# Latest

**URL:** https://discourse.julialang.org/latest.md?page=1444

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

**Page:** 1445

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## [Integration fails: “Warning: Automatic dt set the starting dt as NaN, causing instability”](https://discourse.julialang.org/t/integration-fails-warning-automatic-dt-set-the-starting-dt-as-nan-causing-instability/56030)

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**Author:** [@Michael\_Barmann](https://discourse.julialang.org/u/Michael_Barmann)\
**Replies:** 10\
**Last updated:** [March 27, 2021, 5:38pm UTC](https://discourse.julialang.org/t/integration-fails-warning-automatic-dt-set-the-starting-dt-as-nan-causing-instability/56030 "2021-03-27T17:38:18Z")

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I’ve written some code to perform parameter estimation on a system of ODEs, and I keep getting the following error: ┌ Warning: First function call produced NaNs. Exiting. └ @ OrdinaryDiffEq C:\\Users\\Michael\\.julia\\packa…

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## [Julia vs. Java on embedded](https://discourse.julialang.org/t/julia-vs-java-on-embedded/58032)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 2\
**Last updated:** [March 27, 2021, 4:39pm UTC](https://discourse.julialang.org/t/julia-vs-java-on-embedded/58032 "2021-03-27T16:39:13Z")

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We are working with an embedded device similar to a Pi 3 (well, perhaps in one or two years like a Pi 4) and use Java for our GUI application. We have now 2GB RAM, extending that to 4GB would be possible. Perhaps as cla…

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## [Multiple Module Packages and Project Environment](https://discourse.julialang.org/t/multiple-module-packages-and-project-environment/58079)

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**Author:** [@gideonsimpson](https://discourse.julialang.org/u/gideonsimpson)\
**Replies:** 2\
**Last updated:** [March 27, 2021, 4:36pm UTC](https://discourse.julialang.org/t/multiple-module-packages-and-project-environment/58079 "2021-03-27T16:36:12Z")

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I’ve seen a few other posts on this one, but they don’t seem to quite address the question I have. I have a project I’m working on, and there are several logically distinct modules associated with it, MyModuleA.jl, MyMo…

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## [Julia 1.6 versus 1.5.4](https://discourse.julialang.org/t/julia-1-6-versus-1-5-4/57993)

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**Author:** [@jovansam](https://discourse.julialang.org/u/jovansam)\
**Replies:** 8\
**Last updated:** [March 26, 2021, 12:12pm UTC](https://discourse.julialang.org/t/julia-1-6-versus-1-5-4/57993 "2021-03-26T12:12:38Z")

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I find that Julia 1.5.4 is faster in some use cases than 1.6. Do others experience this? What is the explanation. Below is a piece of code that illustrates this. It finds the value function for an optimal growth problem…

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## [Dynamic graphs](https://discourse.julialang.org/t/dynamic-graphs/43097)

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**Author:** [@erlebach](https://discourse.julialang.org/u/erlebach)\
**Replies:** 3\
**Last updated:** [July 15, 2020, 2:51am UTC](https://discourse.julialang.org/t/dynamic-graphs/43097 "2020-07-15T02:51:57Z")

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I have been using LightGraphs.jl successfully, together with MetaGraphs.jl, and I recommend it to everybody. I am toying with the idea of dynamic networks, where links are created and destroyed according to various pres…

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## [Weird Sys.which() function](https://discourse.julialang.org/t/weird-sys-which-function/58070)

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**Author:** [@j2b2](https://discourse.julialang.org/u/j2b2)\
**Replies:** 3\
**Last updated:** [March 27, 2021, 2:53pm UTC](https://discourse.julialang.org/t/weird-sys-which-function/58070 "2021-03-27T14:53:43Z")

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Hi, IJulia doesn’t work on my system, Ubuntu LTS 20.04. The (bash) command jupyter notebook works fine, but I don’t see julia when I press the “new” button. So I launched julia REPL and tried : julia\> using IJulia juli…

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## [Preventing collect on broadcasting expressions](https://discourse.julialang.org/t/preventing-collect-on-broadcasting-expressions/57996)

