# Latest

**URL:** https://discourse.julialang.org/latest.md?page=1930

[Latest](https://discourse.julialang.org/latest.md) · [Categories](https://discourse.julialang.org/categories.md) · [Tags](https://discourse.julialang.org/tags.md)

**Page:** 1931

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## [Avoid temporary array creation for the argument of \`reduce\`](https://discourse.julialang.org/t/avoid-temporary-array-creation-for-the-argument-of-reduce/4464)

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**Author:** [@fjarri](https://discourse.julialang.org/u/fjarri)\
**Replies:** 8\
**Last updated:** [August 31, 2019, 10:03am UTC](https://discourse.julialang.org/t/avoid-temporary-array-creation-for-the-argument-of-reduce/4464 "2019-08-31T10:03:23Z")

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It is common to reduce (e.g. sum) the result of an array expression without needing the whole resulting array itself. In this case Julia will still create a temporary array to pass to the function, even if you managed to…

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## [Cannot use parametric type within function body](https://discourse.julialang.org/t/cannot-use-parametric-type-within-function-body/28224)

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**Author:** [@vsart](https://discourse.julialang.org/u/vsart)\
**Replies:** 12\
**Last updated:** [August 31, 2019, 1:50am UTC](https://discourse.julialang.org/t/cannot-use-parametric-type-within-function-body/28224 "2019-08-31T01:50:24Z")

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Hello, guys! I’m very confused about parametric typing. I’ve reduced my problem to a minimal working example: using LinearAlgebra function alt(x::Vector{Symmetric{T}}) where {T \<: Real} return T end alt(Vector{S…

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## [Clustering/Voronoi cell identification](https://discourse.julialang.org/t/clustering-voronoi-cell-identification/28211)

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**Author:** [@gideonsimpson](https://discourse.julialang.org/u/gideonsimpson)\
**Replies:** 1\
**Last updated:** [August 31, 2019, 12:33am UTC](https://discourse.julialang.org/t/clustering-voronoi-cell-identification/28211 "2019-08-31T00:33:57Z")

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I’m thinking of the following problem. I have a set of points in the plane which have either been pre-selected or were obtained by a clustering method (i.e., K-means). I thus have an associated Voronoi partition of the…

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## [DifferentialEquations and DAEProblem... strange error messages](https://discourse.julialang.org/t/differentialequations-and-daeproblem-strange-error-messages/28210)

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**Author:** [@BLI](https://discourse.julialang.org/u/BLI)\
**Replies:** 5\
**Last updated:** [August 31, 2019, 12:02am UTC](https://discourse.julialang.org/t/differentialequations-and-daeproblem-strange-error-messages/28210 "2019-08-31T00:02:27Z")

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OK – I used the DAE solver a year ago without problems. Now, it doesn’t work for me: using Plots; pyplot(); using DifferentialEquations; using Sundials; If I run the example at DAE documentation, there are no problems …

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## [GLM linear regression. How to extract the coefficients?](https://discourse.julialang.org/t/glm-linear-regression-how-to-extract-the-coefficients/28219)

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**Author:** [@doomphoenix-qxz](https://discourse.julialang.org/u/doomphoenix-qxz)\
**Replies:** 3\
**Last updated:** [August 30, 2019, 9:56pm UTC](https://discourse.julialang.org/t/glm-linear-regression-how-to-extract-the-coefficients/28219 "2019-08-30T21:56:45Z")

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I fit a simple linear regression using GLM. How do I extract the calculated slope and intercept? I looked through the documentation but didn’t see an example of it. If such an example exists, feel free to point there.

