# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?page=530

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**Page:** 531

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## [Implementing parallel computing in finite element problems](https://discourse.julialang.org/t/implementing-parallel-computing-in-finite-element-problems/13473)

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**Author:** [@thehalfspace](https://discourse.julialang.org/u/thehalfspace)\
**Replies:** 6\
**Last updated:** [August 15, 2018, 3:00pm UTC](https://discourse.julialang.org/t/implementing-parallel-computing-in-finite-element-problems/13473 "2018-08-15T15:00:13Z")

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Hi all, I am very new to parallel programming, and relatively new to Julia. I have a spectral element code (higher order finite element) for numerical simulation of earthquakes, that I wish to parallelize. I have read …

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## [JuMP/Ipopt failing on simple problem](https://discourse.julialang.org/t/jump-ipopt-failing-on-simple-problem/13209)

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**Author:** [@Arrigo\_Benedetti](https://discourse.julialang.org/u/Arrigo_Benedetti)\
**Replies:** 4\
**Last updated:** [August 14, 2018, 10:44pm UTC](https://discourse.julialang.org/t/jump-ipopt-failing-on-simple-problem/13209 "2018-08-14T22:44:38Z")

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In order to debug the issue that I mentioned in the thread https://discourse.julialang.org/t/error-in-jump-nlexpression/13147 I decided to write a simple program to solve a constrained nonlinear optimization problem in o…

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## [Finding Roots with Roots.jl on ODE solutions](https://discourse.julialang.org/t/finding-roots-with-roots-jl-on-ode-solutions/13463)

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**Author:** [@OvidiusCicero](https://discourse.julialang.org/u/OvidiusCicero)\
**Replies:** 6\
**Last updated:** [August 14, 2018, 10:08pm UTC](https://discourse.julialang.org/t/finding-roots-with-roots-jl-on-ode-solutions/13463 "2018-08-14T22:08:03Z")

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I can find roots of an ODE solution nicely in this working, simplified example using DifferentialEquations using Plots using Roots prob = ODEProblem( function(u::Float64,p,t) return -u end, 1.0, (0.0,1.…

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## [Share an already defined variable to all processes](https://discourse.julialang.org/t/share-an-already-defined-variable-to-all-processes/13421)

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**Author:** [@e3c6](https://discourse.julialang.org/u/e3c6)\
**Replies:** 3\
**Last updated:** [August 14, 2018, 5:20pm UTC](https://discourse.julialang.org/t/share-an-already-defined-variable-to-all-processes/13421 "2018-08-14T17:20:55Z")

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If I have a variable already defined in one process, how can I share it with all the other processes? @everywhere foo=1 does this for a new definition of foo. But suppose I already assigned foo to a value in the current…

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## [Solving a system of differential equations with DifferentailEqations.jl](https://discourse.julialang.org/t/solving-a-system-of-differential-equations-with-differentaileqations-jl/13406)

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**Author:** [@OvidiusCicero](https://discourse.julialang.org/u/OvidiusCicero)\
**Replies:** 2\
**Last updated:** [August 13, 2018, 9:27pm UTC](https://discourse.julialang.org/t/solving-a-system-of-differential-equations-with-differentaileqations-jl/13406 "2018-08-13T21:27:08Z")

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Hello there when I try to solve a system of ordinary differential equations with the following code: using DifferentialEquations function dgl(du,u,p,t) du\[1\] = u\[3\] du\[2\] = u\[4\] du\[3\] = -sqrt(u\[4\]^2+u\[5\]^2)\*u\[3\] d…

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## [Way to make radial gradient in 2-d PGFPlot?](https://discourse.julialang.org/t/way-to-make-radial-gradient-in-2-d-pgfplot/13271)

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**Author:** [@djsegal](https://discourse.julialang.org/u/djsegal)\
**Replies:** 2\
**Last updated:** [August 13, 2018, 1:46pm UTC](https://discourse.julialang.org/t/way-to-make-radial-gradient-in-2-d-pgfplot/13271 "2018-08-13T13:46:53Z")

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Let’s say you wanted to make a plot like: How would you make a radial gradient using Plots.jl with the PGFPlots backend?

