# Latest

**URL:** https://discourse.julialang.org/latest.md?page=1788

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

**Page:** 1789

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## [Modifying legend markersize/linelength of a Plots/PyPlot plot after creation](https://discourse.julialang.org/t/modifying-legend-markersize-linelength-of-a-plots-pyplot-plot-after-creation/36723)

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**Author:** [@dapz](https://discourse.julialang.org/u/dapz)\
**Replies:** 0\
**Last updated:** [March 30, 2020, 9:03am UTC](https://discourse.julialang.org/t/modifying-legend-markersize-linelength-of-a-plots-pyplot-plot-after-creation/36723 "2020-03-30T09:03:25Z")

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Hi, I’m using a lot Plots.jl as I like having the common interface, but right now using mostly the PyPlot backend. I don’t want to use directly PyPlot as I coded some Plots recipes that I use. I have trouble with the le…

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## [Error when trying to install JuMP package](https://discourse.julialang.org/t/error-when-trying-to-install-jump-package/36722)

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**Author:** [@FADWA\_NEMER](https://discourse.julialang.org/u/FADWA_NEMER)\
**Replies:** 0\
**Last updated:** [March 30, 2020, 8:57am UTC](https://discourse.julialang.org/t/error-when-trying-to-install-jump-package/36722 "2020-03-30T08:57:34Z")

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I am trying to install JuMP package (command Pkg.add(“JuMP”) from julia using the built-in package manager) on my windows machine and I keep getting the following error . Any reason why I get this error? How can I re…

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## [Somewhat late, but loking for mentorship for GSoC2020, special functions](https://discourse.julialang.org/t/somewhat-late-but-loking-for-mentorship-for-gsoc2020-special-functions/36715)

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**Author:** [@suavesito](https://discourse.julialang.org/u/suavesito)\
**Replies:** 3\
**Last updated:** [March 30, 2020, 8:05am UTC](https://discourse.julialang.org/t/somewhat-late-but-loking-for-mentorship-for-gsoc2020-special-functions/36715 "2020-03-30T08:05:02Z")

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Hi, I know I’m basically in the edge of time, but I’m interested in the GSoc2020 Special functions project. This would be one of my first open source projects, and the second project I do in Julia. I know somewhat about…

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## [Procedural Nonlinear Constaint Generation - String to NLconstraint](https://discourse.julialang.org/t/procedural-nonlinear-constaint-generation-string-to-nlconstraint/34799)

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**Author:** [@r-b0](https://discourse.julialang.org/u/r-b0)\
**Replies:** 9\
**Last updated:** [March 30, 2020, 1:53am UTC](https://discourse.julialang.org/t/procedural-nonlinear-constaint-generation-string-to-nlconstraint/34799 "2020-03-30T01:53:29Z")

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I am implementing a large scale nonlinear program solver using the JuMP interface to IPOPT. The Nonlinear Modeling section of JuMP v0.21.0 documentation clearly explicates that all expressions used in NLconstraint and N…

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## [Zygote docs suggest flux is out of date?](https://discourse.julialang.org/t/zygote-docs-suggest-flux-is-out-of-date/36706)

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**Author:** [@jaynick](https://discourse.julialang.org/u/jaynick)\
**Replies:** 0\
**Last updated:** [March 29, 2020, 11:14pm UTC](https://discourse.julialang.org/t/zygote-docs-suggest-flux-is-out-of-date/36706 "2020-03-29T23:14:26Z")

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In the zygote docs it says However, implicit parameters exist mainly for compatibility with Flux’s current AD; it’s recommended to use the other approaches unless you need this, where implicit parameters refer to the s…

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## [Benchmarking Julia vs NumPy](https://discourse.julialang.org/t/benchmarking-julia-vs-numpy/36695)

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**Author:** [@Tasty\_Minerals](https://discourse.julialang.org/u/Tasty_Minerals)\
**Replies:** 9\
**Last updated:** [March 29, 2020, 9:21pm UTC](https://discourse.julialang.org/t/benchmarking-julia-vs-numpy/36695 "2020-03-29T21:21:38Z")

