# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=509

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**Page:** 510

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## [\[ANN\] AstroTime.jl: Astronomical time keeping in Julia](https://discourse.julialang.org/t/ann-astrotime-jl-astronomical-time-keeping-in-julia/20496)

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**Author:** [@helgee](https://discourse.julialang.org/u/helgee)\
**Replies:** 1\
**Last updated:** [February 7, 2019, 12:24am UTC](https://discourse.julialang.org/t/ann-astrotime-jl-astronomical-time-keeping-in-julia/20496 "2019-02-07T00:24:55Z")

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Hi folks! I have finally published the first version of AstroTime.jl :tada: This one has been an almost astronomically long time in the making (sorry, could not resist :smile:). The first commit (when the code was stil…

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## [Pipeline : from raw data to fitted model?](https://discourse.julialang.org/t/pipeline-from-raw-data-to-fitted-model/20477)

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**Author:** [@kirtsar](https://discourse.julialang.org/u/kirtsar)\
**Replies:** 6\
**Last updated:** [February 6, 2019, 10:22pm UTC](https://discourse.julialang.org/t/pipeline-from-raw-data-to-fitted-model/20477 "2019-02-06T22:22:31Z")

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Hello everyone! I’m a novice in machine learning domain. I’m interested in basic ML pipeline from raw dataframe with missing values and so on to the trained model. Is there any unified process of pipelining such method…

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## [How to fit a GLM to all (unnamed) features of arbitrary design matrix?](https://discourse.julialang.org/t/how-to-fit-a-glm-to-all-unnamed-features-of-arbitrary-design-matrix/20490)

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**Author:** [@murphyk](https://discourse.julialang.org/u/murphyk)\
**Replies:** 2\
**Last updated:** [February 6, 2019, 9:18pm UTC](https://discourse.julialang.org/t/how-to-fit-a-glm-to-all-unnamed-features-of-arbitrary-design-matrix/20490 "2019-02-06T21:18:13Z")

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I want to call the GLM.jl library as a blackbox, which means I want to use a formula of the form “y ~ .”, where y is the target column of my dataframe, and . is all the other features. Specifically, what I would like to…

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## [What other language allows you to do Rational matrix inversion?](https://discourse.julialang.org/t/what-other-language-allows-you-to-do-rational-matrix-inversion/20340)

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**Author:** [@xiaodai](https://discourse.julialang.org/u/xiaodai)\
**Replies:** 15\
**Last updated:** [February 6, 2019, 1:20am UTC](https://discourse.julialang.org/t/what-other-language-allows-you-to-do-rational-matrix-inversion/20340 "2019-02-06T01:20:37Z")

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I was just doing some Hackerrank for fun, in particular this one. Basically, you can describe the problem as a sequence of recurrence relations, and they told you that the solution is in the form of a rational number. S…

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## [Optim - provide gradient with fixed parameters](https://discourse.julialang.org/t/optim-provide-gradient-with-fixed-parameters/20181)

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**Author:** [@itzui](https://discourse.julialang.org/u/itzui)\
**Replies:** 10\
**Last updated:** [February 5, 2019, 8:10pm UTC](https://discourse.julialang.org/t/optim-provide-gradient-with-fixed-parameters/20181 "2019-02-05T20:10:12Z")

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I’m using Optim and the BFGS algarithm in order to minimize a function. In order to speed up the minimization I want to provide the gradient of the objective function. However both, the objective function as well as the …

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## [Any Black-Box Packages for Bayesian Hyperparameter Optimization?](https://discourse.julialang.org/t/any-black-box-packages-for-bayesian-hyperparameter-optimization/20428)

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**Author:** [@ahmetumutdurmus](https://discourse.julialang.org/u/ahmetumutdurmus)\
**Replies:** 2\
**Last updated:** [February 5, 2019, 9:42am UTC](https://discourse.julialang.org/t/any-black-box-packages-for-bayesian-hyperparameter-optimization/20428 "2019-02-05T09:42:55Z")

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Configuring hyperparameters in a machine learning problem can be a dauntingly boring and suboptimal task as each evaluation may be fairly long to conduct and thus performing an exhaustive grid search may be infeasible. B…