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## [System Dynamics packages](https://discourse.julialang.org/t/system-dynamics-packages/8222)

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**Author:** [@smldis](https://discourse.julialang.org/u/smldis)\
**Replies:** 12\
**Last updated:** [August 12, 2018, 8:21pm UTC](https://discourse.julialang.org/t/system-dynamics-packages/8222 "2018-08-12T20:21:52Z")

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Continuing the discussion from this post in 1.0 adoption path?: System dynamics ecosystem in julia needs coordination and development efforts. If anybody wants to discuss in this post I am kind of interested too. @jlper…

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## [JuMP implementation of "Real-Time Order Fulfillment Decisions"](https://discourse.julialang.org/t/jump-implementation-of-real-time-order-fulfillment-decisions/13303)

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**Author:** [@clausherther](https://discourse.julialang.org/u/clausherther)\
**Replies:** 0\
**Last updated:** [August 12, 2018, 3:28pm UTC](https://discourse.julialang.org/t/jump-implementation-of-real-time-order-fulfillment-decisions/13303 "2018-08-12T15:28:32Z")

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Hello, I was wondering if anyone knew of a JuMP (or any other, really) implementation of this paper: “Benefits of Reevaluating Real-Time Order Fulfillment Decisions”. https://www.researchgate.net/publication/220391384…

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## [Clean Numerical Simulation (Taylor Series Method)](https://discourse.julialang.org/t/clean-numerical-simulation-taylor-series-method/12893)

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**Author:** [@m4r35n357](https://discourse.julialang.org/u/m4r35n357)\
**Replies:** 9\
**Last updated:** [August 12, 2018, 1:41pm UTC](https://discourse.julialang.org/t/clean-numerical-simulation-taylor-series-method/12893 "2018-08-12T13:41:30Z")

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Hi all, very new to Julia, and not in academia BTW. I have been investigating the opinions and findings in this paper, and I thought I would contribute some Julia code which performs the aforementioned simulation to pot…

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## [Observables for widgets that get rebuilt?](https://discourse.julialang.org/t/observables-for-widgets-that-get-rebuilt/13285)

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**Author:** [@Raf](https://discourse.julialang.org/u/Raf)\
**Replies:** 0\
**Last updated:** [August 12, 2018, 10:12am UTC](https://discourse.julialang.org/t/observables-for-widgets-that-get-rebuilt/13285 "2018-08-12T10:12:01Z")

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So I have a bunch of models that output the same plots, with parameter control. I want to be able to swap the models and the controller sliders update. Then using the new sliders should update the plots. I have it mostl…

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## [Help with Makie at Hackfest?](https://discourse.julialang.org/t/help-with-makie-at-hackfest/13247)

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**Author:** [@johnh](https://discourse.julialang.org/u/johnh)\
**Replies:** 1\
**Last updated:** [August 11, 2018, 7:08pm UTC](https://discourse.julialang.org/t/help-with-makie-at-hackfest/13247 "2018-08-11T19:08:56Z")

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If anyone is good at using Makie could I have some hints and tips at the Hackfest?

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## [2D Plots... some missing possibilities?](https://discourse.julialang.org/t/2d-plots-some-missing-possibilities/12894)

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**Author:** [@BLI](https://discourse.julialang.org/u/BLI)\
**Replies:** 12\
**Last updated:** [August 10, 2018, 3:40pm UTC](https://discourse.julialang.org/t/2d-plots-some-missing-possibilities/12894 "2018-08-10T15:40:07Z")

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I’m continuing to explore Plots (mainly 2D for now). Some useful things are missing, others are perhaps only hard to find? Figure title – has not been implemented yet. There are some workarounds, but these are somewhat…

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## [Model solving - method error using NLsolve](https://discourse.julialang.org/t/model-solving-method-error-using-nlsolve/13035)

