# Latest

**URL:** https://discourse.julialang.org/latest.md?page=1083

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

**Page:** 1084

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## [Solving a symmetric block tridiagonal system](https://discourse.julialang.org/t/solving-a-symmetric-block-tridiagonal-system/78623)

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**Author:** [@jinml](https://discourse.julialang.org/u/jinml)\
**Replies:** 3\
**Last updated:** [March 29, 2022, 9:13am UTC](https://discourse.julialang.org/t/solving-a-symmetric-block-tridiagonal-system/78623 "2022-03-29T09:13:30Z")

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I have a linear system in a symmetric block tridiagonal form, where each diagonal block is symmetric and invertible, but may be of varying sizes. There is no other structural advantage to make use of as far as I can see …

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## [Inconsistencies in Julia syntax and semantics](https://discourse.julialang.org/t/inconsistencies-in-julia-syntax-and-semantics/78577)

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**Author:** [@nharr](https://discourse.julialang.org/u/nharr)\
**Replies:** 7\
**Last updated:** [March 29, 2022, 9:12am UTC](https://discourse.julialang.org/t/inconsistencies-in-julia-syntax-and-semantics/78577 "2022-03-29T09:12:19Z")

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I’m not sure where is right for an average user to put their thoughts, but I’ll give it a try here. I’m interested in some inconsistencies (as I see them) in Julia that I can only guess arose from its developmental root…

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## [Solving 1+u''(x) = b(x) with DiffEqOperators](https://discourse.julialang.org/t/solving-1-u-x-b-x-with-diffeqoperators/78653)

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**Author:** [@Ruvi\_Lecamwasam](https://discourse.julialang.org/u/Ruvi_Lecamwasam)\
**Replies:** 2\
**Last updated:** [March 29, 2022, 9:02am UTC](https://discourse.julialang.org/t/solving-1-u-x-b-x-with-diffeqoperators/78653 "2022-03-29T09:02:47Z")

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Suppose b(x) is a function of a variable x, and let Dxx represent the second derivative d^2x/dx^2. Then the differential equation 1+Dxx u = b has solution u = (1+Dxx)\\b. I can’t figure out how to do this with DiffEqO…

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## [Correctly splatting for String Tuples](https://discourse.julialang.org/t/correctly-splatting-for-string-tuples/78655)

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**Author:** [@mwhisena](https://discourse.julialang.org/u/mwhisena)\
**Replies:** 3\
**Last updated:** [March 29, 2022, 8:27am UTC](https://discourse.julialang.org/t/correctly-splatting-for-string-tuples/78655 "2022-03-29T08:27:24Z")

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I’m attempting to splat two string tuples (n and m dims) so that they create a n by m array with the combinations of every element together. So if I have data= ( ("1.20e3", "1.08e3", "0.96e3"), …

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## [Cannot submit a new package, because "registry is dirty"](https://discourse.julialang.org/t/cannot-submit-a-new-package-because-registry-is-dirty/78654)

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**Author:** [@nabla](https://discourse.julialang.org/u/nabla)\
**Replies:** 2\
**Last updated:** [March 29, 2022, 8:23am UTC](https://discourse.julialang.org/t/cannot-submit-a-new-package-because-registry-is-dirty/78654 "2022-03-29T08:23:55Z")

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I just tried to submit a new package to the registrator JuliaHub and there’s a failure at the “AutoMerge” test, with message \[ Info: Attempting to \`Pkg.add\` package... Updating registry at \`/tmp/jl\_ORnSsn/registries…

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## [Simple implementation of reverse mode automatic differentiation](https://discourse.julialang.org/t/simple-implementation-of-reverse-mode-automatic-differentiation/78628)

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**Author:** [@A\_C](https://discourse.julialang.org/u/A_C)\
**Replies:** 7\
**Last updated:** [March 29, 2022, 7:22am UTC](https://discourse.julialang.org/t/simple-implementation-of-reverse-mode-automatic-differentiation/78628 "2022-03-29T07:22:08Z")

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I was looking for a simple implementation of reverse mode automatic differentiation. There are a lot of tutorials which show implementation of forward mode using dual numbers. But I could not find anything for reverse mo…

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## [DataFrame: Cannot have duplicated names for indices](https://discourse.julialang.org/t/dataframe-cannot-have-duplicated-names-for-indices/78396)

