# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=290

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**Page:** 291

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## [Flux loss: Gradient wrt input leads to empty gradient wrt parameters or to "can't differentiate foreigncall"](https://discourse.julialang.org/t/flux-loss-gradient-wrt-input-leads-to-empty-gradient-wrt-parameters-or-to-cant-differentiate-foreigncall/79180)

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**Author:** [@JanJereczek](https://discourse.julialang.org/u/JanJereczek)\
**Replies:** 3\
**Last updated:** [April 8, 2022, 1:14pm UTC](https://discourse.julialang.org/t/flux-loss-gradient-wrt-input-leads-to-empty-gradient-wrt-parameters-or-to-cant-differentiate-foreigncall/79180 "2022-04-08T13:14:51Z")

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Hi Everyone, I am stuck with the following problem: I need the gradient (w.r.t. the input variables) of my NN in the loss function and cannot get it working. I have seen a couple of posts on this, however none with a so…

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## [Different solve options within ensemble simulations](https://discourse.julialang.org/t/different-solve-options-within-ensemble-simulations/79102)

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**Author:** [@AndreaRH](https://discourse.julialang.org/u/AndreaRH)\
**Replies:** 2\
**Last updated:** [April 8, 2022, 12:17pm UTC](https://discourse.julialang.org/t/different-solve-options-within-ensemble-simulations/79102 "2022-04-08T12:17:31Z")

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I have an EnsembleProblem. This allows me to remake the problem for each of the different simulations. However, I want to change the keyword arguments for solving the different trajectories of the ensemble problem. For i…

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## [What is the state of Rasterization and Rasterstats in Julia](https://discourse.julialang.org/t/what-is-the-state-of-rasterization-and-rasterstats-in-julia/72366)

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**Author:** [@Ordens\_Ritter](https://discourse.julialang.org/u/Ordens_Ritter)\
**Replies:** 26\
**Last updated:** [April 8, 2022, 11:48am UTC](https://discourse.julialang.org/t/what-is-the-state-of-rasterization-and-rasterstats-in-julia/72366 "2022-04-08T11:48:56Z")

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I have followed the progress of the geo community in Julia every know and than. To me there seams to be a slow but steady progress. That both for raster and vector files. Although, I for instead didn’t found out thinks,…

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## [Custom array (a variations on adjacency matrix for graphs)](https://discourse.julialang.org/t/custom-array-a-variations-on-adjacency-matrix-for-graphs/79196)

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**Author:** [@AlexanderChen](https://discourse.julialang.org/u/AlexanderChen)\
**Replies:** 2\
**Last updated:** [April 8, 2022, 6:18am UTC](https://discourse.julialang.org/t/custom-array-a-variations-on-adjacency-matrix-for-graphs/79196 "2022-04-08T06:18:03Z")

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Hi, So I am doing a project in which i need to heavily use a graph structure. I have tried several graph package in the past, but they are not flexible enough for my use case. So I started to wonder if the following is …

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## [Error when I use the function distribute(array) from the libray DistributedArrays](https://discourse.julialang.org/t/error-when-i-use-the-function-distribute-array-from-the-libray-distributedarrays/16015)

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**Author:** [@dsHitman](https://discourse.julialang.org/u/dsHitman)\
**Replies:** 3\
**Last updated:** [April 7, 2022, 9:57pm UTC](https://discourse.julialang.org/t/error-when-i-use-the-function-distribute-array-from-the-libray-distributedarrays/16015 "2022-04-07T21:57:05Z")

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When I create an array and after I use the distribute() function from the Distributed Arrays library, I get this error: ERROR: On worker 2: KeyError: key DistributedArrays \[aaf54ef3-cdf8-58ed-94cc-d582ad619b94\] not fou…

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## [How do I write @variable(z=x\[1\]+x\[2\])?](https://discourse.julialang.org/t/how-do-i-write-variable-z-x-1-x-2/79149)

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**Author:** [@castlemas](https://discourse.julialang.org/u/castlemas)\
**Replies:** 5\
**Last updated:** [April 7, 2022, 9:32pm UTC](https://discourse.julialang.org/t/how-do-i-write-variable-z-x-1-x-2/79149 "2022-04-07T21:32:38Z")

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Hi, I am trying to solve a min-max optimisation problem that requires me to add in a constraint How do I assign a constraint such that a variable equals to another variable?