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Hello, I decided to make couple of benchmarks against NumPy out of curiosity. Since I don’t know Julia it would be nice if someone could take a second look because based on what I measured it doesn’t look like Julia is …

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## [\[ANN\] OpenSMILES.jl a SMILES parser for Julia!](https://discourse.julialang.org/t/ann-opensmiles-jl-a-smiles-parser-for-julia/36675)

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**Author:** [@anon92994695](https://discourse.julialang.org/u/anon92994695)\
**Replies:** 7\
**Last updated:** [March 29, 2020, 9:03pm UTC](https://discourse.julialang.org/t/ann-opensmiles-jl-a-smiles-parser-for-julia/36675 "2020-03-29T21:03:34Z")

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So if you are a chemist, biochemist, or someone working in those fields you may know what SMILES is. If not it’s basically a string representation for chemicals that preserves their connectivity and implied characteristi…

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## [Urgent call for scientific modellers to support pandemic modelling. UK specific](https://discourse.julialang.org/t/urgent-call-for-scientific-modellers-to-support-pandemic-modelling-uk-specific/36700)

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**Author:** [@johnh](https://discourse.julialang.org/u/johnh)\
**Replies:** 0\
**Last updated:** [March 29, 2020, 9:03pm UTC](https://discourse.julialang.org/t/urgent-call-for-scientific-modellers-to-support-pandemic-modelling-uk-specific/36700 "2020-03-29T21:03:29Z")

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## [PyCall and ExcelReaders error](https://discourse.julialang.org/t/pycall-and-excelreaders-error/36694)

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**Author:** [@Kihong\_Kim](https://discourse.julialang.org/u/Kihong_Kim)\
**Replies:** 3\
**Last updated:** [March 29, 2020, 7:48pm UTC](https://discourse.julialang.org/t/pycall-and-excelreaders-error/36694 "2020-03-29T19:48:28Z")

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ERROR: LoadError: PyCall.PyError("\\$(Expr(:escape, :(ccall(#= C:\\\\Users\\\\KKH\\\\.julia\\\\packages\\\\PyCall\\\\zqDXB\\\\src\\\\pyfncall.jl:43 =# @pysym(:PyObject\_Call), PyPtr, (PyPtr, PyPtr, PyPtr), o, pyargsptr, kw))))", PyObject(…

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## [How to create Libc.FILE from a string](https://discourse.julialang.org/t/how-to-create-libc-file-from-a-string/36637)

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**Author:** [@abulak](https://discourse.julialang.org/u/abulak)\
**Replies:** 4\
**Last updated:** [March 29, 2020, 7:18pm UTC](https://discourse.julialang.org/t/how-to-create-libc-file-from-a-string/36637 "2020-03-29T19:18:43Z")

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I’m looking for a solution to the following problem: A function in c takes a FILE \*rfile argument. If i want to read file I can do open(filename, "r") do file\_hdlr c\_file\_hdlr = Libc.FILE(file\_hdlr) # ccall wit…

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## [AOT compilation (not to create an executable)](https://discourse.julialang.org/t/aot-compilation-not-to-create-an-executable/36461)

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**Author:** [@tencnivel](https://discourse.julialang.org/u/tencnivel)\
**Replies:** 3\
**Last updated:** [March 29, 2020, 6:48pm UTC](https://discourse.julialang.org/t/aot-compilation-not-to-create-an-executable/36461 "2020-03-29T18:48:33Z")

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I try to improve the deployment of the new releases of my Julia web apps. As of now, the users encounter some lags (and sometimes timeouts) every time I deploy a new version because of the JIT compilation. This gets ev…

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## [PyCall error](https://discourse.julialang.org/t/pycall-error/36687)

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**Author:** [@Kihong\_Kim](https://discourse.julialang.org/u/Kihong_Kim)\
**Replies:** 0\
**Last updated:** [March 29, 2020, 6:39pm UTC](https://discourse.julialang.org/t/pycall-error/36687 "2020-03-29T18:39:57Z")

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ERROR: LoadError: PyCall.PyError("\\$(Expr(:escape, :(ccall(#= C:\\\\Users\\\\KKH\\\\.julia\\\\packages\\\\PyCall\\\\zqDXB\\\\src\\\\pyfncall.jl:43 =# @pysym(:PyObject\_Call), PyPtr, (PyPtr, PyPtr, PyPtr), o, pyargsptr, kw))))", PyObject(…

