# Specific Domains

**URL:** https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=496

[Latest](https://discourse.julialang.org/latest.md) · [Categories](https://discourse.julialang.org/categories.md) · [Tags](https://discourse.julialang.org/tags.md)

**Page:** 497

---

## [GPU memory layout for custom type with different array lengths: StructArrays?](https://discourse.julialang.org/t/gpu-memory-layout-for-custom-type-with-different-array-lengths-structarrays/24479)

<div class="topic-metadata">

**Author:** [@floswald](https://discourse.julialang.org/u/floswald)\
**Replies:** 0\
**Last updated:** [May 22, 2019, 3:04pm UTC](https://discourse.julialang.org/t/gpu-memory-layout-for-custom-type-with-different-array-lengths-structarrays/24479 "2019-05-22T15:04:34Z")

</div>

I have the following example of a structure for a data type (real type has more fields): mutable struct Worker id :: Int # name T :: Int # number of periods observed t :: Int # current period w …

---

## [Monte Carlo problem, saving at different time points with 'saveat' from DifferentialEquations pkg](https://discourse.julialang.org/t/monte-carlo-problem-saving-at-different-time-points-with-saveat-from-differentialequations-pkg/24476)

<div class="topic-metadata">

**Author:** [@moesphere](https://discourse.julialang.org/u/moesphere)\
**Replies:** 1\
**Last updated:** [May 22, 2019, 2:17pm UTC](https://discourse.julialang.org/t/monte-carlo-problem-saving-at-different-time-points-with-saveat-from-differentialequations-pkg/24476 "2019-05-22T14:17:51Z")

</div>

Is it possible to save at different time points for each ODE problem in a Monte Carlo study? DifferentialEquations.solve(MCprob, saveat=\[10.0,20.0\]) works fine, but saves each ODE problem at the same time points. I am…

---

## [S3 object stores - current state?](https://discourse.julialang.org/t/s3-object-stores-current-state/24437)

<div class="topic-metadata">

**Author:** [@johnh](https://discourse.julialang.org/u/johnh)\
**Replies:** 7\
**Last updated:** [May 22, 2019, 1:34am UTC](https://discourse.julialang.org/t/s3-object-stores-current-state/24437 "2019-05-22T01:34:25Z")

</div>

What is the current state of packages in Julia for accessing S3 object stores. In particular CEPH. Are people just using boto with PyCall? Forgive me if I have asked this one before. Goldfish bowl memory.

---

## [Optim user-supplied gradient not working](https://discourse.julialang.org/t/optim-user-supplied-gradient-not-working/24417)

<div class="topic-metadata">

**Author:** [@tyleransom](https://discourse.julialang.org/u/tyleransom)\
**Replies:** 6\
**Last updated:** [May 21, 2019, 3:45pm UTC](https://discourse.julialang.org/t/optim-user-supplied-gradient-not-working/24417 "2019-05-21T15:45:56Z")

</div>

I’m estimating a maximum likelihood problem, and I’ve specified both the objective function and the gradient correctly. (I know this because I am able to reproduce estimates using the same exact data as a Stata example.) …

---

## [CouenneNL in version 1.1.1](https://discourse.julialang.org/t/couennenl-in-version-1-1-1/24405)

<div class="topic-metadata">

**Author:** [@Raminel](https://discourse.julialang.org/u/Raminel)\
**Replies:** 5\
**Last updated:** [May 21, 2019, 2:42pm UTC](https://discourse.julialang.org/t/couennenl-in-version-1-1-1/24405 "2019-05-21T14:42:15Z")

</div>

Hi, I am a new user of Julia and trying to solve my MINLP problem using CouenneNL. The problem is non convex so the solution I got from Ipopt is not reliable. How can I use CouenneNL in version v. 1.1.1?

---

## [A small attempt at running CLArrays.jl with julia 1.0](https://discourse.julialang.org/t/a-small-attempt-at-running-clarrays-jl-with-julia-1-0/15208)

<div class="topic-metadata">

**Author:** [@y4lu](https://discourse.julialang.org/u/y4lu)\
**Replies:** 11\
**Last updated:** [May 21, 2019, 2:35pm UTC](https://discourse.julialang.org/t/a-small-attempt-at-running-clarrays-jl-with-julia-1-0/15208 "2019-05-21T14:35:16Z")

</div>

I think I got a fair way through the precompile stage, mostly just replacing immutable’s with struct’s and moving the {T}'s of func{T}() to func() where{T}, but I’ve gotten a bit stuck on an unrecognized :SSAValue, from …

---

## [PDE Solvers in Julia](https://discourse.julialang.org/t/pde-solvers-in-julia/24416)

<div class="topic-metadata">

**Author:** [@xtalax](https://discourse.julialang.org/u/xtalax)\
**Replies:** 3\
**Last updated:** [May 21, 2019, 9:36am UTC](https://discourse.julialang.org/t/pde-solvers-in-julia/24416 "2019-05-21T09:36:13Z")

</div>

Is there a Package that is able to solve PDEs in julia yet?

