# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=46

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**Page:** 47

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## [Can Ipopt provide a dual bound?](https://discourse.julialang.org/t/can-ipopt-provide-a-dual-bound/128354)

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**Author:** [@WalterMadelim](https://discourse.julialang.org/u/WalterMadelim)\
**Replies:** 2\
**Last updated:** [April 24, 2025, 6:57am UTC](https://discourse.julialang.org/t/can-ipopt-provide-a-dual-bound/128354 "2025-04-24T06:57:46Z")

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Continuing the discussion from Getting duals for nonlinear programming problem: As an extension, I asked ChatGPT this problem. Can anyone tell me where is its idea from? Does its reply make sense?

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## [Add lower bound to objective function?](https://discourse.julialang.org/t/add-lower-bound-to-objective-function/36261)

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**Author:** [@gobs](https://discourse.julialang.org/u/gobs)\
**Replies:** 4\
**Last updated:** [April 24, 2025, 2:36am UTC](https://discourse.julialang.org/t/add-lower-bound-to-objective-function/36261 "2025-04-24T02:36:34Z")

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I would like to help the MILP solver used by JuMP by providing it with a lower bound on the objective function. Is there a “smart” way of doing this other than to just add a constraint to the objective fcn expression, e.…

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## [Objective\_bound and Gurobi](https://discourse.julialang.org/t/objective-bound-and-gurobi/46633)

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**Author:** [@arkanver](https://discourse.julialang.org/u/arkanver)\
**Replies:** 2\
**Last updated:** [April 24, 2025, 2:23am UTC](https://discourse.julialang.org/t/objective-bound-and-gurobi/46633 "2025-04-24T02:23:14Z")

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Hello ! I have shared some code with a research associate, aiming to compute the solution to a continuous optimization problem. Due to problem size, we use a time limit. The problem is that I use CPLEX, and my associate…

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## [Warm starting Ipopt with higher discretization points](https://discourse.julialang.org/t/warm-starting-ipopt-with-higher-discretization-points/127974)

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**Author:** [@Dhormir](https://discourse.julialang.org/u/Dhormir)\
**Replies:** 8\
**Last updated:** [April 23, 2025, 9:43pm UTC](https://discourse.julialang.org/t/warm-starting-ipopt-with-higher-discretization-points/127974 "2025-04-23T21:43:01Z")

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Hello, I’m fairly new to Julia and using Ipopt as a solver, and currently I’m facing the following problem. I’m solving an Optimal control problem with a discretization size of N. Then what I want to do is grab the prov…

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## [Websockets invalid value for Enum OpCode](https://discourse.julialang.org/t/websockets-invalid-value-for-enum-opcode/128335)

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**Author:** [@freeman](https://discourse.julialang.org/u/freeman)\
**Replies:** 1\
**Last updated:** [April 23, 2025, 6:54pm UTC](https://discourse.julialang.org/t/websockets-invalid-value-for-enum-opcode/128335 "2025-04-23T18:54:16Z")

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Just flagging that this happened out in the wild. │ e = ArgumentError: invalid value for Enum OpCode: 11 …

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## [Gtk4 dropdown not working](https://discourse.julialang.org/t/gtk4-dropdown-not-working/128334)

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**Author:** [@TheHedgehog2000](https://discourse.julialang.org/u/TheHedgehog2000)\
**Replies:** 0\
**Last updated:** [April 23, 2025, 2:53pm UTC](https://discourse.julialang.org/t/gtk4-dropdown-not-working/128334 "2025-04-23T14:53:30Z")

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I am following the minimum working examples in this link: Dropdown widgets · Gtk4.jl. Neither works for me. In either case, when I try to select a new option from the drop down, nothing happens. Presumably, this is an is…

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## [2025 Summer School on Numerical Methods in Quantum Information Science](https://discourse.julialang.org/t/2025-summer-school-on-numerical-methods-in-quantum-information-science/127769)

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**Author:** [@Krastanov](https://discourse.julialang.org/u/Krastanov)\
**Replies:** 6\
**Last updated:** [April 23, 2025, 12:42pm UTC](https://discourse.julialang.org/t/2025-summer-school-on-numerical-methods-in-quantum-information-science/127769 "2025-04-23T12:42:38Z")

