# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=362

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**Page:** 363

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## [Performance of Ensemble Simulations on GPUs](https://discourse.julialang.org/t/performance-of-ensemble-simulations-on-gpus/61426)

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**Author:** [@knn](https://discourse.julialang.org/u/knn)\
**Replies:** 4\
**Last updated:** [May 28, 2021, 7:13am UTC](https://discourse.julialang.org/t/performance-of-ensemble-simulations-on-gpus/61426 "2021-05-28T07:13:10Z")

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We are currently analyzing the performance of ensemble simlations on CPUs and GPUs. In our case, we noticed that the ensemble simulation on the GPU with EnsembleGPUArray only stresses the GPU for about 6s. Nevertheless, …

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## [Using JuMP in Python Environment](https://discourse.julialang.org/t/using-jump-in-python-environment/61165)

<div class="topic-metadata">

**Author:** [@asavasci](https://discourse.julialang.org/u/asavasci)\
**Replies:** 2\
**Last updated:** [May 28, 2021, 1:52am UTC](https://discourse.julialang.org/t/using-jump-in-python-environment/61165 "2021-05-28T01:52:48Z")

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I am trying to embed JuMP-based Julia script into a Python-based computing framework using PyCall. However, I am facing problems when I define JuMP variable as from julia import Ipopt from julia.JuMP import Model from …

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## [Parametric or normal types for dispatching on materials](https://discourse.julialang.org/t/parametric-or-normal-types-for-dispatching-on-materials/61808)

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**Author:** [@feanor12](https://discourse.julialang.org/u/feanor12)\
**Replies:** 1\
**Last updated:** [May 27, 2021, 5:54am UTC](https://discourse.julialang.org/t/parametric-or-normal-types-for-dispatching-on-materials/61808 "2021-05-27T05:54:42Z")

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When generating a type representing a material would it be better to generate types for every material or to create a parametric material type. What would you suggest and why? abstract type Material end struct Gold \<:…

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## [Solve for Hermitian PSD with non-linear objective in JuMP](https://discourse.julialang.org/t/solve-for-hermitian-psd-with-non-linear-objective-in-jump/61539)

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**Author:** [@nhardy](https://discourse.julialang.org/u/nhardy)\
**Replies:** 19\
**Last updated:** [May 27, 2021, 1:28am UTC](https://discourse.julialang.org/t/solve-for-hermitian-psd-with-non-linear-objective-in-jump/61539 "2021-05-27T01:28:32Z")

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I am new to using JuMP, and was hoping for some help. I am trying to estimate the elements of a matrix that is: Hermitian (in general complex numbers) Semi-positive definite diagonal elements are \>= 0 trace == 1 After…

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## [How to train/predict a very simple feed-forward neural network in Flux?](https://discourse.julialang.org/t/how-to-train-predict-a-very-simple-feed-forward-neural-network-in-flux/39534)

<div class="topic-metadata">

**Author:** [@sylvaticus](https://discourse.julialang.org/u/sylvaticus)\
**Replies:** 6\
**Last updated:** [May 26, 2021, 8:42pm UTC](https://discourse.julialang.org/t/how-to-train-predict-a-very-simple-feed-forward-neural-network-in-flux/39534 "2021-05-26T20:42:40Z")

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I must be idiot but I can’t realise how to do very basic… no Convolution, RNN, gates,… just a basic plain feed-forward neural network design/testing/validation in Flux. Somethink like: l1 = FullyConnectedLayer(tanh,2,3…

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## [Factors for regression models in julia](https://discourse.julialang.org/t/factors-for-regression-models-in-julia/61836)

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**Author:** [@Babou](https://discourse.julialang.org/u/Babou)\
**Replies:** 5\
**Last updated:** [May 26, 2021, 8:35pm UTC](https://discourse.julialang.org/t/factors-for-regression-models-in-julia/61836 "2021-05-26T20:35:50Z")

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I want to build a linear mixed model in Julia but the R code I am basing it on requires the use of factors for the model. I came across a stackoverflow post on just this topic but it was from 2017 and I am hoping ther…

