# General Usage

**URL:** https://discourse.julialang.org/c/usage/6.md?page=38

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**Page:** 39

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## [Reactant.jl and Lux.jl don't work with Adam optimiser](https://discourse.julialang.org/t/reactant-jl-and-lux-jl-dont-work-with-adam-optimiser/132278)

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**Author:** [@flick](https://discourse.julialang.org/u/flick)\
**Replies:** 9\
**Last updated:** [September 30, 2025, 10:54pm UTC](https://discourse.julialang.org/t/reactant-jl-and-lux-jl-dont-work-with-adam-optimiser/132278 "2025-09-30T22:54:14Z")

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I am writing a training program for the VAEAC model, but when I use Optimisers.Adam(lr), I get an error. When I use, for example, Optimisers.Descent(lr), this problem does not occur. Error message: ERROR: MethodError: …

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## [\[ANN\] \`Undigits.jl\` undoes \`Base.digits\` (not registered)](https://discourse.julialang.org/t/ann-undigits-jl-undoes-base-digits-not-registered/132791)

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**Author:** [@jlapeyre](https://discourse.julialang.org/u/jlapeyre)\
**Replies:** 2\
**Last updated:** [September 30, 2025, 6:21pm UTC](https://discourse.julialang.org/t/ann-undigits-jl-undoes-base-digits-not-registered/132791 "2025-09-30T18:21:34Z")

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Undigits.jl This package provides undigits, the reverse of digits. julia\> undigits(\[2, 4\]) 42 julia\> undigits(\[2, 4\]; rev=true) 24 julia\> undigits(UInt8, \[1, 0, 1, 1\]; base=2) 0x0d julia\> n = UInt16(17); undigits(ty…

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## [How do I make a matrix of vectors?](https://discourse.julialang.org/t/how-do-i-make-a-matrix-of-vectors/132765)

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**Author:** [@phma](https://discourse.julialang.org/u/phma)\
**Replies:** 6\
**Last updated:** [September 30, 2025, 5:44pm UTC](https://discourse.julialang.org/t/how-do-i-make-a-matrix-of-vectors/132765 "2025-09-30T17:44:08Z")

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I’m cryptanalyzing a hash function I invented. I get a big amount of data which I want to return as a matrix normalize(cd0a) normalize(cd0b) normalize(cd1a) normalize(cd1b) where the two rows represent using the three …

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## [\[ANN\] InverseGammaFunction.jl (not registered)](https://discourse.julialang.org/t/ann-inversegammafunction-jl-not-registered/132661)

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**Author:** [@jlapeyre](https://discourse.julialang.org/u/jlapeyre)\
**Replies:** 9\
**Last updated:** [September 30, 2025, 5:40pm UTC](https://discourse.julialang.org/t/ann-inversegammafunction-jl-not-registered/132661 "2025-09-30T17:40:34Z")

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This package provides a function to compute the inverse of the gamma function for positive (real) arguments. It supports both branches. It is a very quick implementation using root finding. I don’t plan to register it. …

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## [ParseError in comprehension when whitespace removed](https://discourse.julialang.org/t/parseerror-in-comprehension-when-whitespace-removed/132780)

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**Author:** [@Tigerbyte](https://discourse.julialang.org/u/Tigerbyte)\
**Replies:** 3\
**Last updated:** [September 30, 2025, 1:02pm UTC](https://discourse.julialang.org/t/parseerror-in-comprehension-when-whitespace-removed/132780 "2025-09-30T13:02:53Z")

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julia\> \[ 2\*x + 6 for x in 1:3\] 3-element Vector{Int64}: 8 10 12 julia\> "above as expected, now take away the blank before the 6" "above as expected, now take away the blank before the 6" julia\> \[ 2\*x +6 for x in 1:…

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## [Thread-safe alternative to \`redirect\_stdio\`?](https://discourse.julialang.org/t/thread-safe-alternative-to-redirect-stdio/132749)

