# Latest

**URL:** https://discourse.julialang.org/latest.md?page=477

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

**Page:** 478

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## [What is julia doing with your threads?](https://discourse.julialang.org/t/what-is-julia-doing-with-your-threads/110052)

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**Author:** [@PetrKryslUCSD](https://discourse.julialang.org/u/PetrKryslUCSD)\
**Replies:** 23\
**Last updated:** [February 21, 2024, 10:04pm UTC](https://discourse.julialang.org/t/what-is-julia-doing-with-your-threads/110052 "2024-02-21T22:04:26Z")

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As documented here and in this thread, spinning up julia with a certain number of threads, let us say N, and then starting (N-1) tasks does not necessarily mean that all the tasks will have a thread to run on. It appear…

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## [Macro: extract the method name, arguments and the body](https://discourse.julialang.org/t/macro-extract-the-method-name-arguments-and-the-body/110343)

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**Author:** [@putianyi888](https://discourse.julialang.org/u/putianyi888)\
**Replies:** 3\
**Last updated:** [February 21, 2024, 10:00pm UTC](https://discourse.julialang.org/t/macro-extract-the-method-name-arguments-and-the-body/110343 "2024-02-21T22:00:44Z")

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There are two syntaxes that I know that defines a function: julia\> Meta.@dump function f(x) x end Expr head: Symbol function args: Array{Any}((2,)) 1: Expr head: Symbol call args: Array…

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## [Error when using LawsonEuler method on SplitODE](https://discourse.julialang.org/t/error-when-using-lawsoneuler-method-on-splitode/110495)

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**Author:** [@ian](https://discourse.julialang.org/u/ian)\
**Replies:** 1\
**Last updated:** [February 21, 2024, 9:52pm UTC](https://discourse.julialang.org/t/error-when-using-lawsoneuler-method-on-splitode/110495 "2024-02-21T21:52:32Z")

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Hi all. I have a Split/Semiinear ODE I want to solve efficiently. The docs suggest the LawsonEuler algorithm. I tried to implement but am running into an error I don’t understand. Here is a MWE using DifferentialEquatio…

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## [Symbolics coefficients](https://discourse.julialang.org/t/symbolics-coefficients/110541)

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**Author:** [@jar1](https://discourse.julialang.org/u/jar1)\
**Replies:** 1\
**Last updated:** [February 21, 2024, 9:44pm UTC](https://discourse.julialang.org/t/symbolics-coefficients/110541 "2024-02-21T21:44:54Z")

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What is happening? How do I get 4 out of this? using Symbolics @variables a b julia\> Symbolics.coeff(4a\*b).dict Dict{Any, Any} with 2 entries: a =\> 1 b =\> 1

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## [How to add other arguments to function turned to LinearOperator?](https://discourse.julialang.org/t/how-to-add-other-arguments-to-function-turned-to-linearoperator/110475)

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**Author:** [@erny123](https://discourse.julialang.org/u/erny123)\
**Replies:** 3\
**Last updated:** [February 21, 2024, 9:16pm UTC](https://discourse.julialang.org/t/how-to-add-other-arguments-to-function-turned-to-linearoperator/110475 "2024-02-21T21:16:47Z")

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Trying to write a matrix-free solver using LinearOperators.jl and Krylov.jl However, from this: Introduction to Linear Operators I’m seeing that you can only use functions that follow the 5-argument (and 3) mul! operat…

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## [Plotting ODEProblem solutions with Makie](https://discourse.julialang.org/t/plotting-odeproblem-solutions-with-makie/58096)

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**Author:** [@airpmb](https://discourse.julialang.org/u/airpmb)\
**Replies:** 6\
**Last updated:** [February 21, 2024, 8:39pm UTC](https://discourse.julialang.org/t/plotting-odeproblem-solutions-with-makie/58096 "2024-02-21T20:39:26Z")

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Whatever (plot recipes?) allows for the solution output from solving an ODEProblem in ModelingToolkit.jl (or maybe just OrdinaryDiffEq.jl?) to be just plotted using Plots.jl is wonderful and magical. I love how it’s poss…