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**Author:** [@RainerHeintzmann](https://discourse.julialang.org/u/RainerHeintzmann)\
**Replies:** 6\
**Last updated:** [March 27, 2021, 2:22pm UTC](https://discourse.julialang.org/t/preventing-collect-on-broadcasting-expressions/57996 "2021-03-27T14:22:20Z")

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In writing efficient code for image processing, views are incredibly useful. They can nicely be chained for example to implement a phasor in optics propagation: using IndexFunArrays k0 = 5; phasor = exp.(1im .\* 2pi .\*sq…

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## [Idea for a AST frontend for parsing between Julia and Python](https://discourse.julialang.org/t/idea-for-a-ast-frontend-for-parsing-between-julia-and-python/57963)

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**Author:** [@aliG](https://discourse.julialang.org/u/aliG)\
**Replies:** 3\
**Last updated:** [March 27, 2021, 2:17pm UTC](https://discourse.julialang.org/t/idea-for-a-ast-frontend-for-parsing-between-julia-and-python/57963 "2021-03-27T14:17:57Z")

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Hi, I am interested in parsing projects between Julia and Python. There is a good use case for converting Python code in a symbolic computational library like sympy into equivalent Julia forms. Example would be convert…

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## [JuliaCon proposal for 2022 - Dates outside of vacation!](https://discourse.julialang.org/t/juliacon-proposal-for-2022-dates-outside-of-vacation/57958)

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**Author:** [@Balinus](https://discourse.julialang.org/u/Balinus)\
**Replies:** 7\
**Last updated:** [March 27, 2021, 2:09pm UTC](https://discourse.julialang.org/t/juliacon-proposal-for-2022-dates-outside-of-vacation/57958 "2021-03-27T14:09:07Z")

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Hello! Happened last year and now this year : I plan to attend JuliaCon, but it’s during my summer vacations! :cry: How about the beginning of fall or end of spring? So south and north hemispheres can be present …

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## [Which size for subplots (Plots.jl/GR)](https://discourse.julialang.org/t/which-size-for-subplots-plots-jl-gr/53936)

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**Author:** [@SteffenPL](https://discourse.julialang.org/u/SteffenPL)\
**Replies:** 5\
**Last updated:** [March 27, 2021, 1:40pm UTC](https://discourse.julialang.org/t/which-size-for-subplots-plots-jl-gr/53936 "2021-03-27T13:40:42Z")

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I have 12 plots of size (400px,400px). Each one individually looks fine. But when composing them into a grid(1,12), they start to overlap and the y-labels and ticks have too much distance for the y-axis. I know that I…

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## [Data manipulation using dataframes](https://discourse.julialang.org/t/data-manipulation-using-dataframes/57972)

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**Author:** [@mjanun](https://discourse.julialang.org/u/mjanun)\
**Replies:** 7\
**Last updated:** [March 27, 2021, 1:07pm UTC](https://discourse.julialang.org/t/data-manipulation-using-dataframes/57972 "2021-03-27T13:07:39Z")

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Assume that a dataframe is given as: df\_a = DataFrame(Categ=\["Alpa","Beta","Gamma","Omega","Alpa","Beta","Gamma","Omega"\], T1 =rand(8),T2=rand(8),T3 =rand(8),T4 =rand(8),T5 =rand(8),T6 =rand(8),T7 =rand(8),T8 =rand(8),T…

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## [Training on Simple Loss gives error: No method matching +(::Float64, ::Array{Float64, 2})](https://discourse.julialang.org/t/training-on-simple-loss-gives-error-no-method-matching-float64-array-float64-2/58047)

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**Author:** [@kimlaberinto](https://discourse.julialang.org/u/kimlaberinto)\
**Replies:** 8\
**Last updated:** [March 27, 2021, 12:35pm UTC](https://discourse.julialang.org/t/training-on-simple-loss-gives-error-no-method-matching-float64-array-float64-2/58047 "2021-03-27T12:35:20Z")

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Hello everyone! I’m getting a weird error with Flux/DiffEqFlux with a simple loss function when I try to train. I’m not sure why it’s giving me a ERROR: LoadError: MethodError: no method matching +(::Float64, ::Array{Fl…