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**Author:** [@StevenWhitaker](https://discourse.julialang.org/u/StevenWhitaker)\
**Replies:** 3\
**Last updated:** [September 29, 2025, 10:36pm UTC](https://discourse.julialang.org/t/thread-safe-alternative-to-redirect-stdio/132749 "2025-09-29T22:36:07Z")

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I’m confused at why the following code throws an error. I don’t see any obvious race conditions, especially since each task should have its own Pipe to work with. (I’m assuming Julia’s logging is thread-safe, which I thi…

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## [Using macros to generate NamedTuples](https://discourse.julialang.org/t/using-macros-to-generate-namedtuples/30947)

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**Author:** [@vilim](https://discourse.julialang.org/u/vilim)\
**Replies:** 17\
**Last updated:** [September 29, 2025, 5:28pm UTC](https://discourse.julialang.org/t/using-macros-to-generate-namedtuples/30947 "2025-09-29T17:28:17Z")

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I am a bit confused by using macros to generate expressions. I would like to have a macro to make NamedTuples as follows: a = 1 b = 2 @make\_nt a b which should return an expression that evaluates to NamedTuple{(:a, :b)…

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## [Filtering dataframe row by row procedurally?](https://discourse.julialang.org/t/filtering-dataframe-row-by-row-procedurally/132745)

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**Author:** [@Quantodeluz](https://discourse.julialang.org/u/Quantodeluz)\
**Replies:** 2\
**Last updated:** [September 29, 2025, 1:29pm UTC](https://discourse.julialang.org/t/filtering-dataframe-row-by-row-procedurally/132745 "2025-09-29T13:29:31Z")

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Suppose i have a dataframe which i want to filter using, let’s say, interquartile range, and i want to do it for each column (so if one element is filtered out it’s whole row is filteed out with it), but i don’t know whi…

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## [RecursiveArrayTools.VectorOfArray weirdness](https://discourse.julialang.org/t/recursivearraytools-vectorofarray-weirdness/132726)

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**Author:** [@rveltz](https://discourse.julialang.org/u/rveltz)\
**Replies:** 5\
**Last updated:** [September 28, 2025, 5:35pm UTC](https://discourse.julialang.org/t/recursivearraytools-vectorofarray-weirdness/132726 "2025-09-28T17:35:43Z")

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Hi, I stumbled onto the following weirdness, it seems norm(a,2) is computed in place of norm(a,Inf). julia\> using RecursiveArrayTools julia\> a = VectorOfArray(\[rand(10)\]) VectorOfArray{Float64,2}: 1-element Vector{Vec…

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## [Fitting generates an extreme standard deviation (Dataframes + Easyfit)](https://discourse.julialang.org/t/fitting-generates-an-extreme-standard-deviation-dataframes-easyfit/132718)

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**Author:** [@Quantodeluz](https://discourse.julialang.org/u/Quantodeluz)\
**Replies:** 2\
**Last updated:** [September 27, 2025, 7:07pm UTC](https://discourse.julialang.org/t/fitting-generates-an-extreme-standard-deviation-dataframes-easyfit/132718 "2025-09-27T19:07:44Z")

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Hi, I am trying to fit some data with EasyFit.jl, but i get an unreasonable standard deviation. What could be the cause, and what could i do about it? -------------------- Linear Fit ------------------- Equation: y = a…

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## [Syntax of multiple let assignments vs tuples](https://discourse.julialang.org/t/syntax-of-multiple-let-assignments-vs-tuples/130357)

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**Author:** [@WalterMadelim](https://discourse.julialang.org/u/WalterMadelim)\
**Replies:** 10\
**Last updated:** [September 27, 2025, 2:38pm UTC](https://discourse.julialang.org/t/syntax-of-multiple-let-assignments-vs-tuples/130357 "2025-09-27T14:38:28Z")

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One question has been continually bothering me—why do we have this syntax let x = 1, y = 2? Since we used to write x, y = 1, 2 directly in julia REPL. Otherwise it’s invalid as follows julia\> x = 1, y = 2 ERROR: synta…

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## [How to use PythonCall with a previous Conda environment](https://discourse.julialang.org/t/how-to-use-pythoncall-with-a-previous-conda-environment/87419)