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## [Mul! generates machine noise](https://discourse.julialang.org/t/mul-generates-machine-noise/110477)

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**Author:** [@Enlil50](https://discourse.julialang.org/u/Enlil50)\
**Replies:** 21\
**Last updated:** [February 21, 2024, 8:24pm UTC](https://discourse.julialang.org/t/mul-generates-machine-noise/110477 "2024-02-21T20:24:06Z")

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I have this simple matrix multiplication, but at the last step some machine noise is created and I don’t know why. This doesn’t happen in other programming languages. using LinearAlgebra function myfun1() a = 0.707…

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## [Get length of a fully represented float](https://discourse.julialang.org/t/get-length-of-a-fully-represented-float/110521)

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**Author:** [@HenriDeh](https://discourse.julialang.org/u/HenriDeh)\
**Replies:** 12\
**Last updated:** [February 21, 2024, 7:42pm UTC](https://discourse.julialang.org/t/get-length-of-a-fully-represented-float/110521 "2024-02-21T19:42:57Z")

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Hello, I must work with a dataset of float numerical entries. A few of them (like 0.1%) are really small and thus are written in e-notation (e.g. 1.87589e-17). I’m passing this dataset to a C program via Julia and appar…

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## [Julia Pragma Macros](https://discourse.julialang.org/t/julia-pragma-macros/110532)

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**Author:** [@mnemnion](https://discourse.julialang.org/u/mnemnion)\
**Replies:** 4\
**Last updated:** [February 21, 2024, 7:33pm UTC](https://discourse.julialang.org/t/julia-pragma-macros/110532 "2024-02-21T19:33:22Z")

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Continuing the discussion from Ifelse vs ternary with tuples: Julia has a few “pragma macros” already and I agree more would be nice. The current collection, such as @inline and @inbounds/@boundscheck, focus on compil…

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## [Lazy constraints & issues with presolve](https://discourse.julialang.org/t/lazy-constraints-issues-with-presolve/110449)

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**Author:** [@salvaguerrero](https://discourse.julialang.org/u/salvaguerrero)\
**Replies:** 3\
**Last updated:** [February 21, 2024, 7:32pm UTC](https://discourse.julialang.org/t/lazy-constraints-issues-with-presolve/110449 "2024-02-21T19:32:55Z")

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Good morning community, I’m trying to use lazy constraints, but I’m finding some issues. I would like to solve a problem iterative (benders decomposition) where in each iteration an additional constraint is added as la…

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## [Finite difference Laplacian with five-point stencil](https://discourse.julialang.org/t/finite-difference-laplacian-with-five-point-stencil/25014)

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**Author:** [@Vortico](https://discourse.julialang.org/u/Vortico)\
**Replies:** 8\
**Last updated:** [February 21, 2024, 7:23pm UTC](https://discourse.julialang.org/t/finite-difference-laplacian-with-five-point-stencil/25014 "2024-02-21T19:23:31Z")

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This is my first day learning Julia, and I’m not sure of an elegant way to compute the finite difference Laplacian on an NxM Float32 array. \\Delta f(x,y) \\approx f(x-1,y) + f(x+1,y) + f(x,y-1) + f(x,y+1) - 4f(x,y) Base…

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## [Random seed initialization with splitmix](https://discourse.julialang.org/t/random-seed-initialization-with-splitmix/110426)

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**Author:** [@Enlil50](https://discourse.julialang.org/u/Enlil50)\
**Replies:** 6\
**Last updated:** [February 21, 2024, 7:02pm UTC](https://discourse.julialang.org/t/random-seed-initialization-with-splitmix/110426 "2024-02-21T19:02:16Z")

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I know that to use Xoshiro256++ is better to randomize the seed with a fast rng as splitmix. This enables us to generate the 4 states of xoshiro256++. Is this done by default?