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## [Managing Julia installation on Windows](https://discourse.julialang.org/t/managing-julia-installation-on-windows/58074)

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**Author:** [@SL6Trip](https://discourse.julialang.org/u/SL6Trip)\
**Replies:** 0\
**Last updated:** [March 27, 2021, 12:20pm UTC](https://discourse.julialang.org/t/managing-julia-installation-on-windows/58074 "2021-03-27T12:20:39Z")

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So recently I came across jill.py which seems to be using Python to help with automating the installation and/or upgrading of Julia to newer releases. I think it is a great tool especially on Linux distributions (as I te…

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## [Problem plotting surfaces](https://discourse.julialang.org/t/problem-plotting-surfaces/58065)

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**Author:** [@leopdsf](https://discourse.julialang.org/u/leopdsf)\
**Replies:** 2\
**Last updated:** [March 27, 2021, 12:18pm UTC](https://discourse.julialang.org/t/problem-plotting-surfaces/58065 "2021-03-27T12:18:22Z")

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Hello, there! I’m plotting a surface with the following code: using Plots θ = 1.5 K = J/θ #3D plot y=range(-2,stop=2) θ=range(0.1,stop=2) function f(y,θ) J = 1.0 h = 0.0 -θ\*log(2.0) -θ\*log(exp(-(J/θ)\*y^2/2…

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## [Tullio with LoopVectorization fails with upgrade to 1.6.0](https://discourse.julialang.org/t/tullio-with-loopvectorization-fails-with-upgrade-to-1-6-0/58028)

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**Author:** [@Joris\_Pinkse](https://discourse.julialang.org/u/Joris_Pinkse)\
**Replies:** 11\
**Last updated:** [March 27, 2021, 12:12pm UTC](https://discourse.julialang.org/t/tullio-with-loopvectorization-fails-with-upgrade-to-1-6-0/58028 "2021-03-27T12:12:27Z")

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The following code runs fine on Julia 1.5.3, but fails on 1.6.0. It fails on the Tullio line with error ERROR: LoadError: BoundsError: attempt to access 2-element Vector{Any} at index \[0\] If I disable LoopVectorizatio…

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## [Plotting Function With if-else Using Gadfly.jl](https://discourse.julialang.org/t/plotting-function-with-if-else-using-gadfly-jl/58020)

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**Author:** [@Adam\_Fleischhacker](https://discourse.julialang.org/u/Adam_Fleischhacker)\
**Replies:** 7\
**Last updated:** [March 26, 2021, 5:19pm UTC](https://discourse.julialang.org/t/plotting-function-with-if-else-using-gadfly-jl/58020 "2021-03-26T17:19:55Z")

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I am trying to define and plot a density function. However, it seems the if-else logic of my function is not supported for this kind of plot. Am I doing something wrong? ## graph density of spinner using Gadfly funct…

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## [Modeling Toolkit crash](https://discourse.julialang.org/t/modeling-toolkit-crash/58056)

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**Author:** [@Albert\_Zevelev](https://discourse.julialang.org/u/Albert_Zevelev)\
**Replies:** 4\
**Last updated:** [March 27, 2021, 10:19am UTC](https://discourse.julialang.org/t/modeling-toolkit-crash/58056 "2021-03-27T10:19:17Z")

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The following causes a crash in Julia v 1.6 using ModelingToolkit, NonlinearSolve, Plots @variables c, ℓ, L, K, Y, Π, v, r, w @parameters αK, αL, γ, EH, EK F(K,L,αK, αL) = (K^αK)\*(L^αL) FK(K,L,αK,αL) = αK\*(K^(αK-1…

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## [Iteration over 10 columns to calculate LinearRegression](https://discourse.julialang.org/t/iteration-over-10-columns-to-calculate-linearregression/58036)

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**Author:** [@statspy](https://discourse.julialang.org/u/statspy)\
**Replies:** 4\
**Last updated:** [March 27, 2021, 6:54am UTC](https://discourse.julialang.org/t/iteration-over-10-columns-to-calculate-linearregression/58036 "2021-03-27T06:54:29Z")