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## [First steps in JuliaDB](https://discourse.julialang.org/t/first-steps-in-juliadb/14010)

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**Author:** [@jstrube](https://discourse.julialang.org/u/jstrube)\
**Replies:** 1\
**Last updated:** [February 4, 2019, 9:09pm UTC](https://discourse.julialang.org/t/first-steps-in-juliadb/14010 "2019-02-04T21:09:31Z")

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I’m taking first steps with JuliaDB, but I’m already falling on my face. My first stumble was the difference between loadtable and load. Why do I need a different method name for a different input format? Moving on… I’m…

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## [Getvalue() help](https://discourse.julialang.org/t/getvalue-help/20425)

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**Author:** [@muriloasouza](https://discourse.julialang.org/u/muriloasouza)\
**Replies:** 1\
**Last updated:** [February 4, 2019, 2:25pm UTC](https://discourse.julialang.org/t/getvalue-help/20425 "2019-02-04T14:25:46Z")

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I got a variable, x: @variable(m, x\_min \<= x\[i = 2:4\] \<= x\_max, Int) But after solving my optimization problem, i want to print 2\*x+2. How can this be done? I tried something like: println("x = ", 2\*getvalue(x)+2) B…

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## [Slow first run inside functions](https://discourse.julialang.org/t/slow-first-run-inside-functions/19638)

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**Author:** [@sw2030](https://discourse.julialang.org/u/sw2030)\
**Replies:** 5\
**Last updated:** [February 4, 2019, 12:22pm UTC](https://discourse.julialang.org/t/slow-first-run-inside-functions/19638 "2019-02-04T12:22:10Z")

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Hello, It seems like the first run of norm(not only norm but also other functions) inside function is slower than the second run even after the first time compilation. This is even worse(100x times) in case of heavier f…

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## [GMT Image to ImageView](https://discourse.julialang.org/t/gmt-image-to-imageview/20349)

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**Author:** [@johnh](https://discourse.julialang.org/u/johnh)\
**Replies:** 16\
**Last updated:** [February 3, 2019, 7:00pm UTC](https://discourse.julialang.org/t/gmt-image-to-imageview/20349 "2019-02-03T19:00:30Z")

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Thankyou to @joa-quim I can read Geotiff files using GMT.jl When I run image = gmtread(“world.tif”,img=true) the image is of type GMT.GMTimage GMT.imshow(image) produces a Postscript file Rather stupidly I would lik…

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## [\[Ann\] Sparips.jl: Practical sparsification of Rips complexes (topological data analysis)](https://discourse.julialang.org/t/ann-sparips-jl-practical-sparsification-of-rips-complexes-topological-data-analysis/16422)

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**Author:** [@foobar\_lv2](https://discourse.julialang.org/u/foobar_lv2)\
**Replies:** 31\
**Last updated:** [February 1, 2019, 8:10pm UTC](https://discourse.julialang.org/t/ann-sparips-jl-practical-sparsification-of-rips-complexes-topological-data-analysis/16422 "2019-02-01T20:10:45Z")

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New package: This is not yet registered, and a very early version anyway. So you will need to install it by (v1.0) pkg\> add https://github.com/bbrehm/Sparips.jl (v1.0) pkg\> build Sparips The use and rationale is exp…

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## [Linear regression with a positive definite matrix in GLM.jl?](https://discourse.julialang.org/t/linear-regression-with-a-positive-definite-matrix-in-glm-jl/14638)

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**Author:** [@sebastianskejoe](https://discourse.julialang.org/u/sebastianskejoe)\
**Replies:** 11\
**Last updated:** [February 1, 2019, 7:37pm UTC](https://discourse.julialang.org/t/linear-regression-with-a-positive-definite-matrix-in-glm-jl/14638 "2019-02-01T19:37:47Z")

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Hi I’m trying to perform linear regression on a small dataset (these are just sample data, the real dataset will be much larger), but I’m running into a problem with the matrix not being positive definite, which it very…

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## [Reading Satellite Data](https://discourse.julialang.org/t/reading-satellite-data/20231)

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**Author:** [@johnh](https://discourse.julialang.org/u/johnh)\
**Replies:** 6\
**Last updated:** [February 1, 2019, 11:17am UTC](https://discourse.julialang.org/t/reading-satellite-data/20231 "2019-02-01T11:17:12Z")

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Anybody please tell me how to read Geotiff format files? These are satellite data. I bet there is already a Julia package for this!

