# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=447

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**Page:** 448

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## [Nearest Neighbor Search for points consisting of vectors/arrays](https://discourse.julialang.org/t/nearest-neighbor-search-for-points-consisting-of-vectors-arrays/38893)

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**Author:** [@FrootLoops](https://discourse.julialang.org/u/FrootLoops)\
**Replies:** 4\
**Last updated:** [May 6, 2020, 9:46pm UTC](https://discourse.julialang.org/t/nearest-neighbor-search-for-points-consisting-of-vectors-arrays/38893 "2020-05-06T21:46:45Z")

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Hello everybody, I am trying to use the nearest neighbor package in Julia. I read the documentary and it was very easy to understand the examples for one dimensional problems. In my case it is a little bit more complica…

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## [Cbc and Clp performance](https://discourse.julialang.org/t/cbc-and-clp-performance/38505)

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**Author:** [@Diego](https://discourse.julialang.org/u/Diego)\
**Replies:** 16\
**Last updated:** [May 6, 2020, 9:39pm UTC](https://discourse.julialang.org/t/cbc-and-clp-performance/38505 "2020-05-06T21:39:22Z")

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Hello everyone, I have been testing the solvers of COIN-OR, namely Cbc (MILP solver) and Clp (LP solver). I obtain for Cbc a very good performance, Cbc even outperforms some commertial solvers in numerically complex pr…

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## [Implementing a custom layer](https://discourse.julialang.org/t/implementing-a-custom-layer/38632)

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**Author:** [@jaynick](https://discourse.julialang.org/u/jaynick)\
**Replies:** 2\
**Last updated:** [May 6, 2020, 5:40pm UTC](https://discourse.julialang.org/t/implementing-a-custom-layer/38632 "2020-05-06T17:40:45Z")

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I am hoping to implement a custom “layer” soon. I think the requirements for this are a) it accepts input from previous layer, and produces outputs, b) Flux.params() can find its parameters, c) gpu() can find its pa…

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## [A “Gallery” of fractal rendered mainly with Julia](https://discourse.julialang.org/t/a-gallery-of-fractal-rendered-mainly-with-julia/37435)

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**Author:** [@HaoLi111](https://discourse.julialang.org/u/HaoLi111)\
**Replies:** 5\
**Last updated:** [April 12, 2020, 11:28pm UTC](https://discourse.julialang.org/t/a-gallery-of-fractal-rendered-mainly-with-julia/37435 "2020-04-12T23:28:03Z")

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As I mentioned before, Julia has some natural advantages to create fractals and the site below has a collection. And some codes are shared https://galleryinfractaldimension-temp.weebly.com/blog However, I think the co…

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## [After update 2 hours before plot doesn't work anymore](https://discourse.julialang.org/t/after-update-2-hours-before-plot-doesnt-work-anymore/38880)

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**Author:** [@DKad](https://discourse.julialang.org/u/DKad)\
**Replies:** 6\
**Last updated:** [May 6, 2020, 1:36pm UTC](https://discourse.julialang.org/t/after-update-2-hours-before-plot-doesnt-work-anymore/38880 "2020-05-06T13:36:29Z")

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Hello, after update my plot function hangs. Simply typing using Plots plot(rand(10)) the REPL hangs and I can only recover with an explicitely kill of julia. I have done an Pkg.update(), there has been an update of…

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## [Custom univariate distribution in Turing.jl](https://discourse.julialang.org/t/custom-univariate-distribution-in-turing-jl/38874)

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**Author:** [@SSU](https://discourse.julialang.org/u/SSU)\
**Replies:** 4\
**Last updated:** [May 6, 2020, 10:58am UTC](https://discourse.julialang.org/t/custom-univariate-distribution-in-turing-jl/38874 "2020-05-06T10:58:41Z")

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I’m trying to use customized univariate distribution in Turing.jl. (The domain is 0 ~ +Inf) I implemented Distributions.pdf, logpdf, rand, minimum, maximum etc, referring the document (Advanced Usage). I’m pretty sure…

