# Latest

**URL:** https://discourse.julialang.org/latest.md?page=1786

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

**Page:** 1787

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## [Using Cassette through \`eval\`](https://discourse.julialang.org/t/using-cassette-through-eval/36519)

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**Author:** [@ckfinite](https://discourse.julialang.org/u/ckfinite)\
**Replies:** 1\
**Last updated:** [April 1, 2020, 4:26pm UTC](https://discourse.julialang.org/t/using-cassette-through-eval/36519 "2020-04-01T16:26:19Z")

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I’m working on developing a dynamic analysis system that needs to dynamically track function definitions and invocations, including those made in eval statements. I’ve, so far, been using Cassette to track function invoc…

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## [Optim.jl - How to find local maxima of multivariate function](https://discourse.julialang.org/t/optim-jl-how-to-find-local-maxima-of-multivariate-function/36853)

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**Author:** [@mthelm85](https://discourse.julialang.org/u/mthelm85)\
**Replies:** 3\
**Last updated:** [April 1, 2020, 4:21pm UTC](https://discourse.julialang.org/t/optim-jl-how-to-find-local-maxima-of-multivariate-function/36853 "2020-04-01T16:21:56Z")

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Pardon my ignorance (if you’ve seen any recent posts of mine you’ll know I’ve been studying calculus lately) but I’m trying to understand how to find local maxima of a multivariate function with Optim.jl. Given the follo…

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## [Multiplying an array by the individual elements of a vector](https://discourse.julialang.org/t/multiplying-an-array-by-the-individual-elements-of-a-vector/36856)

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**Author:** [@samantp](https://discourse.julialang.org/u/samantp)\
**Replies:** 4\
**Last updated:** [April 1, 2020, 3:19pm UTC](https://discourse.julialang.org/t/multiplying-an-array-by-the-individual-elements-of-a-vector/36856 "2020-04-01T15:19:19Z")

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So, I have an array, seed\_dvh, and a vector, dvh\_coeff, corresponding to some coefficients I’d like to multiply seed\_dvh by. seed\_dvh is of size 1718x2 and dvh\_coeff is of length 1000. I want to create a 1000 element ve…

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## [Allocations when constructing a matrix from columns](https://discourse.julialang.org/t/allocations-when-constructing-a-matrix-from-columns/36795)

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**Author:** [@mht](https://discourse.julialang.org/u/mht)\
**Replies:** 35\
**Last updated:** [April 1, 2020, 2:12pm UTC](https://discourse.julialang.org/t/allocations-when-constructing-a-matrix-from-columns/36795 "2020-04-01T14:12:51Z")

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Hey all! I’m constructing a matrix from another matrix like this: shapematrix(xs) = \[xs\[:,1\].-xs\[:,4\] xs\[:,2\].-xs\[:,4\] xs\[:,3\].-xs\[:,4\]\] This is somewhat in an inner loop of my program, and I would like to reduce th…

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## [Mapslices() warntype?](https://discourse.julialang.org/t/mapslices-warntype/36844)

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**Author:** [@tomtom](https://discourse.julialang.org/u/tomtom)\
**Replies:** 4\
**Last updated:** [April 1, 2020, 1:24pm UTC](https://discourse.julialang.org/t/mapslices-warntype/36844 "2020-04-01T13:24:55Z")

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I’m wondered seeing that mapslices() gives warntype as below: julia\> const mat = randn(3,2) 3×2 Array{Float64,2}: 1.49498 -1.98461 -0.935659 -0.0317199 0.783414 -0.284129 julia\> mapslices(prod, mat, dims = …

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## [Nice images plus the Julia declaration of intent](https://discourse.julialang.org/t/nice-images-plus-the-julia-declaration-of-intent/36797)

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**Author:** [@johnh](https://discourse.julialang.org/u/johnh)\
**Replies:** 5\
**Last updated:** [April 1, 2020, 12:28pm UTC](https://discourse.julialang.org/t/nice-images-plus-the-julia-declaration-of-intent/36797 "2020-04-01T12:28:51Z")