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**Author:** [@martinmestre](https://discourse.julialang.org/u/martinmestre)\
**Replies:** 9\
**Last updated:** [September 27, 2025, 2:35pm UTC](https://discourse.julialang.org/t/how-to-use-pythoncall-with-a-previous-conda-environment/87419 "2025-09-27T14:35:57Z")

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Hello, I would be very gratefull to understand what is the problem. I followed the instructions: julia \> ENV\["JULIA\_CONDAPKG\_BACKEND"\] = "System" julia \> ENV\["JULIA\_CONDAPKG\_EXE"\] = "/home/mmestre/.conda/envs/cosmos/bi…

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## [Pair of methods for symmetric operator by a single definition](https://discourse.julialang.org/t/pair-of-methods-for-symmetric-operator-by-a-single-definition/132696)

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**Author:** [@DanimirD](https://discourse.julialang.org/u/DanimirD)\
**Replies:** 2\
**Last updated:** [September 27, 2025, 11:41am UTC](https://discourse.julialang.org/t/pair-of-methods-for-symmetric-operator-by-a-single-definition/132696 "2025-09-27T11:41:06Z")

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Hi, I’ve been trying to familiarize myself with Julia lately and I finally stumbled upon a question to which I couldn’t find an answer yet, so I signed up to Discourse :slight\_smile: First of all, thanks to everyone who…

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## [How can I register/align shifted image stacks?](https://discourse.julialang.org/t/how-can-i-register-align-shifted-image-stacks/29244)

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**Author:** [@Moses](https://discourse.julialang.org/u/Moses)\
**Replies:** 45\
**Last updated:** [September 26, 2025, 6:03pm UTC](https://discourse.julialang.org/t/how-can-i-register-align-shifted-image-stacks/29244 "2025-09-26T18:03:13Z")

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Good evening. I have the problem that in many microscopy experiments the sample drifts over time (mainly because a buffer solution is flowing continuously over the sample). I am looking for a way to register/align the …

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## [Standalone window from Plots.jl or GLMakie in jupyter lab?](https://discourse.julialang.org/t/standalone-window-from-plots-jl-or-glmakie-in-jupyter-lab/132674)

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**Author:** [@cpf-work](https://discourse.julialang.org/u/cpf-work)\
**Replies:** 2\
**Last updated:** [September 26, 2025, 2:20pm UTC](https://discourse.julialang.org/t/standalone-window-from-plots-jl-or-glmakie-in-jupyter-lab/132674 "2025-09-26T14:20:26Z")

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I’m using jupyter lab and have trouble to get a standalone window (not inline) from Plots.jl and GLMakie. I tried using Plots scatter(rand(5), rand(5), legend=false) gui() and also plt = plot() scatter!(plt, rand(5), …

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## [Changing the name of a package](https://discourse.julialang.org/t/changing-the-name-of-a-package/14960)

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**Author:** [@heliosdrm](https://discourse.julialang.org/u/heliosdrm)\
**Replies:** 8\
**Last updated:** [September 26, 2025, 7:55am UTC](https://discourse.julialang.org/t/changing-the-name-of-a-package/14960 "2025-09-26T07:55:52Z")

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I have been developing the package RecurrenceAnalysis for some time. I used that name because the usual way of calling what it does looked too long for a package name (“Recurrence Quantification Analysis”), and acronyms…

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## [Passing state variable to handler functions](https://discourse.julialang.org/t/passing-state-variable-to-handler-functions/119268)

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**Author:** [@ehsani63](https://discourse.julialang.org/u/ehsani63)\
**Replies:** 1\
**Last updated:** [September 26, 2025, 4:23am UTC](https://discourse.julialang.org/t/passing-state-variable-to-handler-functions/119268 "2025-09-26T04:23:10Z")

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A general question about Julia web frameworks like Oxygen.jl: Is there an easy way to pass a state variable as an argument to handler functions, or is relying on global variables the only option?

