# Latest

**URL:** https://discourse.julialang.org/latest.md?page=1391

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

**Page:** 1392

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## [Meaning of ";" in PlotlyJS](https://discourse.julialang.org/t/meaning-of-in-plotlyjs/61205)

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**Author:** [@Oto\_Brzobohaty](https://discourse.julialang.org/u/Oto_Brzobohaty)\
**Replies:** 7\
**Last updated:** [May 16, 2021, 1:47am UTC](https://discourse.julialang.org/t/meaning-of-in-plotlyjs/61205 "2021-05-16T01:47:11Z")

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I was always wondered what does “;” means in all examples. The following functions give me the same output. using PlotlyBase function linescatter1() trace1 = scatter(;x=1:4, y=\[10, 15, 13, 17\], mode="markers") …

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## [Need help speeding up ode ensemble problem; preallocation and type instability?](https://discourse.julialang.org/t/need-help-speeding-up-ode-ensemble-problem-preallocation-and-type-instability/61216)

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**Author:** [@ethansigh](https://discourse.julialang.org/u/ethansigh)\
**Replies:** 5\
**Last updated:** [May 16, 2021, 12:37am UTC](https://discourse.julialang.org/t/need-help-speeding-up-ode-ensemble-problem-preallocation-and-type-instability/61216 "2021-05-16T00:37:55Z")

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Hi! I’m writing some particle tracing code with large ensemble sizes and it’s super slow. Because for my simulations I need really small timesteps, the solution is huge, and this takes a very very long time (like couple …

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## [Use ModelingToolkit.jl to solve a maximization problem](https://discourse.julialang.org/t/use-modelingtoolkit-jl-to-solve-a-maximization-problem/61042)

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**Author:** [@Chen](https://discourse.julialang.org/u/Chen)\
**Replies:** 6\
**Last updated:** [May 15, 2021, 7:23pm UTC](https://discourse.julialang.org/t/use-modelingtoolkit-jl-to-solve-a-maximization-problem/61042 "2021-05-15T19:23:08Z")

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I browsed the website of ModelingToolkit.jl and did not find an example that covers a very simple math problem. Let’s say that I’d like to maximize y by choosing a value of x: y = a - b x^2 where a = c + dx - e. The …

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## [Please tell me about the following Turing.jl processing](https://discourse.julialang.org/t/please-tell-me-about-the-following-turing-jl-processing/61202)

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**Author:** [@anon20242138](https://discourse.julialang.org/u/anon20242138)\
**Replies:** 1\
**Last updated:** [May 15, 2021, 5:37pm UTC](https://discourse.julialang.org/t/please-tell-me-about-the-following-turing-jl-processing/61202 "2021-05-15T17:37:37Z")

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What does the following process mean? What does “Observe each prediction.” mean? This code from Turing tutorials ( https://turing.ml/dev/tutorials/3-bayesnn/ ) for i = 1:length(ts) ts\[i\] ~ Bernoulli(preds\[i\]) end

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## [Anyone looking into augmented reality approaches](https://discourse.julialang.org/t/anyone-looking-into-augmented-reality-approaches/61206)

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**Author:** [@anon69491625](https://discourse.julialang.org/u/anon69491625)\
**Replies:** 0\
**Last updated:** [May 15, 2021, 4:42pm UTC](https://discourse.julialang.org/t/anyone-looking-into-augmented-reality-approaches/61206 "2021-05-15T16:42:40Z")

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Hi All I’m interested in OPEN SOURCE augmented reality approaches and wonder if anyone has any experience with them and which one? thanks theakson

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## [Using LinuxPerf for small functions](https://discourse.julialang.org/t/using-linuxperf-for-small-functions/60410)

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**Author:** [@shmiggles](https://discourse.julialang.org/u/shmiggles)\
**Replies:** 7\
**Last updated:** [May 15, 2021, 2:39pm UTC](https://discourse.julialang.org/t/using-linuxperf-for-small-functions/60410 "2021-05-15T14:39:09Z")

