# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=186

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**Page:** 187

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## [How to calculate the Hessian vector product in a Flux model?](https://discourse.julialang.org/t/how-to-calculate-the-hessian-vector-product-in-a-flux-model/100215)

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**Author:** [@taizoooo](https://discourse.julialang.org/u/taizoooo)\
**Replies:** 1\
**Last updated:** [June 13, 2023, 8:42pm UTC](https://discourse.julialang.org/t/how-to-calculate-the-hessian-vector-product-in-a-flux-model/100215 "2023-06-13T20:42:26Z")

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Hello. I implemented the Hessian vector product referring to the following link: Hessian Vector Products on GPU using ForwardDiff, Zygote, and Flux. The implementation works correctly on both CPU and GPU for a flux mod…

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## [Access to underlying GridSpace grid cells](https://discourse.julialang.org/t/access-to-underlying-gridspace-grid-cells/99338)

<div class="topic-metadata">

**Author:** [@cormullion](https://discourse.julialang.org/u/cormullion)\
**Replies:** 5\
**Last updated:** [June 13, 2023, 1:53pm UTC](https://discourse.julialang.org/t/access-to-underlying-gridspace-grid-cells/99338 "2023-06-13T13:53:26Z")

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Beginner user of Agents.jl here … With a space defined as space = GridSpaceSingle(..., is it possible to access the underlying grid and its cells in some way, so as to be able to store and retrieve information, eg abou…

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## [Genetic Algorithm packages](https://discourse.julialang.org/t/genetic-algorithm-packages/100159)

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**Author:** [@jonathanfischer97](https://discourse.julialang.org/u/jonathanfischer97)\
**Replies:** 12\
**Last updated:** [June 13, 2023, 12:58pm UTC](https://discourse.julialang.org/t/genetic-algorithm-packages/100159 "2023-06-13T12:58:52Z")

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For those who run genetic algorithms or similar optimizations methods in Julia, which package do you use? I’ve been using Evolutionary.jl and it works well, but am wondering there are any alternatives worth checking out…

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## [Sampling from a probability distribution on GPU](https://discourse.julialang.org/t/sampling-from-a-probability-distribution-on-gpu/94389)

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**Author:** [@ArjunNarayanan](https://discourse.julialang.org/u/ArjunNarayanan)\
**Replies:** 13\
**Last updated:** [June 13, 2023, 12:52pm UTC](https://discourse.julialang.org/t/sampling-from-a-probability-distribution-on-gpu/94389 "2023-06-13T12:52:00Z")

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I’m interested in doing something like using Distributions: Categorical using CUDA p = cu(\[0.7,0.2,0.1\]) idx = rand(Categorical(p)) Is there a way to sample from a vector of probability masses on the GPU? This kind of…

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## [We don't know how to parse constraints containing expressions of type :generator](https://discourse.julialang.org/t/we-dont-know-how-to-parse-constraints-containing-expressions-of-type-generator/100270)

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**Author:** [@A.Marx](https://discourse.julialang.org/u/A.Marx)\
**Replies:** 3\
**Last updated:** [June 13, 2023, 8:53am UTC](https://discourse.julialang.org/t/we-dont-know-how-to-parse-constraints-containing-expressions-of-type-generator/100270 "2023-06-13T08:53:49Z")

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I am trying to set up the following dispatch optimization problem. However, the capacity constraints gives me the error: \`@constraint(m, \[t in time\], (cfD\[:p\] \>= y\[p, t\] for p = plants))\`: Unsupported constraint express…

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## [Running neural ODE on measurement](https://discourse.julialang.org/t/running-neural-ode-on-measurement/100179)

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**Author:** [@Ordens\_Ritter](https://discourse.julialang.org/u/Ordens_Ritter)\
**Replies:** 7\
**Last updated:** [June 13, 2023, 6:33am UTC](https://discourse.julialang.org/t/running-neural-ode-on-measurement/100179 "2023-06-13T06:33:43Z")

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I am trying get a neural ODE working, that doesn’t have a function/ode as input but a measurement. I want to apply the neural ODE to get the original function expressed by the measurement and not the derivative. I am t…

