# Latest

**URL:** https://discourse.julialang.org/latest.md?page=218

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

**Page:** 219

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## [Storing only rolling mean and variance when solving SDEProblems](https://discourse.julialang.org/t/storing-only-rolling-mean-and-variance-when-solving-sdeproblems/125900)

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**Author:** [@johannesnauta](https://discourse.julialang.org/u/johannesnauta)\
**Replies:** 5\
**Last updated:** [February 17, 2025, 1:51pm UTC](https://discourse.julialang.org/t/storing-only-rolling-mean-and-variance-when-solving-sdeproblems/125900 "2025-02-17T13:51:29Z")

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Hi all, I have been trying to reduce memory overhead as I found that in my systems of interest there were a lot of unnecessary reads/writes as the state was saved at each (specified) interval dt. In fact, for my purpose…

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## [Proposal: Adding Optional Static Interface/Traits Checking to Julia](https://discourse.julialang.org/t/proposal-adding-optional-static-interface-traits-checking-to-julia/125846)

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**Author:** [@Solmantos](https://discourse.julialang.org/u/Solmantos)\
**Replies:** 32\
**Last updated:** [February 17, 2025, 12:09pm UTC](https://discourse.julialang.org/t/proposal-adding-optional-static-interface-traits-checking-to-julia/125846 "2025-02-17T12:09:03Z")

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Adding Optional Static Interface Checking to Julia TL;DR Proposing a system for optional static interface checking in Julia (similar to Python’s mypy) that would: Add compile-time verification of behavioral contracts f…

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## [Second edition for Hands-on Design Patterns and Best Practices with Julia?](https://discourse.julialang.org/t/second-edition-for-hands-on-design-patterns-and-best-practices-with-julia/73940)

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**Author:** [@tk3369](https://discourse.julialang.org/u/tk3369)\
**Replies:** 5\
**Last updated:** [February 17, 2025, 11:58am UTC](https://discourse.julialang.org/t/second-edition-for-hands-on-design-patterns-and-best-practices-with-julia/73940 "2025-02-17T11:58:23Z")

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Hi there! I’m the author of the book, and I’m considering updating it with a second edition. What would you like to add/update/remove? Your opinion counts! :pray: Any new topics or language features? Any suggestions …

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## [Can Julia be installed and used on an iPhone?](https://discourse.julialang.org/t/can-julia-be-installed-and-used-on-an-iphone/99813)

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**Author:** [@WuSiren](https://discourse.julialang.org/u/WuSiren)\
**Replies:** 9\
**Last updated:** [February 17, 2025, 10:16am UTC](https://discourse.julialang.org/t/can-julia-be-installed-and-used-on-an-iphone/99813 "2025-02-17T10:16:27Z")

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I just find Julia language interesting, is it possible to carry it with me on the go? :smiley:

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## [What is the collapsed state by measuring in arbitrary basis](https://discourse.julialang.org/t/what-is-the-collapsed-state-by-measuring-in-arbitrary-basis/125939)

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**Author:** [@yao\_novice](https://discourse.julialang.org/u/yao_novice)\
**Replies:** 2\
**Last updated:** [February 17, 2025, 7:08am UTC](https://discourse.julialang.org/t/what-is-the-collapsed-state-by-measuring-in-arbitrary-basis/125939 "2025-02-17T07:08:52Z")

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Goal: Measure a 2 qubit state \\quad\\displaystyle{ |\\psi\\rangle = \\frac{1}{5} \\begin{pmatrix} 4 \\\\ 2i\\\\ 1\\\\ -2\\\\ \\end{pmatrix} } in the basis of the eigenvectors of operator X \\otimes Y This basis is \\quad\\displaystyle{…

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## [Can not start julia: dependent library libopenlibm.so](https://discourse.julialang.org/t/can-not-start-julia-dependent-library-libopenlibm-so/125973)

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**Author:** [@Stephen](https://discourse.julialang.org/u/Stephen)\
**Replies:** 1\
**Last updated:** [February 17, 2025, 3:40am UTC](https://discourse.julialang.org/t/can-not-start-julia-dependent-library-libopenlibm-so/125973 "2025-02-17T03:40:36Z")