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## [Differentiation of expressions involving arrays](https://discourse.julialang.org/t/differentiation-of-expressions-involving-arrays/78826)

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**Author:** [@natema](https://discourse.julialang.org/u/natema)\
**Replies:** 4\
**Last updated:** [April 7, 2022, 8:42pm UTC](https://discourse.julialang.org/t/differentiation-of-expressions-involving-arrays/78826 "2022-04-07T20:42:46Z")

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Hi. I’m a ModellingToolkit newbie (and DE in general). I wrote some code last December which now throws the error Differentiation of expressions involving arrays and array variables is not yet supported. I saw that rai…

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## [Gurobi 9.5 MemLimit usage](https://discourse.julialang.org/t/gurobi-9-5-memlimit-usage/79045)

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**Author:** [@max](https://discourse.julialang.org/u/max)\
**Replies:** 6\
**Last updated:** [April 7, 2022, 8:31pm UTC](https://discourse.julialang.org/t/gurobi-9-5-memlimit-usage/79045 "2022-04-07T20:31:03Z")

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Hello everyone, i am struggeling with the usage of the MemLimit (https://www.gurobi.com/documentation/9.5/refman/memlimit.html) option which was newly introduced in Gurobi 9.5. Gurobi should throw an error when exceedi…

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## [Is there a way to combine 4+ channels in a single image? (Images.jl)](https://discourse.julialang.org/t/is-there-a-way-to-combine-4-channels-in-a-single-image-images-jl/17249)

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**Author:** [@wrgr](https://discourse.julialang.org/u/wrgr)\
**Replies:** 7\
**Last updated:** [April 7, 2022, 6:53pm UTC](https://discourse.julialang.org/t/is-there-a-way-to-combine-4-channels-in-a-single-image-images-jl/17249 "2022-04-07T18:53:30Z")

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Input: 4-5 intensity channels, represented as 2D arrays with elements in \[0, 1\]. Problem: combine and display them in a single image, giving each channel a specific color, e.g. yellow, red, green, blue for 4 channels, u…

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## [How to extract a differential operator from an expression involving symbolic derivatives (using Symbolics.jl)?](https://discourse.julialang.org/t/how-to-extract-a-differential-operator-from-an-expression-involving-symbolic-derivatives-using-symbolics-jl/76449)

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**Author:** [@jishnub](https://discourse.julialang.org/u/jishnub)\
**Replies:** 6\
**Last updated:** [April 7, 2022, 12:04pm UTC](https://discourse.julialang.org/t/how-to-extract-a-differential-operator-from-an-expression-involving-symbolic-derivatives-using-symbolics-jl/76449 "2022-04-07T12:04:34Z")

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Suppose I have the following operation julia\> @variables t x(t) 2-element Vector{Num}: t x(t) julia\> Dt = Differential(t) (::Differential) (generic function with 2 methods) julia\> ex = expand\_derivatives(Dt(t^2\*x…

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## [Is there a shortcut to construct derivatives of a product using Symbolics?](https://discourse.julialang.org/t/is-there-a-shortcut-to-construct-derivatives-of-a-product-using-symbolics/79144)

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**Author:** [@jishnub](https://discourse.julialang.org/u/jishnub)\
**Replies:** 1\
**Last updated:** [April 7, 2022, 11:47am UTC](https://discourse.julialang.org/t/is-there-a-shortcut-to-construct-derivatives-of-a-product-using-symbolics/79144 "2022-04-07T11:47:53Z")

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This is a rather basic question, as I’ve just started using Symbolics.jl and couldn’t find this in the docs after a brief glance. What I want to do is evaluate f -\> (d/dx)(x \* f). I have figured out one way to achieve th…

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## [Plot one point with a label](https://discourse.julialang.org/t/plot-one-point-with-a-label/79138)

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**Author:** [@Katamari](https://discourse.julialang.org/u/Katamari)\
**Replies:** 3\
**Last updated:** [April 7, 2022, 9:50am UTC](https://discourse.julialang.org/t/plot-one-point-with-a-label/79138 "2022-04-07T09:50:08Z")