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## [How to troubleshoot ForwardDiff](https://discourse.julialang.org/t/how-to-troubleshoot-forwarddiff/99728)

<div class="topic-metadata">

**Author:** [@johnb](https://discourse.julialang.org/u/johnb)\
**Replies:** 18\
**Last updated:** [June 12, 2023, 10:05pm UTC](https://discourse.julialang.org/t/how-to-troubleshoot-forwarddiff/99728 "2023-06-12T22:05:45Z")

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I’ve been trying to write a loss function for a PDE that I’m solving in order to identify parameters and I would like to use the gradient of my loss function in parameter optimization. Unfortunately, ForwardDiff returns …

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## [Building random generator for custom type to generate a specific number of variates](https://discourse.julialang.org/t/building-random-generator-for-custom-type-to-generate-a-specific-number-of-variates/100199)

<div class="topic-metadata">

**Author:** [@atteson](https://discourse.julialang.org/u/atteson)\
**Replies:** 2\
**Last updated:** [June 12, 2023, 2:14pm UTC](https://discourse.julialang.org/t/building-random-generator-for-custom-type-to-generate-a-specific-number-of-variates/100199 "2023-06-12T14:14:02Z")

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I’m writing a random generator for a custom type and, for this type, it is important to know the number of variates being generated for efficient generation. My thought is to generalize Random.Repitition to allow Val{n}…

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## [Doing repeated Euler-steps in a simulation, Differentialequations.jl](https://discourse.julialang.org/t/doing-repeated-euler-steps-in-a-simulation-differentialequations-jl/100221)

<div class="topic-metadata">

**Author:** [@Martin](https://discourse.julialang.org/u/Martin)\
**Replies:** 5\
**Last updated:** [June 12, 2023, 12:55pm UTC](https://discourse.julialang.org/t/doing-repeated-euler-steps-in-a-simulation-differentialequations-jl/100221 "2023-06-12T12:55:43Z")

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Hi! I am researcher working with problems related to optimal stopping/switching problems, and I have an issue where I need to, in a for loop, advance one time step (size dt) of an SDE for lots of previous states. And I …

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## [How to add names to a collection of constraints in JuMP using @constraints](https://discourse.julialang.org/t/how-to-add-names-to-a-collection-of-constraints-in-jump-using-constraints/100130)

<div class="topic-metadata">

**Author:** [@JackaChou](https://discourse.julialang.org/u/JackaChou)\
**Replies:** 4\
**Last updated:** [June 12, 2023, 6:37am UTC](https://discourse.julialang.org/t/how-to-add-names-to-a-collection-of-constraints-in-jump-using-constraints/100130 "2023-06-12T06:37:21Z")

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I want to name different kinds of constraints for enhancing readability and debugging, what’s the right syntax to do it with @constraints, I know this is easy for @constraint(, base\_name = “Name”). Below is my code with…

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## [Change the number of particles in the PF dynamically](https://discourse.julialang.org/t/change-the-number-of-particles-in-the-pf-dynamically/100195)

<div class="topic-metadata">

**Author:** [@josemanuel22](https://discourse.julialang.org/u/josemanuel22)\
**Replies:** 0\
**Last updated:** [June 11, 2023, 5:55pm UTC](https://discourse.julialang.org/t/change-the-number-of-particles-in-the-pf-dynamically/100195 "2023-06-11T17:55:29Z")

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I am trying to create a particle filter method where the number of particles is adaptive, meaning it changes dynamically depending on whether the method is converging or not. I want to take inspiration from the repositor…

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## [Truncated chi-square returning NaNs](https://discourse.julialang.org/t/truncated-chi-square-returning-nans/100187)

<div class="topic-metadata">

**Author:** [@Jad\_Zeitouni](https://discourse.julialang.org/u/Jad_Zeitouni)\
**Replies:** 0\
**Last updated:** [June 11, 2023, 2:48pm UTC](https://discourse.julialang.org/t/truncated-chi-square-returning-nans/100187 "2023-06-11T14:48:42Z")

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I’m trying to sample from a truncated chi-square distribution, defined over \[0, a\], by using the following line of code. rand(Truncated(Chisq(n), 0, a)) This does alright most of the time, but sometimes it returns NaNs…