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## [When to migrate to 1.2-style test-specific dependencies](https://discourse.julialang.org/t/when-to-migrate-to-1-2-style-test-specific-dependencies/28205)

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**Author:** [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Replies:** 3\
**Last updated:** [August 30, 2019, 7:11pm UTC](https://discourse.julialang.org/t/when-to-migrate-to-1-2-style-test-specific-dependencies/28205 "2019-08-30T19:11:19Z")

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Are the semantics for test-specific dependencies with test/Project.toml still being finalized? Who should migrate at this point? (eg adventurous users who don’t mind if things break or change, or more conservative ones …

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## [Trying and trying with Revise](https://discourse.julialang.org/t/trying-and-trying-with-revise/27915)

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**Author:** [@Brad\_Hines](https://discourse.julialang.org/u/Brad_Hines)\
**Replies:** 44\
**Last updated:** [August 30, 2019, 5:11pm UTC](https://discourse.julialang.org/t/trying-and-trying-with-revise/27915 "2019-08-30T17:11:07Z")

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Hi all, I’m really trying here… I’ve been fighting with Revise most of the day. I’ve read the docs and the forums several times over and am just missing something. Maybe somebody can tell me what I’m doing wrong. Her…

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## [UndefRefError: access to undefined reference, how to fix the following error?](https://discourse.julialang.org/t/undefreferror-access-to-undefined-reference-how-to-fix-the-following-error/28213)

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**Author:** [@bsnyh](https://discourse.julialang.org/u/bsnyh)\
**Replies:** 3\
**Last updated:** [August 30, 2019, 3:25pm UTC](https://discourse.julialang.org/t/undefreferror-access-to-undefined-reference-how-to-fix-the-following-error/28213 "2019-08-30T15:25:33Z")

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I’m running some Julia code and the error message I get is as the following: UndefRefError: access to undefined reference in top-level scope at base/None in simulate! at do\_sim.jl:10 #simulate!#46 at so\_sim.jl:…

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## [Parallel computing using Parallel Ensemble Simulations (DiffEq) does not seem to work](https://discourse.julialang.org/t/parallel-computing-using-parallel-ensemble-simulations-diffeq-does-not-seem-to-work/28115)

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**Author:** [@Torkel](https://discourse.julialang.org/u/Torkel)\
**Replies:** 13\
**Last updated:** [August 30, 2019, 2:18pm UTC](https://discourse.julialang.org/t/parallel-computing-using-parallel-ensemble-simulations-diffeq-does-not-seem-to-work/28115 "2019-08-30T14:18:23Z")

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So i regularly run SDE simulations. To get a better idea of the systems behavior I would run several identical, and plot the various results. I figured this probably would be a good task for the Parallel Ensemble Simulat…

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## [Create d-dimensional grid with n points in each direction (where d can be higher than 3)](https://discourse.julialang.org/t/create-d-dimensional-grid-with-n-points-in-each-direction-where-d-can-be-higher-than-3/28197)

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**Author:** [@benzwick](https://discourse.julialang.org/u/benzwick)\
**Replies:** 9\
**Last updated:** [August 30, 2019, 12:44pm UTC](https://discourse.julialang.org/t/create-d-dimensional-grid-with-n-points-in-each-direction-where-d-can-be-higher-than-3/28197 "2019-08-30T12:44:59Z")

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I am trying to write a function that creates a d-dimensional grid (d can be higher than 3) with n points in each direction function grid(d, n) return coordinates of n^d points end So far I have the following: juli…

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## [Generic way to create repeating tiled views?](https://discourse.julialang.org/t/generic-way-to-create-repeating-tiled-views/28207)

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**Author:** [@wsphillips](https://discourse.julialang.org/u/wsphillips)\
**Replies:** 1\
**Last updated:** [August 30, 2019, 12:23pm UTC](https://discourse.julialang.org/t/generic-way-to-create-repeating-tiled-views/28207 "2019-08-30T12:23:35Z")

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LinearAlgebra implements Symmetric, which returns a mirrored view of the upper/lower triangle of a matrix. If I wanted to do something more simple and generic, is it possible using view() or manipulation of ::SubArray ? …

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## [Piping in Julia](https://discourse.julialang.org/t/piping-in-julia/14735)

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**Author:** [@tnederlof](https://discourse.julialang.org/u/tnederlof)\
**Replies:** 13\
**Last updated:** [August 30, 2019, 10:58am UTC](https://discourse.julialang.org/t/piping-in-julia/14735 "2019-08-30T10:58:03Z")