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## [Solver hang when using certain combination of callbacks in DiffEq](https://discourse.julialang.org/t/solver-hang-when-using-certain-combination-of-callbacks-in-diffeq/38846)

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**Author:** [@klaff](https://discourse.julialang.org/u/klaff)\
**Replies:** 3\
**Last updated:** [May 6, 2020, 5:30am UTC](https://discourse.julialang.org/t/solver-hang-when-using-certain-combination-of-callbacks-in-diffeq/38846 "2020-05-06T05:30:07Z")

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Hi, I’m trying to use a PeriodicCallback and two ContinuousCallbacks and I’m running into an issue. Here’s the MWE: using DifferentialEquations function usode!(du,u,p,t) C1 = 1.63e-9 RS = 790.0 C2 = 3.3e-…

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## [How to debug memory issues (when using DifferentialEquations)](https://discourse.julialang.org/t/how-to-debug-memory-issues-when-using-differentialequations/38775)

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**Author:** [@klaff](https://discourse.julialang.org/u/klaff)\
**Replies:** 14\
**Last updated:** [May 6, 2020, 5:13am UTC](https://discourse.julialang.org/t/how-to-debug-memory-issues-when-using-differentialequations/38775 "2020-05-06T05:13:30Z")

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I’m trying to understand an apparent memory issue regarding a simulation I’m doing. Here’s a simplified version of what I’m running: using DifferentialEquations, Plots function usode!(du,u,p,t) C1 = 1.63e-9 R…

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## [JuAFEM shape gradient as a matrix](https://discourse.julialang.org/t/juafem-shape-gradient-as-a-matrix/38825)

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**Author:** [@FrootLoops](https://discourse.julialang.org/u/FrootLoops)\
**Replies:** 4\
**Last updated:** [May 5, 2020, 8:49pm UTC](https://discourse.julialang.org/t/juafem-shape-gradient-as-a-matrix/38825 "2020-05-05T20:49:25Z")

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Hello everybody, I hope I am asking the question in a correct way. I am working with JuAFEM and I have a example code given, which calculates the stiffness matrix elementwise. @inbounds for q\_point in 1:getnquadpoints(…

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## [Distributions.jl structure](https://discourse.julialang.org/t/distributions-jl-structure/38214)

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**Author:** [@Albert\_Zevelev](https://discourse.julialang.org/u/Albert_Zevelev)\
**Replies:** 5\
**Last updated:** [May 5, 2020, 8:38pm UTC](https://discourse.julialang.org/t/distributions-jl-structure/38214 "2020-05-05T20:38:38Z")

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How can I automatically find all univariate continuous cdfs in Distributions.jl? I believe this can make a lot of tasks much easier including maintaining Distributions.jl. Eg MLJ.jl: using MLJ; X, y = @load\_boston; …

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## [Minimize function of matrix subject to matrix equality](https://discourse.julialang.org/t/minimize-function-of-matrix-subject-to-matrix-equality/38701)

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**Author:** [@uncertainly](https://discourse.julialang.org/u/uncertainly)\
**Replies:** 5\
**Last updated:** [May 5, 2020, 3:06am UTC](https://discourse.julialang.org/t/minimize-function-of-matrix-subject-to-matrix-equality/38701 "2020-05-05T03:06:02Z")

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newbie here, both to julia, JuMP, only intermediate at optimization. I would like to solve a problem min(A) subject to C = B\*A where A,B,C are all matrices. Is it possible to express this in JuMP? Any h…

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## [Scatterplot with marginal histograms](https://discourse.julialang.org/t/scatterplot-with-marginal-histograms/37619)

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**Author:** [@Humphrey\_Lee](https://discourse.julialang.org/u/Humphrey_Lee)\
**Replies:** 35\
**Last updated:** [May 5, 2020, 12:53am UTC](https://discourse.julialang.org/t/scatterplot-with-marginal-histograms/37619 "2020-05-05T00:53:36Z")

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Any idea how to do scatterplot with marginal histograms in Gadfly or Plots. Preference is Gadfly. Found similar post in forum below, but it was done in R/ggplot2. Technically, each histograms may have (normalized) cumula…