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LinuxPerf.jl wraps the perf\_event\_open Linux syscall. But using it for small functions gives ridiculous results. The following example reports over 12000 clock cycles and 2000 memory fetches to compute 1+1: using LinuxP…

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## [Problem with BayesNN Demo in Turing.jl](https://discourse.julialang.org/t/problem-with-bayesnn-demo-in-turing-jl/58293)

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**Author:** [@erlebach1](https://discourse.julialang.org/u/erlebach1)\
**Replies:** 1\
**Last updated:** [May 15, 2021, 2:05pm UTC](https://discourse.julialang.org/t/problem-with-bayesnn-demo-in-turing-jl/58293 "2021-05-15T14:05:12Z")

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Hi, When running the BayesNN demo in Turing, I get the error that index nn\_params not found. After checking the code, I found the line: theta = ch\[:nn\_params\].value.data; and I do not see where :nn\_params is defined e…

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## [Why do I get a sparse matrix?](https://discourse.julialang.org/t/why-do-i-get-a-sparse-matrix/61196)

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**Author:** [@stla](https://discourse.julialang.org/u/stla)\
**Replies:** 1\
**Last updated:** [May 15, 2021, 11:42am UTC](https://discourse.julialang.org/t/why-do-i-get-a-sparse-matrix/61196 "2021-05-15T11:42:48Z")

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Hello, I have these two matrices: julia\> L 1×1 Array{Float64,2}: 3.0 julia\> M 2×1 Array{Float64,2}: 2.0 1.0 I do: import LinearAlgebra d = 3 Ctilde = hcat(vcat(L,M), vcat(zeros(size(L,1),d-size(L,1)), LinearAlgeb…

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## [Gadfly Title Size](https://discourse.julialang.org/t/gadfly-title-size/61168)

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**Author:** [@white-c](https://discourse.julialang.org/u/white-c)\
**Replies:** 4\
**Last updated:** [May 15, 2021, 4:30am UTC](https://discourse.julialang.org/t/gadfly-title-size/61168 "2021-05-15T04:30:29Z")

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I want to have a different font size for a Gadfly Guide.title() versus Guide.xlabel(). Setting major\_label\_font\_size affects both. How do I control the title size separately?

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## [Re-Scheduled Julia Beginner AMA | May 2021 | Featuring Featuring Xuan (Sh-YEN) and Alex Lew](https://discourse.julialang.org/t/re-scheduled-julia-beginner-ama-may-2021-featuring-featuring-xuan-sh-yen-and-alex-lew/60652)

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**Author:** [@logankilpatrick](https://discourse.julialang.org/u/logankilpatrick)\
**Replies:** 1\
**Last updated:** [May 15, 2021, 3:56am UTC](https://discourse.julialang.org/t/re-scheduled-julia-beginner-ama-may-2021-featuring-featuring-xuan-sh-yen-and-alex-lew/60652 "2021-05-15T03:56:19Z")

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Hey all! We are excited to have our re-scheduled AMA this month featuring @Alex\_Lew and @Xuan! If you know anyone who might have beginner questions, please send them over. Thanks again as always to @nassarhuda for moder…

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## [Processing JSON from a .txt file and converting to a DataFrame](https://discourse.julialang.org/t/processing-json-from-a-txt-file-and-converting-to-a-dataframe/61119)

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**Author:** [@clibassi](https://discourse.julialang.org/u/clibassi)\
**Replies:** 7\
**Last updated:** [May 15, 2021, 2:06am UTC](https://discourse.julialang.org/t/processing-json-from-a-txt-file-and-converting-to-a-dataframe/61119 "2021-05-15T02:06:35Z")

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Hi all - I’m just looking for some insight into why the below code is returning a dataframe containing just the first line of my json file. If you’d like to try working with the file I’m working with, you can download t…

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## [Possible enum slowness?](https://discourse.julialang.org/t/possible-enum-slowness/59896)

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**Author:** [@lewis](https://discourse.julialang.org/u/lewis)\
**Replies:** 3\
**Last updated:** [May 14, 2021, 11:12pm UTC](https://discourse.julialang.org/t/possible-enum-slowness/59896 "2021-05-14T23:12:10Z")