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## [CairoMakie get 3d plots to respect z order](https://discourse.julialang.org/t/cairomakie-get-3d-plots-to-respect-z-order/110428)

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**Author:** [@p\_f](https://discourse.julialang.org/u/p_f)\
**Replies:** 5\
**Last updated:** [February 21, 2024, 6:09pm UTC](https://discourse.julialang.org/t/cairomakie-get-3d-plots-to-respect-z-order/110428 "2024-02-21T18:09:59Z")

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I’m trying to export figure as a PDF using CairoMakie. Some of my subplots are 3d axes. I’m plotting several surfaces that wrap around each other, so some parts of surface A are behind surface B and some parts are in fro…

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## [Help finding a graphic explaining scientific computing that I have seen here before](https://discourse.julialang.org/t/help-finding-a-graphic-explaining-scientific-computing-that-i-have-seen-here-before/110527)

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**Author:** [@cmichelenstrofer](https://discourse.julialang.org/u/cmichelenstrofer)\
**Replies:** 2\
**Last updated:** [February 21, 2024, 4:44pm UTC](https://discourse.julialang.org/t/help-finding-a-graphic-explaining-scientific-computing-that-i-have-seen-here-before/110527 "2024-02-21T16:44:27Z")

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There’s this graphic I am pretty sure I saw here (maybe as a link) but I can’t find it now :frowning: . Any help is appreciated! Description: It explains what computational scientist (or Research Software Engineer) is.…

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## [2024: Tables.jl vs TableTraits.jl/IterableTables.jl?](https://discourse.julialang.org/t/2024-tables-jl-vs-tabletraits-jl-iterabletables-jl/110524)

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**Author:** [@schlichtanders](https://discourse.julialang.org/u/schlichtanders)\
**Replies:** 1\
**Last updated:** [February 21, 2024, 4:31pm UTC](https://discourse.julialang.org/t/2024-tables-jl-vs-tabletraits-jl-iterabletables-jl/110524 "2024-02-21T16:31:51Z")

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It is 6 years after Tables.jl appeared and when I am searching for this vs TableTraits.jl / IterableTables.jl I still get pointed to this old thread. It seems that the queryverse never switched to Tables.jl, hence this …

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## [Help to find package for DSA (Discrete Stochastic Arithmetic) implementation](https://discourse.julialang.org/t/help-to-find-package-for-dsa-discrete-stochastic-arithmetic-implementation/110391)

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**Author:** [@hungpham3112](https://discourse.julialang.org/u/hungpham3112)\
**Replies:** 5\
**Last updated:** [February 21, 2024, 4:30pm UTC](https://discourse.julialang.org/t/help-to-find-package-for-dsa-discrete-stochastic-arithmetic-implementation/110391 "2024-02-21T16:30:44Z")

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Hi, I’m working in a project where we use DSA method (based-on CESTAC) to validate results of numerical software. Currently, I’m using Cadna (written in C) to solve this problem. The advantage of Cadna is it has example …

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## [Is there a function inverse of \`Logging.disable\_logging\`?](https://discourse.julialang.org/t/is-there-a-function-inverse-of-logging-disable-logging/110525)

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**Author:** [@LaurentPlagne](https://discourse.julialang.org/u/LaurentPlagne)\
**Replies:** 0\
**Last updated:** [February 21, 2024, 4:22pm UTC](https://discourse.julialang.org/t/is-there-a-function-inverse-of-logging-disable-logging/110525 "2024-02-21T16:22:21Z")

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Hi, I find the following function very useful for switching my computations from a dev mode to a production mode: Logging.disable\_logging(Logging.Info) Unfortunately, if I want to switch back, I can’t just remove the …

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## [Passing \`Symbol\` variable allocates when literal does not?](https://discourse.julialang.org/t/passing-symbol-variable-allocates-when-literal-does-not/110518)

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**Author:** [@bremez](https://discourse.julialang.org/u/bremez)\
**Replies:** 4\
**Last updated:** [February 21, 2024, 4:04pm UTC](https://discourse.julialang.org/t/passing-symbol-variable-allocates-when-literal-does-not/110518 "2024-02-21T16:04:44Z")