---

## [Dynamic dimensions of optimization variable in JuMP](https://discourse.julialang.org/t/dynamic-dimensions-of-optimization-variable-in-jump/24399)

<div class="topic-metadata">

**Author:** [@lgo](https://discourse.julialang.org/u/lgo)\
**Replies:** 1\
**Last updated:** [May 20, 2019, 1:22pm UTC](https://discourse.julialang.org/t/dynamic-dimensions-of-optimization-variable-in-jump/24399 "2019-05-20T13:22:29Z")

</div>

Hello, Although my question itself is JuMP related, the underlying problem relates to metaprogramming in general: As the title suggests, I want to create a variable, which dimensions change depending on the numeric inp…

---

## [DifferentialEquations Events](https://discourse.julialang.org/t/differentialequations-events/24393)

<div class="topic-metadata">

**Author:** [@tomaklutfu](https://discourse.julialang.org/u/tomaklutfu)\
**Replies:** 3\
**Last updated:** [May 20, 2019, 10:34am UTC](https://discourse.julialang.org/t/differentialequations-events/24393 "2019-05-20T10:34:53Z")

</div>

I want to simulate a hybrid system with many different parameters. They all have the same event function but the location is dependent on the parameters given. Let’s say we have inverted pendulum and I want to give a rev…

---

## [JuliaDB: efficiently rank subgroups](https://discourse.julialang.org/t/juliadb-efficiently-rank-subgroups/24299)

<div class="topic-metadata">

**Author:** [@jade\_mackay](https://discourse.julialang.org/u/jade_mackay)\
**Replies:** 2\
**Last updated:** [May 20, 2019, 1:04am UTC](https://discourse.julialang.org/t/juliadb-efficiently-rank-subgroups/24299 "2019-05-20T01:04:37Z")

</div>

Hi, I would be grateful for some advice on how to create a column containing the ordinal rank of a score grouped by another column. For example: using JuliaDB using StatsBase Nx, Ny = 4, 3 x = repeat(1:Nx,inner=Ny) # l…

---

## [Flux support for sparse CuArrays](https://discourse.julialang.org/t/flux-support-for-sparse-cuarrays/24387)

<div class="topic-metadata">

**Author:** [@rayegun](https://discourse.julialang.org/u/rayegun)\
**Replies:** 0\
**Last updated:** [May 19, 2019, 9:03pm UTC](https://discourse.julialang.org/t/flux-support-for-sparse-cuarrays/24387 "2019-05-19T21:03:38Z")

</div>

Hey. I opened an issue on GitHub in the CuArrays repo but this may be a better avenue. Does Flux support (fully/partially) the sparse arrays implemented in that repo? Are there any hidden errors/issues I should be aware…

---

## [Can we make a comparison/overview of different GPU computing implementations?](https://discourse.julialang.org/t/can-we-make-a-comparison-overview-of-different-gpu-computing-implementations/24294)

<div class="topic-metadata">

**Author:** [@freemint](https://discourse.julialang.org/u/freemint)\
**Replies:** 6\
**Last updated:** [May 19, 2019, 7:26pm UTC](https://discourse.julialang.org/t/can-we-make-a-comparison-overview-of-different-gpu-computing-implementations/24294 "2019-05-19T19:26:46Z")

</div>

Hello, I am overwhelmed by the sheer number of GPU computing libraries. Every day i look into it i find a new implementation so far i found: CuArrays CUDAnative ArrayFire Knet.Arrays CLArrays AMDGPUnative Vulkan and…

---

## [Makie user defined marker example?](https://discourse.julialang.org/t/makie-user-defined-marker-example/24346)

<div class="topic-metadata">

**Author:** [@LaurentPlagne](https://discourse.julialang.org/u/LaurentPlagne)\
**Replies:** 2\
**Last updated:** [May 19, 2019, 4:38pm UTC](https://discourse.julialang.org/t/makie-user-defined-marker-example/24346 "2019-05-19T16:38:31Z")