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I may have encountered enum slowness–looking for insight. The background is a bit long: just skip to my question below. The application is a Covid simulation using a physical event approach at the level of individuals. …

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## [POST results of multiple checkbox selections](https://discourse.julialang.org/t/post-results-of-multiple-checkbox-selections/61179)

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**Author:** [@fyzycyst](https://discourse.julialang.org/u/fyzycyst)\
**Replies:** 1\
**Last updated:** [May 14, 2021, 11:03pm UTC](https://discourse.julialang.org/t/post-results-of-multiple-checkbox-selections/61179 "2021-05-14T23:03:17Z")

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What I’m attempting: There’s a site (NASA ModelWeb) where one can access online models for Earth’s atmosphere (among many other models). I’m writing code to access this to create an atmospheric profile \[number density o…

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## [Why is this dataframe filter slow?](https://discourse.julialang.org/t/why-is-this-dataframe-filter-slow/61177)

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**Author:** [@Iulian.Cioarca](https://discourse.julialang.org/u/Iulian.Cioarca)\
**Replies:** 5\
**Last updated:** [May 14, 2021, 9:57pm UTC](https://discourse.julialang.org/t/why-is-this-dataframe-filter-slow/61177 "2021-05-14T21:57:49Z")

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I need to extract rows from a dataframe based on values of a specific column. I tried to use filter but it’s slower than traditional findall. Am I missing something? df = DataFrame(a=\["a", "b", "c"\], b=\[1,2,3\]) @elapse…

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## [Linsolve on SparseMatrixCSC{BigFloat}](https://discourse.julialang.org/t/linsolve-on-sparsematrixcsc-bigfloat/60742)

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**Author:** [@MatFi](https://discourse.julialang.org/u/MatFi)\
**Replies:** 2\
**Last updated:** [May 14, 2021, 7:50am UTC](https://discourse.julialang.org/t/linsolve-on-sparsematrixcsc-bigfloat/60742 "2021-05-14T07:50:13Z")

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I want to solve a quite large but sparse DAE system using DifferentialEquaitions.jl I can do it with decent efficiency when using Float64’s Now I would like to do the same thing with higher precision numbers (Double64,…

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## [How do I to transform mapreduce function to work well with CUDA?](https://discourse.julialang.org/t/how-do-i-to-transform-mapreduce-function-to-work-well-with-cuda/61084)

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**Author:** [@Noel\_Araujo](https://discourse.julialang.org/u/Noel_Araujo)\
**Replies:** 5\
**Last updated:** [May 14, 2021, 9:00pm UTC](https://discourse.julialang.org/t/how-do-i-to-transform-mapreduce-function-to-work-well-with-cuda/61084 "2021-05-14T21:00:00Z")

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Hellos I’m playing with CUDA.jl, and I just wish to perform a mapreduce faster. Here a minimal code: using CUDA using LinearAlgebra x = 100 N = ((x^2)÷2 - x÷2) n\_hat = rand(3) A = rand(3,N) b = rand(N) for p=1:10 …

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## [UnicodePlot exercise](https://discourse.julialang.org/t/unicodeplot-exercise/61101)

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**Author:** [@weymouth](https://discourse.julialang.org/u/weymouth)\
**Replies:** 9\
**Last updated:** [May 14, 2021, 8:47pm UTC](https://discourse.julialang.org/t/unicodeplot-exercise/61101 "2021-05-14T20:47:19Z")

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I’ve taken up a little challenge to reproduce a classic plot from Chorin 1973 (maybe the first computerized flow plot ever) and I hoped WaterLily.jl + UnicodePlots.jl could make short work of it. However, to really n…

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## [Running out of letters: Pitfalls of Unicode?](https://discourse.julialang.org/t/running-out-of-letters-pitfalls-of-unicode/61125)

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**Author:** [@ptoche](https://discourse.julialang.org/u/ptoche)\
**Replies:** 11\
**Last updated:** [May 14, 2021, 8:32pm UTC](https://discourse.julialang.org/t/running-out-of-letters-pitfalls-of-unicode/61125 "2021-05-14T20:32:47Z")