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I am preparing a slide to introduce myself to new work colleagues (\*) Does anyone have some nice images which sum up what Julia does? I am also looking for a link to the Julia declaration of intent. It should be easy t…

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## [Is it a bug for the power function?](https://discourse.julialang.org/t/is-it-a-bug-for-the-power-function/36833)

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**Author:** [@gangchern](https://discourse.julialang.org/u/gangchern)\
**Replies:** 9\
**Last updated:** [April 1, 2020, 12:27pm UTC](https://discourse.julialang.org/t/is-it-a-bug-for-the-power-function/36833 "2020-04-01T12:27:23Z")

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The following code seems not works Complex(-0.5)^(0.2) It throw a error.

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## [Selecting text with keyboard (shift+left/right) in Juno under Win10](https://discourse.julialang.org/t/selecting-text-with-keyboard-shift-left-right-in-juno-under-win10/36838)

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**Author:** [@behinger](https://discourse.julialang.org/u/behinger)\
**Replies:** 5\
**Last updated:** [April 1, 2020, 11:36am UTC](https://discourse.julialang.org/t/selecting-text-with-keyboard-shift-left-right-in-juno-under-win10/36838 "2020-04-01T11:36:40Z")

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I try to select text using “shift+left” or “shift+right” in the REPL. But it does not work (a colleague testet it on linux with juno, there it works). I tried google, but I likely look for the wrong keywords. I also don…

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## [Gtk Signal\_connect and piping](https://discourse.julialang.org/t/gtk-signal-connect-and-piping/36829)

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**Author:** [@Igor\_Fomenko](https://discourse.julialang.org/u/Igor_Fomenko)\
**Replies:** 2\
**Last updated:** [April 1, 2020, 9:48am UTC](https://discourse.julialang.org/t/gtk-signal-connect-and-piping/36829 "2020-04-01T09:48:05Z")

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Hi, I decided to try piping instead of do-block but wo success using Gtk b = GtkButton(“Press me”) win = GtkWindow(b, “Callbacks”) id = signal\_connect(b, “clicked”)|\>w-\>println(w, " was clicked!") showall(win) ER…

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## [Install a specific commit for unregistered package?](https://discourse.julialang.org/t/install-a-specific-commit-for-unregistered-package/8468)

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**Author:** [@amrods](https://discourse.julialang.org/u/amrods)\
**Replies:** 8\
**Last updated:** [April 1, 2020, 9:07am UTC](https://discourse.julialang.org/t/install-a-specific-commit-for-unregistered-package/8468 "2020-04-01T09:07:54Z")

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I’m trying to install a specific commit of a unregistered package. I tried with Pkg.pin but that’s only available with registered packages; and Pkg.clone does not have any method for that. Is it possible to install a spe…

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## [Reel.jl Package with Windows](https://discourse.julialang.org/t/reel-jl-package-with-windows/36827)

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**Author:** [@AmburoseSekar](https://discourse.julialang.org/u/AmburoseSekar)\
**Replies:** 2\
**Last updated:** [April 1, 2020, 7:57am UTC](https://discourse.julialang.org/t/reel-jl-package-with-windows/36827 "2020-04-01T07:57:24Z")

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Hi, I’m newbie to Julia, i have use Reel.jl package for animation. The GitHub Reference code i have used. it’s create images default in text/html format. But unfortunately ffmpeg doesn’t support html to GIF format but …

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## [How to plot a 3D sufface graph from a 3D array of data](https://discourse.julialang.org/t/how-to-plot-a-3d-sufface-graph-from-a-3d-array-of-data/36832)

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**Author:** [@Ujku\_KU](https://discourse.julialang.org/u/Ujku_KU)\
**Replies:** 0\
**Last updated:** [April 1, 2020, 7:51am UTC](https://discourse.julialang.org/t/how-to-plot-a-3d-sufface-graph-from-a-3d-array-of-data/36832 "2020-04-01T07:51:30Z")