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Coming from a world where I use dplyr a lot in R for my SQL type operation needs, I find myself very confused on how to use pipes in Julia. In R I would try very hard to have the data be the first argument in a function …

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## [What's the official way to keep track of package test dependencies that are not needed by a Package?](https://discourse.julialang.org/t/whats-the-official-way-to-keep-track-of-package-test-dependencies-that-are-not-needed-by-a-package/28202)

<div class="topic-metadata">

**Author:** [@xiaodai](https://discourse.julialang.org/u/xiaodai)\
**Replies:** 2\
**Last updated:** [August 30, 2019, 10:43am UTC](https://discourse.julialang.org/t/whats-the-official-way-to-keep-track-of-package-test-dependencies-that-are-not-needed-by-a-package/28202 "2019-08-30T10:43:48Z")

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Say I have am developing PkgA and I needed PkgB and PkgC for PkgA to work. I know can just \]add these. What about PkgD and PkgE that I only need in testing my PkgA? What’s the official and recommended way to keep track o…

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## [Is there difference between Meta.eval and eval?](https://discourse.julialang.org/t/is-there-difference-between-meta-eval-and-eval/27392)

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**Author:** [@Dito](https://discourse.julialang.org/u/Dito)\
**Replies:** 3\
**Last updated:** [August 30, 2019, 10:24am UTC](https://discourse.julialang.org/t/is-there-difference-between-meta-eval-and-eval/27392 "2019-08-30T10:24:22Z")

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ex=quote x=1 y=2 x+y end ex.args ex.head Meta.eval(ex.args\[6\]) eval(ex.args\[6\]) julia\> ex.head :block julia\> Meta.eval(ex.args\[6\]) ERROR: UndefVarError: x not defined Stacktrace: \[1\] top-level scope at non…

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## [BFloat16 on ARM for neural networks](https://discourse.julialang.org/t/bfloat16-on-arm-for-neural-networks/28200)

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**Author:** [@johnh](https://discourse.julialang.org/u/johnh)\
**Replies:** 1\
**Last updated:** [August 30, 2019, 9:56am UTC](https://discourse.julialang.org/t/bfloat16-on-arm-for-neural-networks/28200 "2019-08-30T09:56:19Z")

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How does this play with Julia? Someone will now tell me thereis a BFlaot16 type in core already!

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## [Creating an array of tuples (why doesn't filter work on a zip?)](https://discourse.julialang.org/t/creating-an-array-of-tuples-why-doesnt-filter-work-on-a-zip/28173)

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**Author:** [@purplishrock](https://discourse.julialang.org/u/purplishrock)\
**Replies:** 5\
**Last updated:** [August 30, 2019, 6:49am UTC](https://discourse.julialang.org/t/creating-an-array-of-tuples-why-doesnt-filter-work-on-a-zip/28173 "2019-08-30T06:49:59Z")

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I’m pretty sure the answer is that a zip type, is not an Array, BitArray or AbstractArray and that’s what my problem is. I also read the definition for zip and it “runs multiple iterators”, also resultant type is not an…

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## [Syntax highlighting and plotting problems with Jupyter Notebook](https://discourse.julialang.org/t/syntax-highlighting-and-plotting-problems-with-jupyter-notebook/28198)

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**Author:** [@Volker](https://discourse.julialang.org/u/Volker)\
**Replies:** 0\
**Last updated:** [August 30, 2019, 6:37am UTC](https://discourse.julialang.org/t/syntax-highlighting-and-plotting-problems-with-jupyter-notebook/28198 "2019-08-30T06:37:50Z")

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Hi, sometimes Jupyter Notebook loses the syntax highlighting for my Julia Notebooks. Addtionaly then I´m also unable to plot. I´m working on Julia 1.2.0, IJulia v1.20.0, WebIO v0.8.11 and Windows 10. I followed several …

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## [Load Packages inside a function](https://discourse.julialang.org/t/load-packages-inside-a-function/28196)

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**Author:** [@Ajaychat3](https://discourse.julialang.org/u/Ajaychat3)\
**Replies:** 0\
**Last updated:** [August 30, 2019, 6:10am UTC](https://discourse.julialang.org/t/load-packages-inside-a-function/28196 "2019-08-30T06:10:28Z")

