# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=407

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**Page:** 408

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## [Flux differentiation error](https://discourse.julialang.org/t/flux-differentiation-error/49811)

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**Author:** [@Honza9723](https://discourse.julialang.org/u/Honza9723)\
**Replies:** 19\
**Last updated:** [November 19, 2020, 1:20pm UTC](https://discourse.julialang.org/t/flux-differentiation-error/49811 "2020-11-19T13:20:51Z")

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Dear All, I am working on a solution of simple differential equation y(x) - y’(x) = 0 using neural network. I am using a two-layer softplus network for parameterization of y(x). To get y’(x), I am using simple Flux.gra…

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## [Issue querying probabilities using chain](https://discourse.julialang.org/t/issue-querying-probabilities-using-chain/50383)

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**Author:** [@michielver](https://discourse.julialang.org/u/michielver)\
**Replies:** 6\
**Last updated:** [November 19, 2020, 8:18am UTC](https://discourse.julialang.org/t/issue-querying-probabilities-using-chain/50383 "2020-11-19T08:18:23Z")

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Hi, This is my first post, so I will try to make it as clear as possible, otherwise point out anything that is unclear. I am running into an issue with querying probabilities using chains. I tried to reduce it to as sm…

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## [How to query Slurm Array Task ID in Julia?](https://discourse.julialang.org/t/how-to-query-slurm-array-task-id-in-julia/36771)

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**Author:** [@zxjroger](https://discourse.julialang.org/u/zxjroger)\
**Replies:** 15\
**Last updated:** [November 19, 2020, 5:19am UTC](https://discourse.julialang.org/t/how-to-query-slurm-array-task-id-in-julia/36771 "2020-11-19T05:19:05Z")

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I want to parallel 100 Monte Carlo study on 100 compute nodes. Within each node, it should execute the Julia script attached with a unique random seed (so that it will generate a unique fake dataset). Also, within each n…

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## [How do I do a plain old "A=LU" decomposition of sparse matrices?](https://discourse.julialang.org/t/how-do-i-do-a-plain-old-a-lu-decomposition-of-sparse-matrices/49619)

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**Author:** [@casey\_watkins](https://discourse.julialang.org/u/casey_watkins)\
**Replies:** 7\
**Last updated:** [November 19, 2020, 1:16am UTC](https://discourse.julialang.org/t/how-do-i-do-a-plain-old-a-lu-decomposition-of-sparse-matrices/49619 "2020-11-19T01:16:29Z")

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I have a very large sparse matrix A and need to produce L, U such that A=L\*U for the specific type of problem I am solving. I am aware of LinearAlgebra.lu, where setting the “pivot” flag to false accomplishes this. This…

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## [Solving vector field PDE with DiffEqOperators.jl](https://discourse.julialang.org/t/solving-vector-field-pde-with-diffeqoperators-jl/50391)

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**Author:** [@jarias9](https://discourse.julialang.org/u/jarias9)\
**Replies:** 1\
**Last updated:** [November 18, 2020, 7:19pm UTC](https://discourse.julialang.org/t/solving-vector-field-pde-with-diffeqoperators-jl/50391 "2020-11-18T19:19:52Z")

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Hello all, I am wondering if there is a workaround to solving a vector field for lets say Maxwell’s equations such as \\frac{\\partial \\mathbf{E}}{\\partial t} = \\frac{1}{\\varepsilon\_0} \\times \\mathbf{H} \\frac{\\partial…

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## [Query status of the solution when using Roots](https://discourse.julialang.org/t/query-status-of-the-solution-when-using-roots/50328)

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**Author:** [@optimist](https://discourse.julialang.org/u/optimist)\
**Replies:** 4\
**Last updated:** [November 18, 2020, 7:08pm UTC](https://discourse.julialang.org/t/query-status-of-the-solution-when-using-roots/50328 "2020-11-18T19:08:51Z")

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Edited to make it more specific I would like to query status of the solution when using the Roots package, before the function returns an answer. I can see in the source code of “find\_zero.jl” that it has some functiona…

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## [Not sure how to apply a filter](https://discourse.julialang.org/t/not-sure-how-to-apply-a-filter/50265)