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## [Is there a workaround to render symbols from Symbolics.jl in Pluto.jl](https://discourse.julialang.org/t/is-there-a-workaround-to-render-symbols-from-symbolics-jl-in-pluto-jl/61198)

<div class="topic-metadata">

**Author:** [@feanor12](https://discourse.julialang.org/u/feanor12)\
**Replies:** 4\
**Last updated:** [May 26, 2021, 8:27pm UTC](https://discourse.julialang.org/t/is-there-a-workaround-to-render-symbols-from-symbolics-jl-in-pluto-jl/61198 "2021-05-26T20:27:35Z")

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When I use Symbolics.jl in Pluto.jl I get an invalid latex expression (at least for Mathjax). Is there a workaround to remove the text part from the output? I basically makes Symbolics.jl very bothersome to use. I …

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## [Modeling Thermodynamic System in MTK](https://discourse.julialang.org/t/modeling-thermodynamic-system-in-mtk/61095)

<div class="topic-metadata">

**Author:** [@mbologna](https://discourse.julialang.org/u/mbologna)\
**Replies:** 1\
**Last updated:** [May 26, 2021, 8:21pm UTC](https://discourse.julialang.org/t/modeling-thermodynamic-system-in-mtk/61095 "2021-05-26T20:21:44Z")

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I’m working on converting an existing Julia model using DifferentialEquations.jl and solving Stiff ODEs to using MTK. There seems to be some nuance to setting up ODESystems that I don’t understand. I’m modeling pressure …

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## [How to show edges in mesh plot in Makie?](https://discourse.julialang.org/t/how-to-show-edges-in-mesh-plot-in-makie/61820)

<div class="topic-metadata">

**Author:** [@juliohm](https://discourse.julialang.org/u/juliohm)\
**Replies:** 6\
**Last updated:** [May 26, 2021, 6:19pm UTC](https://discourse.julialang.org/t/how-to-show-edges-in-mesh-plot-in-makie/61820 "2021-05-26T18:19:32Z")

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From the documentation, it is easy to plot a mesh given an array of coordinates and an array of connectivities: using GLMakie coords = \[ 0.0 0.0 1.0 0.0 1.0 1.0 0.0 1.0 \] connec = \[ 1 2 3 3 4 1 \] mesh(coo…

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## [How to obtain the critical value F0 of a F-distribution?](https://discourse.julialang.org/t/how-to-obtain-the-critical-value-f0-of-a-f-distribution/36448)

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**Author:** [@Fred](https://discourse.julialang.org/u/Fred)\
**Replies:** 3\
**Last updated:** [May 26, 2021, 12:16pm UTC](https://discourse.julialang.org/t/how-to-obtain-the-critical-value-f0-of-a-f-distribution/36448 "2021-05-26T12:16:50Z")

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Hi, I am not statistician and I need some advises to do a statistical test in Julia. I would like to obtain the critical value F0 of a F-distribution available for example in these tables I read the Distributions.jl d…

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## [Sensitivities with respect to initial conditions in DifferentialEquations.jl](https://discourse.julialang.org/t/sensitivities-with-respect-to-initial-conditions-in-differentialequations-jl/25555)

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**Author:** [@rjpower4](https://discourse.julialang.org/u/rjpower4)\
**Replies:** 17\
**Last updated:** [May 26, 2021, 10:36am UTC](https://discourse.julialang.org/t/sensitivities-with-respect-to-initial-conditions-in-differentialequations-jl/25555 "2021-05-26T10:36:11Z")

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For my research, I perform many differential corrections processes. Often times, for these processes I want the transition matrix, \\Phi(t\_1, t\_0), which is obtained by propagating the linearization of the system alongsid…

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## [Font of annotations?](https://discourse.julialang.org/t/font-of-annotations/14998)

<div class="topic-metadata">

**Author:** [@iwelch](https://discourse.julialang.org/u/iwelch)\
**Replies:** 3\
**Last updated:** [May 26, 2021, 9:24am UTC](https://discourse.julialang.org/t/font-of-annotations/14998 "2021-05-26T09:24:27Z")

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dear Plots wizards—how do I set the font (size) of annotations? using Plots y= 2:20; x=2:20; f(x,y)=x+y; annotations= \[ (x\[i\],y\[j\],round(f(x\[i\],y\[j\]),digits=2)) for i=1:length(x) for j=1:length(y)\]; plot( ; annotations=…