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Hi guys, my question is: how to plot a 3D surface graph using data from a 3D array. For example in my case I have a set of distances and a set of features. I use for my experiments different number of features and differ…

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## [Partially empty 2d histogram Plots.jl](https://discourse.julialang.org/t/partially-empty-2d-histogram-plots-jl/36828)

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**Author:** [@isentropic](https://discourse.julialang.org/u/isentropic)\
**Replies:** 2\
**Last updated:** [April 1, 2020, 7:48am UTC](https://discourse.julialang.org/t/partially-empty-2d-histogram-plots-jl/36828 "2020-04-01T07:48:05Z")

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Attempting plotting a small circle in 2d histogram (with custom bins and limits), gives a natural result in pyplot: However, Plots for some reason gives blank pixels (same image):

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## [Update bands of a CSC Matrix](https://discourse.julialang.org/t/update-bands-of-a-csc-matrix/36800)

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**Author:** [@rveltz](https://discourse.julialang.org/u/rveltz)\
**Replies:** 0\
**Last updated:** [March 31, 2020, 3:25pm UTC](https://discourse.julialang.org/t/update-bands-of-a-csc-matrix/36800 "2020-03-31T15:25:26Z")

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Hi, I would like to update inplace a CSC sparse Matrix A which has several bands like A = spdiagm( 0 =\> ones(10), 1=\> ones(10-1)) What I would like to do is to change the values of the band 1 (for example) by modifyin…

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## [\[ANN\] Update to SolveDSGE](https://discourse.julialang.org/t/ann-update-to-solvedsge/35689)

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**Author:** [@RJDennis](https://discourse.julialang.org/u/RJDennis)\
**Replies:** 8\
**Last updated:** [April 1, 2020, 6:47am UTC](https://discourse.julialang.org/t/ann-update-to-solvedsge/35689 "2020-04-01T06:47:01Z")

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Hi All, I’ve recently released an update to SolveDSGE. The update allows the model that is to be solved to be stored separately in a file that gets read and processed prior to solution. In addition, models can be solv…

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## [New book: Hands-on Design Patterns and Best Practices with Julia](https://discourse.julialang.org/t/new-book-hands-on-design-patterns-and-best-practices-with-julia/33712)

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**Author:** [@tk3369](https://discourse.julialang.org/u/tk3369)\
**Replies:** 29\
**Last updated:** [April 1, 2020, 4:22am UTC](https://discourse.julialang.org/t/new-book-hands-on-design-patterns-and-best-practices-with-julia/33712 "2020-04-01T04:22:33Z")

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Hi, everyone! :wave: I’m pleased announce that my first book Hands-on Design Patterns and Best Practices with Julia has been published. I want to thank everyone who helped me on Discourse / Slack before (too many to me…

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## [Publishing an updated package](https://discourse.julialang.org/t/publishing-an-updated-package/35768)

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**Author:** [@hros](https://discourse.julialang.org/u/hros)\
**Replies:** 3\
**Last updated:** [April 1, 2020, 12:22am UTC](https://discourse.julialang.org/t/publishing-an-updated-package/35768 "2020-04-01T00:22:10Z")

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A few months ago, I have published a package (a wrapper of a C library). Recently, the C library was updated and I decided to make use of the arifacts/jll. My old implementation used BinaryProvider and CI scripts: trav…

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## [Zygote: meaning of @adjoint add(a, b) = add(a, b), Δ -\> (Δ, Δ)](https://discourse.julialang.org/t/zygote-meaning-of-adjoint-add-a-b-add-a-b/36707)

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**Author:** [@jaynick](https://discourse.julialang.org/u/jaynick)\
**Replies:** 4\
**Last updated:** [March 31, 2020, 11:18pm UTC](https://discourse.julialang.org/t/zygote-meaning-of-adjoint-add-a-b-add-a-b/36707 "2020-03-31T23:18:52Z")

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The zygote landing page has the example @adjoint add(a, b) = add(a, b), Δ -\> (Δ, Δ) Can someone explain what the Δ -\> (Δ, Δ) means? I would have expected the derivatives to be 1,1.