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## [GPU sort WIP (GPU 1000x faster than CPU? I must be doing something wrong)](https://discourse.julialang.org/t/gpu-sort-wip-gpu-1000x-faster-than-cpu-i-must-be-doing-something-wrong/20310)

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**Author:** [@xiaodai](https://discourse.julialang.org/u/xiaodai)\
**Replies:** 12\
**Last updated:** [January 31, 2019, 8:46pm UTC](https://discourse.julialang.org/t/gpu-sort-wip-gpu-1000x-faster-than-cpu-i-must-be-doing-something-wrong/20310 "2019-01-31T20:46:10Z")

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I am working on a GPU sort using CUDAnative and CuArrays. This is my generic bitonic sort (can only sort arrays of size 2^N elements for now). I am sorting 2^26=67\_108\_864 Float32s using the optimised Radixsort (CPU) vs…

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## [Most efficient way of \_waiting\_ for GPU results?](https://discourse.julialang.org/t/most-efficient-way-of-waiting-for-gpu-results/19193)

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**Author:** [@anj](https://discourse.julialang.org/u/anj)\
**Replies:** 20\
**Last updated:** [January 31, 2019, 7:25pm UTC](https://discourse.julialang.org/t/most-efficient-way-of-waiting-for-gpu-results/19193 "2019-01-31T19:25:11Z")

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Hello, I am using the following pattern today to synchronize results of the GPU processing back to CPU (CUDAnative, CuArrays, CUDAdrv) # data\_out\_gpu and data\_in\_gpu are CuArrays #do\_some\_gpu\_processing() will launch k…

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## [CuArray/CUDAnative argmin paradoxical performance](https://discourse.julialang.org/t/cuarray-cudanative-argmin-paradoxical-performance/20194)

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**Author:** [@Alex\_Ellison](https://discourse.julialang.org/u/Alex_Ellison)\
**Replies:** 2\
**Last updated:** [January 31, 2019, 5:35pm UTC](https://discourse.julialang.org/t/cuarray-cudanative-argmin-paradoxical-performance/20194 "2019-01-31T17:35:10Z")

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Hey there, I have a kernel which computes some 3D CuArray of float32s, and I’d like to run argmin on one of the axes, resulting in a 2D set of indices. For some reason, if I invoke CUDAnative.argmin on the original host…

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## [How do I tweak spacing in Plots labels?](https://discourse.julialang.org/t/how-do-i-tweak-spacing-in-plots-labels/20316)

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**Author:** [@Noel\_Araujo](https://discourse.julialang.org/u/Noel_Araujo)\
**Replies:** 0\
**Last updated:** [January 31, 2019, 3:18pm UTC](https://discourse.julialang.org/t/how-do-i-tweak-spacing-in-plots-labels/20316 "2019-01-31T15:18:04Z")

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I would like to put the ylabel near the yticks, because the “head” of my Gamma is being “cutted” in GR backend. Is there any option to do that ? using Plots, LaTeXStrings scatter(rand(2000), rand(2000), guidefo…

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## [Trying to identify possible optimizations (or errors) in a graph algorithm](https://discourse.julialang.org/t/trying-to-identify-possible-optimizations-or-errors-in-a-graph-algorithm/19998)

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**Author:** [@opera\_malenky](https://discourse.julialang.org/u/opera_malenky)\
**Replies:** 24\
**Last updated:** [January 31, 2019, 11:09am UTC](https://discourse.julialang.org/t/trying-to-identify-possible-optimizations-or-errors-in-a-graph-algorithm/19998 "2019-01-31T11:09:34Z")

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I am trying to re-implement (in Julia) some old C++ code I wrote a while ago to do certain operations on graphs, however, I’m not confident the performance is as good as I remember it… I was hoping someone might be able …