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## [Modelling heating curves with a PINN](https://discourse.julialang.org/t/modelling-heating-curves-with-a-pinn/99521)

<div class="topic-metadata">

**Author:** [@Ordens\_Ritter](https://discourse.julialang.org/u/Ordens_Ritter)\
**Replies:** 6\
**Last updated:** [June 11, 2023, 1:32pm UTC](https://discourse.julialang.org/t/modelling-heating-curves-with-a-pinn/99521 "2023-06-11T13:32:25Z")

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I am Trying to model some temperature curves with a physically informed NN (PINN). I the physical model I am trying to apply is an FOPDT. NN = Chain( Dense(1 =\> 32, tanh), Dense(32 =\> 32, tanh), Den…

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## [How to plot a spectrum with dB as y-axis with PythonPlot](https://discourse.julialang.org/t/how-to-plot-a-spectrum-with-db-as-y-axis-with-pythonplot/100172)

<div class="topic-metadata">

**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 1\
**Last updated:** [June 11, 2023, 8:01am UTC](https://discourse.julialang.org/t/how-to-plot-a-spectrum-with-db-as-y-axis-with-pythonplot/100172 "2023-06-11T08:01:15Z")

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I am using PythonPlot and want to have a logarithmic y axis formatted in dezibel (dB). In Python I could use the following code: from UliEngineering.Math.Decibel import \* import matplotlib.ticker as mtick def decibel\_fo…

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## [Meaning of Incidence matrix?](https://discourse.julialang.org/t/meaning-of-incidence-matrix/100141)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 3\
**Last updated:** [June 11, 2023, 5:05am UTC](https://discourse.julialang.org/t/meaning-of-incidence-matrix/100141 "2023-06-11T05:05:45Z")

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I defined a nonlinear model and linearized it. I get the following result: julia\> simplified\_sys Model sys with 3 equations States (3): ω(t) \[defaults to 1.04286\] Uest(t) \[defaults to 9.0\] Pgc(t) \[defaults to 2.46…

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## [GeoMakie: Could not find font regular, using TeX Gyre Heros Makie](https://discourse.julialang.org/t/geomakie-could-not-find-font-regular-using-tex-gyre-heros-makie/100092)

<div class="topic-metadata">

**Author:** [@thunderclouds](https://discourse.julialang.org/u/thunderclouds)\
**Replies:** 4\
**Last updated:** [June 11, 2023, 12:24am UTC](https://discourse.julialang.org/t/geomakie-could-not-find-font-regular-using-tex-gyre-heros-makie/100092 "2023-06-11T00:24:32Z")

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I have a question about the fonts in GeoMakie.jl. When I run the following sample code, I get the error “Warning: Could not find font regular, using TeX Gyre Heros Makie”. It seems that this error occurs at the timing w…

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## [Maximum timestep in DIfferential solver](https://discourse.julialang.org/t/maximum-timestep-in-differential-solver/100135)

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**Author:** [@Sarthak\_Choudhury](https://discourse.julialang.org/u/Sarthak_Choudhury)\
**Replies:** 4\
**Last updated:** [June 10, 2023, 5:11pm UTC](https://discourse.julialang.org/t/maximum-timestep-in-differential-solver/100135 "2023-06-10T17:11:19Z")

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Hi, I am currently solving an ODE in DifferentialEquations.jl which has explicit time dependence. I arrive at a solution for a larger time t\_{max} with the solution saved at 1000 time points in between. Now I want to zo…

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## [Is there a symbolic Integrator](https://discourse.julialang.org/t/is-there-a-symbolic-integrator/100140)

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**Author:** [@bombadil224](https://discourse.julialang.org/u/bombadil224)\
**Replies:** 1\
**Last updated:** [June 10, 2023, 4:47pm UTC](https://discourse.julialang.org/t/is-there-a-symbolic-integrator/100140 "2023-06-10T16:47:17Z")

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I have been writing a Homotopy approximation method solver for differential equations. This requires the use of integration, So far I have been using a very simple function for the integration of polynomials. This is cle…

