# Latest

**URL:** https://discourse.julialang.org/latest.md?page=1842

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

**Page:** 1843

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## [How to define matrix objectives in JuMP models](https://discourse.julialang.org/t/how-to-define-matrix-objectives-in-jump-models/33556)

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**Author:** [@tdp](https://discourse.julialang.org/u/tdp)\
**Replies:** 1\
**Last updated:** [January 19, 2020, 7:45pm UTC](https://discourse.julialang.org/t/how-to-define-matrix-objectives-in-jump-models/33556 "2020-01-19T19:45:34Z")

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Hi, How do I declare a matrix objective in JuMP? That is, how do I declare @objective(m, Min, ⋅ ) with ⋅ a matrix? Thank you for any help. Details I am trying to translate the Python code below to Julia. However, the …

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## [Confusing results when searching documentation, 1.3.1](https://discourse.julialang.org/t/confusing-results-when-searching-documentation-1-3-1/33542)

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**Author:** [@mcreel](https://discourse.julialang.org/u/mcreel)\
**Replies:** 4\
**Last updated:** [January 19, 2020, 6:44pm UTC](https://discourse.julialang.org/t/confusing-results-when-searching-documentation-1-3-1/33542 "2020-01-19T18:44:35Z")

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Searching the 1.3.1 documentation for “closure” yields 16 results, one of which is the “Closures” section. Searching for “closures” or “Closures” gives 14 results, which do not contain the section. If desired, I can make…

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## [What function (display?) does IJulia call at the end of each cell?](https://discourse.julialang.org/t/what-function-display-does-ijulia-call-at-the-end-of-each-cell/33554)

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**Author:** [@JeffFessler](https://discourse.julialang.org/u/JeffFessler)\
**Replies:** 2\
**Last updated:** [January 19, 2020, 6:39pm UTC](https://discourse.julialang.org/t/what-function-display-does-ijulia-call-at-the-end-of-each-cell/33554 "2020-01-19T18:39:47Z")

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I have an AbstractArray type with its own display method that gets called correctly in the REPL but in Jupyter/IJulia whatever function is called to display the last argument in each cell is apparently calling a default …

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## [Mutating closure?](https://discourse.julialang.org/t/mutating-closure/33544)

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**Author:** [@mcreel](https://discourse.julialang.org/u/mcreel)\
**Replies:** 2\
**Last updated:** [January 19, 2020, 3:15pm UTC](https://discourse.julialang.org/t/mutating-closure/33544 "2020-01-19T15:15:18Z")

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I am trying to define a closure which mutates its argument, without luck. Is there a way to define a closure which is mutating? Here’s an example of what I’m trying to achieve: Thanks! function a!(x) for i = 1:size…

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## [Tutoring Sessions On-Demand](https://discourse.julialang.org/t/tutoring-sessions-on-demand/33551)

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**Author:** [@quantiota](https://discourse.julialang.org/u/quantiota)\
**Replies:** 0\
**Last updated:** [January 19, 2020, 1:15pm UTC](https://discourse.julialang.org/t/tutoring-sessions-on-demand/33551 "2020-01-19T13:15:38Z")

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I am a PhD in Physics. I am new to programming and am starting to learn Julia Computing. Required Knowledge, Skills and Experiences: PhD degree/ PhD student (at least year 2) Sufficient knowledge of Timeseries.jl, Csv…

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## [Parallel Mersenne Twister](https://discourse.julialang.org/t/parallel-mersenne-twister/27567)

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**Author:** [@cscherrer](https://discourse.julialang.org/u/cscherrer)\
**Replies:** 18\
**Last updated:** [January 19, 2020, 12:32pm UTC](https://discourse.julialang.org/t/parallel-mersenne-twister/27567 "2020-01-19T12:32:01Z")

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Like many people, I’m pretty excited about the new multithreading capabilities in 1.3. But there’s one thing in the announcement that I’m not sure about, so it seems worth some discussion. It says, The approach we’ve …