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## [Enumerating all possible solutions of Knapsack problem](https://discourse.julialang.org/t/enumerating-all-possible-solutions-of-knapsack-problem/61800)

<div class="topic-metadata">

**Author:** [@Tomas\_Pevny](https://discourse.julialang.org/u/Tomas_Pevny)\
**Replies:** 3\
**Last updated:** [May 26, 2021, 3:57am UTC](https://discourse.julialang.org/t/enumerating-all-possible-solutions-of-knapsack-problem/61800 "2021-05-26T03:57:36Z")

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Dear All, I would like to ask, if anyone has experimented with an algorithm to enumerate all possible solutions of the knapsack problem. I have seen scientific papers solving this problem and would like to know, if some…

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## [Help with JuMP variables](https://discourse.julialang.org/t/help-with-jump-variables/61733)

<div class="topic-metadata">

**Author:** [@Dan.phi](https://discourse.julialang.org/u/Dan.phi)\
**Replies:** 1\
**Last updated:** [May 25, 2021, 11:34pm UTC](https://discourse.julialang.org/t/help-with-jump-variables/61733 "2021-05-25T23:34:40Z")

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I am trying to solve a constrained optimization problem using JuMP, but there is apparently a conflict between how I define the variables and one of the packages I call in the objective function. I just started with JuMP…

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## [COSMO.jl & Convex.jl: setting intial values](https://discourse.julialang.org/t/cosmo-jl-convex-jl-setting-intial-values/61381)

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**Author:** [@lrnv](https://discourse.julialang.org/u/lrnv)\
**Replies:** 4\
**Last updated:** [May 25, 2021, 7:49pm UTC](https://discourse.julialang.org/t/cosmo-jl-convex-jl-setting-intial-values/61381 "2021-05-25T19:49:44Z")

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Hi, I’m using COSMO.jl as a solver from Convex.jl. I’m solving tseveral ‘related problems’ over and over again, which correspond to more precise versions of each others. I’d like to use the COSMO.jl warm starting featu…

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## [KeyError: key "Xorg\_libXrender\_jll" not found](https://discourse.julialang.org/t/keyerror-key-xorg-libxrender-jll-not-found/61770)

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**Author:** [@Aquaman](https://discourse.julialang.org/u/Aquaman)\
**Replies:** 0\
**Last updated:** [May 25, 2021, 10:22am UTC](https://discourse.julialang.org/t/keyerror-key-xorg-libxrender-jll-not-found/61770 "2021-05-25T10:22:24Z")

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I cannot install Plots.jl in Julia 1.6.1 due to the error “KeyError: key “Xorg\_libXrender\_jll” not found”

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## [JumpProblem with large number of jumps crashes](https://discourse.julialang.org/t/jumpproblem-with-large-number-of-jumps-crashes/61444)

<div class="topic-metadata">

**Author:** [@gzagatti](https://discourse.julialang.org/u/gzagatti)\
**Replies:** 13\
**Last updated:** [May 25, 2021, 8:00am UTC](https://discourse.julialang.org/t/jumpproblem-with-large-number-of-jumps-crashes/61444 "2021-05-25T08:00:06Z")

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Hello, I am trying to solve a JumpProblem defined on a network. The problem consists of a SIR model in which I am trying to model every node of the network separately. I have a working code that works with a small net…

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## [Trying to understand the use of shared memory on GPUs](https://discourse.julialang.org/t/trying-to-understand-the-use-of-shared-memory-on-gpus/61240)

<div class="topic-metadata">

**Author:** [@Ferran\_Mazzanti](https://discourse.julialang.org/u/Ferran_Mazzanti)\
**Replies:** 3\
**Last updated:** [May 25, 2021, 5:47am UTC](https://discourse.julialang.org/t/trying-to-understand-the-use-of-shared-memory-on-gpus/61240 "2021-05-25T05:47:38Z")

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Hi, I’m trying to learn how to use shared memory on the GPU by following the very nice write-up in https://jenni-westoby.github.io/Julia\_GPU\_examples/dev/Vector\_dot\_product/ however, I fail to understand basic things …