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I would like to plot labeled points. The code I wrote to try it out is below. using CairoMakie function point(x; label=L"%$x") scatter!((x, 0);color=:black) text!(label, position=(x-0.05, 0.1)) end fig, ax=lines…

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## [Is there a direct link function for chemical process simulator like Aspen plus in Julia like in Matlab or python through COM technology?](https://discourse.julialang.org/t/is-there-a-direct-link-function-for-chemical-process-simulator-like-aspen-plus-in-julia-like-in-matlab-or-python-through-com-technology/79133)

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**Author:** [@JackaChou](https://discourse.julialang.org/u/JackaChou)\
**Replies:** 4\
**Last updated:** [April 7, 2022, 6:55am UTC](https://discourse.julialang.org/t/is-there-a-direct-link-function-for-chemical-process-simulator-like-aspen-plus-in-julia-like-in-matlab-or-python-through-com-technology/79133 "2022-04-07T06:55:50Z")

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Something like Aspen Plus - Matlab Link - File Exchange - MATLAB Central

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## [How to determine conditions of bistability](https://discourse.julialang.org/t/how-to-determine-conditions-of-bistability/78431)

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**Author:** [@Dragolonth](https://discourse.julialang.org/u/Dragolonth)\
**Replies:** 4\
**Last updated:** [April 7, 2022, 6:08am UTC](https://discourse.julialang.org/t/how-to-determine-conditions-of-bistability/78431 "2022-04-07T06:08:28Z")

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Hello everyone! I’m new to Julia and would consider myself a beginner to programming in general. Currently, I am using Catalyst.jl to define a system of ODEs as a reaction network. I have the parameters and initial condi…

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## [Training FLUX models with larger datasets](https://discourse.julialang.org/t/training-flux-models-with-larger-datasets/79057)

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**Author:** [@lgmendes](https://discourse.julialang.org/u/lgmendes)\
**Replies:** 4\
**Last updated:** [April 7, 2022, 1:45am UTC](https://discourse.julialang.org/t/training-flux-models-with-larger-datasets/79057 "2022-04-07T01:45:44Z")

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Hi, I’m trying to train a FLUX model (ResNet50) with a medium-size dataset (~ 30K images (512X512X3)) on a computer with 128GB of RAM and Three NVIDIA GeForce GTX 1080 Ti. I’m loading the data with Dataloader using a B…

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## [Adding Error Bars To Legend](https://discourse.julialang.org/t/adding-error-bars-to-legend/79018)

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**Author:** [@cmdenis](https://discourse.julialang.org/u/cmdenis)\
**Replies:** 2\
**Last updated:** [April 6, 2022, 7:18pm UTC](https://discourse.julialang.org/t/adding-error-bars-to-legend/79018 "2022-04-06T19:18:52Z")

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Hi, I’m trying to make a plot (with Plots) with some data points. I’d like to be able to add an entry to the legend labeling the error bars. So far I have something of the sort: scatter( rand(10), yerr = rand(…

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## [Incorrect function evaluation in Zygote when swapping variables](https://discourse.julialang.org/t/incorrect-function-evaluation-in-zygote-when-swapping-variables/79082)

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**Author:** [@goerz](https://discourse.julialang.org/u/goerz)\
**Replies:** 1\
**Last updated:** [April 6, 2022, 5:42pm UTC](https://discourse.julialang.org/t/incorrect-function-evaluation-in-zygote-when-swapping-variables/79082 "2022-04-06T17:42:36Z")

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I have a relatively concise routine cheby that evaluates Φ = exp(-i H dt) Ψ for a Hermitian matrix H and a complex vector Ψ by expanding the exponential into Cheybchev polynomials. A minimal working example adapted from t…

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## [Optimization Technique in JuMP model](https://discourse.julialang.org/t/optimization-technique-in-jump-model/79108)

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**Author:** [@iAnkiit](https://discourse.julialang.org/u/iAnkiit)\
**Replies:** 1\
**Last updated:** [April 6, 2022, 4:57pm UTC](https://discourse.julialang.org/t/optimization-technique-in-jump-model/79108 "2022-04-06T16:57:55Z")

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Could someone please tell , which optimization technique /algorithm JuMP model uses ? like, when we perform : “optimize! (model)” ? Or, is it completely solver dependent ?