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**Author:** [@klaff](https://discourse.julialang.org/u/klaff)\
**Replies:** 7\
**Last updated:** [November 18, 2020, 4:11pm UTC](https://discourse.julialang.org/t/not-sure-how-to-apply-a-filter/50265 "2020-11-18T16:11:53Z")

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I’ve constructed a filter as follows: filter1 = let f1 = 6.31 f2 = 1258.9 Q1 = 0.71 f3 = 15.915 f4 = 15.915 Q2 = 0.64 SecondOrderSections(\[ Biquad(4π^2\*f2^2,0.0,0.0,2π\*f1/Q1, 4π^2\*f1^2), Biquad(0.0,0.0,1.0,…

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## [How can I set a Specific chain name for a Structure？(BioStrcuture Package)](https://discourse.julialang.org/t/how-can-i-set-a-specific-chain-name-for-a-structure-biostrcuture-package/50211)

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**Author:** [@Wang-Lin-boop](https://discourse.julialang.org/u/Wang-Lin-boop)\
**Replies:** 6\
**Last updated:** [November 18, 2020, 3:26pm UTC](https://discourse.julialang.org/t/how-can-i-set-a-specific-chain-name-for-a-structure-biostrcuture-package/50211 "2020-11-18T15:26:13Z")

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Recently, I was working on a project dealing with a large number of coordinate files, which required me to convert each chain in some coordinate files with MMCIF/PDBXML/MMTF/PDB format into PDB format. Some of the chains…

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## [New Gurobi.jl syntax trouble](https://discourse.julialang.org/t/new-gurobi-jl-syntax-trouble/50344)

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**Author:** [@afazevedo](https://discourse.julialang.org/u/afazevedo)\
**Replies:** 2\
**Last updated:** [November 18, 2020, 1:04pm UTC](https://discourse.julialang.org/t/new-gurobi-jl-syntax-trouble/50344 "2020-11-18T13:04:16Z")

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Hi all I’ve got some issues in adapting to the new Gurobi.jl syntax. For example, this is a callback that I made in the old syntax: function cb(cb\_data, cb\_where) if cb\_where == CB\_MIPNODE #first node …

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## [Sum-Of-Squares SOC constraint in JuMP](https://discourse.julialang.org/t/sum-of-squares-soc-constraint-in-jump/50091)

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**Author:** [@andrewrosemberg](https://discourse.julialang.org/u/andrewrosemberg)\
**Replies:** 5\
**Last updated:** [November 16, 2020, 8:52am UTC](https://discourse.julialang.org/t/sum-of-squares-soc-constraint-in-jump/50091 "2020-11-16T08:52:04Z")

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I’m trying to add a constraint of type (x'Ax \<= b) in JuMP to be interpreted as SOC by the solver. A is Positive definite. Seems to be the same error as presented in this issue, but A+A' has positive eigenvalues: eigv…

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## [Gpu\_rand inside @cuda](https://discourse.julialang.org/t/gpu-rand-inside-cuda/50322)

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**Author:** [@dgatey](https://discourse.julialang.org/u/dgatey)\
**Replies:** 2\
**Last updated:** [November 18, 2020, 10:41am UTC](https://discourse.julialang.org/t/gpu-rand-inside-cuda/50322 "2020-11-18T10:41:14Z")

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Hey Everyone, I’ve managed to use gpu\_rand via gpu\_call but was wondering if it is possible to use gpu\_rand via @cuda as I’m currently using a 2D block. The @cuda function call only accepts bit types so I’m struggling …

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## [Arpack and MKL](https://discourse.julialang.org/t/arpack-and-mkl/50291)

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**Author:** [@Jonas](https://discourse.julialang.org/u/Jonas)\
**Replies:** 1\
**Last updated:** [November 18, 2020, 9:07am UTC](https://discourse.julialang.org/t/arpack-and-mkl/50291 "2020-11-18T09:07:20Z")

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Hello everyone, I wrote some code to calculate the first n eigenvalues and eigenvectors of a generalized eigenvalue problem over a two-dimensional mesh. For this I used the function eigs() of the package Arpack. Since t…

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## [Julia DifferentialEquations: increase maxiter](https://discourse.julialang.org/t/julia-differentialequations-increase-maxiter/50318)