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I tried to load a package inside a function and it did not work. Then I came across this post. https://stackoverflow.com/questions/47141374/load-a-package-within-a-function The post says that this can be done ’ @eval u…

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## [Power Balance reference in PowerModels.jl](https://discourse.julialang.org/t/power-balance-reference-in-powermodels-jl/27865)

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**Author:** [@andrewrosemberg](https://discourse.julialang.org/u/andrewrosemberg)\
**Replies:** 5\
**Last updated:** [August 30, 2019, 4:19am UTC](https://discourse.julialang.org/t/power-balance-reference-in-powermodels-jl/27865 "2019-08-30T04:19:20Z")

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I’m running an OPF problem with SDPWRMForm and SOCWRConicForm formulations (AbstractWForms) and I’m trying to retrieve the duals from the power balance constraints (lam\_kcl\_r in the output). However, it seams that the re…

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## [Does it possible to use XLSX.openxlsx() in parallel threads?](https://discourse.julialang.org/t/does-it-possible-to-use-xlsx-openxlsx-in-parallel-threads/28191)

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**Author:** [@BMval](https://discourse.julialang.org/u/BMval)\
**Replies:** 0\
**Last updated:** [August 30, 2019, 12:22am UTC](https://discourse.julialang.org/t/does-it-possible-to-use-xlsx-openxlsx-in-parallel-threads/28191 "2019-08-30T00:22:57Z")

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Does it possible to use XLSX.openxlsx in parallel threads? Does somebody do it before?

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## [How to change the same DataFrame thought different threads](https://discourse.julialang.org/t/how-to-change-the-same-dataframe-thought-different-threads/28188)

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**Author:** [@BMval](https://discourse.julialang.org/u/BMval)\
**Replies:** 0\
**Last updated:** [August 29, 2019, 11:25pm UTC](https://discourse.julialang.org/t/how-to-change-the-same-dataframe-thought-different-threads/28188 "2019-08-29T23:25:21Z")

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How to change the same DataFrame thought different threads? I have a simple example, but I use the same practics for large task, there are errors. So Would you suggest, the best practics, how to do it? Here is an exam…

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## [Reading binary file in julia 1.0](https://discourse.julialang.org/t/reading-binary-file-in-julia-1-0/13951)

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**Author:** [@feboccaccio](https://discourse.julialang.org/u/feboccaccio)\
**Replies:** 13\
**Last updated:** [August 29, 2019, 10:38pm UTC](https://discourse.julialang.org/t/reading-binary-file-in-julia-1-0/13951 "2019-08-29T22:38:35Z")

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The following function used to work fine in julia 0.6 for reading a file. I am having a hard time trying to use it in julia 1.0 (I get the message: no method matching read(::IOStream, ::Type{Float32}, ::Int64)) functio…

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## [Error in creating own data type](https://discourse.julialang.org/t/error-in-creating-own-data-type/28178)

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**Author:** [@iamsuddhasattwa](https://discourse.julialang.org/u/iamsuddhasattwa)\
**Replies:** 2\
**Last updated:** [August 29, 2019, 9:11pm UTC](https://discourse.julialang.org/t/error-in-creating-own-data-type/28178 "2019-08-29T21:11:17Z")

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I am trying to create my own pointer structure for a binary tree. I am starting with this simple code type int\_BST key::Int64 left::Nullable{int\_BST} right::Nullable{int\_BST} end but I keep getting the erro…

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## [Package for generating random field](https://discourse.julialang.org/t/package-for-generating-random-field/28180)

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**Author:** [@shipengcheng1230](https://discourse.julialang.org/u/shipengcheng1230)\
**Replies:** 0\
**Last updated:** [August 29, 2019, 8:41pm UTC](https://discourse.julialang.org/t/package-for-generating-random-field/28180 "2019-08-29T20:41:40Z")

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I see one option GaussianRandomFields.jl but seems it’s abandoned for quite a long time. Is there any other alternative for this task and more than just Gaussian, like von Karman or Generalized Whittle–Matérn or so. Tha…