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It’s a silly question. Here is the dilemma. I’m sort of running out of letters in the sense that I would like to use A for two things in the same project: a float and a matrix. I would normally resolve the dilemma with a…

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## [Video tutorial: setting up Julia and VSCode, installing, reading and developing packages](https://discourse.julialang.org/t/video-tutorial-setting-up-julia-and-vscode-installing-reading-and-developing-packages/61174)

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**Author:** [@mohamed82008](https://discourse.julialang.org/u/mohamed82008)\
**Replies:** 0\
**Last updated:** [May 14, 2021, 8:28pm UTC](https://discourse.julialang.org/t/video-tutorial-setting-up-julia-and-vscode-installing-reading-and-developing-packages/61174 "2021-05-14T20:28:43Z")

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I recently organized the first Julia Programming meetup at Canberra, Australia. I recorded my talk which is a general introduction to using and developing in Julia targeted at beginner to intermediate users and users loo…

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## [Dependency build failure and current path](https://discourse.julialang.org/t/dependency-build-failure-and-current-path/59842)

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**Author:** [@George9000](https://discourse.julialang.org/u/George9000)\
**Replies:** 1\
**Last updated:** [May 14, 2021, 7:59pm UTC](https://discourse.julialang.org/t/dependency-build-failure-and-current-path/59842 "2021-05-14T19:59:30Z")

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I encounter a recurring error with packages failing to build due to a dependency on Emoji\_Entities. That package fails to build with the error “Package JSON not found in current path”. This error has been raised as an is…

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## [SubString of splitted IOStream line can't be compared with \`in\`](https://discourse.julialang.org/t/substring-of-splitted-iostream-line-cant-be-compared-with-in/60939)

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**Author:** [@JanKap](https://discourse.julialang.org/u/JanKap)\
**Replies:** 6\
**Last updated:** [May 14, 2021, 7:16pm UTC](https://discourse.julialang.org/t/substring-of-splitted-iostream-line-cant-be-compared-with-in/60939 "2021-05-14T19:16:27Z")

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Dear all, I might be too naive doing a line by line file read and throw out duplicated columns and write it back to another file. The first loop iteration runs well but then an error LoadError: MethodError: objects of …

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## [Print string with multiple lines without identation](https://discourse.julialang.org/t/print-string-with-multiple-lines-without-identation/61171)

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**Author:** [@lmiq](https://discourse.julialang.org/u/lmiq)\
**Replies:** 3\
**Last updated:** [May 14, 2021, 6:15pm UTC](https://discourse.julialang.org/t/print-string-with-multiple-lines-without-identation/61171 "2021-05-14T18:15:38Z")

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Is there some macro that allows me to write strings with multiple lines removing the identiation of the code? Meaning: julia\> println("function f(x) y = x + 1 return y …

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## [Piping input and output](https://discourse.julialang.org/t/piping-input-and-output/61157)

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**Author:** [@lmiq](https://discourse.julialang.org/u/lmiq)\
**Replies:** 4\
**Last updated:** [May 14, 2021, 5:22pm UTC](https://discourse.julialang.org/t/piping-input-and-output/61157 "2021-05-14T17:22:48Z")

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I would like to do something as simple as: grep AA \< box.inp \> box.out using run. Is the only way to do this one of the cumbersome options discussed here? (meaning using pipeline etc?) Or is there a simple alternative…

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## [Integrating functions with additional parameters](https://discourse.julialang.org/t/integrating-functions-with-additional-parameters/61169)

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**Author:** [@dkiese](https://discourse.julialang.org/u/dkiese)\
**Replies:** 2\
**Last updated:** [May 14, 2021, 4:47pm UTC](https://discourse.julialang.org/t/integrating-functions-with-additional-parameters/61169 "2021-05-14T16:47:22Z")

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Hello everyone, I have a question regarding performance of the following mwe: using BenchmarkTools function integrate!(f!, buf, a, b, N) h = (b - a) / N buf .= 0.0 for i in 1 : N f!(bu…

