# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=431

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**Page:** 432

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## [Beginner Question: How to use JuMP model variables in different functions](https://discourse.julialang.org/t/beginner-question-how-to-use-jump-model-variables-in-different-functions/43909)

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**Author:** [@GerhardTotschnig](https://discourse.julialang.org/u/GerhardTotschnig)\
**Replies:** 2\
**Last updated:** [July 29, 2020, 7:38pm UTC](https://discourse.julialang.org/t/beginner-question-how-to-use-jump-model-variables-in-different-functions/43909 "2020-07-29T19:38:45Z")

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I want to create a JUMP energy system model, where different features can be added or not. So my idea was to use different functions which can be called if needed for adding new equations to the model. Cannot figure out…

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## [Minimal integer solution to homogeneous system of linear equations](https://discourse.julialang.org/t/minimal-integer-solution-to-homogeneous-system-of-linear-equations/43848)

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**Author:** [@anon37204545](https://discourse.julialang.org/u/anon37204545)\
**Replies:** 4\
**Last updated:** [July 29, 2020, 2:44pm UTC](https://discourse.julialang.org/t/minimal-integer-solution-to-homogeneous-system-of-linear-equations/43848 "2020-07-29T14:44:54Z")

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As the title says, I’m looking for a way to find a minimal integer solution of the homogeneous system of linear equations. Such systems have infinitely many solutions (since you can multiply by constant or linearly comb…

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## [Using MLJ with Gaussian Process Regression](https://discourse.julialang.org/t/using-mlj-with-gaussian-process-regression/43883)

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**Author:** [@gideonsimpson](https://discourse.julialang.org/u/gideonsimpson)\
**Replies:** 0\
**Last updated:** [July 29, 2020, 2:00pm UTC](https://discourse.julialang.org/t/using-mlj-with-gaussian-process-regression/43883 "2020-07-29T14:00:01Z")

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I have a data set on which I would like to perform binary classification, and I would like to see how well Gaussian Process Regression (GPR) does with it. Since I’ve already been experimenting with MLJ, I figured I migh…

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## [Which GPU should I ask for?](https://discourse.julialang.org/t/which-gpu-should-i-ask-for/43861)

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**Author:** [@sylvaticus](https://discourse.julialang.org/u/sylvaticus)\
**Replies:** 4\
**Last updated:** [July 29, 2020, 1:43pm UTC](https://discourse.julialang.org/t/which-gpu-should-i-ask-for/43861 "2020-07-29T13:43:08Z")

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Hello, we have a remote server (not VPS) and I would like to ask the company managing it to add a GPU for machine learning computations (using CUDA.jl I suppose). Is there a list of supported GPU? How they are organise…

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## [User Callback nodeid](https://discourse.julialang.org/t/user-callback-nodeid/43847)

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**Author:** [@afazevedo](https://discourse.julialang.org/u/afazevedo)\
**Replies:** 3\
**Last updated:** [July 29, 2020, 1:34pm UTC](https://discourse.julialang.org/t/user-callback-nodeid/43847 "2020-07-29T13:34:26Z")

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Is there any way to retrieve the node id on user callback? On the Gurobi callback, cbget\_mipnode\_nodcnt serves well. But I want to use the MOI user callback, instead. Thanks in advance!

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## [Enforce a matrix to be positive semidefinite in JuMP](https://discourse.julialang.org/t/enforce-a-matrix-to-be-positive-semidefinite-in-jump/43853)

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**Author:** [@Rasoul](https://discourse.julialang.org/u/Rasoul)\
**Replies:** 1\
**Last updated:** [July 29, 2020, 9:34am UTC](https://discourse.julialang.org/t/enforce-a-matrix-to-be-positive-semidefinite-in-jump/43853 "2020-07-29T09:34:10Z")

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Hi All, I want to enforce a square matrix in my code (i.e. W) to be positive semidefinite. I am using Gurobi solver. I have added the following constraint in my code to fulfill the task. @constraint (model, W in PSDcon…