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## [Building thread-safe data structures](https://discourse.julialang.org/t/building-thread-safe-data-structures/33537)

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**Author:** [@Ali\_Mamdouh](https://discourse.julialang.org/u/Ali_Mamdouh)\
**Replies:** 0\
**Last updated:** [January 19, 2020, 8:03am UTC](https://discourse.julialang.org/t/building-thread-safe-data-structures/33537 "2020-01-19T08:03:08Z")

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i am thinking about start contributing to julia by writing some thread-safe data structures, i want to know what the to make to make my pull request get merged, e.g what the interface should, if you think of some languag…

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## [Improve type handling in skipmissing](https://discourse.julialang.org/t/improve-type-handling-in-skipmissing/33513)

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**Author:** [@Alex1](https://discourse.julialang.org/u/Alex1)\
**Replies:** 8\
**Last updated:** [January 19, 2020, 3:08am UTC](https://discourse.julialang.org/t/improve-type-handling-in-skipmissing/33513 "2020-01-19T03:08:19Z")

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Would be nice to improve skipmissing, maybe always apply collect? If the reason not to apply it is the performance, I would say - predictability and principle of least surprise is more important than performance. serie …

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## [Saving julia dataframes efficiently (in terms of size on the disk)](https://discourse.julialang.org/t/saving-julia-dataframes-efficiently-in-terms-of-size-on-the-disk/32151)

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**Author:** [@curious](https://discourse.julialang.org/u/curious)\
**Replies:** 13\
**Last updated:** [January 19, 2020, 2:41am UTC](https://discourse.julialang.org/t/saving-julia-dataframes-efficiently-in-terms-of-size-on-the-disk/32151 "2020-01-19T02:41:46Z")

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What is a good format to store Julia DataFrames efficiently (in terms of size on the disk)? I have a dataset that is about 2.1GB as a Feather file. It is almost 1.9GB in Stata .dta format. But if I open it in R and save…

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## [Basic question about Distributions, drawing random sample and related documentaion](https://discourse.julialang.org/t/basic-question-about-distributions-drawing-random-sample-and-related-documentaion/33532)

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**Author:** [@curious](https://discourse.julialang.org/u/curious)\
**Replies:** 2\
**Last updated:** [January 19, 2020, 2:40am UTC](https://discourse.julialang.org/t/basic-question-about-distributions-drawing-random-sample-and-related-documentaion/33532 "2020-01-19T02:40:11Z")

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Julia version Julia 1.0.5 What I want to do: I want to draw a random sample from a continuous uniform distribution, U\[10, 50\]. A way to do it in Julia The following works: import Distributions unifdist = Distribut…

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## [\[ANN\] DirectSum.jl, AbstractTensors.jl : dispatch on VectorBundle \<: Manifold{n}](https://discourse.julialang.org/t/ann-directsum-jl-abstracttensors-jl-dispatch-on-vectorbundle-manifold-n/20870)

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**Author:** [@chakravala](https://discourse.julialang.org/u/chakravala)\
**Replies:** 4\
**Last updated:** [January 19, 2020, 2:32am UTC](https://discourse.julialang.org/t/ann-directsum-jl-abstracttensors-jl-dispatch-on-vectorbundle-manifold-n/20870 "2020-01-19T02:32:59Z")

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In my work, I found it necessary to create an abstract TensorAlgebra type. Searching on github, I found that many others had also devised some sort of AsbtractTensor concept. As a multilinear map, a tensor is defined on…

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## [What concurrency tools you think will be useful to add to julia?](https://discourse.julialang.org/t/what-concurrency-tools-you-think-will-be-useful-to-add-to-julia/33530)

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**Author:** [@Ali\_Mamdouh](https://discourse.julialang.org/u/Ali_Mamdouh)\
**Replies:** 2\
**Last updated:** [January 19, 2020, 1:48am UTC](https://discourse.julialang.org/t/what-concurrency-tools-you-think-will-be-useful-to-add-to-julia/33530 "2020-01-19T01:48:47Z")

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i am exciting to contribute to julia by implementing some concurrency tools, so i want some suggestions about things i can do.

