# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=495

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**Page:** 496

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## [Differential Equation Parameter Estimation Using Only A Subset of Variables](https://discourse.julialang.org/t/differential-equation-parameter-estimation-using-only-a-subset-of-variables/23423)

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**Author:** [@alewolf](https://discourse.julialang.org/u/alewolf)\
**Replies:** 32\
**Last updated:** [May 30, 2019, 3:52pm UTC](https://discourse.julialang.org/t/differential-equation-parameter-estimation-using-only-a-subset-of-variables/23423 "2019-05-30T15:52:34Z")

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Hi, I have a DAE problem with 37 variables - I only have data for 12 of those variables - I would like to run parameter estimation with an L2Loss function based only on the 12 variables for which I actually have data. …

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## [Efficient QR factorization](https://discourse.julialang.org/t/efficient-qr-factorization/24767)

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**Author:** [@raphaelsaavedra](https://discourse.julialang.org/u/raphaelsaavedra)\
**Replies:** 3\
**Last updated:** [May 30, 2019, 2:49pm UTC](https://discourse.julialang.org/t/efficient-qr-factorization/24767 "2019-05-30T14:49:52Z")

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Hello, I’m having some issues with QR factorization in Julia 1.0. I want to efficiently compute the QR factorization of the transpose of a matrix and save only Q. Back in 0.6, there were LAPACK functions that did this e…

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## [Shock Decompositions in Julia](https://discourse.julialang.org/t/shock-decompositions-in-julia/24761)

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**Author:** [@nik.ltin](https://discourse.julialang.org/u/nik.ltin)\
**Replies:** 5\
**Last updated:** [May 30, 2019, 2:42pm UTC](https://discourse.julialang.org/t/shock-decompositions-in-julia/24761 "2019-05-30T14:42:57Z")

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Hello, I’m attempting to do historical cumulated shock decompositions in Julia similar to those done in Matlab’s Dynare (attached an example below). Not sure as to how to go about doing this? Using Plots.jl to match up e…

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## [Zygote load error on recent Julia version](https://discourse.julialang.org/t/zygote-load-error-on-recent-julia-version/24763)

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**Author:** [@tanders](https://discourse.julialang.org/u/tanders)\
**Replies:** 2\
**Last updated:** [May 30, 2019, 12:34pm UTC](https://discourse.julialang.org/t/zygote-load-error-on-recent-julia-version/24763 "2019-05-30T12:34:11Z")

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Dear all, I am trying to use Zygote on a recent Julia installation, but ran into a load error. The details are reported at the link below. https://github.com/FluxML/Zygote.jl/issues/206 I am very new still to this fie…

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## [Approximating a Quadratic Function with Flux](https://discourse.julialang.org/t/approximating-a-quadratic-function-with-flux/24034)

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**Author:** [@mboutros](https://discourse.julialang.org/u/mboutros)\
**Replies:** 6\
**Last updated:** [May 30, 2019, 8:24am UTC](https://discourse.julialang.org/t/approximating-a-quadratic-function-with-flux/24034 "2019-05-30T08:24:57Z")

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I’m trying to get familiar with neural networks and Flux by estimating a series of simple models. First, I can successfully estimate a linear model using Flux: using Plots using Flux using Flux: @epochs gridsize = 100;…

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## [How to remove the bar strokeline in Plots.jl](https://discourse.julialang.org/t/how-to-remove-the-bar-strokeline-in-plots-jl/24753)

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**Author:** [@babaq](https://discourse.julialang.org/u/babaq)\
**Replies:** 3\
**Last updated:** [May 30, 2019, 6:25am UTC](https://discourse.julialang.org/t/how-to-remove-the-bar-strokeline-in-plots-jl/24753 "2019-05-30T06:25:03Z")

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Hi, I am trying to do a bar plot, with no gap between them, but I don’t know how to remove the black stroke lines around each bar. Anyone knows how to achieve this in Plots? Thanks

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## [Normalized Laplacian with LightGraphs.jl](https://discourse.julialang.org/t/normalized-laplacian-with-lightgraphs-jl/24748)