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I have the following snippet: function preparearrays!(arrays, N, L; mode = :all) for n in 0:(length(arrays)-1) if mode === :all for m in 0:(L-1) # run till length L to zero all bits …

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## [Mean Reversion Strategy in Julia](https://discourse.julialang.org/t/mean-reversion-strategy-in-julia/110523)

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**Author:** [@jaketothepast](https://discourse.julialang.org/u/jaketothepast)\
**Replies:** 0\
**Last updated:** [February 21, 2024, 3:53pm UTC](https://discourse.julialang.org/t/mean-reversion-strategy-in-julia/110523 "2024-02-21T15:53:00Z")

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Hello all! I love Julia, I’ve been using it off-and-on for many years. I’m doing a challenge where I ship 12 projects this year, and this month’s project was to dive into Quant. I’m extremely interested in the world of …

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## [Newbie delete elements from array question](https://discourse.julialang.org/t/newbie-delete-elements-from-array-question/110481)

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**Author:** [@brombo](https://discourse.julialang.org/u/brombo)\
**Replies:** 10\
**Last updated:** [February 21, 2024, 3:29pm UTC](https://discourse.julialang.org/t/newbie-delete-elements-from-array-question/110481 "2024-02-21T15:29:20Z")

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I have an 1-D array A and an array of integers index that contains some of the indices of array A. I want to compute a new array from A with the elements with indices in index removed. Is there a slick Julia way of doi…

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## [Julia documentation not available from Firefox](https://discourse.julialang.org/t/julia-documentation-not-available-from-firefox/110502)

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**Author:** [@tvali](https://discourse.julialang.org/u/tvali)\
**Replies:** 9\
**Last updated:** [February 21, 2024, 2:00pm UTC](https://discourse.julialang.org/t/julia-documentation-not-available-from-firefox/110502 "2024-02-21T14:00:33Z")

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Hello! I cannot access installed Julia html documentation from firefox - it says Acess Denied. The documentation is located at file:///snap/julia/92/share/doc/julia/html/en/index.html and is the one, which comes with th…

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## [Storing comparisons](https://discourse.julialang.org/t/storing-comparisons/110513)

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**Author:** [@Enlil50](https://discourse.julialang.org/u/Enlil50)\
**Replies:** 1\
**Last updated:** [February 21, 2024, 1:58pm UTC](https://discourse.julialang.org/t/storing-comparisons/110513 "2024-02-21T13:58:54Z")

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I have a program which computes a number, stores it and uses it for many times. Then it proceeds to the next iteration (it’s a loop), generates another number, stores it and uses it as well for many times. Considering …

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## [Non-GPL sparse arrays and/or 3D+ sparse](https://discourse.julialang.org/t/non-gpl-sparse-arrays-and-or-3d-sparse/110510)

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**Author:** [@Palli](https://discourse.julialang.org/u/Palli)\
**Replies:** 0\
**Last updated:** [February 21, 2024, 12:21pm UTC](https://discourse.julialang.org/t/non-gpl-sparse-arrays-and-or-3d-sparse/110510 "2024-02-21T12:21:00Z")

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Currently Julia is GPLed, seemingly, even in 1.11-DEV: julia\> Base.USE\_GPL\_LIBS true I thought the SuiteSparse GPL dependency had been dropped (making Julia non-copyleft in 1.10) and SparseArrays.jl independent of it. …

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## [How to use Registrator.jl for private registry](https://discourse.julialang.org/t/how-to-use-registrator-jl-for-private-registry/110453)

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**Author:** [@SunnyUser](https://discourse.julialang.org/u/SunnyUser)\
**Replies:** 4\
**Last updated:** [February 21, 2024, 11:48am UTC](https://discourse.julialang.org/t/how-to-use-registrator-jl-for-private-registry/110453 "2024-02-21T11:48:01Z")

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Hi all :slight\_smile: I’m currently setting up a private registry for our company packages. I checked out LocalRegistry.jl and Registrator.jl. Seems like Registrator.jl is only used for the general registry though. My …