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ERROR: Unable to load dependent library /home/rzhli/.julia/juliaup/julia-1.11.3+0.x64.linux.gnu/bin/../lib/julia/libopenlibm.so Message:/home/rzhli/.julia/juliaup/julia-1.11.3+0.x64.linux.gnu/bin/../lib/julia/libopenlibm…

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## [Installation of Plots package fails on Ubuntu 18.04](https://discourse.julialang.org/t/installation-of-plots-package-fails-on-ubuntu-18-04/125932)

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**Author:** [@fanzhy171](https://discourse.julialang.org/u/fanzhy171)\
**Replies:** 16\
**Last updated:** [February 17, 2025, 2:20am UTC](https://discourse.julialang.org/t/installation-of-plots-package-fails-on-ubuntu-18-04/125932 "2025-02-17T02:20:15Z")

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Hello everyone. I met a problem when install Plots.jl package. The problem is I always failed to precompile a few things. I tried to look it up, but the solution of the past post is not clear enough for me, so I just sta…

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## [Macro to substitute parameters used for JuMP model](https://discourse.julialang.org/t/macro-to-substitute-parameters-used-for-jump-model/125936)

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**Author:** [@KSepetanc](https://discourse.julialang.org/u/KSepetanc)\
**Replies:** 2\
**Last updated:** [February 16, 2025, 11:27pm UTC](https://discourse.julialang.org/t/macro-to-substitute-parameters-used-for-jump-model/125936 "2025-02-16T23:27:24Z")

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I read available topics on macros but still can not make working macro to substitute parameter. What I want is instead of creating new variable (for example Pmax) to use @Pmax macro that will expand @Pmax(g) to data\[:gen…

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## [Parameters of the neural network not updating after training in a Neural ODE problem](https://discourse.julialang.org/t/parameters-of-the-neural-network-not-updating-after-training-in-a-neural-ode-problem/125554)

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**Author:** [@Ashima\_Kalathingal](https://discourse.julialang.org/u/Ashima_Kalathingal)\
**Replies:** 13\
**Last updated:** [February 16, 2025, 10:57pm UTC](https://discourse.julialang.org/t/parameters-of-the-neural-network-not-updating-after-training-in-a-neural-ode-problem/125554 "2025-02-16T22:57:09Z")

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Hello, I have been struggling with this problem for some time now. I have constructed an example neural ode problem related to my work using the following example. https://docs.sciml.ai/Overview/stable/showcase/missing\_…

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## [How to easily save Julia data?](https://discourse.julialang.org/t/how-to-easily-save-julia-data/125955)

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**Author:** [@Xu\_Shan](https://discourse.julialang.org/u/Xu_Shan)\
**Replies:** 5\
**Last updated:** [February 16, 2025, 8:32pm UTC](https://discourse.julialang.org/t/how-to-easily-save-julia-data/125955 "2025-02-16T20:32:24Z")

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Hi guys, I am wondering is there a way like pickle in python to save the output data from Julia calculations? maybe it can support arrays, dict, tuples? for example, if I have a dict of which each key stores a different…

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## [USD format?](https://discourse.julialang.org/t/usd-format/22064)

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**Author:** [@Orbots](https://discourse.julialang.org/u/Orbots)\
**Replies:** 3\
**Last updated:** [February 16, 2025, 8:39pm UTC](https://discourse.julialang.org/t/usd-format/22064 "2025-02-16T20:39:14Z")

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Are there any current packages around that support USD in some form? https://graphics.pixar.com/usd/docs/Introduction-to-USD.html Looks like it’s becoming the way to exchange 3D scenes between applications. I’m inter…

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## [Reducing app size](https://discourse.julialang.org/t/reducing-app-size/125957)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 1\
**Last updated:** [February 16, 2025, 1:23pm UTC](https://discourse.julialang.org/t/reducing-app-size/125957 "2025-02-16T13:23:34Z")

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I have a package that I want deploy as application in a docker container. I am trying to reduce the size. Current sizes: 1,7G /tmp/testdepot/ 514M /tmp/test The second item is mainly the compiled system image. I…

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## [Metaprogramming to automatically test new versions of code](https://discourse.julialang.org/t/metaprogramming-to-automatically-test-new-versions-of-code/125899)