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## [Cxx.jl Compatability with Julia 1.5+](https://discourse.julialang.org/t/cxx-jl-compatability-with-julia-1-5/53782)

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**Author:** [@cadojo](https://discourse.julialang.org/u/cadojo)\
**Replies:** 7\
**Last updated:** [May 25, 2021, 4:57am UTC](https://discourse.julialang.org/t/cxx-jl-compatability-with-julia-1-5/53782 "2021-05-25T04:57:52Z")

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The package Cxx.jl seems to be partially compatible with Julia 1.3, and not compatible with Julia 1.5+ (as referenced by this discourse post and #464). Does Julia 1.5 introduce permanent incompatibilities with a project…

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## [JSON3.jl parse custom type with NaN](https://discourse.julialang.org/t/json3-jl-parse-custom-type-with-nan/61295)

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**Author:** [@ohmsweetohm1](https://discourse.julialang.org/u/ohmsweetohm1)\
**Replies:** 3\
**Last updated:** [May 25, 2021, 3:45am UTC](https://discourse.julialang.org/t/json3-jl-parse-custom-type-with-nan/61295 "2021-05-25T03:45:49Z")

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The following works: struct Foo a::Vector{Float64} b::Float64 end JSON3.StructType(::Type{Foo}) = JSON3.Struct() str = JSON3.write(Foo(\[NaN, 2.3\], NaN), allow\_inf=true) JSON3.read(str, Foo, allow\_inf=true) Wi…

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## [Fatal error while reading in messy data using DataFrames, CSV](https://discourse.julialang.org/t/fatal-error-while-reading-in-messy-data-using-dataframes-csv/61314)

<div class="topic-metadata">

**Author:** [@jessecm](https://discourse.julialang.org/u/jessecm)\
**Replies:** 6\
**Last updated:** [May 25, 2021, 3:28am UTC](https://discourse.julialang.org/t/fatal-error-while-reading-in-messy-data-using-dataframes-csv/61314 "2021-05-25T03:28:22Z")

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Hi, while reading in a large, messy dataset, I got the message: using DataFrames, CSV, Random, Tables GBIF\_chordate = CSV.read("occurrence.txt", DataFrame; header = true); \*\*ERROR:\*\* thread = 1 fatal error, encountered …

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## [Reshaping ID and STatus by CATegory](https://discourse.julialang.org/t/reshaping-id-and-status-by-category/61716)

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**Author:** [@rocco\_sprmnt21](https://discourse.julialang.org/u/rocco_sprmnt21)\
**Replies:** 2\
**Last updated:** [May 24, 2021, 7:55pm UTC](https://discourse.julialang.org/t/reshaping-id-and-status-by-category/61716 "2021-05-24T19:55:42Z")

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I would like to see (some of) the different ways in which we can transform the following dataframe df=DataFrame(CAT=\["A","B","C","A","B","C","D","E","A","C","D"\], ID=\[1,1,1,2,2,2,2,2,3,3,3\], ST=\["q","q"…

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## [Reading Multiple Files in a Folder Into a tensor in Julia](https://discourse.julialang.org/t/reading-multiple-files-in-a-folder-into-a-tensor-in-julia/61324)

<div class="topic-metadata">

**Author:** [@phantom](https://discourse.julialang.org/u/phantom)\
**Replies:** 8\
**Last updated:** [May 24, 2021, 7:43pm UTC](https://discourse.julialang.org/t/reading-multiple-files-in-a-folder-into-a-tensor-in-julia/61324 "2021-05-24T19:43:04Z")

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New to Julia and programming in general so this is a two part question. Suppose I have a Folder with 3,000 CSV files. Each file is roughly 7,000 x 7. (The number of rows may vary from file to file but the number of co…

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## [How to implement a real time DAE solver](https://discourse.julialang.org/t/how-to-implement-a-real-time-dae-solver/61719)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 12\
**Last updated:** [May 24, 2021, 4:13pm UTC](https://discourse.julialang.org/t/how-to-implement-a-real-time-dae-solver/61719 "2021-05-24T16:13:27Z")