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## [Convert collection (Array, DataFrame, ...) to concrete eltype](https://discourse.julialang.org/t/convert-collection-array-dataframe-to-concrete-eltype/28168)

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**Author:** [@aplavin](https://discourse.julialang.org/u/aplavin)\
**Replies:** 5\
**Last updated:** [August 29, 2019, 8:30pm UTC](https://discourse.julialang.org/t/convert-collection-array-dataframe-to-concrete-eltype/28168 "2019-08-29T20:30:33Z")

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Suppose I have a collection, e.g. DataFrame, with Any eltype but all elements having same concrete type: df = DataFrame(a=Any\[1, 2, 3\]) For further processing I need to make it type-stable, but don’t see how to do that…

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## [Rearranging panes causes Juno to hang](https://discourse.julialang.org/t/rearranging-panes-causes-juno-to-hang/28150)

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**Author:** [@glemieux](https://discourse.julialang.org/u/glemieux)\
**Replies:** 2\
**Last updated:** [August 29, 2019, 7:49pm UTC](https://discourse.julialang.org/t/rearranging-panes-causes-juno-to-hang/28150 "2019-08-29T19:49:18Z")

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I recently installed Juno via JuliaPro1.1.1.1 (operating system is Pop!\_OS 19.04). If I try to rearrange any of the panes, the IDE hangs and I have to force quit to shut it down. This also seems to happen if I try and …

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## [Loop Scope works differently for Int and Arrays. Why?](https://discourse.julialang.org/t/loop-scope-works-differently-for-int-and-arrays-why/28172)

<div class="topic-metadata">

**Author:** [@BMval](https://discourse.julialang.org/u/BMval)\
**Replies:** 16\
**Last updated:** [August 29, 2019, 6:55pm UTC](https://discourse.julialang.org/t/loop-scope-works-differently-for-int-and-arrays-why/28172 "2019-08-29T18:55:36Z")

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Loop Scope works differently for Int and Arrays. Why? Here is an example. Array w is changed inside the loop, but variable w isn’t. w=zeros(2) println(w) for i=1:2 w\[i\]=i end println(w) q=0 println(q) for i=1:…

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## [Understanding distributed memory garbage collection](https://discourse.julialang.org/t/understanding-distributed-memory-garbage-collection/8726)

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**Author:** [@Pbellive](https://discourse.julialang.org/u/Pbellive)\
**Replies:** 5\
**Last updated:** [August 29, 2019, 5:35pm UTC](https://discourse.julialang.org/t/understanding-distributed-memory-garbage-collection/8726 "2019-08-29T17:35:45Z")

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Hello, In running some large scale parallel computations a colleague of mine has run into problems with memory leakage. To be more specific, the amount of memory used by the offending program gradually increases over th…

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## [Code isolation side discussion](https://discourse.julialang.org/t/code-isolation-side-discussion/28108)

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**Author:** [@TsurHerman](https://discourse.julialang.org/u/TsurHerman)\
**Replies:** 14\
**Last updated:** [August 29, 2019, 4:19pm UTC](https://discourse.julialang.org/t/code-isolation-side-discussion/28108 "2019-08-29T16:19:03Z")

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It seems to me that: This is a security liability for the language, meaning it can not be used in anything critical. Which is another reason why I think that some form of isolation like I proposed in contextual dispat…

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## [Problem in Power Flow using Julia](https://discourse.julialang.org/t/problem-in-power-flow-using-julia/1491)

<div class="topic-metadata">

**Author:** [@ashefa](https://discourse.julialang.org/u/ashefa)\
**Replies:** 18\
**Last updated:** [August 29, 2019, 4:18pm UTC](https://discourse.julialang.org/t/problem-in-power-flow-using-julia/1491 "2019-08-29T16:18:02Z")

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I started writing “Power Flow” in two software, GAMS and Julialang, simultaneously. In addition to i did “Power Flow” in GAMS, i receive to results of “State Estimation” problem, but in Julia (using JuMP) yet i couldn’t …

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