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## [Counting in dataframes](https://discourse.julialang.org/t/counting-in-dataframes/99907)

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**Author:** [@optimist](https://discourse.julialang.org/u/optimist)\
**Replies:** 7\
**Last updated:** [June 7, 2023, 1:49pm UTC](https://discourse.julialang.org/t/counting-in-dataframes/99907 "2023-06-07T13:49:21Z")

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I have a dataframe in which I need to count the number of occurences of values in a given list. Suppose I have a dataframe df: df= DataFrame(:B1 =\> \[1,1,2,2,3,4,5\], :B2 =\> \[1,7,7,2,2,5,5\],:B3 =\> \[2,2,2,3,3,3,3\] ) 7×3 …

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## [MCMC Sampling Method Overview/Comparison?](https://discourse.julialang.org/t/mcmc-sampling-method-overview-comparison/88496)

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**Author:** [@Alec\_Loudenback](https://discourse.julialang.org/u/Alec_Loudenback)\
**Replies:** 7\
**Last updated:** [June 10, 2023, 5:50am UTC](https://discourse.julialang.org/t/mcmc-sampling-method-overview-comparison/88496 "2023-06-10T05:50:19Z")

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Is there a reference that compares the different sampling techniques available for Turing.jl? I don’t see a consistently preferred chain and it’s not clear to me (a beginner bayesian) why one would prefer a given sampler…

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## [Very large performance difference between Turing and Stan \[Gaussian Process\]](https://discourse.julialang.org/t/very-large-performance-difference-between-turing-and-stan-gaussian-process/93663)

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**Author:** [@jdossgollin](https://discourse.julialang.org/u/jdossgollin)\
**Replies:** 9\
**Last updated:** [June 10, 2023, 5:42am UTC](https://discourse.julialang.org/t/very-large-performance-difference-between-turing-and-stan-gaussian-process/93663 "2023-06-10T05:42:59Z")

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A student I’m working with is working on a Gaussian Process model in Turing, but it was very slow. Out of frustration, they reimplemented in stan and it’s much faster. For context, it fits (1000 samples from 1 chain) in …

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## [Warning: Linking two modules of different target triples: 'bcloader' ... 'start'](https://discourse.julialang.org/t/warning-linking-two-modules-of-different-target-triples-bcloader-start/93864)

<div class="topic-metadata">

**Author:** [@albheim](https://discourse.julialang.org/u/albheim)\
**Replies:** 5\
**Last updated:** [June 10, 2023, 4:28am UTC](https://discourse.julialang.org/t/warning-linking-two-modules-of-different-target-triples-bcloader-start/93864 "2023-06-10T04:28:18Z")

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Started getting the warnings warning: Linking two modules of different target triples: 'bcloader' is 'x86\_64-unknown-linux-gnu' whereas 'start' is 'x86\_64-linux-gnu' warning: Linking two modules of different target tri…

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## [Simple Enzyme AD on CUDA GPU](https://discourse.julialang.org/t/simple-enzyme-ad-on-cuda-gpu/99966)

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**Author:** [@Thaegy](https://discourse.julialang.org/u/Thaegy)\
**Replies:** 5\
**Last updated:** [June 9, 2023, 11:00pm UTC](https://discourse.julialang.org/t/simple-enzyme-ad-on-cuda-gpu/99966 "2023-06-09T23:00:08Z")

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Hi there, I have just started thinking about moving some of my JAX code to Julia and wanted to have a go using Enzyme for my AD. I am looking to make use of CUDA GPUs. I have started with a simple program to verify thin…

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## [Instability detected in solving ODE with DifferentialEquations.jl](https://discourse.julialang.org/t/instability-detected-in-solving-ode-with-differentialequations-jl/99792)

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**Author:** [@Rezair](https://discourse.julialang.org/u/Rezair)\
**Replies:** 7\
**Last updated:** [June 9, 2023, 10:23pm UTC](https://discourse.julialang.org/t/instability-detected-in-solving-ode-with-differentialequations-jl/99792 "2023-06-09T22:23:22Z")

