# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=446

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**Page:** 447

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## [Conditional NLconstraint, Couenne](https://discourse.julialang.org/t/conditional-nlconstraint-couenne/26801)

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**Author:** [@Raminel](https://discourse.julialang.org/u/Raminel)\
**Replies:** 4\
**Last updated:** [May 11, 2020, 4:50pm UTC](https://discourse.julialang.org/t/conditional-nlconstraint-couenne/26801 "2020-05-11T16:50:26Z")

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Hi all, I am trying to solve a MINLP problem with Couenne. I have difficulty implementing an NLconstraint of this form: if x\[i,j\] == 0, y\[i,j\] == 0 else y\[i,j\] = 1/x\[i,j\], I have checked the Syntax notes and I still can…

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## [PackageCompiler Executable - Plots not showing up](https://discourse.julialang.org/t/packagecompiler-executable-plots-not-showing-up/32630)

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**Author:** [@mtwhite4](https://discourse.julialang.org/u/mtwhite4)\
**Replies:** 4\
**Last updated:** [December 25, 2019, 6:11am UTC](https://discourse.julialang.org/t/packagecompiler-executable-plots-not-showing-up/32630 "2019-12-25T06:11:46Z")

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Hi all, I just figured out how to compile my code into an executable using PackageCompiler. This has worked great. However, upon running the code, none of the plot windows show up. For my project it is necessary that th…

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## [RDataset: Error while running examples](https://discourse.julialang.org/t/rdataset-error-while-running-examples/39255)

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**Author:** [@v-i-s-h](https://discourse.julialang.org/u/v-i-s-h)\
**Replies:** 2\
**Last updated:** [May 11, 2020, 11:59am UTC](https://discourse.julialang.org/t/rdataset-error-while-running-examples/39255 "2020-05-11T11:59:01Z")

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Hi, I am trying to use RDatasets. In the github README, the following code is given as an example using RDatasets iris = dataset("datasets", "iris") neuro = dataset("boot", "neuro") But I’m getting the following error…

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## [PDAL Plugin](https://discourse.julialang.org/t/pdal-plugin/37999)

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**Author:** [@Julian\_Fell](https://discourse.julialang.org/u/Julian_Fell)\
**Replies:** 18\
**Last updated:** [May 11, 2020, 7:30am UTC](https://discourse.julialang.org/t/pdal-plugin/37999 "2020-05-11T07:30:09Z")

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Hi everyone. I’ve been working on an experimental plugin for using Julia as an embedded stage in PDAL. There is a similar feature for using Python already. I’d like to get a feel for how much people are using Julia for …

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## ["gradcheck" in Flux?](https://discourse.julialang.org/t/gradcheck-in-flux/39158)

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**Author:** [@jaynick](https://discourse.julialang.org/u/jaynick)\
**Replies:** 2\
**Last updated:** [May 11, 2020, 5:53am UTC](https://discourse.julialang.org/t/gradcheck-in-flux/39158 "2020-05-11T05:53:19Z")

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Is there a function to check the Zygote gradient against a finite-difference? I think I had seen something in discussions here but cannot find it, also not in the docs

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## [Flux Activations() computes the forward pass again](https://discourse.julialang.org/t/flux-activations-computes-the-forward-pass-again/38904)

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**Author:** [@jaynick](https://discourse.julialang.org/u/jaynick)\
**Replies:** 2\
**Last updated:** [May 11, 2020, 5:50am UTC](https://discourse.julialang.org/t/flux-activations-computes-the-forward-pass-again/38904 "2020-05-11T05:50:43Z")

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It looks like the activations() function (in basic.jl) computes the forward pass to obtain the activations, which would mean that it is computed twice. I guess a fix for this would be to implement a custom alternative …

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## [How to make dynamic plots with slider bars](https://discourse.julialang.org/t/how-to-make-dynamic-plots-with-slider-bars/30698)