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## [JuMP Optimization Help](https://discourse.julialang.org/t/jump-optimization-help/38740)

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**Author:** [@mthelm85](https://discourse.julialang.org/u/mthelm85)\
**Replies:** 5\
**Last updated:** [May 4, 2020, 11:44pm UTC](https://discourse.julialang.org/t/jump-optimization-help/38740 "2020-05-04T23:44:44Z")

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I’m brand new to JuMP.jl and optimization and I’m running into a bit of a roadblock figuring out how to solve what I thought would be a fairly straightforward problem. Imagine 6 jars of marbles, divided into two groups. …

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## [Skew normal distribution?](https://discourse.julialang.org/t/skew-normal-distribution/21549)

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**Author:** [@bsprung](https://discourse.julialang.org/u/bsprung)\
**Replies:** 9\
**Last updated:** [May 4, 2020, 10:32pm UTC](https://discourse.julialang.org/t/skew-normal-distribution/21549 "2020-05-04T22:32:39Z")

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Hi, does anyone know if there is an implementation in any package of the skew normal distribution? There doesn’t appear to be one in Distributions.jl. Thank you!

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## [How to set Cbc Parameters](https://discourse.julialang.org/t/how-to-set-cbc-parameters/38516)

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**Author:** [@lausilvag](https://discourse.julialang.org/u/lausilvag)\
**Replies:** 3\
**Last updated:** [May 4, 2020, 10:28pm UTC](https://discourse.julialang.org/t/how-to-set-cbc-parameters/38516 "2020-05-04T22:28:58Z")

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Hi I am trying to set parameters for Cbc Solver Z\_OP = Model(with\_optimizer(Cbc.Optimizer)) set\_parameter(Z\_OP, "preProcess", off) set\_parameter(Z\_OP, "CliqueCuts", Root) error: UndefVarError: Off not defined …

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## [Dynamic programming](https://discourse.julialang.org/t/dynamic-programming/38512)

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**Author:** [@lausilvag](https://discourse.julialang.org/u/lausilvag)\
**Replies:** 4\
**Last updated:** [May 4, 2020, 10:28pm UTC](https://discourse.julialang.org/t/dynamic-programming/38512 "2020-05-04T22:28:12Z")

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Hi I am new to Julia and I would like to know if there is any MIP optimization solver that performs dynamic search. I have an optimization problem that exceeds 1000 variables allowed by student/research CPLEX license. …

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## [New machine learning package, Julia implementation of XGBoost ](https://discourse.julialang.org/t/new-machine-learning-package-julia-implementation-of-xgboost/8912)

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**Author:** [@statfactory](https://discourse.julialang.org/u/statfactory)\
**Replies:** 32\
**Last updated:** [March 10, 2020, 6:47am UTC](https://discourse.julialang.org/t/new-machine-learning-package-julia-implementation-of-xgboost/8912 "2020-03-10T06:47:49Z")

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Hi, I am working on a new Julia machine learning package. What I have now is a pure Julia implementation of XGBoost in \< 500 lines of code: https://github.com/Statfactory/JuML.jl It seems to be as fast as original XGB…

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## [Tables.jl: columntable to rowtable](https://discourse.julialang.org/t/tables-jl-columntable-to-rowtable/36112)

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**Author:** [@aplavin](https://discourse.julialang.org/u/aplavin)\
**Replies:** 6\
**Last updated:** [May 4, 2020, 7:58pm UTC](https://discourse.julialang.org/t/tables-jl-columntable-to-rowtable/36112 "2020-05-04T19:58:01Z")

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I’m trying to implement an interface to a column-based table storage backend, but struggle to make it work efficiently. The minimal implementation looks like this: import Tables struct MyTable \<: Tables.AbstractColumns…

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## [Regression in Flux.jl](https://discourse.julialang.org/t/regression-in-flux-jl/38733)

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**Author:** [@amrods](https://discourse.julialang.org/u/amrods)\
**Replies:** 5\
**Last updated:** [May 4, 2020, 5:09pm UTC](https://discourse.julialang.org/t/regression-in-flux-jl/38733 "2020-05-04T17:09:44Z")