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## [Passing tuple of structs to a CUDA.jl kernel](https://discourse.julialang.org/t/passing-tuple-of-structs-to-a-cuda-jl-kernel/79064)

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**Author:** [@lodygaw](https://discourse.julialang.org/u/lodygaw)\
**Replies:** 4\
**Last updated:** [April 6, 2022, 11:52am UTC](https://discourse.julialang.org/t/passing-tuple-of-structs-to-a-cuda-jl-kernel/79064 "2022-04-06T11:52:51Z")

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Hi, I have a problem with passing a tuple of structs to a CUDA.jl kernel. This is MWE: using CUDA, Adapt, StaticArrays struct MyType1 end struct MyType2 end struct MyStruct{T,N,L} type :: T data :: SMatrix{N,2,Flo…

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## [ParallelStencil w/MPI](https://discourse.julialang.org/t/parallelstencil-w-mpi/79077)

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**Author:** [@wkharold](https://discourse.julialang.org/u/wkharold)\
**Replies:** 2\
**Last updated:** [April 6, 2022, 9:41am UTC](https://discourse.julialang.org/t/parallelstencil-w-mpi/79077 "2022-04-06T09:41:47Z")

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Is the CPU parallelism in the ParallelStencil.jl Concise single/multi-XPU miniapps limited to threads, or since it’s built on/with ImplicitGlobalGrid can it do MPI as well? I don’t see anything that looks like MPI suppo…

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## [Linear problem with multiple shifts](https://discourse.julialang.org/t/linear-problem-with-multiple-shifts/69086)

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**Author:** [@Jae-Mo\_Lihm](https://discourse.julialang.org/u/Jae-Mo_Lihm)\
**Replies:** 8\
**Last updated:** [April 6, 2022, 9:49am UTC](https://discourse.julialang.org/t/linear-problem-with-multiple-shifts/69086 "2022-04-06T09:49:58Z")

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I want to solve (A - c\_i) \* x = b for multiple shifts c\_i. A is a Hermitian matrix, where A\*x is efficient than obtaining A directly. A - c\_i \* I is positive definite. I know that one can use Krylov subspace methods (Lan…

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## [JuMP/MOI performance overhead vs XPress api](https://discourse.julialang.org/t/jump-moi-performance-overhead-vs-xpress-api/78994)

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**Author:** [@Marie](https://discourse.julialang.org/u/Marie)\
**Replies:** 12\
**Last updated:** [April 6, 2022, 9:17am UTC](https://discourse.julialang.org/t/jump-moi-performance-overhead-vs-xpress-api/78994 "2022-04-06T09:17:47Z")

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Solving exactly same lp problem using XPress api is way faster than using JuMP/MOI: 2 ses vs 9 secs for a simple case; then 452 secs vs 1796 for more complex case. Is this overhead a known issue? Is there a way to optimi…

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## [Dropmissing(!) is undefined for GroupedDataFrames](https://discourse.julialang.org/t/dropmissing-is-undefined-for-groupeddataframes/79037)

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**Author:** [@Joseph\_Bradley](https://discourse.julialang.org/u/Joseph_Bradley)\
**Replies:** 15\
**Last updated:** [April 6, 2022, 7:35am UTC](https://discourse.julialang.org/t/dropmissing-is-undefined-for-groupeddataframes/79037 "2022-04-06T07:35:54Z")

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Hi, The following code throws an error: df.ticker = vcat(\["AAPL" for i in 1:10\], \["TSLA" for i in 1:10\]) df.prices = vcat(rand(19), missing) gdf = groupby(df, :ticker) dropmissing!(gdf) The only solution I have at …

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## [Interpolations over Shape Fitted Grids](https://discourse.julialang.org/t/interpolations-over-shape-fitted-grids/79033)

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**Author:** [@Whyborn](https://discourse.julialang.org/u/Whyborn)\
**Replies:** 3\
**Last updated:** [April 6, 2022, 12:04am UTC](https://discourse.julialang.org/t/interpolations-over-shape-fitted-grids/79033 "2022-04-06T00:04:23Z")