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## [Strange ImageFiltering.imfilter behaviour. (differs from matlab)](https://discourse.julialang.org/t/strange-imagefiltering-imfilter-behaviour-differs-from-matlab/36678)

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**Author:** [@Kunz-David](https://discourse.julialang.org/u/Kunz-David)\
**Replies:** 2\
**Last updated:** [March 29, 2020, 4:55pm UTC](https://discourse.julialang.org/t/strange-imagefiltering-imfilter-behaviour-differs-from-matlab/36678 "2020-03-29T16:55:47Z")

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Hello. I was debugging my code and ran into something I don’t understand. When using imfilter (and imfilter!) from ImageFiltering on a simple zero and one matrix the output matrix is scrambled in a specific way. The r…

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## [Which operators are parsed as chains?](https://discourse.julialang.org/t/which-operators-are-parsed-as-chains/36633)

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**Author:** [@phg](https://discourse.julialang.org/u/phg)\
**Replies:** 4\
**Last updated:** [March 29, 2020, 4:50pm UTC](https://discourse.julialang.org/t/which-operators-are-parsed-as-chains/36633 "2020-03-29T16:50:31Z")

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I asked this over at the metaprogramming Slack channel but got no replies, so another try: I thought all repeated binary operators are parsed as a chain, but apprearently that is not the case: julia\> Meta.show\_sexpr(:(…

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## [ANN: CUDAnative 3.0 and CuArrays 2.0](https://discourse.julialang.org/t/ann-cudanative-3-0-and-cuarrays-2-0/36506)

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**Author:** [@maleadt](https://discourse.julialang.org/u/maleadt)\
**Replies:** 3\
**Last updated:** [March 29, 2020, 4:15pm UTC](https://discourse.julialang.org/t/ann-cudanative-3-0-and-cuarrays-2-0/36506 "2020-03-29T16:15:19Z")

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I’ve just tagged CUDAnative 3.0 and CuArrays 2.0 (will be merged shortly), with some exciting new features: automatic installation of CUDA and libraries using artifacts (you still need to install the drivers though) fu…

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## [SciML: An Open Source Software Organization for Scientific Machine Learning](https://discourse.julialang.org/t/sciml-an-open-source-software-organization-for-scientific-machine-learning/36676)

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**Author:** [@ChrisRackauckas](https://discourse.julialang.org/u/ChrisRackauckas)\
**Replies:** 5\
**Last updated:** [March 29, 2020, 2:53pm UTC](https://discourse.julialang.org/t/sciml-an-open-source-software-organization-for-scientific-machine-learning/36676 "2020-03-29T14:53:16Z")

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Hello Julia community, Today we are introducing the SciML Open Source Software Organization for Scientific Machine Learning: high performance differential equation solving with automated model fitting and discovery plus…

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## [Installation problem -- First time install give "Invalid instruction..." when starting julia](https://discourse.julialang.org/t/installation-problem-first-time-install-give-invalid-instruction-when-starting-julia/36643)

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**Author:** [@rjmoses](https://discourse.julialang.org/u/rjmoses)\
**Replies:** 5\
**Last updated:** [March 29, 2020, 2:21pm UTC](https://discourse.julialang.org/t/installation-problem-first-time-install-give-invalid-instruction-when-starting-julia/36643 "2020-03-29T14:21:52Z")

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I just learned about julia and am interested in trying it. I downloaded JuliaPro-1.4.0-1\_build-87.sh and installed on a Linux Mint 19.2 system (runs under Virtualbox on a Windows 10 system). When starting julia, either…

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## [DataFrame by new columns containing arrays](https://discourse.julialang.org/t/dataframe-by-new-columns-containing-arrays/36614)

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**Author:** [@yakir12](https://discourse.julialang.org/u/yakir12)\
**Replies:** 13\
**Last updated:** [March 29, 2020, 1:59pm UTC](https://discourse.julialang.org/t/dataframe-by-new-columns-containing-arrays/36614 "2020-03-29T13:59:45Z")