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This July we are again running a summer school on numerical methods in quantum information science, mostly in Julia. It will be in Amherst, Massachusetts, on the campus of UMass Amherst, a whole week, for just 90$ thanks…

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## [Is it possible to pass arbitrary types into MTK?](https://discourse.julialang.org/t/is-it-possible-to-pass-arbitrary-types-into-mtk/128304)

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**Author:** [@Matthew1](https://discourse.julialang.org/u/Matthew1)\
**Replies:** 9\
**Last updated:** [April 23, 2025, 8:58am UTC](https://discourse.julialang.org/t/is-it-possible-to-pass-arbitrary-types-into-mtk/128304 "2025-04-23T08:58:48Z")

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Based on the following docs (https://docs.sciml.ai/ModelingToolkit/stable/comparison/), which says ‘Modelica is a declarative programming language. ModelingToolkit.jl is a declarative symbolic modeling language’, I would…

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## [What is the best practice plotting workflow in julia?](https://discourse.julialang.org/t/what-is-the-best-practice-plotting-workflow-in-julia/128288)

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**Author:** [@hz-xiaxz](https://discourse.julialang.org/u/hz-xiaxz)\
**Replies:** 4\
**Last updated:** [April 23, 2025, 7:40am UTC](https://discourse.julialang.org/t/what-is-the-best-practice-plotting-workflow-in-julia/128288 "2025-04-23T07:40:59Z")

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Hi, don’t know if this is a duplicated question. Using Makie.jl to plot in Julia has been a wonderful experience. But I’m wondering if there is a more convenient way to plot like using Matplotlib in python? In plotting …

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## [Ipopt does NOT memorize a best solution found so far](https://discourse.julialang.org/t/ipopt-does-not-memorize-a-best-solution-found-so-far/127244)

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**Author:** [@WalterMadelim](https://discourse.julialang.org/u/WalterMadelim)\
**Replies:** 7\
**Last updated:** [April 23, 2025, 7:24am UTC](https://discourse.julialang.org/t/ipopt-does-not-memorize-a-best-solution-found-so-far/127244 "2025-04-23T07:24:14Z")

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The title is expounded through optimizing this function function g(x) return sin(7 \* x) + 1.2 \* cos(4.7 \* x) + 1.3 \* x end which can be visualized via, e.g. using CairoMakie f = Figure(); Axis(f\[1, 1\]); xs = LinRange(…

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## [Passing a variable that isn't integrated by MTK to DiffEqParamEstim objective function](https://discourse.julialang.org/t/passing-a-variable-that-isnt-integrated-by-mtk-to-diffeqparamestim-objective-function/128308)

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**Author:** [@Jarrod-Angove](https://discourse.julialang.org/u/Jarrod-Angove)\
**Replies:** 2\
**Last updated:** [April 22, 2025, 10:46pm UTC](https://discourse.julialang.org/t/passing-a-variable-that-isnt-integrated-by-mtk-to-diffeqparamestim-objective-function/128308 "2025-04-22T22:46:01Z")

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I’m still a bit new to MTK, please excuse me if I’m missing something simple here. I have an ODE model that integrates over two variables, V\_a and V\_b. However, I can only measure the total volume, V\_tot, so I have cons…

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## [CUDA(.jl) memory errors for very large kernels](https://discourse.julialang.org/t/cuda-jl-memory-errors-for-very-large-kernels/125831)

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**Author:** [@AntonReinhard](https://discourse.julialang.org/u/AntonReinhard)\
**Replies:** 24\
**Last updated:** [April 22, 2025, 6:45pm UTC](https://discourse.julialang.org/t/cuda-jl-memory-errors-for-very-large-kernels/125831 "2025-04-22T18:45:39Z")

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I have some questions about what some CUDA errors mean and what I can do about them. I’m dynamically generating code that I can successfully compile for both CPU and GPU targets (the GPU I’m using here is an A30 with 24…

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## [Reproducibility of problems in Modelling Toolkit (MTK)](https://discourse.julialang.org/t/reproducibility-of-problems-in-modelling-toolkit-mtk/128216)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 7\
**Last updated:** [April 22, 2025, 5:57pm UTC](https://discourse.julialang.org/t/reproducibility-of-problems-in-modelling-toolkit-mtk/128216 "2025-04-22T17:57:17Z")