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## [Error when rebuilding sysimage after building MKL; Julia 1.3.1, Windows 10](https://discourse.julialang.org/t/error-when-rebuilding-sysimage-after-building-mkl-julia-1-3-1-windows-10/33199)

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**Author:** [@razvangheorghe](https://discourse.julialang.org/u/razvangheorghe)\
**Replies:** 2\
**Last updated:** [January 19, 2020, 12:00am UTC](https://discourse.julialang.org/t/error-when-rebuilding-sysimage-after-building-mkl-julia-1-3-1-windows-10/33199 "2020-01-19T00:00:32Z")

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Hello. I’m trying to build Julia against MKL. Julia Version 1.3.1 Commit 2d5741174c (2019-12-30 21:36 UTC) Platform Info: OS: Windows (x86\_64-w64-mingw32) CPU: Intel(R) Core(TM) i5-8500 CPU @ 3.00GHz WORD\_SIZE: 64…

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## [Parallel worlds ages don't match](https://discourse.julialang.org/t/parallel-worlds-ages-dont-match/33496)

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**Author:** [@pbayer](https://discourse.julialang.org/u/pbayer)\
**Replies:** 5\
**Last updated:** [January 18, 2020, 2:01pm UTC](https://discourse.julialang.org/t/parallel-worlds-ages-dont-match/33496 "2020-01-18T14:01:42Z")

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Im currently developing the multithreading in Simulate.jl. Now – with the current development version – I create a master clock and setup three parallel clocks: using Simulate clk = Clock() multiply!(clk) got 3 threads…

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## [Error on starting julia 1.3.1 from juno julia-client 0.11.3 (but it still starts)](https://discourse.julialang.org/t/error-on-starting-julia-1-3-1-from-juno-julia-client-0-11-3-but-it-still-starts/33118)

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**Author:** [@lel4866](https://discourse.julialang.org/u/lel4866)\
**Replies:** 3\
**Last updated:** [January 18, 2020, 6:42pm UTC](https://discourse.julialang.org/t/error-on-starting-julia-1-3-1-from-juno-julia-client-0-11-3-but-it-still-starts/33118 "2020-01-18T18:42:23Z")

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I get the following when I start julia from the repl window in Juno. I do not get the error when I start julia without juno: Add-Type : (0) : Source file ‘C:\\Windows\\TEMP\\jmrvm0rd.0.cs’ could not be found (1) : using S…

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## [Findall function](https://discourse.julialang.org/t/findall-function/33484)

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**Author:** [@anirudhpammi](https://discourse.julialang.org/u/anirudhpammi)\
**Replies:** 10\
**Last updated:** [January 18, 2020, 5:40pm UTC](https://discourse.julialang.org/t/findall-function/33484 "2020-01-18T17:40:13Z")

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I have a question regarding the internal code of the findall function. I have an array and I want to find elements that satisfy two conditions. I know that I can use something like findall(f:function,A) where A is the ar…

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## [Error with same type called from different modules](https://discourse.julialang.org/t/error-with-same-type-called-from-different-modules/22609)

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**Author:** [@yosinlpet](https://discourse.julialang.org/u/yosinlpet)\
**Replies:** 3\
**Last updated:** [January 18, 2020, 4:38pm UTC](https://discourse.julialang.org/t/error-with-same-type-called-from-different-modules/22609 "2020-01-18T16:38:09Z")

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How could I avoid the following error ? ERROR: LoadError: MethodError: no method matching getlinearspeedcoeffs(::Main.MultiPro.ProfileMod.VortexElement.LinearPanel, ::Main.MultiPro.ProfileMod.VortexElement.LinearPanel,…

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## [String comparison by template, something like str=="us\*", where \* is mean any symbol](https://discourse.julialang.org/t/string-comparison-by-template-something-like-str-us-where-is-mean-any-symbol/33455)