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**Author:** [@andferrari](https://discourse.julialang.org/u/andferrari)\
**Replies:** 0\
**Last updated:** [May 29, 2019, 9:08pm UTC](https://discourse.julialang.org/t/normalized-laplacian-with-lightgraphs-jl/24748 "2019-05-29T21:08:00Z")

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I want to compute the Normalized Laplacian of a graph g. Is there something more straightforward than? adjmat = LightGraphs.LinAlg.CombinatorialAdjacency(adjacency\_matrix(g)) Ln = I - Diagonal(adjmat.D.^(-1/2))\*(adjmat…

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## [Special method for finding eigenvalues of a large sparse symmetric matrix?](https://discourse.julialang.org/t/special-method-for-finding-eigenvalues-of-a-large-sparse-symmetric-matrix/9621)

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**Author:** [@406700](https://discourse.julialang.org/u/406700)\
**Replies:** 17\
**Last updated:** [May 29, 2019, 5:50pm UTC](https://discourse.julialang.org/t/special-method-for-finding-eigenvalues-of-a-large-sparse-symmetric-matrix/9621 "2019-05-29T17:50:37Z")

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Hi, I am looking to solve the eigenvalues of sparse symmetric matrix of ~ 14000x14000. Eigfact is too slow, and didn’t give results after an hour running. (8gb ram i7 processor) Are there special iteritive methods? …

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## [Lifting a Julia function into a Flux "layer"](https://discourse.julialang.org/t/lifting-a-julia-function-into-a-flux-layer/13712)

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**Author:** [@cscherrer](https://discourse.julialang.org/u/cscherrer)\
**Replies:** 7\
**Last updated:** [May 29, 2019, 4:11pm UTC](https://discourse.julialang.org/t/lifting-a-julia-function-into-a-flux-layer/13712 "2019-05-29T16:11:11Z")

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Flux confused me for a long time. I got the first example in the docs to work: using Flux.Tracker W = param(rand(2, 5)) b = param(rand(2)) predict(x) = W\*x .+ b loss(x, y) = sum((predict(x) .- y).^2) x, y = rand(5), …

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## [Integer variable as index of input matrix](https://discourse.julialang.org/t/integer-variable-as-index-of-input-matrix/24725)

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**Author:** [@Raminel](https://discourse.julialang.org/u/Raminel)\
**Replies:** 2\
**Last updated:** [May 29, 2019, 2:08pm UTC](https://discourse.julialang.org/t/integer-variable-as-index-of-input-matrix/24725 "2019-05-29T14:08:14Z")

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Hi people, Can I formulate an expression in Julia and use an integer variable as an index of an input matrix? @variable(m, 1 \<= t\[1:3, 1:3\] \<= 8, Int) P = \[ 90 80 60 70 50 30 10 0\] for i = 1:3 for j = 1:3 M\[i,j\] =…

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## [Gaussian process in Julia](https://discourse.julialang.org/t/gaussian-process-in-julia/22900)

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**Author:** [@yusri-dh](https://discourse.julialang.org/u/yusri-dh)\
**Replies:** 13\
**Last updated:** [May 29, 2019, 1:33pm UTC](https://discourse.julialang.org/t/gaussian-process-in-julia/22900 "2019-05-29T13:33:29Z")

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Hello all, Julia newbie here. I am sorry I am not sure whether this is the right place to ask this question. If no I will delete it later. Is there any well-maintained package dedicated for gaussian process in Julia lik…

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## [Reading/parsing .ab1 sequencing files](https://discourse.julialang.org/t/reading-parsing-ab1-sequencing-files/23555)

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**Author:** [@solf1re2](https://discourse.julialang.org/u/solf1re2)\
**Replies:** 10\
**Last updated:** [May 29, 2019, 12:42pm UTC](https://discourse.julialang.org/t/reading-parsing-ab1-sequencing-files/23555 "2019-05-29T12:42:27Z")

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Hi, We currently get some sequencing done on 96 well plates. The lab guys manually check the chromatograms (ab1) files for clean reads. But I was wondering if there was a julia package able to open and retrieve the info…