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We are trying to cache the simplified model of an MTK model in a file. Currently we using the serialize() function of base Julia. Observation: The serialized file is different each time we generate it, even if the origi…

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## [Optimization Modeling & Deployment sessions at INFORMS Annual 2025](https://discourse.julialang.org/t/optimization-modeling-deployment-sessions-at-informs-annual-2025/128252)

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**Author:** [@4er](https://discourse.julialang.org/u/4er)\
**Replies:** 0\
**Last updated:** [April 20, 2025, 3:54pm UTC](https://discourse.julialang.org/t/optimization-modeling-deployment-sessions-at-informs-annual-2025/128252 "2025-04-20T15:54:15Z")

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We (Susanne Heipcke, Bob Fourer) are organizing sessions in the area of “Optimization Modeling & Deployment Software” at the 2025 INFORMS Annual Meeting, to be held October 26-29, 2025 in Atlanta, Georgia. Talks on new …

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## [Interactive subplots inspection with Makie](https://discourse.julialang.org/t/interactive-subplots-inspection-with-makie/128231)

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**Author:** [@henry2004y](https://discourse.julialang.org/u/henry2004y)\
**Replies:** 5\
**Last updated:** [April 21, 2025, 2:39pm UTC](https://discourse.julialang.org/t/interactive-subplots-inspection-with-makie/128231 "2025-04-21T14:39:39Z")

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Hi, I am using Makie for exploring the data of particle trajectories. Currently, my output looks like this: The trajectories can be long, and I may wish to zoom-in to a specific time interval for careful inspection.…

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## [Efficient Algorithms for exponential martingales generated by SDE with jumps](https://discourse.julialang.org/t/efficient-algorithms-for-exponential-martingales-generated-by-sde-with-jumps/127917)

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**Author:** [@paolo-mgi](https://discourse.julialang.org/u/paolo-mgi)\
**Replies:** 2\
**Last updated:** [April 21, 2025, 11:23am UTC](https://discourse.julialang.org/t/efficient-algorithms-for-exponential-martingales-generated-by-sde-with-jumps/127917 "2025-04-21T11:23:11Z")

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Hello, I am experimenting with jump processes, and in particular with stochastic diffrential equations of the form dμ(t)=μ(t) λ (dν(t)−r dt ) where dν(t)= increment of Poisson process r dt= compensator The result s…

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## [Another UndefRefError: access to undefined reference](https://discourse.julialang.org/t/another-undefreferror-access-to-undefined-reference/126039)

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**Author:** [@steveo314](https://discourse.julialang.org/u/steveo314)\
**Replies:** 21\
**Last updated:** [April 21, 2025, 12:41am UTC](https://discourse.julialang.org/t/another-undefreferror-access-to-undefined-reference/126039 "2025-04-21T00:41:35Z")

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Is there any way to check a Dataframe to see why this error would be returned when running a function on a DF? The error message is too vague. I got this error when running: unique!(df,\[col1,col2,col3\]) I’ve only have …

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## [Random independent set with GenericTensorNetworks.jl](https://discourse.julialang.org/t/random-independent-set-with-generictensornetworks-jl/127900)

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**Author:** [@slwu89](https://discourse.julialang.org/u/slwu89)\
**Replies:** 4\
**Last updated:** [April 20, 2025, 4:47pm UTC](https://discourse.julialang.org/t/random-independent-set-with-generictensornetworks-jl/127900 "2025-04-20T16:47:38Z")

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Hi @1115, I’m looking at the GenericTensorNetworks.jl package, and I a question regarding finding a single maximum independent set Independent set problem · GenericTensorNetworks.jl, is the solution sampled uniformly at …

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## [Val{N} + LinearIndices Causes Massive Compile-Time Unrolling](https://discourse.julialang.org/t/val-n-linearindices-causes-massive-compile-time-unrolling/128248)

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**Author:** [@0samuraiE](https://discourse.julialang.org/u/0samuraiE)\
**Replies:** 2\
**Last updated:** [April 20, 2025, 2:47pm UTC](https://discourse.julialang.org/t/val-n-linearindices-causes-massive-compile-time-unrolling/128248 "2025-04-20T14:47:46Z")

