-load-cuarrays/31214)

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**Author:** [@Ferran\_Mazzanti](https://discourse.julialang.org/u/Ferran_Mazzanti)\
**Replies:** 17\
**Last updated:** [June 22, 2020, 10:42am UTC](https://discourse.julialang.org/t/cant-load-cuarrays/31214 "2020-06-22T10:42:08Z")

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Hi, this is ubuntu 18.04 (I think). I have installed julia and the sysop has installed CUDA, but I get using CuArrays \[ Info: CUDAdrv.jl failed to initialize, GPU functionality unavailable (set JULIA\_CUDA\_SILENT or JU…

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## [Parallel optimization/Genetic algorithm/Genetic programming](https://discourse.julialang.org/t/parallel-optimization-genetic-algorithm-genetic-programming/36805)

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**Author:** [@Neurovium](https://discourse.julialang.org/u/Neurovium)\
**Replies:** 4\
**Last updated:** [June 21, 2020, 10:18pm UTC](https://discourse.julialang.org/t/parallel-optimization-genetic-algorithm-genetic-programming/36805 "2020-06-21T22:18:41Z")

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Hi, I was planning to fully port a project to Julia. Checking the evolutionary optimization packages in Julia, I came across a few. It seems that the most mature one, Wallace (GitHub - ChrisTimperley/Wallace.jl: High-pe…

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