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I have a data frame with 10 columns(features) COL0 to COL9 and a column RESP. How do I calculate a LinearRegression Model for each pair COL0 to COL9 ~ RESP? I am expecting to get 10 graphs showing the Model and also a…

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## [Factor out field access of \`AbstractArray\` and/or iterator interface](https://discourse.julialang.org/t/factor-out-field-access-of-abstractarray-and-or-iterator-interface/41493)

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**Author:** [@goretkin](https://discourse.julialang.org/u/goretkin)\
**Replies:** 5\
**Last updated:** [March 27, 2021, 2:44am UTC](https://discourse.julialang.org/t/factor-out-field-access-of-abstractarray-and-or-iterator-interface/41493 "2021-03-27T02:44:51Z")

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Take function foo(a) for x in a x.field # do something with x.field end end function foo2(a) for x in a x # do something with x directly end end The foo2 version accesses elements direc…

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## [How much can hard-coded indexing be avoided in Julia?](https://discourse.julialang.org/t/how-much-can-hard-coded-indexing-be-avoided-in-julia/55699)

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**Author:** [@wherrera](https://discourse.julialang.org/u/wherrera)\
**Replies:** 41\
**Last updated:** [March 3, 2021, 9:59am UTC](https://discourse.julialang.org/t/how-much-can-hard-coded-indexing-be-avoided-in-julia/55699 "2021-03-03T09:59:39Z")

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I’ve noticed a trend toward Julia’s new keywords trending towards using keywords and functions instead of integer indexing in Julia. For example, first(array) instead of array\[1\], or eachindex(array) instead of 1:length…

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## [Distributed Optimization | Working with multiple JuMP models](https://discourse.julialang.org/t/distributed-optimization-working-with-multiple-jump-models/58050)

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**Author:** [@asavasci](https://discourse.julialang.org/u/asavasci)\
**Replies:** 1\
**Last updated:** [March 26, 2021, 10:55pm UTC](https://discourse.julialang.org/t/distributed-optimization-working-with-multiple-jump-models/58050 "2021-03-26T22:55:23Z")

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Hi All, What is the best way to build a distributed optimization framework with JuMP? I have global variables associated with the central problem. I have local copies of the central variables associated with each subp…

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## [Change discourse date display format](https://discourse.julialang.org/t/change-discourse-date-display-format/49632)

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**Author:** [@maxfreu](https://discourse.julialang.org/u/maxfreu)\
**Replies:** 7\
**Last updated:** [March 26, 2021, 9:43pm UTC](https://discourse.julialang.org/t/change-discourse-date-display-format/49632 "2021-03-26T21:43:29Z")

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Hi! I find the way discourse displays dates extremely annoying. E.g. Oct '16 vs Oct 16; the quote is just not visible enough. Do you have control over this? Please switch to the more verbose ISO 8601 date formats (e.g. 2…

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## [Which is the most efficient way to add matrices/arrays in Julia 1.x?](https://discourse.julialang.org/t/which-is-the-most-efficient-way-to-add-matrices-arrays-in-julia-1-x/39602)

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**Author:** [@KZiemian](https://discourse.julialang.org/u/KZiemian)\
**Replies:** 11\
**Last updated:** [March 26, 2021, 8:17pm UTC](https://discourse.julialang.org/t/which-is-the-most-efficient-way-to-add-matrices-arrays-in-julia-1-x/39602 "2021-03-26T20:17:58Z")

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Adding matrices is very important thing in numerical computations and I fell that discusion of results of benchmarking this in Julia 1.x should take place here. Because I don’t find such topic on Julia Discourse I put wh…

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## [Findall/Findfirst across multiple columns in dataframe](https://discourse.julialang.org/t/findall-findfirst-across-multiple-columns-in-dataframe/57969)

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**Author:** [@yogi1](https://discourse.julialang.org/u/yogi1)\
**Replies:** 15\
**Last updated:** [March 26, 2021, 9:13pm UTC](https://discourse.julialang.org/t/findall-findfirst-across-multiple-columns-in-dataframe/57969 "2021-03-26T21:13:01Z")

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Hi all, I’m trying to check whether a value exists in a dataframe or not and if so return “in dataframe”. In the past I have used: findall(x → x==“value I want”, Dataframe) Is there anyway to adapt this formula to sea…