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**Author:** [@JADekker](https://discourse.julialang.org/u/JADekker)\
**Replies:** 9\
**Last updated:** [February 16, 2025, 6:32am UTC](https://discourse.julialang.org/t/metaprogramming-to-automatically-test-new-versions-of-code/125899 "2025-02-16T06:32:56Z")

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In writing my code, I often find that I wish to test if a certain function, say f, can be made quicker. One way of doing this is to find a place within my code where the function gets used and run f and some f\_quick base…

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## [How to constraint the inner type of \`Val\` by an abstract type](https://discourse.julialang.org/t/how-to-constraint-the-inner-type-of-val-by-an-abstract-type/125944)

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**Author:** [@zsoerenm](https://discourse.julialang.org/u/zsoerenm)\
**Replies:** 4\
**Last updated:** [February 16, 2025, 4:25am UTC](https://discourse.julialang.org/t/how-to-constraint-the-inner-type-of-val-by-an-abstract-type/125944 "2025-02-16T04:25:20Z")

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How can I constraint the parametric type within Val by an abstract type? Consider the following function using Unitful: Frequency, Hz function foo(q::Val{Q}) where Q \<: Frequency return q end I’d like to Q to be …

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## [Question about compilation time of the whole language](https://discourse.julialang.org/t/question-about-compilation-time-of-the-whole-language/125882)

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**Author:** [@CiccioPasticcio](https://discourse.julialang.org/u/CiccioPasticcio)\
**Replies:** 7\
**Last updated:** [February 15, 2025, 8:56pm UTC](https://discourse.julialang.org/t/question-about-compilation-time-of-the-whole-language/125882 "2025-02-15T20:56:18Z")

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Hello everyone, I was trying in these days for the first time to work on julia internals. I havea a question about the time it takes to compile the whole language. So my usual workflow is: modify some code, compile the l…

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## [How to create an equation with a symbolic matrix using SymPy.jl?](https://discourse.julialang.org/t/how-to-create-an-equation-with-a-symbolic-matrix-using-sympy-jl/125937)

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**Author:** [@jcbritobr](https://discourse.julialang.org/u/jcbritobr)\
**Replies:** 2\
**Last updated:** [February 15, 2025, 7:07pm UTC](https://discourse.julialang.org/t/how-to-create-an-equation-with-a-symbolic-matrix-using-sympy-jl/125937 "2025-02-15T19:07:06Z")

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Hello, good morning. How to build an equation using a symbolic matrix with SymPy.jl? Using python, I would just call sympy.Matrix class. In julia, we have Matrix in SymPy package, but it seems not create a symbol, and …

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## [Interpreting TuringBenchmarking.jl output?](https://discourse.julialang.org/t/interpreting-turingbenchmarking-jl-output/119356)

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**Author:** [@rkube](https://discourse.julialang.org/u/rkube)\
**Replies:** 1\
**Last updated:** [February 15, 2025, 6:13pm UTC](https://discourse.julialang.org/t/interpreting-turingbenchmarking-jl-output/119356 "2025-02-15T18:13:01Z")

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Hi, I’m trying to benchmark a turing model as described here and it’s not really clear to me what the output means: 2-element BenchmarkTools.BenchmarkGroup: tags: \[\] "evaluation" =\> 2-element BenchmarkTools.Benchma…

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## [\[DICE: GAMS -\> JuMP\] How to debug JuMP model errors (find the culpit)?](https://discourse.julialang.org/t/dice-gams-jump-how-to-debug-jump-model-errors-find-the-culpit/125578)

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**Author:** [@sylvaticus](https://discourse.julialang.org/u/sylvaticus)\
**Replies:** 6\
**Last updated:** [February 15, 2025, 4:15pm UTC](https://discourse.julialang.org/t/dice-gams-jump-how-to-debug-jump-model-errors-find-the-culpit/125578 "2025-02-15T16:15:00Z")

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Hello, this post il dual :slight\_smile: It’s at the same time a request for help for a specific case, but also a much more general question. I am trying to port the Nordhaus’s DICE climate change model v2023 to Julia, …