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## [UndefVarError: θ not defined](https://discourse.julialang.org/t/undefvarerror-not-defined/43820)

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**Author:** [@Irene](https://discourse.julialang.org/u/Irene)\
**Replies:** 7\
**Last updated:** [July 29, 2020, 8:14am UTC](https://discourse.julialang.org/t/undefvarerror-not-defined/43820 "2020-07-29T08:14:43Z")

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Hi, I stumbled upon this very nice example from @SebastianCallh in which Neural ODE are used to model and forecast the weather in the city of Delhi. I have a keen interest in learning how to apply differential equations…

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## [NeuralODE and ModelingToolkit](https://discourse.julialang.org/t/neuralode-and-modelingtoolkit/43855)

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**Author:** [@Jagirhussan](https://discourse.julialang.org/u/Jagirhussan)\
**Replies:** 2\
**Last updated:** [July 29, 2020, 5:07am UTC](https://discourse.julialang.org/t/neuralode-and-modelingtoolkit/43855 "2020-07-29T05:07:31Z")

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I would like to do statespace analysis. ModelingToolkit provides some very useful constructs to do this. I was wondering if there is a way to analyse NeuralODE’s (trained using DiffEqFlux) using ModelingToolkit? Thanks

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## [PowerModelsAnnex.jl obtaining duals](https://discourse.julialang.org/t/powermodelsannex-jl-obtaining-duals/43535)

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**Author:** [@fnbillimoria](https://discourse.julialang.org/u/fnbillimoria)\
**Replies:** 5\
**Last updated:** [July 29, 2020, 4:17am UTC](https://discourse.julialang.org/t/powermodelsannex-jl-obtaining-duals/43535 "2020-07-29T04:17:10Z")

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I have downloaded the PowerModelsAnnex.jl files. I am using the build\_qc\_opf functions, and wish to obtain dual prices from the solution. The specific dual prices I wish to obtain are the duals of the power balance or …

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## [LAPACK exception with gels!](https://discourse.julialang.org/t/lapack-exception-with-gels/43620)

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**Author:** [@Joris\_Pinkse](https://discourse.julialang.org/u/Joris_Pinkse)\
**Replies:** 1\
**Last updated:** [July 28, 2020, 7:43pm UTC](https://discourse.julialang.org/t/lapack-exception-with-gels/43620 "2020-07-28T19:43:28Z")

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If I run the following program then Julia quits with an exception. I suspect this has something to do with rounding in the factorization. The matrix B below can be replaced with a matrix of zeros of the same size and t…

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## [Setting a small case in PowerModels as m file](https://discourse.julialang.org/t/setting-a-small-case-in-powermodels-as-m-file/43821)

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**Author:** [@mayar](https://discourse.julialang.org/u/mayar)\
**Replies:** 3\
**Last updated:** [July 28, 2020, 6:57pm UTC](https://discourse.julialang.org/t/setting-a-small-case-in-powermodels-as-m-file/43821 "2020-07-28T18:57:44Z")

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hello there, I want to test a small 3 bus system on PowerModels and I had to modify the case5.m into case3.m since there was no smaller system than 5 bus network however I get this error when I run my julia file with t…

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## [Gurobi - Branch Priority](https://discourse.julialang.org/t/gurobi-branch-priority/43826)

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**Author:** [@afazevedo](https://discourse.julialang.org/u/afazevedo)\
**Replies:** 3\
**Last updated:** [July 28, 2020, 6:39pm UTC](https://discourse.julialang.org/t/gurobi-branch-priority/43826 "2020-07-28T18:39:55Z")

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I wish I could use the Gurobi attribute “Branch Priority”. So I tried to use it that way and it gave an error. Is there a smarter way to do this? MOI.set(model,Gurobi.ModelAttribute("BranchPriority"), u) u is the varia…

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## [Benders decomposition in JuMP](https://discourse.julialang.org/t/benders-decomposition-in-jump/43678)