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**Author:** [@tlorans](https://discourse.julialang.org/u/tlorans)\
**Replies:** 6\
**Last updated:** [March 24, 2022, 3:13pm UTC](https://discourse.julialang.org/t/dataframe-cannot-have-duplicated-names-for-indices/78396 "2022-03-24T15:13:39Z")

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Hello everyone, I’d just spent 5 hours on a simple issue with joining two dataframes. I’ve basically two dataframes, one with a column of sectors and value, the other with new sectors mapped to the previous one as well…

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## [What is so different in each of these matrix operations?](https://discourse.julialang.org/t/what-is-so-different-in-each-of-these-matrix-operations/78637)

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**Author:** [@csubhodeep](https://discourse.julialang.org/u/csubhodeep)\
**Replies:** 3\
**Last updated:** [March 29, 2022, 7:06am UTC](https://discourse.julialang.org/t/what-is-so-different-in-each-of-these-matrix-operations/78637 "2022-03-29T07:06:14Z")

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Hello all, I am fairly new to Julia and have just started learning the basics of Matrix. I wanted to get a brief understanding of what is so different under the hood that is causing the huge time differences in each of …

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## [SQLite: query with duplicate column names |\> DataFrame](https://discourse.julialang.org/t/sqlite-query-with-duplicate-column-names-dataframe/64518)

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**Author:** [@viraltux](https://discourse.julialang.org/u/viraltux)\
**Replies:** 15\
**Last updated:** [March 29, 2022, 5:36am UTC](https://discourse.julialang.org/t/sqlite-query-with-duplicate-column-names-dataframe/64518 "2022-03-29T05:36:08Z")

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Hi guys, The following query with duplicate column names works however when converting to a DataFrame I have a "not unique" error. using SQLite db = SQLite.DB(); Q = q -\> DBInterface.execute(db, q); DataFrame(rand(10,…

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## [Random OPEN Julia publications / thesis / scholar papers / pre-prints](https://discourse.julialang.org/t/random-open-julia-publications-thesis-scholar-papers-pre-prints/78649)

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**Author:** [@ImreSamu](https://discourse.julialang.org/u/ImreSamu)\
**Replies:** 1\
**Last updated:** [March 29, 2022, 3:15am UTC](https://discourse.julialang.org/t/random-open-julia-publications-thesis-scholar-papers-pre-prints/78649 "2022-03-29T03:15:23Z")

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\*\*Random - Julia related OPEN publications / thesis / scholar papers / pre-prints \*\* If you find an “open” AND not yet in the list: https://julialang.org/research/ THEN just add this thread! Please add some text, key…

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## [Forking of unmaintained package: Snappy.jl](https://discourse.julialang.org/t/forking-of-unmaintained-package-snappy-jl/77431)

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**Author:** [@ExpandingMan](https://discourse.julialang.org/u/ExpandingMan)\
**Replies:** 9\
**Last updated:** [March 29, 2022, 3:16am UTC](https://discourse.julialang.org/t/forking-of-unmaintained-package-snappy-jl/77431 "2022-03-29T03:16:19Z")

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The maintainer of Snappy.jl (a wrapper of a C lib for a compression format) seems to be MIA. The package should require very little maintenance as it is a very simple wrapper, however the current version does not use bi…

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## [Type stability, passing type as argument, where keyword](https://discourse.julialang.org/t/type-stability-passing-type-as-argument-where-keyword/78630)

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**Author:** [@stepanzh](https://discourse.julialang.org/u/stepanzh)\
**Replies:** 5\
**Last updated:** [March 29, 2022, 2:54am UTC](https://discourse.julialang.org/t/type-stability-passing-type-as-argument-where-keyword/78630 "2022-03-29T02:54:12Z")

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I’m working on a general interface for a package. I were surprised when I checked code stability. Now I’m feeling that I’m missing something very important about parametric methods. My question is Why foobar\_clsr\_1 is …

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## [Make - How to change the color of axes & grids in LScene?](https://discourse.julialang.org/t/make-how-to-change-the-color-of-axes-grids-in-lscene/78641)