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**Author:** [@BMval](https://discourse.julialang.org/u/BMval)\
**Replies:** 4\
**Last updated:** [January 18, 2020, 4:28pm UTC](https://discourse.julialang.org/t/string-comparison-by-template-something-like-str-us-where-is-mean-any-symbol/33455 "2020-01-18T16:28:14Z")

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Would somebody suggest: string comparison by template, something like str==“us\*”, where \* is mean any symbol thanks

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## [New Artifact System, Data, and OneDrive](https://discourse.julialang.org/t/new-artifact-system-data-and-onedrive/33250)

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**Author:** [@Crown421](https://discourse.julialang.org/u/Crown421)\
**Replies:** 12\
**Last updated:** [January 18, 2020, 2:11pm UTC](https://discourse.julialang.org/t/new-artifact-system-data-and-onedrive/33250 "2020-01-18T14:11:18Z")

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Dear all, today instead of doing my work, I learned about the new artifact system, and I am absolutely fascinated. I am currently working on a project that uses some data files, which I store in my Onedrive for Busines…

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## [Performance advice needed](https://discourse.julialang.org/t/performance-advice-needed/33467)

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**Author:** [@Jakub\_Wronowski](https://discourse.julialang.org/u/Jakub_Wronowski)\
**Replies:** 17\
**Last updated:** [January 17, 2020, 5:55pm UTC](https://discourse.julialang.org/t/performance-advice-needed/33467 "2020-01-17T17:55:02Z")

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Hi, I am working on a function with calculation that have structure similar to FFT. I’m a bit disappointed, cause I hoped it will be 10x slower than FFTW but benchmarks show its 100x slower. i tried to put @simd and @in…

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## [In Cxx, how to supply compiler flags like -O2 or --std==c++17](https://discourse.julialang.org/t/in-cxx-how-to-supply-compiler-flags-like-o2-or-std-c-17/33435)

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**Author:** [@JJB](https://discourse.julialang.org/u/JJB)\
**Replies:** 4\
**Last updated:** [January 18, 2020, 8:59am UTC](https://discourse.julialang.org/t/in-cxx-how-to-supply-compiler-flags-like-o2-or-std-c-17/33435 "2020-01-18T08:59:39Z")

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When using the Cxx package, how can I supply flags to Clang like -O2 or --std==c++17?

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## [Question about optimal thread allocation for vector of problems of differing sizes](https://discourse.julialang.org/t/question-about-optimal-thread-allocation-for-vector-of-problems-of-differing-sizes/33464)

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**Author:** [@Sean\_Matthews](https://discourse.julialang.org/u/Sean_Matthews)\
**Replies:** 7\
**Last updated:** [January 17, 2020, 11:09pm UTC](https://discourse.julialang.org/t/question-about-optimal-thread-allocation-for-vector-of-problems-of-differing-sizes/33464 "2020-01-17T23:09:15Z")

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I have a question about multithreading. I have a vector of pairwise thread safe problems v, say of length 16, and I have four threads. As I understand it, if I write Threads.@theads for i in 1:16 do\_problem(v\[i\]) en…

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## [Ref not change](https://discourse.julialang.org/t/ref-not-change/33503)

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**Author:** [@andrey2185](https://discourse.julialang.org/u/andrey2185)\
**Replies:** 6\
**Last updated:** [January 17, 2020, 9:14pm UTC](https://discourse.julialang.org/t/ref-not-change/33503 "2020-01-17T21:14:32Z")

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Hello! x = 10 ax = Ref(x) x = 90 println(ax\[\]) # why 10 ?