<div class="topic-metadata">

**Author:** [@JohnZ](https://discourse.julialang.org/u/JohnZ)\
**Replies:** 4\
**Last updated:** [July 28, 2020, 6:10pm UTC](https://discourse.julialang.org/t/benders-decomposition-in-jump/43678 "2020-07-28T18:10:44Z")

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Hello, I have been experimenting with JuMP and I have coded a CVaR optimisation problem using the method introduced by Rockfeller and Uryasev. My implementation given below uses extensive form of the stochastic program. …

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## [Flux: GPU not working as expected](https://discourse.julialang.org/t/flux-gpu-not-working-as-expected/43759)

<div class="topic-metadata">

**Author:** [@Ruan\_Stander](https://discourse.julialang.org/u/Ruan_Stander)\
**Replies:** 6\
**Last updated:** [July 28, 2020, 5:50pm UTC](https://discourse.julialang.org/t/flux-gpu-not-working-as-expected/43759 "2020-07-28T17:50:40Z")

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https://github.com/FluxML/model-zoo/blob/master/vision/mnist/mlp.jl Adapting above example to my own set of inputs. The example works as expected When I change input from 28x28 MNIST pictures to my input ( 10x5 Array{…

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## [Implementing one-class SVM for Novelty Detection](https://discourse.julialang.org/t/implementing-one-class-svm-for-novelty-detection/1357)

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**Author:** [@KrishnaKanhaiya](https://discourse.julialang.org/u/KrishnaKanhaiya)\
**Replies:** 11\
**Last updated:** [July 28, 2020, 10:58am UTC](https://discourse.julialang.org/t/implementing-one-class-svm-for-novelty-detection/1357 "2020-07-28T10:58:50Z")

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Hi, I want to implement one-class SVM in Julia(SVM.jl) very similar to scikit-learn in python (here). I see that SVM.jl is unmaintained and will be removed from the metadata shortly. Is it going to be removed for sure?…

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## [Implementing dosing regimens in diffeq](https://discourse.julialang.org/t/implementing-dosing-regimens-in-diffeq/43173)

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**Author:** [@Janssena](https://discourse.julialang.org/u/Janssena)\
**Replies:** 2\
**Last updated:** [July 28, 2020, 6:15am UTC](https://discourse.julialang.org/t/implementing-dosing-regimens-in-diffeq/43173 "2020-07-28T06:15:18Z")

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Hey all, I’ve been working to implement a complex dosing regimen consisting of both IV bolus doses and continuous IV infusions. An example would be: t = -80, dose = 1000, rate = 0 t = -2, dose = 2500, rate = 100 t =…

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## [Clearing a scene in Makie](https://discourse.julialang.org/t/clearing-a-scene-in-makie/43790)

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**Author:** [@pauljurczak](https://discourse.julialang.org/u/pauljurczak)\
**Replies:** 1\
**Last updated:** [July 28, 2020, 3:54am UTC](https://discourse.julialang.org/t/clearing-a-scene-in-makie/43790 "2020-07-28T03:54:28Z")

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I have a visualization with sub-scenes. scene2 displays a polyline with text labels. Polylines change depending on mouse selections in scene1. I would like to be able to clear scene2 in example below at commented line: u…

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## [Question about writting custom training function using Flux.jl](https://discourse.julialang.org/t/question-about-writting-custom-training-function-using-flux-jl/43743)

<div class="topic-metadata">

**Author:** [@XiaodongMa-MRI](https://discourse.julialang.org/u/XiaodongMa-MRI)\
**Replies:** 2\
**Last updated:** [July 28, 2020, 1:27am UTC](https://discourse.julialang.org/t/question-about-writting-custom-training-function-using-flux-jl/43743 "2020-07-28T01:27:02Z")

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Hello, I am trying to write a custom training function instead of using Flux!train, following the documentation https://fluxml.ai/Flux.jl/stable/training/training/#Model-parameters-1, but it will pop up error message “O…

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## [Julia+JuMP performances](https://discourse.julialang.org/t/julia-jump-performances/43766)