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**Author:** [@Luigi\_Marongiu](https://discourse.julialang.org/u/Luigi_Marongiu)\
**Replies:** 6\
**Last updated:** [November 18, 2020, 7:57am UTC](https://discourse.julialang.org/t/julia-differentialequations-increase-maxiter/50318 "2020-11-18T07:57:54Z")

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Hello, I have set an ODEProblem object, but the procedure is stopped (although I still get t a solution) because a higher maxiters is needed. How can I check what is the default value and what is the syntax to increase…

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## [Julia DifferentialEquations: add delay into ODE](https://discourse.julialang.org/t/julia-differentialequations-add-delay-into-ode/50337)

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**Author:** [@Luigi\_Marongiu](https://discourse.julialang.org/u/Luigi_Marongiu)\
**Replies:** 3\
**Last updated:** [November 18, 2020, 7:03am UTC](https://discourse.julialang.org/t/julia-differentialequations-add-delay-into-ode/50337 "2020-11-18T07:03:01Z")

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Hello, I have a set of ODE to model the growth of bacteria nad phages: function multiInfect!(du, u, p, t) μ, ν, κ, φ, ψ, ω, β, Β, ρ, τ, η, Η = p #= du\[1\] = resident susceptible du\[2\] = resident infected…

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## [Some structures cannot be differentiated automatically?](https://discourse.julialang.org/t/some-structures-cannot-be-differentiated-automatically/50358)

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**Author:** [@yeruoforever](https://discourse.julialang.org/u/yeruoforever)\
**Replies:** 0\
**Last updated:** [November 18, 2020, 5:46am UTC](https://discourse.julialang.org/t/some-structures-cannot-be-differentiated-automatically/50358 "2020-11-18T05:46:43Z")

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Dear All, I am a student learning neural network. I implemented a small graph neural network model using Flux and MetaGraphs, but there was a problem that puzzled me. I posted the problematic code below, hope my friends…

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## [\[ANN\] PopGen.jl v0.4.0 and PopGenSims.jl v0.0.2](https://discourse.julialang.org/t/ann-popgen-jl-v0-4-0-and-popgensims-jl-v0-0-2/50316)

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**Author:** [@pdimens](https://discourse.julialang.org/u/pdimens)\
**Replies:** 4\
**Last updated:** [November 17, 2020, 9:47pm UTC](https://discourse.julialang.org/t/ann-popgen-jl-v0-4-0-and-popgensims-jl-v0-0-2/50316 "2020-11-17T21:47:05Z")

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Hello all, I’m thrilled to announce the next release of PopGen.jl v0.4.0 (although incorrectly versioned in the release, oops). Internal tweaks removing CategoricalArrays in favor of PooledArrays cleaning up and adding…

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## [JuMP model Polyhedron](https://discourse.julialang.org/t/jump-model-polyhedron/50108)

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**Author:** [@JohnZ](https://discourse.julialang.org/u/JohnZ)\
**Replies:** 11\
**Last updated:** [November 18, 2020, 1:33am UTC](https://discourse.julialang.org/t/jump-model-polyhedron/50108 "2020-11-18T01:33:34Z")

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Hi, I am trying to plot the feasible set of a JuMP model as a 3D figure. I have used the syntax provided in Polyhedra.jl documentation to create a polyhedron: Optimization · Polyhedra A simple example is given below: …

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## [How to get better performance from NUTS in Turing?](https://discourse.julialang.org/t/how-to-get-better-performance-from-nuts-in-turing/50349)

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**Author:** [@mkarikom](https://discourse.julialang.org/u/mkarikom)\
**Replies:** 0\
**Last updated:** [November 18, 2020, 12:54am UTC](https://discourse.julialang.org/t/how-to-get-better-performance-from-nuts-in-turing/50349 "2020-11-18T00:54:32Z")

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I’m wondering if anyone has further performance tips to speed this up? This MWE is an attempt to use NUTS on data that is similar in size to my actual use case, following the model introduced in this post, but no longer…

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## [DBnomics - World Economic Database](https://discourse.julialang.org/t/dbnomics-world-economic-database/50242)