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## [Struggling with parallel code in MCMC simulation](https://discourse.julialang.org/t/struggling-with-parallel-code-in-mcmc-simulation/33448)

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**Author:** [@johnheyer](https://discourse.julialang.org/u/johnheyer)\
**Replies:** 7\
**Last updated:** [January 17, 2020, 7:52pm UTC](https://discourse.julialang.org/t/struggling-with-parallel-code-in-mcmc-simulation/33448 "2020-01-17T19:52:50Z")

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Hi! I’m really struggling with parallel code execution in Julia. I have implemented an MCMC sampler that depends on packages such as Distributions, Random, etc., as well as two other julia files which I have written. T…

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## [Core.tuple() warntype](https://discourse.julialang.org/t/core-tuple-warntype/33375)

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**Author:** [@tomtom](https://discourse.julialang.org/u/tomtom)\
**Replies:** 22\
**Last updated:** [January 17, 2020, 7:33pm UTC](https://discourse.julialang.org/t/core-tuple-warntype/33375 "2020-01-17T19:33:29Z")

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I’m studying Tuples and find that (in base/tuple.jl) a lot of methods to create them (e.g. map(), NTuple{}(), etc.) at the end would return something like (x..., ), which calls Core.tuple(). However, I found that this c…

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## [@printf thread safety in Julia 1.3?](https://discourse.julialang.org/t/printf-thread-safety-in-julia-1-3/30551)

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**Author:** [@Zhong\_Pan](https://discourse.julialang.org/u/Zhong_Pan)\
**Replies:** 1\
**Last updated:** [January 17, 2020, 7:23pm UTC](https://discourse.julialang.org/t/printf-thread-safety-in-julia-1-3/30551 "2020-01-17T19:23:13Z")

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I heard that in Julia 1.3 I/O will be thread safe. Is it so? In a multi-threaded for loop, if I’m using @printf to write to DIFFERENT files (one file per thread id), should I still use lock/unlock to guard the file writi…

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## [Postdoc @ LANL](https://discourse.julialang.org/t/postdoc-lanl/31109)

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**Author:** [@monty](https://discourse.julialang.org/u/monty)\
**Replies:** 23\
**Last updated:** [January 17, 2020, 4:47pm UTC](https://discourse.julialang.org/t/postdoc-lanl/31109 "2020-01-17T16:47:02Z")

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The Computational Earth Science Group at Los Alamos National Laboratory (LANL) has immediate openings for Postdoctoral Research Associates with applied math and computational science skills. The postdoctoral research wil…

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## [Using Turing as a replacement of Klara](https://discourse.julialang.org/t/using-turing-as-a-replacement-of-klara/32152)

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**Author:** [@marouane1994](https://discourse.julialang.org/u/marouane1994)\
**Replies:** 26\
**Last updated:** [January 17, 2020, 3:14pm UTC](https://discourse.julialang.org/t/using-turing-as-a-replacement-of-klara/32152 "2020-01-17T15:14:16Z")

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i used to use Klara for MCMC sampler where i just call back the log density of the target function and it was working the way i wanted and now when i want to go back where i’m using it i found problems since i can’t use K…

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## [Configuring Cxx.jl](https://discourse.julialang.org/t/configuring-cxx-jl/33458)

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**Author:** [@kumarbalachandran](https://discourse.julialang.org/u/kumarbalachandran)\
**Replies:** 4\
**Last updated:** [January 17, 2020, 2:55pm UTC](https://discourse.julialang.org/t/configuring-cxx-jl/33458 "2020-01-17T14:55:27Z")

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I am attempting to use the Arraymaker.cpp as a test for the installation of Cxx.jl and I get a failure on the precompilation stage: test Cxx Testing Cxx Resolving package versions… Status \[userdir\]\\AppData\\Local\\Temp…

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## [Expression interpolation](https://discourse.julialang.org/t/expression-interpolation/33472)

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**Author:** [@tomtom](https://discourse.julialang.org/u/tomtom)\
**Replies:** 7\
**Last updated:** [January 17, 2020, 2:46pm UTC](https://discourse.julialang.org/t/expression-interpolation/33472 "2020-01-17T14:46:00Z")

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in doc, the following example is given: julia\> ex = :(a in $:((1, 2, 3) ) ) :(a in (1, 2, 3)) I don’t get the meaning of “expression interpolation”, as: julia\> ex2 = :(a in (1, 2, 3) ) :(a in (1, 2, 3)) julia\> ex == …

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