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## [Why can't I use hcat in a for-loop?](https://discourse.julialang.org/t/why-cant-i-use-hcat-in-a-for-loop/125935)

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**Author:** [@Xu\_Shan](https://discourse.julialang.org/u/Xu_Shan)\
**Replies:** 9\
**Last updated:** [February 15, 2025, 4:10pm UTC](https://discourse.julialang.org/t/why-cant-i-use-hcat-in-a-for-loop/125935 "2025-02-15T16:10:21Z")

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Hi guys, I am trying to concatenate rows into an empty dataframe using a for-loop like this: sensitivity\_mean\_df = DataFrame() base\_df = DataFrame() for variable in variables if isempty(base\_df) base\_df = D…

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## [PyCall returning numpy arrays](https://discourse.julialang.org/t/pycall-returning-numpy-arrays/125836)

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**Author:** [@RainerHeintzmann](https://discourse.julialang.org/u/RainerHeintzmann)\
**Replies:** 19\
**Last updated:** [February 15, 2025, 9:35am UTC](https://discourse.julialang.org/t/pycall-returning-numpy-arrays/125836 "2025-02-15T09:35:54Z")

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I am trying to return a numpy array to Julia without copying. It took me some time to understand that pycall(py"myPythonFunctionReturningaNumPyArray", PyArray, filename) seems to be the only way to prevent the system …

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## [Invitation to participate in the International Symposium on Symbolic and Algebraic Computation](https://discourse.julialang.org/t/invitation-to-participate-in-the-international-symposium-on-symbolic-and-algebraic-computation/125930)

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**Author:** [@suavesito](https://discourse.julialang.org/u/suavesito)\
**Replies:** 0\
**Last updated:** [February 15, 2025, 2:29am UTC](https://discourse.julialang.org/t/invitation-to-participate-in-the-international-symposium-on-symbolic-and-algebraic-computation/125930 "2025-02-15T02:29:22Z")

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This year, the International Symposium on Symbolic and Algebraic Computation (ISSAC) will take place from July 28 to August 1, 2025 (dates and topics page) at CIMAT Guanajuato, Mexico, where I study. I wanted to invite …

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## [Trouble trying to implement DifferentialEquations.jl integrator in an agent\_step() for a model in Agents.jl?](https://discourse.julialang.org/t/trouble-trying-to-implement-differentialequations-jl-integrator-in-an-agent-step-for-a-model-in-agents-jl/125920)

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**Author:** [@raylv17](https://discourse.julialang.org/u/raylv17)\
**Replies:** 1\
**Last updated:** [February 14, 2025, 11:41pm UTC](https://discourse.julialang.org/t/trouble-trying-to-implement-differentialequations-jl-integrator-in-an-agent-step-for-a-model-in-agents-jl/125920 "2025-02-14T23:41:59Z")

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I have created a continuous ABM model using Agents.jl, however, I wish to incorporate an Integrator from the DifferentialEquations.jl package to be used in the agent\_step!() function. Though I am having trouble in the im…

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## [Prioritization of multiple submissions per person](https://discourse.julialang.org/t/prioritization-of-multiple-submissions-per-person/125927)

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**Author:** [@GabrielKS](https://discourse.julialang.org/u/GabrielKS)\
**Replies:** 1\
**Last updated:** [February 14, 2025, 11:28pm UTC](https://discourse.julialang.org/t/prioritization-of-multiple-submissions-per-person/125927 "2025-02-14T23:28:21Z")

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Hello! I will be submitting to JuliaCon 2025 a 30-minute talk proposal on a package I develop as part of my day job. I’m also interested in submitting a lightning talk, “experience,” or poster on a recreational Julia sid…

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## [Trouble using Mmap](https://discourse.julialang.org/t/trouble-using-mmap/125924)

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**Author:** [@ilanggear](https://discourse.julialang.org/u/ilanggear)\
**Replies:** 5\
**Last updated:** [February 14, 2025, 11:00pm UTC](https://discourse.julialang.org/t/trouble-using-mmap/125924 "2025-02-14T23:00:07Z")

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Hi, I’m exploring the use of mmap and getting the error below when mmap is called The line is: countIndex = mmap(“tmp”, Matrix{UInt32}, (NUM\_BIGRAMS,30); shared=false) I’ve also tried a file handle as produced by ‘ope…