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Trying to get started with Flux.jl. I’m trying estimate a linear regression. I have the following: using Flux using Random Random.seed!(1234) β = \[10., 20., 30.\] # true parameters predict(x) = (x\*β) function loss(x,…

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## [DataFrames, aggregate with missings](https://discourse.julialang.org/t/dataframes-aggregate-with-missings/38737)

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**Author:** [@donquicote](https://discourse.julialang.org/u/donquicote)\
**Replies:** 2\
**Last updated:** [May 4, 2020, 3:25pm UTC](https://discourse.julialang.org/t/dataframes-aggregate-with-missings/38737 "2020-05-04T15:25:45Z")

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Hi! I’m facing the following problem: using DataFrames, Statistics df = DataFrame(A = \[1, 2, missing, missing, missing, 3, 4, 5\], B = \[1, 1, 2, 2, 3, 3, 4, 4\]) df\_mean = aggregate(df, :B, x -\> mean(sk…

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## [Scatter plots with annotations of points](https://discourse.julialang.org/t/scatter-plots-with-annotations-of-points/37887)

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**Author:** [@Tomas\_Pevny](https://discourse.julialang.org/u/Tomas_Pevny)\
**Replies:** 3\
**Last updated:** [May 4, 2020, 1:07pm UTC](https://discourse.julialang.org/t/scatter-plots-with-annotations-of-points/37887 "2020-05-04T13:07:32Z")

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Dear All, I would like to visualize the output of UMAP in form of a scatterplot, such that when I hover on points, it would show some additional information in textual form (or rendered HTML would be super nice). Thank…

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## [Gadfly - error if shape count more than 15](https://discourse.julialang.org/t/gadfly-error-if-shape-count-more-than-15/38727)

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**Author:** [@Humphrey\_Lee](https://discourse.julialang.org/u/Humphrey_Lee)\
**Replies:** 1\
**Last updated:** [May 4, 2020, 11:47am UTC](https://discourse.julialang.org/t/gadfly-error-if-shape-count-more-than-15/38727 "2020-05-04T11:47:52Z")

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Gadfly shows error if plot has more than 15 shapes (limit!). See code below. using Gadfly x = \[0.025, 0.028, 0.035, 0.036, 0.037, 0.039, 0.039, 0.041, 0.041, 0.041, 0.042, 0.043, 0.045, 0.047, 0.049, 0.051, 0.053, 0.05…

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## [Change SVD.S::Vector{Tr} to SVD.S::AbstractVector{Tr}](https://discourse.julialang.org/t/change-svd-s-vector-tr-to-svd-s-abstractvector-tr/38693)

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**Author:** [@rrhiemstra](https://discourse.julialang.org/u/rrhiemstra)\
**Replies:** 3\
**Last updated:** [May 4, 2020, 10:56am UTC](https://discourse.julialang.org/t/change-svd-s-vector-tr-to-svd-s-abstractvector-tr/38693 "2020-05-04T10:56:39Z")

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I am developing a new package for Kronecker product matrices A ⊗ B ⊗ .... I want to support efficient factorizations for these type of matrices and want to use the types in LinearAlgebra.jl Here follows the type defi…

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## [How do I extract the coefficients and RHS's of all constraints in a JuMP linear program? (Need for KKT)](https://discourse.julialang.org/t/how-do-i-extract-the-coefficients-and-rhss-of-all-constraints-in-a-jump-linear-program-need-for-kkt/38525)

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**Author:** [@nlaws](https://discourse.julialang.org/u/nlaws)\
**Replies:** 14\
**Last updated:** [May 4, 2020, 3:28am UTC](https://discourse.julialang.org/t/how-do-i-extract-the-coefficients-and-rhss-of-all-constraints-in-a-jump-linear-program-need-for-kkt/38525 "2020-05-04T03:28:04Z")

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I am building a bilevel problem and I need to construct the KKT conditions of a linear program written in JuMP. I am wondering if it is possible to extract all the coefficients and right-hand-sides (RHS) of the constrai…