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**Author:** [@Bob\_Bass](https://discourse.julialang.org/u/Bob_Bass)\
**Replies:** 0\
**Last updated:** [March 29, 2022, 12:24am UTC](https://discourse.julialang.org/t/make-how-to-change-the-color-of-axes-grids-in-lscene/78641 "2022-03-29T00:24:27Z")

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Hi. I prefer a grey or darker background for my plots, but then I can’t see the grid lines or axes. How do I change the color of the grids/axes, if possible? I am using the LScene function rather than the Axis3 functi…

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## [Exponential Curve Fit Equation](https://discourse.julialang.org/t/exponential-curve-fit-equation/78608)

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**Author:** [@Mahmoud](https://discourse.julialang.org/u/Mahmoud)\
**Replies:** 6\
**Last updated:** [March 28, 2022, 10:10pm UTC](https://discourse.julialang.org/t/exponential-curve-fit-equation/78608 "2022-03-28T22:10:26Z")

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I am trying to fit my data in figure 1 to be like figure 2 (exponential fit) but my code does not do that using LsqFit #days = \[1,2,3,4,5,6,7,8,9 ,...........\] #y = some code to update y value @. model(days, p) =…

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## [Why same calculations on matrices yield different results?](https://discourse.julialang.org/t/why-same-calculations-on-matrices-yield-different-results/78573)

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**Author:** [@csubhodeep](https://discourse.julialang.org/u/csubhodeep)\
**Replies:** 4\
**Last updated:** [March 28, 2022, 8:58pm UTC](https://discourse.julialang.org/t/why-same-calculations-on-matrices-yield-different-results/78573 "2022-03-28T20:58:22Z")

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Hello all, I am fairly new to Julia but I come from the Python world. While I am still learning the basic machinery of the Matrix. I noticed a small difference in the way a “self-declared identity” matrix is being used …

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## [Is it possible to broadcast the property of a structure?](https://discourse.julialang.org/t/is-it-possible-to-broadcast-the-property-of-a-structure/78615)

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**Author:** [@sylvaticus](https://discourse.julialang.org/u/sylvaticus)\
**Replies:** 2\
**Last updated:** [March 28, 2022, 8:43pm UTC](https://discourse.julialang.org/t/is-it-possible-to-broadcast-the-property-of-a-structure/78615 "2022-03-28T20:43:36Z")

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Often I need to “broadcast” the field of a given structure, e.g.: struct Foo id::Int64 end mylist = \[Foo(1),Foo(2),Foo(1)\] \[e.id for e in mylist\] There is no way to broadcast the dot indicating field ownership, e.g…

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## [Makie - How to get a (single) random color for a line/scatter/segment, etc?](https://discourse.julialang.org/t/makie-how-to-get-a-single-random-color-for-a-line-scatter-segment-etc/78634)

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**Author:** [@Bob\_Bass](https://discourse.julialang.org/u/Bob_Bass)\
**Replies:** 2\
**Last updated:** [March 28, 2022, 8:06pm UTC](https://discourse.julialang.org/t/makie-how-to-get-a-single-random-color-for-a-line-scatter-segment-etc/78634 "2022-03-28T20:06:16Z")

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Makie.jl question: This code puts a red dot in a 2d axes scatter(\[1\],\[2\], color=:red) but I want to have a dot with a random color. The docs say that I can pass a Real number to the color attribute, but when I do th…

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## [How do I get the memory size of a BigInt?](https://discourse.julialang.org/t/how-do-i-get-the-memory-size-of-a-bigint/78524)

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**Author:** [@MHellmund](https://discourse.julialang.org/u/MHellmund)\
**Replies:** 8\
**Last updated:** [March 28, 2022, 7:22pm UTC](https://discourse.julialang.org/t/how-do-i-get-the-memory-size-of-a-bigint/78524 "2022-03-28T19:22:14Z")

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How do I get the memory size of a BigInt? What I tried: julia\> x=big(3)^300 1368914790585883759913260273820883159664636956253374364714801900783689971774990765938002061556889413882504844405979940428135127327656957745660…

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## [Is it possible to detect if Julia is ahead-of-time precompiling?](https://discourse.julialang.org/t/is-it-possible-to-detect-if-julia-is-ahead-of-time-precompiling/78631)