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## [SparseMatrix is very slow](https://discourse.julialang.org/t/sparsematrix-is-very-slow/36809)

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**Author:** [@Tong\_Zhou](https://discourse.julialang.org/u/Tong_Zhou)\
**Replies:** 9\
**Last updated:** [March 31, 2020, 9:00pm UTC](https://discourse.julialang.org/t/sparsematrix-is-very-slow/36809 "2020-03-31T21:00:16Z")

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Hi I have the following simple code: import SparseArrays function func0(K::Array{Float64,2}, M::Array{Float64,2}, r::Array{Float64,2}, x::Array{Float64,2}, row::Array{Int32,1}, col::Array{Int32,1}, data::Array{Float64,…

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## [Constructing a block tri-diagonal matrix](https://discourse.julialang.org/t/constructing-a-block-tri-diagonal-matrix/36704)

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**Author:** [@e3c6](https://discourse.julialang.org/u/e3c6)\
**Replies:** 7\
**Last updated:** [March 31, 2020, 8:16pm UTC](https://discourse.julialang.org/t/constructing-a-block-tri-diagonal-matrix/36704 "2020-03-31T20:16:01Z")

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I need to construct a matrix of this form: where A1, A2, ..., A\_M are given (rectangular) matrices, and the zeros are blocks of appropriate sizes. How can I do this in Julia, with as less code as possible? Maybe ther…

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## [Number of constraints](https://discourse.julialang.org/t/number-of-constraints/36798)

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**Author:** [@angeloaliano1](https://discourse.julialang.org/u/angeloaliano1)\
**Replies:** 1\
**Last updated:** [March 31, 2020, 7:59pm UTC](https://discourse.julialang.org/t/number-of-constraints/36798 "2020-03-31T19:59:57Z")

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Dear all, The command num\_constraints() can determine the number of equality constraints in a given model? How can I find this?

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## [Guix importer](https://discourse.julialang.org/t/guix-importer/36802)

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**Author:** [@bijang](https://discourse.julialang.org/u/bijang)\
**Replies:** 0\
**Last updated:** [March 31, 2020, 4:42pm UTC](https://discourse.julialang.org/t/guix-importer/36802 "2020-03-31T16:42:38Z")

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Would there be any interest in making a julia importer for the guix package manager which already acceses CRAN pypi Texlive Crate and few others?

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## [Parameter estimation with algebraic output variable and discrete callbacks](https://discourse.julialang.org/t/parameter-estimation-with-algebraic-output-variable-and-discrete-callbacks/34996)

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**Author:** [@rotton](https://discourse.julialang.org/u/rotton)\
**Replies:** 4\
**Last updated:** [March 31, 2020, 3:12pm UTC](https://discourse.julialang.org/t/parameter-estimation-with-algebraic-output-variable-and-discrete-callbacks/34996 "2020-03-31T15:12:25Z")

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Trying to setup a Parameter Estimation in Julia with DifferentialEquations, I started reading the documentation and some topics here on Discourse. But it seems I am actually facing three issues at once, which is why I am…

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## [Extending function with new keyword argument fails](https://discourse.julialang.org/t/extending-function-with-new-keyword-argument-fails/36770)

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**Author:** [@SEA](https://discourse.julialang.org/u/SEA)\
**Replies:** 2\
**Last updated:** [March 31, 2020, 3:04pm UTC](https://discourse.julialang.org/t/extending-function-with-new-keyword-argument-fails/36770 "2020-03-31T15:04:39Z")

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I ran into this problem while trying to extend stdlib’s cholesky with a new keyword argument. This is a minimal example. import LinearAlgebra: cholesky struct T end cholesky(A::AbstractMatrix, ::Val{false} = Val(false);…

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## [I can't use the PackageCompiler](https://discourse.julialang.org/t/i-cant-use-the-packagecompiler/35732)