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## [Evaluating the rhs of ODE](https://discourse.julialang.org/t/evaluating-the-rhs-of-ode/61144)

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**Author:** [@Chilperic](https://discourse.julialang.org/u/Chilperic)\
**Replies:** 7\
**Last updated:** [May 14, 2021, 1:40pm UTC](https://discourse.julialang.org/t/evaluating-the-rhs-of-ode/61144 "2021-05-14T13:40:53Z")

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Hi! I am a beginner with Julia, just a week since I started learning Julia. I am having an issue with evaluating the rhs of a big ODE with 46 variables and more than a hundred parameters. The ODE was originally written …

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## [Makie not passing all tests after update](https://discourse.julialang.org/t/makie-not-passing-all-tests-after-update/61135)

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**Author:** [@diogoribeiro98](https://discourse.julialang.org/u/diogoribeiro98)\
**Replies:** 2\
**Last updated:** [May 14, 2021, 1:30pm UTC](https://discourse.julialang.org/t/makie-not-passing-all-tests-after-update/61135 "2021-05-14T13:30:59Z")

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I just updated Makie and it stopped passing all tests. I am unable to use popup windows and I can’t seem to get it working. Here is the test result: (@v1.5) pkg\> test GLMakie Testing GLMakie Status \`C:\\Users\\diogo…

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## [Solving Grad-Shafranov Equation with ModelingToolkit](https://discourse.julialang.org/t/solving-grad-shafranov-equation-with-modelingtoolkit/60513)

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**Author:** [@lstagner](https://discourse.julialang.org/u/lstagner)\
**Replies:** 19\
**Last updated:** [May 14, 2021, 1:30pm UTC](https://discourse.julialang.org/t/solving-grad-shafranov-equation-with-modelingtoolkit/60513 "2021-05-14T13:30:37Z")

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I am trying to solve the Grad-Shafranov partial differential equation and I am running into the following error using ModelingToolkit R0 = 2.0 C = 1.0 A = 1.0 #ψ(r,z) = (1/2)\*(A\*R0^2 +a0\*r^2)\*z^2 + (1/8)\*(C−a0)(r^2−R0^…

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## [Optimising a non-linear user-defined function using NLopt](https://discourse.julialang.org/t/optimising-a-non-linear-user-defined-function-using-nlopt/61141)

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**Author:** [@Debasish](https://discourse.julialang.org/u/Debasish)\
**Replies:** 5\
**Last updated:** [May 14, 2021, 1:21pm UTC](https://discourse.julialang.org/t/optimising-a-non-linear-user-defined-function-using-nlopt/61141 "2021-05-14T13:21:34Z")

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Dear Julia experts, This is my second Julia code. I have a physical problem to solve in which a waving filament in fluid medium propels itself (think of a beating sperm tail). I have a MATLAB code which optimises the s…

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## [Flux precompilation takes way too long (1.6.1)](https://discourse.julialang.org/t/flux-precompilation-takes-way-too-long-1-6-1/61018)

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**Author:** [@lmiq](https://discourse.julialang.org/u/lmiq)\
**Replies:** 6\
**Last updated:** [May 14, 2021, 12:28pm UTC](https://discourse.julialang.org/t/flux-precompilation-takes-way-too-long-1-6-1/61018 "2021-05-14T12:28:23Z")

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I am not able to use Flux (Linux 64 bits, Julia 1.6.1). Precompilation takes forever. Killing it and using it in a new section goes down the same road and precompilation never ends. I do not get any error message, though…

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## [Understanding issorted's lt keyword](https://discourse.julialang.org/t/understanding-issorteds-lt-keyword/60918)

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**Author:** [@mkitti](https://discourse.julialang.org/u/mkitti)\
**Replies:** 88\
**Last updated:** [May 14, 2021, 12:23pm UTC](https://discourse.julialang.org/t/understanding-issorteds-lt-keyword/60918 "2021-05-14T12:23:52Z")

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The lt keyword for issorted and sort! is defying my intuition. From reading the source code, I understand why I get the following results, but I am finding it counterintuitive. From the documentation for sort!: the lt…

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