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**Author:** [@axelle](https://discourse.julialang.org/u/axelle)\
**Replies:** 15\
**Last updated:** [August 10, 2018, 9:12am UTC](https://discourse.julialang.org/t/model-solving-method-error-using-nlsolve/13035 "2018-08-10T09:12:14Z")

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Hi, I am stuck with a code (solving an economic model) and would need some help. I am sorry if the mistake is obvious, but I am new to this and would really need some help there. I have the following code: function bk\_o…

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## [Error in JuMP @NLexpression](https://discourse.julialang.org/t/error-in-jump-nlexpression/13147)

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**Author:** [@Arrigo\_Benedetti](https://discourse.julialang.org/u/Arrigo_Benedetti)\
**Replies:** 0\
**Last updated:** [August 10, 2018, 6:34am UTC](https://discourse.julialang.org/t/error-in-jump-nlexpression/13147 "2018-08-10T06:34:09Z")

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I am running the following code with Julia 0.6.4: using JuMP using NLopt using FastGaussQuadrature using SpecialFunctions function FisherInf(args...) N = 32 t = \[x\[i\] for i=1:N\] lambda = \[args\[i\] for i…

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## [Flux: GPU slower than CPU?](https://discourse.julialang.org/t/flux-gpu-slower-than-cpu/13072)

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**Author:** [@rkat](https://discourse.julialang.org/u/rkat)\
**Replies:** 7\
**Last updated:** [August 10, 2018, 5:55am UTC](https://discourse.julialang.org/t/flux-gpu-slower-than-cpu/13072 "2018-08-10T05:55:08Z")

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I have a loss function which I’ve defined using Flux. On my boring old CPU on one batch, it performs like this: julia\> @time loss(x, y) 0.071089 seconds (402 allocations: 20.235 MiB, 4.37% gc time) 1.3092503770133925 …

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## [JLD and FileIO StackOverflowError: error when saving EPL fixtures data](https://discourse.julialang.org/t/jld-and-fileio-stackoverflowerror-error-when-saving-epl-fixtures-data/13139)

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**Author:** [@xiaodai](https://discourse.julialang.org/u/xiaodai)\
**Replies:** 0\
**Last updated:** [August 10, 2018, 3:05am UTC](https://discourse.julialang.org/t/jld-and-fileio-stackoverflowerror-error-when-saving-epl-fixtures-data/13139 "2018-08-10T03:05:40Z")

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I run the below code, which should work on your computer if you have all the packages installed. Basically it downloads some CSV from football-data.co.uk and tries to save it as a JLD file. The last line always gives an …

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## [CLBlast, a tuned OpenCL BLAS library](https://discourse.julialang.org/t/clblast-a-tuned-opencl-blas-library/13082)

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**Author:** [@ranocha](https://discourse.julialang.org/u/ranocha)\
**Replies:** 6\
**Last updated:** [August 9, 2018, 2:54pm UTC](https://discourse.julialang.org/t/clblast-a-tuned-opencl-blas-library/13082 "2018-08-09T14:54:22Z")

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I’ve written a wrapper for CLBlast, a " tuned OpenCL BLAS library", which can be found at GitHub - ranocha/CLBlast.jl: Julia wrapper of CLBlast, a "tuned OpenCL BLAS library".. Most parts seem to work and there is a perf…

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## [SatelliteToolbox.jl and ReferenceFrameRotations.jl has now full support for Julia 0.7 and 1.0](https://discourse.julialang.org/t/satellitetoolbox-jl-and-referenceframerotations-jl-has-now-full-support-for-julia-0-7-and-1-0/13054)

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**Author:** [@Ronis\_BR](https://discourse.julialang.org/u/Ronis_BR)\
**Replies:** 0\
**Last updated:** [August 9, 2018, 2:38am UTC](https://discourse.julialang.org/t/satellitetoolbox-jl-and-referenceframerotations-jl-has-now-full-support-for-julia-0-7-and-1-0/13054 "2018-08-09T02:38:07Z")