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**Author:** [@tlorans](https://discourse.julialang.org/u/tlorans)\
**Replies:** 1\
**Last updated:** [November 18, 2020, 12:28am UTC](https://discourse.julialang.org/t/dbnomics-world-economic-database/50242 "2020-11-18T00:28:32Z")

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Hello everybody, This is my first post in this forum. :slight\_smile: I would like to point out the existence of a Julia version of the DBnomics API. The DBnomics project is led by French academics and aims to concatena…

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## [Substituting state and parameter values in jacobian of DifferentialEquations.jl system using ModelingToolkit](https://discourse.julialang.org/t/substituting-state-and-parameter-values-in-jacobian-of-differentialequations-jl-system-using-modelingtoolkit/50264)

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**Author:** [@claudio20497](https://discourse.julialang.org/u/claudio20497)\
**Replies:** 2\
**Last updated:** [November 17, 2020, 11:48pm UTC](https://discourse.julialang.org/t/substituting-state-and-parameter-values-in-jacobian-of-differentialequations-jl-system-using-modelingtoolkit/50264 "2020-11-17T23:48:31Z")

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So I would like to explicitly evaluate the R\_0 of an epidemiological model written in DifferentialEquations.jl using ModelingToolkit.jl. Here is a simple SIRD model: using DifferentialEquations, ModelingToolkit # Mode…

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## [Float64 error when using ForwardDiff.gradient for nested functions](https://discourse.julialang.org/t/float64-error-when-using-forwarddiff-gradient-for-nested-functions/50343)

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**Author:** [@yips](https://discourse.julialang.org/u/yips)\
**Replies:** 0\
**Last updated:** [November 17, 2020, 11:22pm UTC](https://discourse.julialang.org/t/float64-error-when-using-forwarddiff-gradient-for-nested-functions/50343 "2020-11-17T23:22:54Z")

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I am trying to use ForwardDiff.gradient find the gradient of the following function: function loss\_test(x::Array{T,2},SecreteFuncs,pInf::Array{T,2},cmat::Array{T,2}) where {T \<: Real} cmat\_sol = Findcss(x,SecreteFuncs…

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## [Optimization of Curves](https://discourse.julialang.org/t/optimization-of-curves/50312)

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**Author:** [@brett\_knoss](https://discourse.julialang.org/u/brett_knoss)\
**Replies:** 8\
**Last updated:** [November 17, 2020, 8:50pm UTC](https://discourse.julialang.org/t/optimization-of-curves/50312 "2020-11-17T20:50:55Z")

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What is a good option for finding the x value of a tangent point of a curve (such as matching price and value), or finding the minimum or maximum of a curve.

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## [Scatter3d and pyplot backend in Plots.jl](https://discourse.julialang.org/t/scatter3d-and-pyplot-backend-in-plots-jl/50238)

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**Author:** [@keithjlee](https://discourse.julialang.org/u/keithjlee)\
**Replies:** 4\
**Last updated:** [November 17, 2020, 3:43pm UTC](https://discourse.julialang.org/t/scatter3d-and-pyplot-backend-in-plots-jl/50238 "2020-11-17T15:43:46Z")

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Hello! I’m having a very strange issue trying to visualize a 3D scatterplot using the pyplot backend in Plots.jl. The Z-axis position of my inputted coordinates do not seem to register, and only stays on the 0 value, whi…

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## [DifferentialEquations - Derivatives in ODE function/ nesting AD](https://discourse.julialang.org/t/differentialequations-derivatives-in-ode-function-nesting-ad/50100)

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**Author:** [@Andreas\_Schlaginhauf](https://discourse.julialang.org/u/Andreas_Schlaginhauf)\
**Replies:** 6\
**Last updated:** [November 17, 2020, 2:57pm UTC](https://discourse.julialang.org/t/differentialequations-derivatives-in-ode-function-nesting-ad/50100 "2020-11-17T14:57:21Z")

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If the ODE function of a neural ODE includes the gradient f’(x) of a neural network f(x), we need to calculate second order gradients of f(x) in the backward pass. For me this led to all sorts of problems when the AD met…

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## [Colorbar cutoff in Plots.jl with pyplot](https://discourse.julialang.org/t/colorbar-cutoff-in-plots-jl-with-pyplot/48178)

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**Author:** [@gideonsimpson](https://discourse.julialang.org/u/gideonsimpson)\
**Replies:** 2\
**Last updated:** [November 17, 2020, 12:47pm UTC](https://discourse.julialang.org/t/colorbar-cutoff-in-plots-jl-with-pyplot/48178 "2020-11-17T12:47:06Z")

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I’ve got the following issue (see attached figure), where, with my font selections, the colorbar tick labels are cutoff. How do I expand the figure to include them or shrink the width of the colorbar?