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**Author:** [@HenriDeh](https://discourse.julialang.org/u/HenriDeh)\
**Replies:** 7\
**Last updated:** [May 10, 2020, 7:09pm UTC](https://discourse.julialang.org/t/how-to-make-dynamic-plots-with-slider-bars/30698 "2020-05-10T19:09:46Z")

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I have a routine that given some arguments outputs a plot. I would like to create an interface where I can change each argument using a slider bar and the plot would update in real-time. Is there a package that allows su…

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## [Five argument mul! in FFTW](https://discourse.julialang.org/t/five-argument-mul-in-fftw/35443)

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**Author:** [@ranocha](https://discourse.julialang.org/u/ranocha)\
**Replies:** 3\
**Last updated:** [May 10, 2020, 10:01am UTC](https://discourse.julialang.org/t/five-argument-mul-in-fftw/35443 "2020-05-10T10:01:58Z")

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I couldn’t find a 5 argument method of mul! in FFTW.jl for FFTW.rFFTWPlan and its siblings. Would it be reasonable to add such methods? In particular, I would like to be able to do something like julia\> using LinearAlge…

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## [Get POST parameters using a HTTP server](https://discourse.julialang.org/t/get-post-parameters-using-a-http-server/39113)

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**Author:** [@dmolina](https://discourse.julialang.org/u/dmolina)\
**Replies:** 5\
**Last updated:** [May 9, 2020, 1:52pm UTC](https://discourse.julialang.org/t/get-post-parameters-using-a-http-server/39113 "2020-05-09T13:52:14Z")

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Dear all, I want to do a small server using Julia. This service implies to receive POST parameters and returns a file. Because I want to include it inside my package, I have chosen HTTP.jl (instead of Genie) to reduce t…

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## [A implementation of ResNet-18 uses lot of GPU memory](https://discourse.julialang.org/t/a-implementation-of-resnet-18-uses-lot-of-gpu-memory/36389)

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**Author:** [@OTapio](https://discourse.julialang.org/u/OTapio)\
**Replies:** 10\
**Last updated:** [May 9, 2020, 5:50am UTC](https://discourse.julialang.org/t/a-implementation-of-resnet-18-uses-lot-of-gpu-memory/36389 "2020-05-09T05:50:22Z")

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I have been trying to create ResNet-18 on Julia. I have managed to create a functional one but it is slow and uses lot of GPU memory. This is puzzling since similar architecture on Tensorflow runs 5-10 times faster and u…

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## [Constraints in a loop in the PowerModels](https://discourse.julialang.org/t/constraints-in-a-loop-in-the-powermodels/38573)

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**Author:** [@Rasoul](https://discourse.julialang.org/u/Rasoul)\
**Replies:** 7\
**Last updated:** [May 9, 2020, 12:16am UTC](https://discourse.julialang.org/t/constraints-in-a-loop-in-the-powermodels/38573 "2020-05-09T00:16:33Z")

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I want to enforce linear envelopes on the cosine function in PowerModelsAnnex. I implement the following code for doing that. for (bp, buspair) in ref\[:buspairs\] for k=1:length(linear\_envelopes1) @constraint(model, cs…

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## [Questions on parallel programming terminology](https://discourse.julialang.org/t/questions-on-parallel-programming-terminology/38996)

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**Author:** [@juliohm](https://discourse.julialang.org/u/juliohm)\
**Replies:** 7\
**Last updated:** [May 8, 2020, 10:20pm UTC](https://discourse.julialang.org/t/questions-on-parallel-programming-terminology/38996 "2020-05-08T22:20:26Z")

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I am using this week to learn the parallel programming features of the language in more depth. I confess that I am a bit confused with the terminology used throughout the documentation, and would like to ask a few questi…

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## [Problem with DifferentialEquations & StaticArrays](https://discourse.julialang.org/t/problem-with-differentialequations-staticarrays/39129)

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**Author:** [@mleprovost](https://discourse.julialang.org/u/mleprovost)\
**Replies:** 4\
**Last updated:** [May 8, 2020, 8:18pm UTC](https://discourse.julialang.org/t/problem-with-differentialequations-staticarrays/39129 "2020-05-08T20:18:24Z")