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Hi guys! I just tagged v0.3.0 of both SatelliteToolbox.jl and ReferenceFrameRotations.jl. With those new version, full support for v0.7 and v1.0 is added (no more warnings! :tada::tada::tada:). Unfortunately, together …

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## [Deleting @NLconstraint from JuMP model](https://discourse.julialang.org/t/deleting-nlconstraint-from-jump-model/13002)

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**Author:** [@chkwon](https://discourse.julialang.org/u/chkwon)\
**Replies:** 3\
**Last updated:** [August 8, 2018, 3:19pm UTC](https://discourse.julialang.org/t/deleting-nlconstraint-from-jump-model/13002 "2018-08-08T15:19:59Z")

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JuMP v0.18: When I want to delete all @NLconstraints added to the JuMP model, is it safe and sufficient to do the following? m.nlpdata.nlconstr = Array{JuMP.GenericRangeConstraint{JuMP.NonlinearExprData},1}(0)

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## [Memory allocation in multi-thread vs single-thread](https://discourse.julialang.org/t/memory-allocation-in-multi-thread-vs-single-thread/12999)

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**Author:** [@aabrkay](https://discourse.julialang.org/u/aabrkay)\
**Replies:** 0\
**Last updated:** [August 7, 2018, 3:23pm UTC](https://discourse.julialang.org/t/memory-allocation-in-multi-thread-vs-single-thread/12999 "2018-08-07T15:23:38Z")

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Dear All, I have a question about the significant difference in memory allocation between the multi-threads and single threads. I was experimenting Walk on Sphere method for Poisson equation, which is an embarrassingly p…

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## [Gadfly Performance Issue](https://discourse.julialang.org/t/gadfly-performance-issue/12982)

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**Author:** [@GantZA](https://discourse.julialang.org/u/GantZA)\
**Replies:** 2\
**Last updated:** [August 7, 2018, 11:39am UTC](https://discourse.julialang.org/t/gadfly-performance-issue/12982 "2018-08-07T11:39:55Z")

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I’m trying to create a QQ plot for about 400 000 inter-arrival times, but the resulting plot takes far too long to open or julia crashes. Is there a way to plot more efficiently? plot\_test = plot( x = test1\[:ita\], …

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## [ANN: MetaFields.jl and Flatten.jl - packages for writing composable models](https://discourse.julialang.org/t/ann-metafields-jl-and-flatten-jl-packages-for-writing-composable-models/12849)

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**Author:** [@Raf](https://discourse.julialang.org/u/Raf)\
**Replies:** 10\
**Last updated:** [August 7, 2018, 10:14am UTC](https://discourse.julialang.org/t/ann-metafields-jl-and-flatten-jl-packages-for-writing-composable-models/12849 "2018-08-07T10:14:35Z")

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I’ve been putting together a few biophysical models over the last year, and have constantly encountered what I feel to be the core software problem in my field: sharing high performance code in general ways never happens…

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## [Has anyone made scatter plots with hexagonal binning?](https://discourse.julialang.org/t/has-anyone-made-scatter-plots-with-hexagonal-binning/12909)

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**Author:** [@djsegal](https://discourse.julialang.org/u/djsegal)\
**Replies:** 7\
**Last updated:** [August 7, 2018, 8:01am UTC](https://discourse.julialang.org/t/has-anyone-made-scatter-plots-with-hexagonal-binning/12909 "2018-08-07T08:01:59Z")

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Something came up in my research where I’m doing a scatter plot with way too many points. Has anyone had experience making hexagonally binned plots like the ones seen here: // preferably with pgfplots (or plots.jl), …

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## [JuMP joins NumFOCUS](https://discourse.julialang.org/t/jump-joins-numfocus/12954)

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**Author:** [@miles.lubin](https://discourse.julialang.org/u/miles.lubin)\
**Replies:** 0\
**Last updated:** [August 6, 2018, 6:53pm UTC](https://discourse.julialang.org/t/jump-joins-numfocus/12954 "2018-08-06T18:53:51Z")

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Enjoy JuliaCon!