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I have the following solver: differential\_vars = ones(Bool, 36) prob = DAEProblem(residual!, yd0, y0, tspan, differential\_vars=differential\_vars) solver = IDA(linear\_solver=:Dense) @time sol = solve(prob, solver, save…

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## [Plotting a closed curve in 3D](https://discourse.julialang.org/t/plotting-a-closed-curve-in-3d/61691)

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**Author:** [@e3c6](https://discourse.julialang.org/u/e3c6)\
**Replies:** 4\
**Last updated:** [May 24, 2021, 2:23pm UTC](https://discourse.julialang.org/t/plotting-a-closed-curve-in-3d/61691 "2021-05-24T14:23:06Z")

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How do you plot a closed curve in Julia? For instance using Plots.jl. I would like to draw an ellipse into a 3-dimensional plot.

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## [Macro capturing intermediate values](https://discourse.julialang.org/t/macro-capturing-intermediate-values/61715)

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**Author:** [@MeinAccount](https://discourse.julialang.org/u/MeinAccount)\
**Replies:** 0\
**Last updated:** [May 24, 2021, 10:15am UTC](https://discourse.julialang.org/t/macro-capturing-intermediate-values/61715 "2021-05-24T10:15:30Z")

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I just wanted to show of a fun little macro I wrote. Doing a course on stochastic simulation, I’m writing small functions that simulate some process. For performance reasons I don’t want to emit all the intermediate valu…

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## [Transforming dataframe columns selected via regex while keeping the other columns](https://discourse.julialang.org/t/transforming-dataframe-columns-selected-via-regex-while-keeping-the-other-columns/61702)

<div class="topic-metadata">

**Author:** [@anon71627001](https://discourse.julialang.org/u/anon71627001)\
**Replies:** 4\
**Last updated:** [May 24, 2021, 10:03am UTC](https://discourse.julialang.org/t/transforming-dataframe-columns-selected-via-regex-while-keeping-the-other-columns/61702 "2021-05-24T10:03:40Z")

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Let’s say I have df = DataFrame(ax = 1:3, bx = 4:6, cy = 7:9, dy = 10:12) and want to double the values of each column that has an “x” in its header, while leaving the columns that don’t have an “x” in their header uncha…

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## [SDDiP: Could not solve for Lagrangian duals. Iteration limit exceeded](https://discourse.julialang.org/t/sddip-could-not-solve-for-lagrangian-duals-iteration-limit-exceeded/61673)

<div class="topic-metadata">

**Author:** [@BYS](https://discourse.julialang.org/u/BYS)\
**Replies:** 5\
**Last updated:** [May 24, 2021, 8:44am UTC](https://discourse.julialang.org/t/sddip-could-not-solve-for-lagrangian-duals-iteration-limit-exceeded/61673 "2021-05-24T08:44:09Z")

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I have tried a SDDP model including integer using “integrality\_handler=SDDP.SDDiP()”, and I set SDDP.train(model; iteration\_limit = 10) The results are as follows, ERROR: LoadError: Could not solve for Lagrangian dual…

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## [Save multiple plots on separate pages of one PDF](https://discourse.julialang.org/t/save-multiple-plots-on-separate-pages-of-one-pdf/41953)

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**Author:** [@corbat](https://discourse.julialang.org/u/corbat)\
**Replies:** 3\
**Last updated:** [May 24, 2021, 5:42am UTC](https://discourse.julialang.org/t/save-multiple-plots-on-separate-pages-of-one-pdf/41953 "2021-05-24T05:42:26Z")

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Hi, is there a way to save multiple plots, more precisely multiple figures generated with Plots.jl, on separate pages of a single PDF file?

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## [Optim.jl vs NLopt.jl vs?](https://discourse.julialang.org/t/optim-jl-vs-nlopt-jl-vs/61692)

<div class="topic-metadata">

**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 8\
**Last updated:** [May 24, 2021, 4:00am UTC](https://discourse.julialang.org/t/optim-jl-vs-nlopt-jl-vs/61692 "2021-05-24T04:00:08Z")

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I have a kind of hard nonlinear optimization problem. 12 variables, I know the result of the function should be zero, but how to find the combination of 12 values that give a very low residual? So far I tried Optim.jl a…

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