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In DataFrames we can do this: by(iris, :Species, \[:PetalLength, :SepalLength\] =\> x -\> (a=mean(x.PetalLength)/mean(x.SepalLength), b=sum(x.PetalLength))) 3×3 DataFrame │ Row │ Species │ a │ b …

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## [Cannot Pkg.resolve the new REQUIRE of a package in development](https://discourse.julialang.org/t/cannot-pkg-resolve-the-new-require-of-a-package-in-development/12623)

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**Author:** [@pochoi](https://discourse.julialang.org/u/pochoi)\
**Replies:** 7\
**Last updated:** [March 29, 2020, 10:30am UTC](https://discourse.julialang.org/t/cannot-pkg-resolve-the-new-require-of-a-package-in-development/12623 "2020-03-29T10:30:08Z")

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I am developing a forked package, namely ExpmV. Recently I created a new branch and add Compat in the REQUIRE. When I try to load the package in new branch, I got the error julia\> using ExpmV ERROR: LoadError: ArgumentE…

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## [Design patterns for generic code with reusable caches for intermediate values](https://discourse.julialang.org/t/design-patterns-for-generic-code-with-reusable-caches-for-intermediate-values/36627)

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**Author:** [@jlperla](https://discourse.julialang.org/u/jlperla)\
**Replies:** 3\
**Last updated:** [March 29, 2020, 7:47am UTC](https://discourse.julialang.org/t/design-patterns-for-generic-code-with-reusable-caches-for-intermediate-values/36627 "2020-03-29T07:47:35Z")

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We have an expensive algorithm with is run many, many times for different parameter values and want to design the interface for caching the memory preallocation. A few principles: We should have enough information to …

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## [Throw control-c to @spawn task?](https://discourse.julialang.org/t/throw-control-c-to-spawn-task/36656)

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**Author:** [@wherrera](https://discourse.julialang.org/u/wherrera)\
**Replies:** 6\
**Last updated:** [March 29, 2020, 7:22am UTC](https://discourse.julialang.org/t/throw-control-c-to-spawn-task/36656 "2020-03-29T07:22:38Z")

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Is there a way to throw a control-c break to a task running as @spawn? The specific case is that, when running the SoX commandline music player, one sends control-c to tell the player to stop play, ie p = @spawn(run(\`pl…

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## [add("IJulia") Question](https://discourse.julialang.org/t/add-ijulia-question/36663)

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**Author:** [@mehalter](https://discourse.julialang.org/u/mehalter)\
**Replies:** 0\
**Last updated:** [March 29, 2020, 2:22am UTC](https://discourse.julialang.org/t/add-ijulia-question/36663 "2020-03-29T02:22:16Z")

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Can I skip the automatic jupyter kernel installation step when running add(“IJulia”), or at least change the kernel name for the initial installation?

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## [(not julia) Help make PPE for Hospitals (3-D printer required)](https://discourse.julialang.org/t/not-julia-help-make-ppe-for-hospitals-3-d-printer-required/36648)

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**Author:** [@anon92994695](https://discourse.julialang.org/u/anon92994695)\
**Replies:** 1\
**Last updated:** [March 29, 2020, 1:55am UTC](https://discourse.julialang.org/t/not-julia-help-make-ppe-for-hospitals-3-d-printer-required/36648 "2020-03-29T01:55:27Z")

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Many hospitals especially in the USA are in dire need of PPE and may not get it on time given the pandemic. For instance University of Michigan Hospital is accepting 3-D printed face shields (Ann Arbor residents join eff…

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## [How do people handle name collisions with function defined in other packages?](https://discourse.julialang.org/t/how-do-people-handle-name-collisions-with-function-defined-in-other-packages/36553)

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**Author:** [@pixel27](https://discourse.julialang.org/u/pixel27)\
**Replies:** 19\
**Last updated:** [March 29, 2020, 1:32am UTC](https://discourse.julialang.org/t/how-do-people-handle-name-collisions-with-function-defined-in-other-packages/36553 "2020-03-29T01:32:15Z")

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As an example I’m using Cairo to create an image. I defined a method: using Cairo function image(size::Int) .... end This function just does some base work for creating an image of size x size for me. However can…