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I am trying to solve an equation in Julia but I get Unstable retcode, I have solved the same eqaution in MATLAB with no issues. here is a simplified version of the code: using DifferentialEquations struct RosslerMSF …

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## [Perform Bayesian estimations of ODE parameters when variables were not measured simultaneously](https://discourse.julialang.org/t/perform-bayesian-estimations-of-ode-parameters-when-variables-were-not-measured-simultaneously/100033)

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**Author:** [@zeyang.sun](https://discourse.julialang.org/u/zeyang.sun)\
**Replies:** 3\
**Last updated:** [June 9, 2023, 10:08pm UTC](https://discourse.julialang.org/t/perform-bayesian-estimations-of-ode-parameters-when-variables-were-not-measured-simultaneously/100033 "2023-06-09T22:08:27Z")

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Greetings everyone! Recently I need to use Bayesian method to estimate the parameters of a chemical kinetic model which can be described by ordinary differential equations. I found Turing.jl or DiffeqBayes.jl might be t…

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## [How to get live plotting of data into gui](https://discourse.julialang.org/t/how-to-get-live-plotting-of-data-into-gui/100115)

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**Author:** [@blckbart](https://discourse.julialang.org/u/blckbart)\
**Replies:** 0\
**Last updated:** [June 9, 2023, 3:57pm UTC](https://discourse.julialang.org/t/how-to-get-live-plotting-of-data-into-gui/100115 "2023-06-09T15:57:34Z")

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Hi All, I am looking for a good example GUI made using glade and GTK. Specifically I want to be able to live update a plot. Any help would be appreciated. Thanks!

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## [Getting 3D shapes without illumination](https://discourse.julialang.org/t/getting-3d-shapes-without-illumination/100091)

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**Author:** [@peremato](https://discourse.julialang.org/u/peremato)\
**Replies:** 5\
**Last updated:** [June 9, 2023, 2:45pm UTC](https://discourse.julialang.org/t/getting-3d-shapes-without-illumination/100091 "2023-06-09T14:45:28Z")

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I am plotting with GLMakie my own 3D solids by defining GeometryBasics.faces(...) and GeometryBasics.coordinates(...) for each type. Then I plot the solids using a code like this: m = GeometryBasics.mesh(solid) po…

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## [Laguerre polynomials on GPU](https://discourse.julialang.org/t/laguerre-polynomials-on-gpu/99571)

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**Author:** [@albertomercurio](https://discourse.julialang.org/u/albertomercurio)\
**Replies:** 27\
**Last updated:** [June 9, 2023, 11:35am UTC](https://discourse.julialang.org/t/laguerre-polynomials-on-gpu/99571 "2023-06-09T11:35:19Z")

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Hello, I’m currently able to calculate the generalized Laguerre polynomials on the CPU using HypergeometricFunctions \_genlaguerre(n, α, x) = binomial(n+α,n) \* HypergeometricFunctions.M(-n, α+1, x) A = rand(1000, 1000)…

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## [Resume chains Turing](https://discourse.julialang.org/t/resume-chains-turing/66282)

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**Author:** [@marcobonici](https://discourse.julialang.org/u/marcobonici)\
**Replies:** 12\
**Last updated:** [June 9, 2023, 8:13am UTC](https://discourse.julialang.org/t/resume-chains-turing/66282 "2023-06-09T08:13:21Z")

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Hi to everybody, I want to use Turing on the lsf cluster of my university. Following the official documentation and using the ClusterManager package I was able to run Turing on my cluster. using Turing using Distribute…

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## [How to find Shadow Price in JuMP](https://discourse.julialang.org/t/how-to-find-shadow-price-in-jump/99887)

<div class="topic-metadata">

**Author:** [@Gagan\_Meena](https://discourse.julialang.org/u/Gagan_Meena)\
**Replies:** 6\
**Last updated:** [June 9, 2023, 4:38am UTC](https://discourse.julialang.org/t/how-to-find-shadow-price-in-jump/99887 "2023-06-09T04:38:47Z")

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How to find the shadow price for the equality constraint in the following code? using JuMP, Gurobi include("Data.jl") Market\_dt = PlanningData function Market\_Clearing(Market\_dt) # Sets and Indices n …

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