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## [How to map JuMP VariableRef to NLPModelMeta indices?](https://discourse.julialang.org/t/how-to-map-jump-variableref-to-nlpmodelmeta-indices/38681)

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**Author:** [@nlaws](https://discourse.julialang.org/u/nlaws)\
**Replies:** 2\
**Last updated:** [May 4, 2020, 2:52am UTC](https://discourse.julialang.org/t/how-to-map-jump-variableref-to-nlpmodelmeta-indices/38681 "2020-05-04T02:52:07Z")

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I am developing a large scale bilevel problem (1M+ variables), and as a first step I am extracting the constraint coefficient matrix of the lower level linear program using NLPModelMeta (see this post). Here is a simple …

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## [JuliaDB documentation down?](https://discourse.julialang.org/t/juliadb-documentation-down/38703)

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**Author:** [@clibassi](https://discourse.julialang.org/u/clibassi)\
**Replies:** 2\
**Last updated:** [May 4, 2020, 2:43am UTC](https://discourse.julialang.org/t/juliadb-documentation-down/38703 "2020-05-04T02:43:25Z")

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Hi all, Been trying to do some work with memory that is too large for my computer’s memory and so have turned to testing out what I understand to be JuliaDB’s strength in this context, but as I went to read up on it I k…

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## [Boolean matrix factorization in julia?](https://discourse.julialang.org/t/boolean-matrix-factorization-in-julia/38668)

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**Author:** [@Ken-B](https://discourse.julialang.org/u/Ken-B)\
**Replies:** 2\
**Last updated:** [May 3, 2020, 9:29pm UTC](https://discourse.julialang.org/t/boolean-matrix-factorization-in-julia/38668 "2020-05-03T21:29:10Z")

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Anyone know of a package that can do Boolean Matrix Factorization (BMF) in julia? Basically for a boolean matrix A {m x n} and a rank k, find boolean matrix X {m x k} and boolean matrix Y {k x n} such that A = X \* Y (ap…

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## [How do you deserialize stateful optimizers in Flux?](https://discourse.julialang.org/t/how-do-you-deserialize-stateful-optimizers-in-flux/38644)

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**Author:** [@findmyway](https://discourse.julialang.org/u/findmyway)\
**Replies:** 4\
**Last updated:** [May 3, 2020, 7:47am UTC](https://discourse.julialang.org/t/how-do-you-deserialize-stateful-optimizers-in-flux/38644 "2020-05-03T07:47:39Z")

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For some stateful optimizers, like ADAM, it has an IdDict field to store momentums of parameters. When deserializing the optimizer with BSON, the id info is lost in the newly created IdDict. This makes it hard to truly r…

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## [How to convert an array to a CuArray efficiently](https://discourse.julialang.org/t/how-to-convert-an-array-to-a-cuarray-efficiently/38612)

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**Author:** [@Dustin\_Hess](https://discourse.julialang.org/u/Dustin_Hess)\
**Replies:** 3\
**Last updated:** [May 2, 2020, 11:26pm UTC](https://discourse.julialang.org/t/how-to-convert-an-array-to-a-cuarray-efficiently/38612 "2020-05-02T23:26:40Z")

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Please forgive me as I am taking my first step in using GPU’s in Julia. My use case is I want to do some processioning of electron microscope image stacks from a TEM. So I have everything setup and I have some micrograph…

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## [Zygote error. "Only reference types can be differentiated with \`Params\`."](https://discourse.julialang.org/t/zygote-error-only-reference-types-can-be-differentiated-with-params/38224)

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**Author:** [@Emmanuel-R8](https://discourse.julialang.org/u/Emmanuel-R8)\
**Replies:** 8\
**Last updated:** [May 2, 2020, 11:01pm UTC](https://discourse.julialang.org/t/zygote-error-only-reference-types-can-be-differentiated-with-params/38224 "2020-05-02T23:01:47Z")

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I have been updating the Lotka-Volterra example in the model zoo. The call to train! fails with an error in Zygote src/compiler/interface.jl line 129 with the error in the title. The reason for the error is a mystery to…

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