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## [Subplots CairoMakie](https://discourse.julialang.org/t/subplots-cairomakie/110504)

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**Author:** [@Sergey\_Novak](https://discourse.julialang.org/u/Sergey_Novak)\
**Replies:** 4\
**Last updated:** [February 21, 2024, 9:43am UTC](https://discourse.julialang.org/t/subplots-cairomakie/110504 "2024-02-21T09:43:43Z")

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Hello, i want plot N subplots and off for all subplots ticks on axis. For example i do it in python with matplotlib. How can i do this with CairoMakie? Thank you for your helps

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## [Ifelse vs ternary with tuples](https://discourse.julialang.org/t/ifelse-vs-ternary-with-tuples/110423)

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**Author:** [@moble](https://discourse.julialang.org/u/moble)\
**Replies:** 6\
**Last updated:** [February 21, 2024, 9:03am UTC](https://discourse.julialang.org/t/ifelse-vs-ternary-with-tuples/110423 "2024-02-21T09:03:02Z")

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I believe I have the basic idea of when to use ifelse instead of the ternary operator. Basically, ifelse avoids an expensive branch, but computes the two possibilities — which may be more expensive. (Also ifelse may be…

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## [How to hand-craft an edge into a Pluto's a computational graph?](https://discourse.julialang.org/t/how-to-hand-craft-an-edge-into-a-plutos-a-computational-graph/108619)

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**Author:** [@vvbond](https://discourse.julialang.org/u/vvbond)\
**Replies:** 11\
**Last updated:** [February 21, 2024, 9:00am UTC](https://discourse.julialang.org/t/how-to-hand-craft-an-edge-into-a-plutos-a-computational-graph/108619 "2024-02-21T09:00:33Z")

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Consider the following contrived example of a Pluto notebook: First of all, I have a hard time even to visualise the corresponding computational graph. Below is my attempt to indicate by the dashed arrow that the com…

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## [How come a struct is type unstable, if too many different field types?](https://discourse.julialang.org/t/how-come-a-struct-is-type-unstable-if-too-many-different-field-types/110447)

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**Author:** [@Ahmed\_Salih](https://discourse.julialang.org/u/Ahmed_Salih)\
**Replies:** 2\
**Last updated:** [February 21, 2024, 12:38am UTC](https://discourse.julialang.org/t/how-come-a-struct-is-type-unstable-if-too-many-different-field-types/110447 "2024-02-21T00:38:27Z")

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Hello! The real code is a bit of a mess, so just giving an example and looking for a hint. I have defined a struct as: @with\_kw struct CLL{I,T,D} Points::Vector{SVector{D,T}} MaxValidIndex::Base.RefValue{Int} =…

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## [KrylovKit, syntax issue](https://discourse.julialang.org/t/krylovkit-syntax-issue/110359)

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**Author:** [@Enlil50](https://discourse.julialang.org/u/Enlil50)\
**Replies:** 28\
**Last updated:** [February 21, 2024, 8:25am UTC](https://discourse.julialang.org/t/krylovkit-syntax-issue/110359 "2024-02-21T08:25:37Z")

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So, I’m trying to use Lanczos diagnalization of a sparse marix of float64. Now I don’t want to specify the hint x0, so i just use rand(): Energy\[i\], psi\_ground, info = eigsolve(H\_super, rand(Float64, m\*2), 1, :SR, Lancz…

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## [List of matrices](https://discourse.julialang.org/t/list-of-matrices/110456)

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**Author:** [@Enlil50](https://discourse.julialang.org/u/Enlil50)\
**Replies:** 6\
**Last updated:** [February 21, 2024, 7:33am UTC](https://discourse.julialang.org/t/list-of-matrices/110456 "2024-02-21T07:33:14Z")

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Is there something better than this, to hold matrices? (not that i complain, just curious) C = Vector{AbstractMatrix{Float64}}(undef, 2) for i = 1:2 A = rand(Float64, i\*2, i\*2) display(A) C\[i\] = A end displa…

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