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## [Changing the name of package during the registration waiting period?](https://discourse.julialang.org/t/changing-the-name-of-package-during-the-registration-waiting-period/132660)

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**Author:** [@myersm0](https://discourse.julialang.org/u/myersm0)\
**Replies:** 3\
**Last updated:** [September 25, 2025, 7:01pm UTC](https://discourse.julialang.org/t/changing-the-name-of-package-during-the-registration-waiting-period/132660 "2025-09-25T19:01:04Z")

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I found this helpful topic about changing the name of a package, but I have an additional question regarding the special case of changing a package name during the registration process. Here are the steps that have occu…

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## [Allocation Behavior Depending on Code Size](https://discourse.julialang.org/t/allocation-behavior-depending-on-code-size/132576)

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**Author:** [@mraic1](https://discourse.julialang.org/u/mraic1)\
**Replies:** 16\
**Last updated:** [September 25, 2025, 3:36pm UTC](https://discourse.julialang.org/t/allocation-behavior-depending-on-code-size/132576 "2025-09-25T15:36:24Z")

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Dear all, I am experimenting a bit on stream processing. To cope with this, Julia has a beautifully designed system of channels and tasks. However, the latter appear rather slow, even very slow when the channels are not…

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## [\`hasfield\` and \`getkey\` in namedtuple](https://discourse.julialang.org/t/hasfield-and-getkey-in-namedtuple/132616)

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**Author:** [@Marco\_Lombardi](https://discourse.julialang.org/u/Marco_Lombardi)\
**Replies:** 5\
**Last updated:** [September 25, 2025, 8:32am UTC](https://discourse.julialang.org/t/hasfield-and-getkey-in-namedtuple/132616 "2025-09-25T08:32:59Z")

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Just a curiosity: is there any particular reason for the slightly odd choice of access functions for named tuples? I would expect to have hasfield and getfield, or alternatively haskey and getkey, but I see a mixture of …

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## [QuadGK returning zero when bounds Inf](https://discourse.julialang.org/t/quadgk-returning-zero-when-bounds-inf/132648)

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**Author:** [@rand5](https://discourse.julialang.org/u/rand5)\
**Replies:** 1\
**Last updated:** [September 25, 2025, 6:26am UTC](https://discourse.julialang.org/t/quadgk-returning-zero-when-bounds-inf/132648 "2025-09-25T06:26:13Z")

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Any help understanding the behavior of QuadGK here would be greatly appreciated. I have two well behaved functions, pdf(Normal(1.,0.1),x) and cdf(Normal(-3.,0.1),x) and I’d like to integrate their product. quadgk(x -\> p…

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## [World Age Problem Explanation](https://discourse.julialang.org/t/world-age-problem-explanation/9714)

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**Author:** [@LS64](https://discourse.julialang.org/u/LS64)\
**Replies:** 21\
**Last updated:** [September 24, 2025, 11:20pm UTC](https://discourse.julialang.org/t/world-age-problem-explanation/9714 "2025-09-24T23:20:20Z")

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Hello. Recently I have faced the “world age problem” several times. That means, after searching for my problems, this website came up with themes like “world age workaround” or “How to Bypass the World Age Problem”. I …

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## [Deploy Documenter docs locally](https://discourse.julialang.org/t/deploy-documenter-docs-locally/5463)

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**Author:** [@baggepinnen](https://discourse.julialang.org/u/baggepinnen)\
**Replies:** 6\
**Last updated:** [September 24, 2025, 9:09pm UTC](https://discourse.julialang.org/t/deploy-documenter-docs-locally/5463 "2025-09-24T21:09:28Z")

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As I understand it, the function deploydocs in Documenter.jl is designed to work with travis only. I have a private repository I would like to generate documentation for, and would like a deploydocs function that could d…

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## [Can I avoid dynamic dispatch here ? (recursive parameter in struct )](https://discourse.julialang.org/t/can-i-avoid-dynamic-dispatch-here-recursive-parameter-in-struct/132609)

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**Author:** [@filchristou](https://discourse.julialang.org/u/filchristou)\
**Replies:** 6\
**Last updated:** [September 24, 2025, 4:01pm UTC](https://discourse.julialang.org/t/can-i-avoid-dynamic-dispatch-here-recursive-parameter-in-struct/132609 "2025-09-24T16:01:05Z")