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**Author:** [@Darione](https://discourse.julialang.org/u/Darione)\
**Replies:** 12\
**Last updated:** [March 31, 2020, 2:12pm UTC](https://discourse.julialang.org/t/i-cant-use-the-packagecompiler/35732 "2020-03-31T14:12:00Z")

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I am retrying to use PackageCompiler, for the second time (the first, I was unable to produce an executable, because it gave me error). I am following - again - the instruction on https://julialang.github.io/PackageCom…

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## [Cannot interpolate function signature into function definition expression](https://discourse.julialang.org/t/cannot-interpolate-function-signature-into-function-definition-expression/36761)

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**Author:** [@benninkrs](https://discourse.julialang.org/u/benninkrs)\
**Replies:** 2\
**Last updated:** [March 31, 2020, 2:09pm UTC](https://discourse.julialang.org/t/cannot-interpolate-function-signature-into-function-definition-expression/36761 "2020-03-31T14:09:18Z")

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This seems to be a parser weakness: julia\> foosig = :( foo(x) ) :(foo(x)) julia\> :( function $foosig 2\*x end ) ERROR: syntax: expected "end" in definition of function "($ foosig)" The error message is miselading: the …

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## [Thomas algorithm for banded matrices](https://discourse.julialang.org/t/thomas-algorithm-for-banded-matrices/23262)

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**Author:** [@rveltz](https://discourse.julialang.org/u/rveltz)\
**Replies:** 13\
**Last updated:** [March 31, 2020, 12:29pm UTC](https://discourse.julialang.org/t/thomas-algorithm-for-banded-matrices/23262 "2020-03-31T12:29:36Z")

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Dear All, I am trying to solve linear systems Ax = rhs where A has a tridiagonal shape. When the type of A is tridiagonal, one can use the thomas algo to solve it. I find it faster than defining A as a Tridiagonal and c…

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## [Using ImageView in combination with Revise on MacOS slows everything to a crawl](https://discourse.julialang.org/t/using-imageview-in-combination-with-revise-on-macos-slows-everything-to-a-crawl/36752)

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**Author:** [@Kunz-David](https://discourse.julialang.org/u/Kunz-David)\
**Replies:** 7\
**Last updated:** [March 31, 2020, 10:35am UTC](https://discourse.julialang.org/t/using-imageview-in-combination-with-revise-on-macos-slows-everything-to-a-crawl/36752 "2020-03-31T10:35:24Z")

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Hello, I am having a weird issue where using ImageView slows down my whole Julia session. It happens when I am using Revise (loaded in the startup.jl as per the Revise instructions) and I am using ImageView. After this…

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## [Images imfilter performance drops when using ImageView](https://discourse.julialang.org/t/images-imfilter-performance-drops-when-using-imageview/36630)

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**Author:** [@wizebt](https://discourse.julialang.org/u/wizebt)\
**Replies:** 2\
**Last updated:** [March 31, 2020, 10:35am UTC](https://discourse.julialang.org/t/images-imfilter-performance-drops-when-using-imageview/36630 "2020-03-31T10:35:03Z")

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Hi, imfilter exibit a huge variable performance drop when used in conjonction with ImageView. Here is the test code: using Images # ImageView function test\_imfilter() gk = Kernel.gaussian(2.0f0) I = rand(Float32,1…

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## [Typing with "where" statements leads to UndefVarError error?](https://discourse.julialang.org/t/typing-with-where-statements-leads-to-undefvarerror-error/36767)

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**Author:** [@Mikael\_Ohman](https://discourse.julialang.org/u/Mikael_Ohman)\
**Replies:** 4\
**Last updated:** [March 31, 2020, 10:04am UTC](https://discourse.julialang.org/t/typing-with-where-statements-leads-to-undefvarerror-error/36767 "2020-03-31T10:04:19Z")

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Hi all. I’m very new to Julia. Using 1.2.0 in these examples. I hit upon a little snag when i wanted to partially specify the return types for a function. E.g, specifying that the output will be SVector{N,Int} for any N …

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