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Hello, I would like to solve the Lorenz-96 problem with static arrays. The state size is 40. I have followed the tutorial Optimizing DiffEq Code but I have the following error message: using StaticArrays using Differe…

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## [Does @asyc or Threads.@spawn affect performance](https://discourse.julialang.org/t/does-asyc-or-threads-spawn-affect-performance/39118)

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**Author:** [@samuel\_okon](https://discourse.julialang.org/u/samuel_okon)\
**Replies:** 2\
**Last updated:** [May 8, 2020, 8:00pm UTC](https://discourse.julialang.org/t/does-asyc-or-threads-spawn-affect-performance/39118 "2020-05-08T20:00:00Z")

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To my understanding @async creates a closure which may box a variable. And the docs say boxing affects performance. Or is there something am getting wrong. ? (Am aware of the interpolation operator in julia \>= 1.4).

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## [JuMP dual model formulation and impact on performance](https://discourse.julialang.org/t/jump-dual-model-formulation-and-impact-on-performance/39124)

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**Author:** [@martincornejo](https://discourse.julialang.org/u/martincornejo)\
**Replies:** 1\
**Last updated:** [May 8, 2020, 7:38pm UTC](https://discourse.julialang.org/t/jump-dual-model-formulation-and-impact-on-performance/39124 "2020-05-08T19:38:33Z")

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For context: I have a SDP problem that is formulated in the dual form (I don’t think its possible to formulate it in the primal form), for the solver to be able to optimize it I use Dualization.jl and apply it to the s…

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## [Image Processing using Julia on the web](https://discourse.julialang.org/t/image-processing-using-julia-on-the-web/20653)

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**Author:** [@akane](https://discourse.julialang.org/u/akane)\
**Replies:** 3\
**Last updated:** [May 8, 2020, 5:24pm UTC](https://discourse.julialang.org/t/image-processing-using-julia-on-the-web/20653 "2020-05-08T17:24:16Z")

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Hi everyone, I am trying to create a website that takes in an image from the user using a HTML form, processes it using Julia (I am binarizing the image, although that is not relevant) and then display the processed ima…

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## [Error encountered for Geom.density2d with logarithmic scale in Gadfly](https://discourse.julialang.org/t/error-encountered-for-geom-density2d-with-logarithmic-scale-in-gadfly/38460)

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**Author:** [@Humphrey\_Lee](https://discourse.julialang.org/u/Humphrey_Lee)\
**Replies:** 7\
**Last updated:** [May 8, 2020, 5:06pm UTC](https://discourse.julialang.org/t/error-encountered-for-geom-density2d-with-logarithmic-scale-in-gadfly/38460 "2020-05-08T17:06:46Z")

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Gadfly displayed error when trying to do Geom.density2d with logarithmic axis/scale. Code below. The first two plots are OK, but not the third plot. using Gadfly x = \[0.025, 0.028, 0.035, 0.036, 0.037, 0.039, 0.039, 0.…

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## [Which async web server should I use?](https://discourse.julialang.org/t/which-async-web-server-should-i-use/38755)

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**Author:** [@Laszlo\_Nagy](https://discourse.julialang.org/u/Laszlo_Nagy)\
**Replies:** 25\
**Last updated:** [May 8, 2020, 2:54pm UTC](https://discourse.julialang.org/t/which-async-web-server-should-i-use/38755 "2020-05-08T14:54:10Z")

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Hello there! I’m a Python programmer with 20+ years of programming background. I just recently read about Julia and read about 100 pages from the official documentation at once. I’m facinated by Julia’s type system, I r…

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## [Audio issues on DataFrames tutorials?](https://discourse.julialang.org/t/audio-issues-on-dataframes-tutorials/39081)

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**Author:** [@nickeubank](https://discourse.julialang.org/u/nickeubank)\
**Replies:** 1\
**Last updated:** [May 8, 2020, 1:06pm UTC](https://discourse.julialang.org/t/audio-issues-on-dataframes-tutorials/39081 "2020-05-08T13:06:50Z")