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There has been a while that I sense I might have some misconceptions about dynamic dispatch, and maybe this use case represents my doubts well.. So.. find myself in the unpleasant situation of having to use abstract con…

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## [Any way to use custom unicode inside of Julia terminal / VS Code?](https://discourse.julialang.org/t/any-way-to-use-custom-unicode-inside-of-julia-terminal-vs-code/132594)

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**Author:** [@Ahmed\_Salih](https://discourse.julialang.org/u/Ahmed_Salih)\
**Replies:** 5\
**Last updated:** [September 24, 2025, 12:39am UTC](https://discourse.julialang.org/t/any-way-to-use-custom-unicode-inside-of-julia-terminal-vs-code/132594 "2025-09-24T00:39:50Z")

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For example the following: Kind regards

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## [How to implement performance regression tests?](https://discourse.julialang.org/t/how-to-implement-performance-regression-tests/132578)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 5\
**Last updated:** [September 23, 2025, 9:54pm UTC](https://discourse.julialang.org/t/how-to-implement-performance-regression-tests/132578 "2025-09-23T21:54:26Z")

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I added a performance test to my package KiteModels.jl: Benchmark simplify operation by ufechner7 · Pull Request #250 · OpenSourceAWE/KiteModels.jl · GitHub. If you run the script, you get an output like: julia\> includ…

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## [Plugging DifferentiationInterface.jl into pytorch](https://discourse.julialang.org/t/plugging-differentiationinterface-jl-into-pytorch/132598)

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**Author:** [@mattsignorelli](https://discourse.julialang.org/u/mattsignorelli)\
**Replies:** 5\
**Last updated:** [September 23, 2025, 7:32pm UTC](https://discourse.julialang.org/t/plugging-differentiationinterface-jl-into-pytorch/132598 "2025-09-23T19:32:28Z")

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I preface this with saying that I really am not very experienced with both pytorch and juliatorch, and apologize for any misunderstandings that I have. We are developing a physics simulation ecosystem that can be differ…

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## [Skip Package Precompile](https://discourse.julialang.org/t/skip-package-precompile/132601)

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**Author:** [@andrewkc](https://discourse.julialang.org/u/andrewkc)\
**Replies:** 1\
**Last updated:** [September 23, 2025, 6:42pm UTC](https://discourse.julialang.org/t/skip-package-precompile/132601 "2025-09-23T18:42:56Z")

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I’m working on a cluster computer that has two nodes: a login node with low resources (memory, cpu) a compute node with no internet acess For this reason, it seems like the best workflow is to download packages on the…

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## [Julia cron like event scheduler](https://discourse.julialang.org/t/julia-cron-like-event-scheduler/6899)

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**Author:** [@scelles](https://discourse.julialang.org/u/scelles)\
**Replies:** 6\
**Last updated:** [September 23, 2025, 2:40pm UTC](https://discourse.julialang.org/t/julia-cron-like-event-scheduler/6899 "2025-09-23T14:40:16Z")

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Hello, I’m looking for a cron like scheduler written in Julia (something comparable to APScheduler or sched or schedule for Python) I haven’t found it in the Julia ecosystem… but maybe someone here know a package like…

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## [Large Sparse Hermitian Matrix - Intermediate Eigenvalue Problem](https://discourse.julialang.org/t/large-sparse-hermitian-matrix-intermediate-eigenvalue-problem/131600)

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**Author:** [@Neilis](https://discourse.julialang.org/u/Neilis)\
**Replies:** 9\
**Last updated:** [September 23, 2025, 2:22pm UTC](https://discourse.julialang.org/t/large-sparse-hermitian-matrix-intermediate-eigenvalue-problem/131600 "2025-09-23T14:22:14Z")

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Hi, I am trying to find eigenvalues and eigenvectors for a rather large, sparse, hermitian matrix (size ~1E7 x 1E7). I am mainly interested in around 40 eigenvalues in the middle of the spectrum. To solve this original…

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