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I am trying to interpolate on a grid that is body fitted (in a Computational Fluid Dynamics context). The grid cannot be simply described by vectors describing the grid spacing in each dimensions, instead the points are …

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## [Solving differential equations with derivatives on both sides of the equation](https://discourse.julialang.org/t/solving-differential-equations-with-derivatives-on-both-sides-of-the-equation/79070)

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**Author:** [@CameronBieganek](https://discourse.julialang.org/u/CameronBieganek)\
**Replies:** 4\
**Last updated:** [April 5, 2022, 9:21pm UTC](https://discourse.julialang.org/t/solving-differential-equations-with-derivatives-on-both-sides-of-the-equation/79070 "2022-04-05T21:21:22Z")

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I have two coupled, first order, non-linear ODEs that I’m trying to solve. However, both of the two equations contain additional derivatives on the right-hand sides of the equation (and there don’t seem to be any obvious…

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## [Automatic Speech Recognition in Julia](https://discourse.julialang.org/t/automatic-speech-recognition-in-julia/79003)

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**Author:** [@jbrea](https://discourse.julialang.org/u/jbrea)\
**Replies:** 2\
**Last updated:** [April 5, 2022, 8:13pm UTC](https://discourse.julialang.org/t/automatic-speech-recognition-in-julia/79003 "2022-04-05T20:13:44Z")

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Does anyone have (or work on) an implementation of modern automatic speech recognition tools like conformers or wav2vec2.0 in one of Julia’s deep learning frameworks Flux/Knet/Avalon? Ideally pretrained on LibriSpeech …

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## [One example from \`GPU programming in Julia | Workshop | JuliaCon 2021\`](https://discourse.julialang.org/t/one-example-from-gpu-programming-in-julia-workshop-juliacon-2021/79060)

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**Author:** [@DennisFang](https://discourse.julialang.org/u/DennisFang)\
**Replies:** 0\
**Last updated:** [April 5, 2022, 4:21pm UTC](https://discourse.julialang.org/t/one-example-from-gpu-programming-in-julia-workshop-juliacon-2021/79060 "2022-04-05T16:21:51Z")

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When I run the following example from the Workshop, the result is false in my computer. function my\_sum(a::AbstractArray{T}) where {T} b = CUDA.zeros(T, 1) kernel = @cuda launch=false reduce\_grid\_atomic\_shmem(+…

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## [ORC file format](https://discourse.julialang.org/t/orc-file-format/79041)

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**Author:** [@Krzysztof\_Langner](https://discourse.julialang.org/u/Krzysztof_Langner)\
**Replies:** 1\
**Last updated:** [April 5, 2022, 11:49am UTC](https://discourse.julialang.org/t/orc-file-format/79041 "2022-04-05T11:49:56Z")

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Hello, Is there any package or code example to read ORC file format? https://orc.apache.org/specification/ORCv1/ Can’t find anything with google.

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## [Best way to cache data during DifferentialEquations.jl integration](https://discourse.julialang.org/t/best-way-to-cache-data-during-differentialequations-jl-integration/78996)

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**Author:** [@josuagrw](https://discourse.julialang.org/u/josuagrw)\
**Replies:** 1\
**Last updated:** [April 5, 2022, 11:44am UTC](https://discourse.julialang.org/t/best-way-to-cache-data-during-differentialequations-jl-integration/78996 "2022-04-05T11:44:35Z")

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I have a problem which could be written (not exactly) as \\dot u = \\min\_w f(u,w) Naturally, I would like use some previous value of \\dot u as the starting point for the optimization problem on the r.h.s. — I might even…

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## [Calculating Jacobian from two matrices](https://discourse.julialang.org/t/calculating-jacobian-from-two-matrices/78966)

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**Author:** [@Iddingsite](https://discourse.julialang.org/u/Iddingsite)\
**Replies:** 4\
**Last updated:** [April 5, 2022, 10:48am UTC](https://discourse.julialang.org/t/calculating-jacobian-from-two-matrices/78966 "2022-04-05T10:48:09Z")

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Hi everyone, I would like to compute a Jacobian for one of my problem for a PDE, but I don’t have a function linking the unknown to my function. So I only have 2 matrices, 1 with the values of the function and 1 with th…

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