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**Author:** [@mamo](https://discourse.julialang.org/u/mamo)\
**Replies:** 2\
**Last updated:** [July 27, 2020, 4:24pm UTC](https://discourse.julialang.org/t/julia-jump-performances/43766 "2020-07-27T16:24:29Z")

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A question for Julia community. The problem I have has: \_nvars = 2483610 \_ncons = 1269620 \_total\_solve\_time = 91.625 sec Solver is AMPL+CPLEX. Is this a feasible problem for JuMP + GLPK? Anybody compared performanc…

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## [Which JuMP.jl solver for this problem?](https://discourse.julialang.org/t/which-jump-jl-solver-for-this-problem/43350)

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**Author:** [@mthelm85](https://discourse.julialang.org/u/mthelm85)\
**Replies:** 19\
**Last updated:** [July 27, 2020, 12:04pm UTC](https://discourse.julialang.org/t/which-jump-jl-solver-for-this-problem/43350 "2020-07-27T12:04:53Z")

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I’ve been struggling for a couple of days now to coerce JuMP to solve a particular problem. The goal is fairly simple and I’ll describe a simplified version of my real problem here, along with the code: Given the latitu…

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## [Juniper...Solver gets only local optimum point](https://discourse.julialang.org/t/juniper-solver-gets-only-local-optimum-point/43676)

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**Author:** [@mayar](https://discourse.julialang.org/u/mayar)\
**Replies:** 10\
**Last updated:** [July 26, 2020, 8:53pm UTC](https://discourse.julialang.org/t/juniper-solver-gets-only-local-optimum-point/43676 "2020-07-26T20:53:35Z")

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Hello there, Congratulations on the amazing conference of 2020 at first…Let me tell you my problem briefly I have a non convex NLP (OPF or Optimal Power Flow) and I want to try different solvers on this problem. I deci…

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## [Adding a new function to the PowerModelsAnnex](https://discourse.julialang.org/t/adding-a-new-function-to-the-powermodelsannex/43634)

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**Author:** [@Rasoul](https://discourse.julialang.org/u/Rasoul)\
**Replies:** 5\
**Last updated:** [July 26, 2020, 4:37pm UTC](https://discourse.julialang.org/t/adding-a-new-function-to-the-powermodelsannex/43634 "2020-07-26T16:37:50Z")

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Hi all, I have written a function, i.e, sdp\_opf, to solve the OPF problem via SDP relaxation which exports the build\_sdp\_opf. However, when I want to run my code via build\_sdp\_opf(case,model) I get the following error…

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## [Why do I get Infeasible Solution (JuMP with Optimizer Ipopt)](https://discourse.julialang.org/t/why-do-i-get-infeasible-solution-jump-with-optimizer-ipopt/43141)

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**Author:** [@mayar](https://discourse.julialang.org/u/mayar)\
**Replies:** 31\
**Last updated:** [July 26, 2020, 4:36pm UTC](https://discourse.julialang.org/t/why-do-i-get-infeasible-solution-jump-with-optimizer-ipopt/43141 "2020-07-26T16:36:41Z")

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hello, I have developed a code that optimizes a power system and then I find that JuMP return infeasible solution My constraints are non linear and my objective is non linear too Am I utilizing the wrong solver or wh…

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## [JuMP development sprints](https://discourse.julialang.org/t/jump-development-sprints/42433)

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**Author:** [@odow](https://discourse.julialang.org/u/odow)\
**Replies:** 5\
**Last updated:** [July 26, 2020, 2:42pm UTC](https://discourse.julialang.org/t/jump-development-sprints/42433 "2020-07-26T14:42:59Z")

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Edit: Please read this Google doc, which has all the information. Dear all, Ever wanted to contribute to JuMP but not known where to start? Now’s your chance! Over the next few months, we will be holding a series of …

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## [Slower code after migrating from MathProgBase](https://discourse.julialang.org/t/slower-code-after-migrating-from-mathprogbase/43650)