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**Author:** [@cjdoris](https://discourse.julialang.org/u/cjdoris)\
**Replies:** 2\
**Last updated:** [March 28, 2022, 6:32pm UTC](https://discourse.julialang.org/t/is-it-possible-to-detect-if-julia-is-ahead-of-time-precompiling/78631 "2022-03-28T18:32:15Z")

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I’d like to be able to tell at run-time (in \_\_init\_\_() in a package) whether the package is being “ahead-of-time precompiled” or not, in the sense that Pkg.precompile() is running (or similarly if precompiling automatica…

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## [Deprecate finalizers? As done in Java 18](https://discourse.julialang.org/t/deprecate-finalizers-as-done-in-java-18/78632)

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**Author:** [@Palli](https://discourse.julialang.org/u/Palli)\
**Replies:** 1\
**Last updated:** [March 28, 2022, 6:23pm UTC](https://discourse.julialang.org/t/deprecate-finalizers-as-done-in-java-18/78632 "2022-03-28T18:23:11Z")

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I believe Julia has finalizers (never looked into very carefully). Otherwise just ignore, read as Java trivia. Java 1 introduced finalizers (and just released Java 18 deprecated them). Are they similiar enough in Julia …

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## [In Nearest Neighbours are trees other than BruteTree worth it for sets with between n=2^3 and n=2^20ish for KNN in 2D cartesian space](https://discourse.julialang.org/t/in-nearest-neighbours-are-trees-other-than-brutetree-worth-it-for-sets-with-between-n-2-3-and-n-2-20ish-for-knn-in-2d-cartesian-space/78561)

<div class="topic-metadata">

**Author:** [@AlanAylmer](https://discourse.julialang.org/u/AlanAylmer)\
**Replies:** 2\
**Last updated:** [March 28, 2022, 6:15pm UTC](https://discourse.julialang.org/t/in-nearest-neighbours-are-trees-other-than-brutetree-worth-it-for-sets-with-between-n-2-3-and-n-2-20ish-for-knn-in-2d-cartesian-space/78561 "2022-03-28T18:15:41Z")

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I know the colossal @kristoffer.carlsson has been busy recently but I wonder if anyone else knows the A to my Q… I am running a teaching group on grouping waveforms. The waveform side of it is okay but I want to unders…

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## [Optim.jl single iteration](https://discourse.julialang.org/t/optim-jl-single-iteration/78619)

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**Author:** [@vmmhep](https://discourse.julialang.org/u/vmmhep)\
**Replies:** 4\
**Last updated:** [March 28, 2022, 5:57pm UTC](https://discourse.julialang.org/t/optim-jl-single-iteration/78619 "2022-03-28T17:57:01Z")

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I can’t seem to find this anywhere and I’m sorry in advance if my trivial question is indeed elsewhere… I have a differentiable periodic function: function fitness(x::Vector) LV = ones(105) QV = ones(105,10) …

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## [Fighting latency and the future of FunctionWrappers](https://discourse.julialang.org/t/fighting-latency-and-the-future-of-functionwrappers/78597)

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**Author:** [@pablosanjose](https://discourse.julialang.org/u/pablosanjose)\
**Replies:** 5\
**Last updated:** [March 28, 2022, 3:33pm UTC](https://discourse.julialang.org/t/fighting-latency-and-the-future-of-functionwrappers/78597 "2022-03-28T15:33:52Z")

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In our constant battle to reduce time-to-first-X, I’m finding it very, very valuable to use the precompile approach of my bottleneck functions (diagnosed with the amazing SnoopCompile frameworks, thanks a bunch for that!…

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## [ERROR: GitError(Code:ERROR, Class:Index, Invalid data in index - incorrect header signature)](https://discourse.julialang.org/t/error-giterror-code-error-class-index-invalid-data-in-index-incorrect-header-signature/12756)

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**Author:** [@Ian-B](https://discourse.julialang.org/u/Ian-B)\
**Replies:** 0\
**Last updated:** [July 30, 2018, 10:47pm UTC](https://discourse.julialang.org/t/error-giterror-code-error-class-index-invalid-data-in-index-incorrect-header-signature/12756 "2018-07-30T22:47:22Z")

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Hi! I’ve been trying to use Julia but I keep getting the same error when i try to install a package. I get this: julia\> Pkg.update() INFO: Updating METADATA… ERROR: GitError(Code:ERROR, Class:Index, Invalid data in in…