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I’m delighted to see that JuliaLang is posting some DataFrames materials, and will have a Q&A later today! However, both this new video and the last set of DataFrames tutorials have some major audio issues. Any chance t…

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## [JuAFEM difference between apply! and apply\_zero!](https://discourse.julialang.org/t/juafem-difference-between-apply-and-apply-zero/39072)

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**Author:** [@FrootLoops](https://discourse.julialang.org/u/FrootLoops)\
**Replies:** 1\
**Last updated:** [May 8, 2020, 12:01pm UTC](https://discourse.julialang.org/t/juafem-difference-between-apply-and-apply-zero/39072 "2020-05-08T12:01:07Z")

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In some examples for JuAFEM I often see people using either “apply!()” or “apply\_zero!()” to apply the boundary conditions. Can someone explain me the difference: apply!(K, f, dbc) apply\_zero!(K, f, dbc…

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## [Struggling to figure out how I should use shared arrays on a slurm cluster using remote workers](https://discourse.julialang.org/t/struggling-to-figure-out-how-i-should-use-shared-arrays-on-a-slurm-cluster-using-remote-workers/38970)

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**Author:** [@HarrisonWilde](https://discourse.julialang.org/u/HarrisonWilde)\
**Replies:** 11\
**Last updated:** [May 8, 2020, 10:22am UTC](https://discourse.julialang.org/t/struggling-to-figure-out-how-i-should-use-shared-arrays-on-a-slurm-cluster-using-remote-workers/38970 "2020-05-08T10:22:11Z")

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Hi so I am using a large distributed map function like so: using ClusterManagers using Distributed addprocs\_slurm(parse(Int, ENV\["SLURM\_NTASKS"\])) ... SETUP EXPERIMENT results = SharedArray{Float64, 2}((total\_steps, 1…

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## [Showing shaded areas in StatPlots](https://discourse.julialang.org/t/showing-shaded-areas-in-statplots/24803)

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**Author:** [@nik.ltin](https://discourse.julialang.org/u/nik.ltin)\
**Replies:** 6\
**Last updated:** [May 8, 2020, 7:40am UTC](https://discourse.julialang.org/t/showing-shaded-areas-in-statplots/24803 "2020-05-08T07:40:16Z")

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Hi everyone. I have a time-series dataset which I’ve plotted in Julia using StatPlots.jl, and now would like to impose these grey bars on the plot to emphasize certain periods of time (such as wars/recessions etc.), I’ve…

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## [Help with first non-trivial Turing example](https://discourse.julialang.org/t/help-with-first-non-trivial-turing-example/38964)

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**Author:** [@bdeonovic](https://discourse.julialang.org/u/bdeonovic)\
**Replies:** 17\
**Last updated:** [May 7, 2020, 8:29pm UTC](https://discourse.julialang.org/t/help-with-first-non-trivial-turing-example/38964 "2020-05-07T20:29:10Z")

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I’d like some help with writing my first example in Turing.jl. I’m not even sure if this model is possible to be expressed in the Turing modeling framework. Below is the code I have so far and the current error: # Impor…

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## [Solver Cplex](https://discourse.julialang.org/t/solver-cplex/38915)

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**Author:** [@lausilvag](https://discourse.julialang.org/u/lausilvag)\
**Replies:** 2\
**Last updated:** [May 7, 2020, 4:12pm UTC](https://discourse.julialang.org/t/solver-cplex/38915 "2020-05-07T16:12:29Z")

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Hi!! Our binary programming problem has an objective function B. \* x, where B is an mxn matrix and x is an mxn variable matrix. Some of the B values will not exist in the problem to be solved. Question: How can I assi…

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## [Using a machine file on a cluster but also propagating environment to the remote workers](https://discourse.julialang.org/t/using-a-machine-file-on-a-cluster-but-also-propagating-environment-to-the-remote-workers/38948)