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I’m seeing strange behavior when using @code\_warntype on a function that takes a Val{N} parameter and creates a LinearIndices object with size (N, N, N). Here’s a minimal example: function test(::Val{N}) where {N} L…

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## [Some questions about an MOI wrapper](https://discourse.julialang.org/t/some-questions-about-an-moi-wrapper/128175)

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**Author:** [@Lester](https://discourse.julialang.org/u/Lester)\
**Replies:** 8\
**Last updated:** [April 20, 2025, 2:07pm UTC](https://discourse.julialang.org/t/some-questions-about-an-moi-wrapper/128175 "2025-04-20T14:07:50Z")

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Hi everyone. I’m currently working on an SQP solver and now trying to use that to solve optimal control problem. The optimal control problems are trancripted to NLPs in the framework of JuMP, which means if I want to use…

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## [PWM using Discrete Callbacks in Modeling Toolkit](https://discourse.julialang.org/t/pwm-using-discrete-callbacks-in-modeling-toolkit/127569)

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**Author:** [@twarczi](https://discourse.julialang.org/u/twarczi)\
**Replies:** 5\
**Last updated:** [April 20, 2025, 9:46am UTC](https://discourse.julialang.org/t/pwm-using-discrete-callbacks-in-modeling-toolkit/127569 "2025-04-20T09:46:23Z")

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I’m trying to create a PWM voltage source using modeling toolkit. I tried used the @discrete\_events macro within the @mtkmodel block but doing so throws an error: ERROR: KeyError: key pwm₊output₊u(t) not found when runni…

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## [Implementing Three-Dimensional Interpolation, ODEProblem, and Gradient Computation with sensealg=GaussAdjoint(autojacvec=EnzymeVJP())](https://discourse.julialang.org/t/implementing-three-dimensional-interpolation-odeproblem-and-gradient-computation-with-sensealg-gaussadjoint-autojacvec-enzymevjp/128204)

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**Author:** [@chooron](https://discourse.julialang.org/u/chooron)\
**Replies:** 2\
**Last updated:** [April 20, 2025, 3:23am UTC](https://discourse.julialang.org/t/implementing-three-dimensional-interpolation-odeproblem-and-gradient-computation-with-sensealg-gaussadjoint-autojacvec-enzymevjp/128204 "2025-04-20T03:23:11Z")

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Hello, the problem I am currently facing is solving an ordinary differential equation (ODE) with interpolated data inputs. The problem can be visualized as a snow layer, where the snow layer represents the intermediate s…

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## [Save a simplified ModelingToolkit problem as text](https://discourse.julialang.org/t/save-a-simplified-modelingtoolkit-problem-as-text/128124)

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**Author:** [@Bart\_van\_de\_Lint](https://discourse.julialang.org/u/Bart_van_de_Lint)\
**Replies:** 6\
**Last updated:** [April 19, 2025, 7:56pm UTC](https://discourse.julialang.org/t/save-a-simplified-modelingtoolkit-problem-as-text/128124 "2025-04-19T19:56:03Z")

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Because structural\_simplify is slow, I want to write the simplified system to a file, from where I can load it later. Using serialize("sys.bin", sys) works, but this causes problems when switching between julia versions,…

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## [Possible to design a compiler for Raspberry Pi GPU?](https://discourse.julialang.org/t/possible-to-design-a-compiler-for-raspberry-pi-gpu/128224)

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**Author:** [@mj2984](https://discourse.julialang.org/u/mj2984)\
**Replies:** 0\
**Last updated:** [April 19, 2025, 2:55pm UTC](https://discourse.julialang.org/t/possible-to-design-a-compiler-for-raspberry-pi-gpu/128224 "2025-04-19T14:55:58Z")

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I came across this blog post, of bare metal GPU assembly on Raspberry Pi. Programming a GPU on bare metal I am curious if it is possible to make a compiler that could transform generic Julia code (or SIMD optimized Jul…

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## [Best way to plot (discrete) 2d distribution](https://discourse.julialang.org/t/best-way-to-plot-discrete-2d-distribution/128213)