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## [Viewing columns and datatype in dataframe](https://discourse.julialang.org/t/viewing-columns-and-datatype-in-dataframe/78621)

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**Author:** [@janilin](https://discourse.julialang.org/u/janilin)\
**Replies:** 3\
**Last updated:** [March 28, 2022, 3:25pm UTC](https://discourse.julialang.org/t/viewing-columns-and-datatype-in-dataframe/78621 "2022-03-28T15:25:04Z")

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I created a dataframe first: using DataFrames df = DataFrame(id=\[1,2,3\], salary=4500, age=\[30, 30, 32\]) To view column names and datatypes, used: Dict(names(df) .=\> eltype.(eachcol(df))) However, it gets th…

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## [Julia 1.9.0-DEV.239 with CUDA CuArray](https://discourse.julialang.org/t/julia-1-9-0-dev-239-with-cuda-cuarray/78350)

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**Author:** [@sjinwsu](https://discourse.julialang.org/u/sjinwsu)\
**Replies:** 12\
**Last updated:** [March 28, 2022, 2:37pm UTC](https://discourse.julialang.org/t/julia-1-9-0-dev-239-with-cuda-cuarray/78350 "2022-03-28T14:37:09Z")

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Hello, I would like to ask if the following error regarding CuArray is Julia version specific. I was able to run the following basic CuArray test with Julia 1.8.0-Dev.1370, but when I tried with the latest release of Jul…

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## [Finding the new order of shuffled array](https://discourse.julialang.org/t/finding-the-new-order-of-shuffled-array/78611)

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**Author:** [@Kali](https://discourse.julialang.org/u/Kali)\
**Replies:** 2\
**Last updated:** [March 28, 2022, 1:19pm UTC](https://discourse.julialang.org/t/finding-the-new-order-of-shuffled-array/78611 "2022-03-28T13:19:46Z")

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Hello Julia users! I was having a problem while writing some code that I hope you can help with. So basically what I want to do is that I have an original array A of some length which contains some integers. This array h…

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## [Double integration inside a function](https://discourse.julialang.org/t/double-integration-inside-a-function/78602)

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**Author:** [@eijizero](https://discourse.julialang.org/u/eijizero)\
**Replies:** 1\
**Last updated:** [March 28, 2022, 10:10am UTC](https://discourse.julialang.org/t/double-integration-inside-a-function/78602 "2022-03-28T10:10:48Z")

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Hi I want to perform a double integration. using HCubature f(x,y) = x^2 + y^2; I, e = hcubature(f, (0, 0), (1, 2)) But, why is there an error when I write it like this? could you help me solving this? thanks functio…

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## [CUDA.jl - Variable Sized Local Arrays Inside CUDA Kernel](https://discourse.julialang.org/t/cuda-jl-variable-sized-local-arrays-inside-cuda-kernel/78567)

<div class="topic-metadata">

**Author:** [@moukann](https://discourse.julialang.org/u/moukann)\
**Replies:** 2\
**Last updated:** [March 28, 2022, 11:13am UTC](https://discourse.julialang.org/t/cuda-jl-variable-sized-local-arrays-inside-cuda-kernel/78567 "2022-03-28T11:13:53Z")

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Hello all, I am trying to parallelize a computational mechanics code. I encountered a problem which I cannot solve. I am trying to allocate variable sized arrays for every thread. However, for a particular thread, the s…

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## [CUDA.jl - Sub-Vector Indexing Problem Inside CUDA Kernel](https://discourse.julialang.org/t/cuda-jl-sub-vector-indexing-problem-inside-cuda-kernel/78526)

<div class="topic-metadata">

**Author:** [@moukann](https://discourse.julialang.org/u/moukann)\
**Replies:** 2\
**Last updated:** [March 28, 2022, 11:13am UTC](https://discourse.julialang.org/t/cuda-jl-sub-vector-indexing-problem-inside-cuda-kernel/78526 "2022-03-28T11:13:18Z")

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Hello all, I’ve been experimenting with CUDA Julia. Formerly, I used CUDA Python but it was so limited and restrictive. So I migrated to Julia. Thanks for the great effort and flexible framework to everybody working on …

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