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## [UndefVarError: ClpSolver not defined](https://discourse.julialang.org/t/undefvarerror-clpsolver-not-defined/19481)

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**Author:** [@Rajat\_Sanyal](https://discourse.julialang.org/u/Rajat_Sanyal)\
**Replies:** 9\
**Last updated:** [January 31, 2019, 7:02am UTC](https://discourse.julialang.org/t/undefvarerror-clpsolver-not-defined/19481 "2019-01-31T07:02:17Z")

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Hi, I am written a small code to elaborate the error which I am facing: using JuMP using Cbc m = Model(solver = ClpSolver()) @variable(m, 0 \<= x \<= 2 ) @variable(m, 0 \<= y \<= 30 ) @objective(m, Max, 5x + 3y ) @constrain…

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## [Generic CPU and GPU loops with tiled iteration](https://discourse.julialang.org/t/generic-cpu-and-gpu-loops-with-tiled-iteration/20295)

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**Author:** [@datnamer](https://discourse.julialang.org/u/datnamer)\
**Replies:** 3\
**Last updated:** [January 31, 2019, 3:55am UTC](https://discourse.julialang.org/t/generic-cpu-and-gpu-loops-with-tiled-iteration/20295 "2019-01-31T03:55:11Z")

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Can Tilediteration be used to write loops that work on GPU and CPUs without having to have separate kernels for the latter or stuff everything into broadcast(s)? @tim.holy

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## [How can I change the series order of the legend in Plots?](https://discourse.julialang.org/t/how-can-i-change-the-series-order-of-the-legend-in-plots/20278)

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**Author:** [@NiclasMattsson](https://discourse.julialang.org/u/NiclasMattsson)\
**Replies:** 2\
**Last updated:** [January 30, 2019, 9:46pm UTC](https://discourse.julialang.org/t/how-can-i-change-the-series-order-of-the-legend-in-plots/20278 "2019-01-30T21:46:50Z")

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When making stacked bar plots or stacked area plots, the default series order in the legend appears upside-down compared to the order in the plot itself. Example using the groupedbar() recipe provided by StatPlots: usin…

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## [Web site with deep learning examples](https://discourse.julialang.org/t/web-site-with-deep-learning-examples/20230)

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**Author:** [@johnh](https://discourse.julialang.org/u/johnh)\
**Replies:** 3\
**Last updated:** [January 30, 2019, 10:15am UTC](https://discourse.julialang.org/t/web-site-with-deep-learning-examples/20230 "2019-01-30T10:15:00Z")

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Sorry to ask a simple question. There is a website with live examples of Julia machine learning. I have searched but cannot find it. If I recall it is a .io site IF this rings a bell with anyone please let me have the a…

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## [Parallel data loading to GPU arrays](https://discourse.julialang.org/t/parallel-data-loading-to-gpu-arrays/11321)

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**Author:** [@kolia](https://discourse.julialang.org/u/kolia)\
**Replies:** 3\
**Last updated:** [January 30, 2019, 3:07am UTC](https://discourse.julialang.org/t/parallel-data-loading-to-gpu-arrays/11321 "2019-01-30T03:07:54Z")

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Anyone have pointers to loading data into CuArrays with background tasks while the main thread or process is busy training a Flux model? Flux seems to have the same if not more flexibility than pytorch, so they fall in …

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## [How does StatsBase.skewness work?](https://discourse.julialang.org/t/how-does-statsbase-skewness-work/20146)

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**Author:** [@Gunter\_Faes](https://discourse.julialang.org/u/Gunter_Faes)\
**Replies:** 29\
**Last updated:** [January 29, 2019, 9:31pm UTC](https://discourse.julialang.org/t/how-does-statsbase-skewness-work/20146 "2019-01-29T21:31:39Z")

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Hello, It is about the application of the skewness function. But I admit that I am not (yet) a Julia expert. But to my question: I have a DataFrame Rotwein and when I make the following function call … julia\> StatsBas…

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## [Writing fast stencil computation kernels that work on both CPUs and GPUs](https://discourse.julialang.org/t/writing-fast-stencil-computation-kernels-that-work-on-both-cpus-and-gpus/20200)