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## [Building JuMP models through functions](https://discourse.julialang.org/t/building-jump-models-through-functions/24636)

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**Author:** [@iharjunk](https://discourse.julialang.org/u/iharjunk)\
**Replies:** 5\
**Last updated:** [May 29, 2019, 10:48am UTC](https://discourse.julialang.org/t/building-jump-models-through-functions/24636 "2019-05-29T10:48:15Z")

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Hello all, I would like to make my Julia/JuMP code more flexible and prepare it for larger test cases. For this I would need to Read in data from a given directory Build a model based on it - here since the model is l…

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## [Monte Carlo problem (distributed computing, DifferentialEquations pkg) with ForwardDiff AD for parameter estimation](https://discourse.julialang.org/t/monte-carlo-problem-distributed-computing-differentialequations-pkg-with-forwarddiff-ad-for-parameter-estimation/24697)

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**Author:** [@moesphere](https://discourse.julialang.org/u/moesphere)\
**Replies:** 1\
**Last updated:** [May 28, 2019, 4:41pm UTC](https://discourse.julialang.org/t/monte-carlo-problem-distributed-computing-differentialequations-pkg-with-forwarddiff-ad-for-parameter-estimation/24697 "2019-05-28T16:41:44Z")

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I am trying to use a Monte Carlo problem (distributed computing) from the Differential Equations package for parameter estimation using AD from ForwardDiff. It is working when I define the objective function directly in…

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## [DiffEqFlux / diffeq\_adjoint: no method matching back!(::Float64)](https://discourse.julialang.org/t/diffeqflux-diffeq-adjoint-no-method-matching-back-float64/24648)

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**Author:** [@mihai](https://discourse.julialang.org/u/mihai)\
**Replies:** 3\
**Last updated:** [May 28, 2019, 1:36pm UTC](https://discourse.julialang.org/t/diffeqflux-diffeq-adjoint-no-method-matching-back-float64/24648 "2019-05-28T13:36:18Z")

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Hi all, I’m new to julia and ML, so maybe it’s something obvious, but I’m a bit lost now. I would like to optimize a large set of parameters (N ODE’s with N \> 2k) to fit to data. From reading the documentation of DiffEq…

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## [DataFramesMeta custom filter: by groups of A, apply filter on B](https://discourse.julialang.org/t/dataframesmeta-custom-filter-by-groups-of-a-apply-filter-on-b/24557)

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**Author:** [@floswald](https://discourse.julialang.org/u/floswald)\
**Replies:** 4\
**Last updated:** [May 27, 2019, 6:44pm UTC](https://discourse.julialang.org/t/dataframesmeta-custom-filter-by-groups-of-a-apply-filter-on-b/24557 "2019-05-27T18:44:08Z")

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I need to subset a dataframe by groups. that is, in each group there is a different filtering condition to apply. here is a MWE using DataFrames, DataFramesMeta julia\> df = DataFrame(A = repeat(1:3,3), B = rand(1:9,9),…

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## [DataDeps post\_fetch\_method](https://discourse.julialang.org/t/datadeps-post-fetch-method/24649)

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**Author:** [@yakir12](https://discourse.julialang.org/u/yakir12)\
**Replies:** 6\
**Last updated:** [May 27, 2019, 4:52pm UTC](https://discourse.julialang.org/t/datadeps-post-fetch-method/24649 "2019-05-27T16:52:26Z")

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I have a bunch of zipped .csv files on an S3 repo. I’m using the excellent DataDeps to retrieve them. Next, I use the also excellent JuliaDB to loadtable the .csvs into tables, and then from there it’s processing etc etc…

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## [Plots: Only one series as primary plot](https://discourse.julialang.org/t/plots-only-one-series-as-primary-plot/24616)

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**Author:** [@baggepinnen](https://discourse.julialang.org/u/baggepinnen)\
**Replies:** 17\
**Last updated:** [May 26, 2019, 3:31pm UTC](https://discourse.julialang.org/t/plots-only-one-series-as-primary-plot/24616 "2019-05-26T15:31:47Z")