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## [\`norm\` function error on CuDeviceArray](https://discourse.julialang.org/t/norm-function-error-on-cudevicearray/50273)

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**Author:** [@HaoxuanGuo](https://discourse.julialang.org/u/HaoxuanGuo)\
**Replies:** 1\
**Last updated:** [November 17, 2020, 7:12am UTC](https://discourse.julialang.org/t/norm-function-error-on-cudevicearray/50273 "2020-11-17T07:12:21Z")

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This code will get an error about norm function using CUDA using Adapt using LinearAlgebra struct TestType{T\<:AbstractArray} a::T b::T c::Float32 end Adapt.adapt\_structure(to, x::TestType) = TestType(adapt…

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## [In-place orthogonal/unitary transforms?](https://discourse.julialang.org/t/in-place-orthogonal-unitary-transforms/50111)

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**Author:** [@pkairys](https://discourse.julialang.org/u/pkairys)\
**Replies:** 12\
**Last updated:** [November 17, 2020, 10:46am UTC](https://discourse.julialang.org/t/in-place-orthogonal-unitary-transforms/50111 "2020-11-17T10:46:43Z")

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Say I want to perform a unitary/orthogonal transformation of an operator: U^\\dagger A U Is there a way to do this without allocating a new array? I see that there is a method for lmul!(A,B) that will do AB and place t…

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## [Random walks inside a model](https://discourse.julialang.org/t/random-walks-inside-a-model/49994)

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**Author:** [@Camilo1704](https://discourse.julialang.org/u/Camilo1704)\
**Replies:** 4\
**Last updated:** [November 17, 2020, 8:49am UTC](https://discourse.julialang.org/t/random-walks-inside-a-model/49994 "2020-11-17T08:49:02Z")

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Hi guys, I’m wondering if there is a way to include a variable which is a random walk in a model. Particularly, if inside my model I have the lines of code shown below, is there a walk around to do it more efficiently? …

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## [Are there any way to copy a Union Array to GPU with CUDA.jl?](https://discourse.julialang.org/t/are-there-any-way-to-copy-a-union-array-to-gpu-with-cuda-jl/50272)

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**Author:** [@HaoxuanGuo](https://discourse.julialang.org/u/HaoxuanGuo)\
**Replies:** 1\
**Last updated:** [November 17, 2020, 7:13am UTC](https://discourse.julialang.org/t/are-there-any-way-to-copy-a-union-array-to-gpu-with-cuda-jl/50272 "2020-11-17T07:13:41Z")

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Look at this example abstract type AbstractTest end struct ATest \<: AbstractTest end struct BTest \<: AbstractTest end struct CTest{T \<: AbstractTest} a::T end using CUDA CuArray(\[CTest(ATest()), CTest(BTest())\]) …

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## [Are there any way to copy a Dict or a custom datatype which contains an Array to GPU by CUDA?](https://discourse.julialang.org/t/are-there-any-way-to-copy-a-dict-or-a-custom-datatype-which-contains-an-array-to-gpu-by-cuda/50217)

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**Author:** [@HaoxuanGuo](https://discourse.julialang.org/u/HaoxuanGuo)\
**Replies:** 6\
**Last updated:** [November 17, 2020, 7:13am UTC](https://discourse.julialang.org/t/are-there-any-way-to-copy-a-dict-or-a-custom-datatype-which-contains-an-array-to-gpu-by-cuda/50217 "2020-11-17T07:13:01Z")

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I want to use the LinearAlgebra library to simplify my programming. So, I warp some Arrays in an struct. But I find I can not copy it to GPU because it is a non-bitstype. Similarly, I want to look up some tables which i…

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