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**Author:** [@Torkel](https://discourse.julialang.org/u/Torkel)\
**Replies:** 1\
**Last updated:** [April 19, 2025, 10:57am UTC](https://discourse.julialang.org/t/best-way-to-plot-discrete-2d-distribution/128213 "2025-04-19T10:57:22Z")

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I have a MxN matrix. What is the best way to plot it? I tried using histogram2d, but its example just uses two vectors, and with my matrix the result is weird. I also tried something like using Plots x=range(1,stop=50,l…

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## [Overdetermined ODEProblem after upgrading from MTK v8.75.0 to MTK v9.72.0](https://discourse.julialang.org/t/overdetermined-odeproblem-after-upgrading-from-mtk-v8-75-0-to-mtk-v9-72-0/128163)

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**Author:** [@celia.bat](https://discourse.julialang.org/u/celia.bat)\
**Replies:** 2\
**Last updated:** [April 18, 2025, 7:25am UTC](https://discourse.julialang.org/t/overdetermined-odeproblem-after-upgrading-from-mtk-v8-75-0-to-mtk-v9-72-0/128163 "2025-04-18T07:25:03Z")

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Hi all :waving\_hand: I’m currently upgrading a model from ModelingToolkit v8.75.0 (which worked fine), to v9.72.0. I’m now running into an issue where my ODEProblem fails to initialize, even though my model contains c…

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## [Error with jac\_prototype in Mass Matrix Form of ODEFunction (svd! on Sparse Matrix)](https://discourse.julialang.org/t/error-with-jac-prototype-in-mass-matrix-form-of-odefunction-svd-on-sparse-matrix/127513)

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**Author:** [@sanjeev](https://discourse.julialang.org/u/sanjeev)\
**Replies:** 5\
**Last updated:** [April 18, 2025, 3:31am UTC](https://discourse.julialang.org/t/error-with-jac-prototype-in-mass-matrix-form-of-odefunction-svd-on-sparse-matrix/127513 "2025-04-18T03:31:04Z")

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Hi all, I’m solving a DAE system using DifferentialEquations.jl in the mass matrix form. The issue arises when I include jac\_prototype in the ODEFunction. If I define ODEFunction without jac\_prototype, everything works …

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## [IncompleteLU.jl efficiency much worse than Matlab ilu](https://discourse.julialang.org/t/incompletelu-jl-efficiency-much-worse-than-matlab-ilu/106062)

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**Author:** [@rli1996](https://discourse.julialang.org/u/rli1996)\
**Replies:** 3\
**Last updated:** [April 17, 2025, 6:01pm UTC](https://discourse.julialang.org/t/incompletelu-jl-efficiency-much-worse-than-matlab-ilu/106062 "2025-04-17T18:01:11Z")

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Hello Julia user, I’m developing a model with large matrix and systems of linear equation solver. I plan to change the original matlab code in Julia as I heard Julia is much faster than MatLab. However, I found ilu in …

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## [Pointers of Float to be used in MPI?](https://discourse.julialang.org/t/pointers-of-float-to-be-used-in-mpi/128146)

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**Author:** [@jsjie](https://discourse.julialang.org/u/jsjie)\
**Replies:** 0\
**Last updated:** [April 17, 2025, 2:46am UTC](https://discourse.julialang.org/t/pointers-of-float-to-be-used-in-mpi/128146 "2025-04-17T02:46:04Z")

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The following is a MWE that fails: using MPI MPI.Init() mutable struct Foo bar::Float64 end rank = MPI.Comm\_rank(MPI.COMM\_WORLD) foo = Foo(rank) println("$(rank)\\t$(foo.bar)") if rank == 0 MPI.API.MPI\_Recv(Re…

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## [Automatic Unit Conversion Function](https://discourse.julialang.org/t/automatic-unit-conversion-function/128121)

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**Author:** [@HSnowden](https://discourse.julialang.org/u/HSnowden)\
**Replies:** 0\
**Last updated:** [April 16, 2025, 10:57am UTC](https://discourse.julialang.org/t/automatic-unit-conversion-function/128121 "2025-04-16T10:57:33Z")

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Hi Is it possible in Unitful.jl or DynamicQuantities.jl given a set of preferred units e.g. \[u"ms",u"mm",u"mJ",u"g"\] to have a function that can convert any given value e.g. 10u"W" to the correct units. I have tried upr…

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