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## [Performance of Optim.jl vs. Matlab's fminunc](https://discourse.julialang.org/t/performance-of-optim-jl-vs-matlabs-fminunc/12866)

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**Author:** [@tyleransom](https://discourse.julialang.org/u/tyleransom)\
**Replies:** 12\
**Last updated:** [August 6, 2018, 11:43am UTC](https://discourse.julialang.org/t/performance-of-optim-jl-vs-matlabs-fminunc/12866 "2018-08-06T11:43:54Z")

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I’ve been comparing the performance of Optim.jl with Matlab’s fminunc. Surprisingly, Optim’s L-BFGS algorithm doesn’t always beat fminunc. I was wondering if anyone knows why this might be. Here’s the set up: Use a si…

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## [Julia interface to Bullet Physics?](https://discourse.julialang.org/t/julia-interface-to-bullet-physics/12617)

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**Author:** [@jbrea](https://discourse.julialang.org/u/jbrea)\
**Replies:** 19\
**Last updated:** [August 6, 2018, 8:42am UTC](https://discourse.julialang.org/t/julia-interface-to-bullet-physics/12617 "2018-08-06T08:42:49Z")

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I came across the Bullet Physics SDK and was impressed by the rich collection of examples. Now I wonder: Is anybody interested in a Julia interface to the Bullet Physics SDK? Did somebody already start working on this? …

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## [Blink webserver](https://discourse.julialang.org/t/blink-webserver/12832)

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**Author:** [@Raf](https://discourse.julialang.org/u/Raf)\
**Replies:** 4\
**Last updated:** [August 6, 2018, 2:53am UTC](https://discourse.julialang.org/t/blink-webserver/12832 "2018-08-06T02:53:44Z")

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So I have Blink.jl running electron locally, with widgets, plotting and simulation visuals etc. But I’d like to run it on a server. Apparently Blink facilitates using Mux to serve a simple app: “Pages may be served over…

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## [Julia Plots.jl: changing marker colour from series recipe](https://discourse.julialang.org/t/julia-plots-jl-changing-marker-colour-from-series-recipe/12914)

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**Author:** [@tanhevg](https://discourse.julialang.org/u/tanhevg)\
**Replies:** 3\
**Last updated:** [August 5, 2018, 7:06pm UTC](https://discourse.julialang.org/t/julia-plots-jl-changing-marker-colour-from-series-recipe/12914 "2018-08-05T19:06:05Z")

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I am trying to put together a Plots.jl user recipe, that would create several scatter plots and histograms arranged in a grid. The scatter plots should occupy the lower triangle of the grid. Histograms go on the diagon…

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## [Should ::SVD \\ ::Vector fall back on pinv?](https://discourse.julialang.org/t/should-svd-vector-fall-back-on-pinv/12900)

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**Author:** [@mohamed82008](https://discourse.julialang.org/u/mohamed82008)\
**Replies:** 4\
**Last updated:** [August 5, 2018, 3:57pm UTC](https://discourse.julialang.org/t/should-svd-vector-fall-back-on-pinv/12900 "2018-08-05T15:57:16Z")

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At the back of my head, I was wrongly assuming that svd(A) \\ b should be falling back on an efficient pinv(A) \* b. For instance I find it surprising that julia\> qr(zeros(3,3), Val(true)) \\ ones(3) 3-element Array{Float6…

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## [Guroubi decides not to apply usercuts during the search?](https://discourse.julialang.org/t/guroubi-decides-not-to-apply-usercuts-during-the-search/12886)

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**Author:** [@CBongiova](https://discourse.julialang.org/u/CBongiova)\
**Replies:** 0\
**Last updated:** [August 4, 2018, 8:21am UTC](https://discourse.julialang.org/t/guroubi-decides-not-to-apply-usercuts-during-the-search/12886 "2018-08-04T08:21:27Z")

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\*\* Same question posted on Github at: https://github.com/JuliaOpt/JuMP.jl/issues/1391#issuecomment-410490319 Hello, I have an MILP which I solve through a branch-and-cut procedure (hence using a callback function). I a…

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