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**Author:** [@PolarizedPoutine](https://discourse.julialang.org/u/PolarizedPoutine)\
**Replies:** 3\
**Last updated:** [January 29, 2019, 2:04pm UTC](https://discourse.julialang.org/t/writing-fast-stencil-computation-kernels-that-work-on-both-cpus-and-gpus/20200 "2019-01-29T14:04:13Z")

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Hi everyone, I am developing a 3D finite volume ocean model in Julia (Oceananigans.jl). For now I have the model running reasonably fast on a CPU and I’m trying to get it to run efficiently on a GPU using CUDAnative and…

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## [How to do Arpack.eigs(v-\>A\*v, ...)?](https://discourse.julialang.org/t/how-to-do-arpack-eigs-v-a-v/20192)

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**Author:** [@bsxfan](https://discourse.julialang.org/u/bsxfan)\
**Replies:** 4\
**Last updated:** [January 29, 2019, 1:05pm UTC](https://discourse.julialang.org/t/how-to-do-arpack-eigs-v-a-v/20192 "2019-01-29T13:05:47Z")

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I need to find a few of the principal eigenvalues and eigenvectors of a very large (symmetric, real) matrix that is implicitly defined via its matrix-vector product. I know Arpack can do this, because it only needs to do…

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## [Problem MathProgBase.LinearQuadraticModel with Gurobi](https://discourse.julialang.org/t/problem-mathprogbase-linearquadraticmodel-with-gurobi/19910)

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**Author:** [@Pierre-Louis\_Poirion](https://discourse.julialang.org/u/Pierre-Louis_Poirion)\
**Replies:** 3\
**Last updated:** [January 28, 2019, 2:44pm UTC](https://discourse.julialang.org/t/problem-mathprogbase-linearquadraticmodel-with-gurobi/19910 "2019-01-28T14:44:38Z")

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Hello, I have got a problem with this 2 lines m\_internal = MathProgBase.LinearQuadraticModel(GurobiSolver()) MathProgBase.loadproblem!(m\_internal, s) where s is a mps file the error is \*\*UndefVarError: getconstrLB n…

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## [Cholesky factorization for slightly non-Hermitian matrices](https://discourse.julialang.org/t/cholesky-factorization-for-slightly-non-hermitian-matrices/20063)

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**Author:** [@caldwellshane](https://discourse.julialang.org/u/caldwellshane)\
**Replies:** 18\
**Last updated:** [January 28, 2019, 12:30pm UTC](https://discourse.julialang.org/t/cholesky-factorization-for-slightly-non-hermitian-matrices/20063 "2019-01-28T12:30:39Z")

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I wrote a function to rotate the coordinates of a 2D MvNormal distribution, and in the course of testing it I discovered this, surprising to me, behavior of the Cholesky factorization: julia\> VERSION v"1.1.0" julia\> ro…

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## [Waiting on a Remote Condition](https://discourse.julialang.org/t/waiting-on-a-remote-condition/20170)

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**Author:** [@rohanmclure](https://discourse.julialang.org/u/rohanmclure)\
**Replies:** 0\
**Last updated:** [January 28, 2019, 5:33am UTC](https://discourse.julialang.org/t/waiting-on-a-remote-condition/20170 "2019-01-28T05:33:52Z")

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I’m hoping to use Conditions to synchronise communication between a master and worker process. The notify function will wake up only the tasks that are already waiting on a condition. If we do not know which of the foll…

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## [How to update JuMP?](https://discourse.julialang.org/t/how-to-update-jump/20153)

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**Author:** [@mpal](https://discourse.julialang.org/u/mpal)\
**Replies:** 3\
**Last updated:** [January 28, 2019, 2:07am UTC](https://discourse.julialang.org/t/how-to-update-jump/20153 "2019-01-28T02:07:02Z")

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I am using JuMP v"0.18.5+". But in this version, const MOI = JuMP.MathOptInterface results, UndefVarError: MathOptInterface not defined Stacktrace: \[1\] getproperty(::Module, ::Symbol) at ./sysimg.jl:13 \[2\] top-leve…

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