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I frequently make figures that look like this m = randn(100) n = m .+ randn(100,50) plot(m, lab="mean", l=(5,)) plot!(n; lab="realizations", l=(:black, 0.1)) Here, I would prefer to only have one of the “realizations…

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## [Custom types in ForwardDiff](https://discourse.julialang.org/t/custom-types-in-forwarddiff/24610)

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**Author:** [@tamasgal](https://discourse.julialang.org/u/tamasgal)\
**Replies:** 8\
**Last updated:** [May 25, 2019, 9:06pm UTC](https://discourse.julialang.org/t/custom-types-in-forwarddiff/24610 "2019-05-25T21:06:21Z")

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This might be trivial but I am currently fighting with JuMP to accept my quality function for the minimisation procedure. I figured out that my custom type: struct Position \<: FieldVector{3, Float64} x::Float64 …

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## [Animation with timeline and play/pause](https://discourse.julialang.org/t/animation-with-timeline-and-play-pause/24575)

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**Author:** [@Seanny123](https://discourse.julialang.org/u/Seanny123)\
**Replies:** 2\
**Last updated:** [May 25, 2019, 6:30am UTC](https://discourse.julialang.org/t/animation-with-timeline-and-play-pause/24575 "2019-05-25T06:30:21Z")

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Often, I want to watch a visual system over time with the same basic controls as a video. Specifically: Play/Pause Drag around on a timeline Encoding a basic SVG animation is often overkill, so in Python, I awkwardly …

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## [Avoiding Memory leaks using CuArrays](https://discourse.julialang.org/t/avoiding-memory-leaks-using-cuarrays/24325)

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**Author:** [@HenriDeh](https://discourse.julialang.org/u/HenriDeh)\
**Replies:** 3\
**Last updated:** [May 24, 2019, 2:51pm UTC](https://discourse.julialang.org/t/avoiding-memory-leaks-using-cuarrays/24325 "2019-05-24T14:51:53Z")

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Hello, I have read that there is no garbage collection in GPUs. I have an algorithm where I use an Array{Array{CuArrays{Float32,1},1}} as a buffer. From that I sample a batch that I transform in a NTuple{CuArrays, N} to…

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## [Function getindex does not accept keyword arguments](https://discourse.julialang.org/t/function-getindex-does-not-accept-keyword-arguments/24564)

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**Author:** [@Octarosu](https://discourse.julialang.org/u/Octarosu)\
**Replies:** 1\
**Last updated:** [May 24, 2019, 1:21pm UTC](https://discourse.julialang.org/t/function-getindex-does-not-accept-keyword-arguments/24564 "2019-05-24T13:21:05Z")

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Hello, I implemented this function for economic dispatch function solve\_ed(g\_max, g\_min, c\_g, c\_w, d, w\_f) #Define the economic dispatch (ED) model ed=Model() # Define decision variables @defVar(ed, 0 \<= g\[i=1:2…

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## [Shallow water equations with DifferentialEquations.jl](https://discourse.julialang.org/t/shallow-water-equations-with-differentialequations-jl/2691)

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**Author:** [@juliohm](https://discourse.julialang.org/u/juliohm)\
**Replies:** 22\
**Last updated:** [May 24, 2019, 12:31am UTC](https://discourse.julialang.org/t/shallow-water-equations-with-differentialequations-jl/2691 "2019-05-24T00:31:41Z")

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I am really interested in using the DifferentialEquations.jl framework to solve the shallow water equations over a 2D domain efficiently instead of coding my own solution. How would you formulate the problem in Differen…

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## [CUDAnative tests failing on Windows 10](https://discourse.julialang.org/t/cudanative-tests-failing-on-windows-10/24465)

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**Author:** [@manderson](https://discourse.julialang.org/u/manderson)\
**Replies:** 5\
**Last updated:** [May 23, 2019, 7:57pm UTC](https://discourse.julialang.org/t/cudanative-tests-failing-on-windows-10/24465 "2019-05-23T19:57:07Z")