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**Author:** [@josePereiro](https://discourse.julialang.org/u/josePereiro)\
**Replies:** 10\
**Last updated:** [July 25, 2020, 8:04pm UTC](https://discourse.julialang.org/t/slower-code-after-migrating-from-mathprogbase/43650 "2020-07-25T20:04:27Z")

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Hi, after updating some packages I got this error: \`ClpSolver\` is no longer supported. If you are using JuMP, upgrade to the latest version and use \`Clp.Optimizer\` instead. If you are using MathProgBase (e.g., via \`lin…

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## [Unstack-stack-unstack-stack](https://discourse.julialang.org/t/unstack-stack-unstack-stack/43591)

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**Author:** [@victorialena](https://discourse.julialang.org/u/victorialena)\
**Replies:** 1\
**Last updated:** [July 25, 2020, 3:45pm UTC](https://discourse.julialang.org/t/unstack-stack-unstack-stack/43591 "2020-07-25T15:45:45Z")

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any ideas on how to make this more efficient? I don’t know how to broadcast the functions more efficiently than a for loop and matrix multiplications in 3D didn’t really work for me. Can someone help? # input has size …

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## [Building some Data analysis Tutorials](https://discourse.julialang.org/t/building-some-data-analysis-tutorials/40455)

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**Author:** [@dlakelan](https://discourse.julialang.org/u/dlakelan)\
**Replies:** 35\
**Last updated:** [July 24, 2020, 11:46pm UTC](https://discourse.julialang.org/t/building-some-data-analysis-tutorials/40455 "2020-07-24T23:46:44Z")

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For several years I’ve wanted to jump into Julia. I tried last summer but wound up with no time because my wife was teaching a course and I had the kids full time. Now I have got a couple projects where I’m using Julia a…

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## [Correct use of the sparsity pattern in NLsolve.jl for Diagonal Jacobians](https://discourse.julialang.org/t/correct-use-of-the-sparsity-pattern-in-nlsolve-jl-for-diagonal-jacobians/43469)

<div class="topic-metadata">

**Author:** [@mleprovost](https://discourse.julialang.org/u/mleprovost)\
**Replies:** 6\
**Last updated:** [July 24, 2020, 11:34pm UTC](https://discourse.julialang.org/t/correct-use-of-the-sparsity-pattern-in-nlsolve-jl-for-diagonal-jacobians/43469 "2020-07-24T23:34:01Z")

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Hello, I would like to solve \\sim 400 nonlinear equations using NLsolve.jl for which the Jacobian matrix is diagonal, i.e. the components are independent of each other. I would like to use the sparsity pattern to sp…

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## [Polynomials.fit causing LinearAlgebra.LAPACKException error on 1 computer](https://discourse.julialang.org/t/polynomials-fit-causing-linearalgebra-lapackexception-error-on-1-computer/43594)

<div class="topic-metadata">

**Author:** [@Zhong\_Pan](https://discourse.julialang.org/u/Zhong_Pan)\
**Replies:** 1\
**Last updated:** [July 24, 2020, 10:58pm UTC](https://discourse.julialang.org/t/polynomials-fit-causing-linearalgebra-lapackexception-error-on-1-computer/43594 "2020-07-24T22:58:56Z")

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A very strange problem I met that I can reproduce every time with the original code, but I am not able to create a minimal example to reproduce it. Hence I am posting here to see if anybody has seen something similar ins…

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## [Calculate joint probability from Turing model](https://discourse.julialang.org/t/calculate-joint-probability-from-turing-model/43545)

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**Author:** [@treichelt](https://discourse.julialang.org/u/treichelt)\
**Replies:** 3\
**Last updated:** [July 24, 2020, 2:35pm UTC](https://discourse.julialang.org/t/calculate-joint-probability-from-turing-model/43545 "2020-07-24T14:35:30Z")

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Given a model defined in Turing I would like to calculate the joint probability function over all the variables. Say I have the model @model function model(y) mu ~ Normal(0, 1) y ~ Normal(mu, 1) end y\_obs = 1 m…

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