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**Author:** [@HarrisonWilde](https://discourse.julialang.org/u/HarrisonWilde)\
**Replies:** 15\
**Last updated:** [May 7, 2020, 3:49pm UTC](https://discourse.julialang.org/t/using-a-machine-file-on-a-cluster-but-also-propagating-environment-to-the-remote-workers/38948 "2020-05-07T15:49:36Z")

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Hi, I am trying to run some distributed code on a slurm cluster using an sbatch file as below: #!/bin/bash #SBATCH --nodes=1 #SBATCH --tasks-per-node=28 #SBATCH --mem-per-cpu=4571 #SBATCH --time=24:00:00 #SBATCH -o slur…

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## [Inexact error when plotting, possibly due to small value changes?](https://discourse.julialang.org/t/inexact-error-when-plotting-possibly-due-to-small-value-changes/38953)

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**Author:** [@HarrisonWilde](https://discourse.julialang.org/u/HarrisonWilde)\
**Replies:** 0\
**Last updated:** [May 7, 2020, 1:36pm UTC](https://discourse.julialang.org/t/inexact-error-when-plotting-possibly-due-to-small-value-changes/38953 "2020-05-07T13:36:02Z")

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Please see the following MWE below for an issue I am currently facing, I have raised an issue on the Plots.jl repo as well but thought I would ask the community in case people have seen similar bugs, I noted some similar…

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## [Deleting variables in quadratic constraints in JuMP](https://discourse.julialang.org/t/deleting-variables-in-quadratic-constraints-in-jump/38929)

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**Author:** [@pulsipher](https://discourse.julialang.org/u/pulsipher)\
**Replies:** 1\
**Last updated:** [May 7, 2020, 10:43am UTC](https://discourse.julialang.org/t/deleting-variables-in-quadratic-constraints-in-jump/38929 "2020-05-07T10:43:36Z")

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It appears that when a variable is deleted in JuMP and it is part of a quadratic term, the entire term is dropped: julia\> using JuMP; m = Model(); @variable(m, x\[1:2\]); julia\> @constraint(m, c, 2 \* x\[1\] \* x\[2\] == 0) c …

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## [UndefRefError: access to undefined reference, when I use NLsolve.jl](https://discourse.julialang.org/t/undefreferror-access-to-undefined-reference-when-i-use-nlsolve-jl/38795)

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**Author:** [@PearsonCHEN](https://discourse.julialang.org/u/PearsonCHEN)\
**Replies:** 10\
**Last updated:** [May 7, 2020, 6:05am UTC](https://discourse.julialang.org/t/undefreferror-access-to-undefined-reference-when-i-use-nlsolve-jl/38795 "2020-05-07T06:05:27Z")

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I am new to Julia and the Julia community. I’d appreciate it if someone can help me with this error. I have also opened an issue in the package NLsolve.jl. I tried to use variables and parameters with type Float64 and a…

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## [Propagation of available/assigned worker-IDs in hierarchical computations?](https://discourse.julialang.org/t/propagation-of-available-assigned-worker-ids-in-hierarchical-computations/38670)

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**Author:** [@oschulz](https://discourse.julialang.org/u/oschulz)\
**Replies:** 21\
**Last updated:** [May 7, 2020, 4:59am UTC](https://discourse.julialang.org/t/propagation-of-available-assigned-worker-ids-in-hierarchical-computations/38670 "2020-05-07T04:59:35Z")

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I’ve been thinking about ways to propagate information about available workers (and possibly other resources) in scenarios with nested computations. Say we have 10000 workers available and want to run a high-level distri…

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## [Slower @threads than serial for array computations](https://discourse.julialang.org/t/slower-threads-than-serial-for-array-computations/23522)

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**Author:** [@dataDiver](https://discourse.julialang.org/u/dataDiver)\
**Replies:** 26\
**Last updated:** [May 7, 2020, 1:29am UTC](https://discourse.julialang.org/t/slower-threads-than-serial-for-array-computations/23522 "2020-05-07T01:29:17Z")

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I am doing computations on an array using @threads in the Base.Threads package. I am getting VERY slow performance for the threaded version and when the matrix gets very large the threaded version is killed. Here is an e…

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