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Hello, I’m having some platform dependent problems getting CUDAnative working all the way. On my Ubuntu system I am having no problems, but on my windows machines the tests for the package are failing and I cannot make …

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## [Code optimization a (simple) advection difference scheme](https://discourse.julialang.org/t/code-optimization-a-simple-advection-difference-scheme/24532)

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**Author:** [@fdevuyst](https://discourse.julialang.org/u/fdevuyst)\
**Replies:** 2\
**Last updated:** [May 23, 2019, 6:43pm UTC](https://discourse.julialang.org/t/code-optimization-a-simple-advection-difference-scheme/24532 "2019-05-23T18:43:50Z")

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Hi, I’m beginner in Julia. I tried a simple code, but was a little bit disappointed with the performance. Could you give me hints in optimizing this snippet ? Kind regards, Florian 2D advection equation, periodic boun…

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## [Recipe to plot unit points](https://discourse.julialang.org/t/recipe-to-plot-unit-points/24510)

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**Author:** [@kellertuer](https://discourse.julialang.org/u/kellertuer)\
**Replies:** 7\
**Last updated:** [May 23, 2019, 4:17pm UTC](https://discourse.julialang.org/t/recipe-to-plot-unit-points/24510 "2019-05-23T16:17:58Z")

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I am bring to define a Recipe for my own data type, but following any thread here (for example Understanding recipes in Plots.jl ) I always end up with No user recipe defined for MyType errors and I would like to unders…

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## [Multi-cut Benders decomposition?](https://discourse.julialang.org/t/multi-cut-benders-decomposition/23472)

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**Author:** [@deschase](https://discourse.julialang.org/u/deschase)\
**Replies:** 4\
**Last updated:** [May 23, 2019, 11:57am UTC](https://discourse.julialang.org/t/multi-cut-benders-decomposition/23472 "2019-05-23T11:57:57Z")

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I have coded a Benders decomposition with JuMP, but it is currently running too slow for my needs. I have a way to speed up the process theoretically by collecting several solutions from the solver at each iteration of m…

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## [CUDAnative: ^ and other operators](https://discourse.julialang.org/t/cudanative-and-other-operators/24506)

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**Author:** [@samo](https://discourse.julialang.org/u/samo)\
**Replies:** 0\
**Last updated:** [May 23, 2019, 9:58am UTC](https://discourse.julialang.org/t/cudanative-and-other-operators/24506 "2019-05-23T09:58:47Z")

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A simple question: is there a particular reason why there is no ^ operator in CUDAnative, but only CUDAnative.pow(x, y)? Could we have something like: x^y = pow(x,y) What about other operators? Can this be added? Tha…

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## [Lagrange Interpolation Function Generator](https://discourse.julialang.org/t/lagrange-interpolation-function-generator/3427)

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**Author:** [@anodos](https://discourse.julialang.org/u/anodos)\
**Replies:** 3\
**Last updated:** [May 22, 2019, 10:31pm UTC](https://discourse.julialang.org/t/lagrange-interpolation-function-generator/3427 "2019-05-22T22:31:59Z")

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I couldn’t find an implementation of Lagrange Interpolation in Julia, so built my own. This function simply takes a set of points, as stored in the two vectors xvals and yvals, and spits out the Lagrange Polynomial that …

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## [JuMP (0.18): summing up elements of solution vector allocates memory?](https://discourse.julialang.org/t/jump-0-18-summing-up-elements-of-solution-vector-allocates-memory/24488)

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**Author:** [@mike\_k](https://discourse.julialang.org/u/mike_k)\
**Replies:** 9\
**Last updated:** [May 22, 2019, 8:09pm UTC](https://discourse.julialang.org/t/jump-0-18-summing-up-elements-of-solution-vector-allocates-memory/24488 "2019-05-22T20:09:07Z")

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Dear folks, I observe a strange behavior (note that the following snippets are embedded in a function): let x be some decision vector of size n. Then, sum\_x = 0.0 x\_val = getvalue( model\[:x\] ) println("typeof x\_val: ",…

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