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## [Why isn't ArgParse.jl part of Base?](https://discourse.julialang.org/t/why-isnt-argparse-jl-part-of-base/57882)

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**Author:** [@mkarikom](https://discourse.julialang.org/u/mkarikom)\
**Replies:** 4\
**Last updated:** [March 26, 2021, 8:09pm UTC](https://discourse.julialang.org/t/why-isnt-argparse-jl-part-of-base/57882 "2021-03-26T20:09:01Z")

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The ArgParse package seems to work great, but it’s such an essential feature (maybe even more essential than Distributed?) that it seems weird not to be in Base. My hunch is that since a lot of us use julia for scientif…

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## [Needs help on \[IPOPT + coinhsl\] installation](https://discourse.julialang.org/t/needs-help-on-ipopt-coinhsl-installation/40583)

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**Author:** [@SingingKim](https://discourse.julialang.org/u/SingingKim)\
**Replies:** 5\
**Last updated:** [March 26, 2021, 7:28pm UTC](https://discourse.julialang.org/t/needs-help-on-ipopt-coinhsl-installation/40583 "2021-03-26T19:28:37Z")

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Hi, I would like to know a way to connect a linear solver other than MUMPS on Ipopt. m = Model(Ipopt.Optimizer) set\_optimizer\_attribute(m, "linear\_solver", "ma86") @variable(m, x \<= 5) @objective(m, Max, x) JuMP.optimiz…

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## [Function interface to \`^Q\` shortcut behavior and generalization to get last stacktrace](https://discourse.julialang.org/t/function-interface-to-q-shortcut-behavior-and-generalization-to-get-last-stacktrace/58038)

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**Author:** [@goretkin](https://discourse.julialang.org/u/goretkin)\
**Replies:** 0\
**Last updated:** [March 26, 2021, 6:41pm UTC](https://discourse.julialang.org/t/function-interface-to-q-shortcut-behavior-and-generalization-to-get-last-stacktrace/58038 "2021-03-26T18:41:04Z")

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The ^Q shortcut lets a user jump to a source code line corresponding to a method or stackframe. It is just awesome. (It makes Julia a bit more like \[the good parts of\] SmallTalk) What about a non-shortcut way to access …

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## [Flux -- decompose layers + parameters?](https://discourse.julialang.org/t/flux-decompose-layers-parameters/58026)

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**Author:** [@BLI](https://discourse.julialang.org/u/BLI)\
**Replies:** 3\
**Last updated:** [March 26, 2021, 6:01pm UTC](https://discourse.julialang.org/t/flux-decompose-layers-parameters/58026 "2021-03-26T18:01:53Z")

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A silly question… I used simple Flux networks 2 years ago, and I notice there have been some changes… Suppose I have a network named md (…model…): In the old system, I could pick out layer no. i by md.layers\[i\]. → Am…

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## [Ad-hoc equality test for struct after definition](https://discourse.julialang.org/t/ad-hoc-equality-test-for-struct-after-definition/4615)

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**Author:** [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Replies:** 13\
**Last updated:** [March 26, 2021, 5:59pm UTC](https://discourse.julialang.org/t/ad-hoc-equality-test-for-struct-after-definition/4615 "2021-03-26T17:59:06Z")

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I am trying to streamline some unit tests. Most of them work by generating a value and comparing it to a known value. I want something like ==, but I only want to define it in the tests, not the package source, since equ…

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## [Optimizing semiclassical simulation for a lattice system](https://discourse.julialang.org/t/optimizing-semiclassical-simulation-for-a-lattice-system/58014)

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**Author:** [@Joh11](https://discourse.julialang.org/u/Joh11)\
**Replies:** 7\
**Last updated:** [March 26, 2021, 4:55pm UTC](https://discourse.julialang.org/t/optimizing-semiclassical-simulation-for-a-lattice-system/58014 "2021-03-26T16:55:13Z")

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Hi everyone, I am currently working on implementing an implementation of semiclassical Monte Carlo for a lattice system (https://github.com/Joh11/semiclassical-monte-carlo). I would like to make my code faster. The bot…

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