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## [Installation troubles](https://discourse.julialang.org/t/installation-troubles/36634)

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**Author:** [@leiteiro](https://discourse.julialang.org/u/leiteiro)\
**Replies:** 4\
**Last updated:** [March 28, 2020, 10:22pm UTC](https://discourse.julialang.org/t/installation-troubles/36634 "2020-03-28T22:22:32Z")

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I am on Windows64, Julia 1.4.0, using VS Code. (1) In the terminal: julia\> using HTTP julia\> HTTP.get("http://google.com") HTTP.Messages.Response: HTTP/1.1 200 OK ... (2) Executing my program returns in the output win…

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## [Overloading \`getproperty\` in a type-stable manner](https://discourse.julialang.org/t/overloading-getproperty-in-a-type-stable-manner/36638)

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**Author:** [@Datseris](https://discourse.julialang.org/u/Datseris)\
**Replies:** 4\
**Last updated:** [March 28, 2020, 6:30pm UTC](https://discourse.julialang.org/t/overloading-getproperty-in-a-type-stable-manner/36638 "2020-03-28T18:30:50Z")

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Hi, I am trying to overload getproperty for a struct I have. I do: function Base.getproperty(m::ABM, s::Symbol) if s ∈ (:agents, :space, :scheduler, :properties) return Base.getfield(m, s) else …

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## [Extended Slack PPL discussion](https://discourse.julialang.org/t/extended-slack-ppl-discussion/36623)

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**Author:** [@cscherrer](https://discourse.julialang.org/u/cscherrer)\
**Replies:** 5\
**Last updated:** [March 28, 2020, 5:25pm UTC](https://discourse.julialang.org/t/extended-slack-ppl-discussion/36623 "2020-03-28T17:25:51Z")

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Hi, there was a nice thread today on the Julia Slack PPL channel. Because it’s the free version, this will scroll into oblivion, so I thought I’d capture it for reference and in case it’s useful to anyone else: I had …

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## [Repeatedly multiplying a Float64 is fastest in chunks of \<51 terms](https://discourse.julialang.org/t/repeatedly-multiplying-a-float64-is-fastest-in-chunks-of-51-terms/36527)

<div class="topic-metadata">

**Author:** [@frank](https://discourse.julialang.org/u/frank)\
**Replies:** 11\
**Last updated:** [March 28, 2020, 3:26pm UTC](https://discourse.julialang.org/t/repeatedly-multiplying-a-float64-is-fastest-in-chunks-of-51-terms/36527 "2020-03-28T15:26:51Z")

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I’ve written a fast Julia-only permutation (n P r) function intended for perms small enough to fit into a Float64 (at the expense of some precision). Thus, if a permutation doesn’t exceed 1.7976931348623157e308, one can …

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## [Why is this line like this in Base.Random?](https://discourse.julialang.org/t/why-is-this-line-like-this-in-base-random/36626)

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**Author:** [@xzackli](https://discourse.julialang.org/u/xzackli)\
**Replies:** 3\
**Last updated:** [March 28, 2020, 3:09pm UTC](https://discourse.julialang.org/t/why-is-this-line-like-this-in-base-random/36626 "2020-03-28T15:09:11Z")

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The Base.Random implementation of per-thread global RNGs seems to be a pattern for thread-safe mutations in Julia. I’m trying to implement something similar for a problem that strongly benefits from caching intermediate …

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## [Solving an optimal control problem with Optim.jl](https://discourse.julialang.org/t/solving-an-optimal-control-problem-with-optim-jl/36635)

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**Author:** [@roi.holtzman](https://discourse.julialang.org/u/roi.holtzman)\
**Replies:** 4\
**Last updated:** [March 28, 2020, 2:17pm UTC](https://discourse.julialang.org/t/solving-an-optimal-control-problem-with-optim-jl/36635 "2020-03-28T14:17:57Z")

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I am trying to solve an optimal control problem in Julia. I tried using NLOptControl.jl and JuMP.jl but ran into some difficulties. See this post. Therefore I am trying to use Optim.jl as an optimizer. Since my optimiza…

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