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## [Another sorting algorithm](https://discourse.julialang.org/t/another-sorting-algorithm/125884)

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**Author:** [@xiaodai](https://discourse.julialang.org/u/xiaodai)\
**Replies:** 1\
**Last updated:** [February 14, 2025, 10:02pm UTC](https://discourse.julialang.org/t/another-sorting-algorithm/125884 "2025-02-14T22:02:53Z")

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Julia has the base sort which has massive improved and also a couple of more experimental libraries including SortingAlgorithms.jl and SortingLab.jl. I saw a sorting algorithm on Hacker News today which genuinely sounds…

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## [Local macros](https://discourse.julialang.org/t/local-macros/125539)

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**Author:** [@Mark\_Nahabedian](https://discourse.julialang.org/u/Mark_Nahabedian)\
**Replies:** 4\
**Last updated:** [February 14, 2025, 6:42pm UTC](https://discourse.julialang.org/t/local-macros/125539 "2025-02-14T18:42:38Z")

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In CommonLisp one can define local macros using MACROLET. Julia doesn’t have local macros, but one can imagine that a given global macro could provide local macros for use wwithin its body using a code walker and rules …

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## [Elapsed + allocated?](https://discourse.julialang.org/t/elapsed-allocated/125910)

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**Author:** [@Sarah\_Groves](https://discourse.julialang.org/u/Sarah_Groves)\
**Replies:** 4\
**Last updated:** [February 14, 2025, 5:08pm UTC](https://discourse.julialang.org/t/elapsed-allocated/125910 "2025-02-14T17:08:53Z")

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I am familiar with the @elapsed and @allocated functions that allow me to save as a variable either the elapsed time and allocated memory during a function run (respectively). Is there a method that will return both vari…

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## [Why is the NamedTuple slower? When/How would it be faster? Is it still allocated on the stack?](https://discourse.julialang.org/t/why-is-the-namedtuple-slower-when-how-would-it-be-faster-is-it-still-allocated-on-the-stack/125902)

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**Author:** [@Vik1](https://discourse.julialang.org/u/Vik1)\
**Replies:** 6\
**Last updated:** [February 14, 2025, 4:54pm UTC](https://discourse.julialang.org/t/why-is-the-namedtuple-slower-when-how-would-it-be-faster-is-it-still-allocated-on-the-stack/125902 "2025-02-14T16:54:48Z")

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In the following case, the Dict beats the NamedTuple in the creation and in the lookup? Why is this the case? Am I missing something? using BenchmarkTools tup1 = NamedTuple(k =\> v for (k, v) in \[(:a, 5), (:b, 10)\]) tup…

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## [Compilation problem](https://discourse.julialang.org/t/compilation-problem/125907)

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**Author:** [@gustave\_Robichon](https://discourse.julialang.org/u/gustave_Robichon)\
**Replies:** 3\
**Last updated:** [February 14, 2025, 4:21pm UTC](https://discourse.julialang.org/t/compilation-problem/125907 "2025-02-14T16:21:29Z")

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Hello :slight\_smile: I am using the package QuantumOptics. I use the function : timeevolution.master\_h(T, rho0, H, L). I get this compilation error (see below). I think I have updated the packages, and a version changed…

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## [ForwardDiff + Adaptive ODE Solvers: Timestep Issue Leads to Incorrect Derivatives](https://discourse.julialang.org/t/forwarddiff-adaptive-ode-solvers-timestep-issue-leads-to-incorrect-derivatives/125870)

<div class="topic-metadata">

**Author:** [@abavoil](https://discourse.julialang.org/u/abavoil)\
**Replies:** 5\
**Last updated:** [February 14, 2025, 3:08pm UTC](https://discourse.julialang.org/t/forwarddiff-adaptive-ode-solvers-timestep-issue-leads-to-incorrect-derivatives/125870 "2025-02-14T15:08:36Z")

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Hello dear Julia community, TLDR; Passing dual numbers (ForwardDiff.jl) into an adaptative-step ODE solver (OrdinaryDiffEq.jl) affects the timestep choice, making the derivative incorrect. Let’s say we have a function …

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