</div>

Hi, It try to set up an animation for colliding polygons with Makie. It is OK if a use poly! and pass new polygon coordinates at each time steps but I guess that it would be more efficient If I use scatter! with user d…

---

## [Polynomial Roots With Multiplicities](https://discourse.julialang.org/t/polynomial-roots-with-multiplicities/24309)

<div class="topic-metadata">

**Author:** [@Hans\_W\_Borchers](https://discourse.julialang.org/u/Hans_W_Borchers)\
**Replies:** 8\
**Last updated:** [May 18, 2019, 9:12pm UTC](https://discourse.julialang.org/t/polynomial-roots-with-multiplicities/24309 "2019-05-18T21:12:54Z")

</div>

When using the roots function from the Polynomials package, the values found for multiple roots can be quite inaccurate. Just as an example, here is the polynomial with zeros at 1 and -1, each of multiplicity 4. julia\> …

---

## [Use of MINLP in Julia](https://discourse.julialang.org/t/use-of-minlp-in-julia/22161)

<div class="topic-metadata">

**Author:** [@angeloaliano1](https://discourse.julialang.org/u/angeloaliano1)\
**Replies:** 11\
**Last updated:** [May 18, 2019, 7:01pm UTC](https://discourse.julialang.org/t/use-of-minlp-in-julia/22161 "2019-05-18T19:01:27Z")

</div>

Hello people, all rigth? I need to solve a nonlinear integer nonconvex problem. The objective and constraints are nonlinear functions. First question: What the ideal package and solve to solve this problem? Is there …

---

## [Thread to create a list of desired new packages](https://discourse.julialang.org/t/thread-to-create-a-list-of-desired-new-packages/24342)

<div class="topic-metadata">

**Author:** [@Juan](https://discourse.julialang.org/u/Juan)\
**Replies:** 8\
**Last updated:** [May 18, 2019, 2:41pm UTC](https://discourse.julialang.org/t/thread-to-create-a-list-of-desired-new-packages/24342 "2019-05-18T14:41:42Z")

</div>

Hello. It could be a good idea to have a thread where people show their interest in new Julia packages with features non-existent yet, and other people can also get ideas about what packages to develop. For example, I …

---

## [3D plot in VRML or U3D format](https://discourse.julialang.org/t/3d-plot-in-vrml-or-u3d-format/24351)

<div class="topic-metadata">

**Author:** [@zimmermm](https://discourse.julialang.org/u/zimmermm)\
**Replies:** 0\
**Last updated:** [May 18, 2019, 12:57pm UTC](https://discourse.julialang.org/t/3d-plot-in-vrml-or-u3d-format/24351 "2019-05-18T12:57:42Z")

</div>

Is anyone aware of a julia package that allows exporting 3d plots in VRML format? (Or better directly creates U3D pdf)

---

## [How to launch workers on specific allocation node?](https://discourse.julialang.org/t/how-to-launch-workers-on-specific-allocation-node/24336)

<div class="topic-metadata">

**Author:** [@aramirezreyes](https://discourse.julialang.org/u/aramirezreyes)\
**Replies:** 1\
**Last updated:** [May 17, 2019, 11:02pm UTC](https://discourse.julialang.org/t/how-to-launch-workers-on-specific-allocation-node/24336 "2019-05-17T23:02:01Z")

</div>

Hi! I am doing some process that uses a ton of memory. The way I thought of doing it is to request 2 nodes via slurm and then send the memory-intensive part to a second node. My process looks like: salloc --nodes 2 -…

---

## [Flux & Julia v. 1.1.1](https://discourse.julialang.org/t/flux-julia-v-1-1-1/24317)

<div class="topic-metadata">

**Author:** [@BLI](https://discourse.julialang.org/u/BLI)\
**Replies:** 2\
**Last updated:** [May 17, 2019, 3:59pm UTC](https://discourse.julialang.org/t/flux-julia-v-1-1-1/24317 "2019-05-17T15:59:20Z")

</div>

I just upgraded Julia to v. 1.1.1, and have updated packages. When I run using Flux, I get error messages. The status of Flux is: (v1.1) pkg\> status Flux Status \`C:\\Users\\my\_username\\.julia\\environments\\v1.1\\Projec…

---

## [Back and forth transfer of data between GPU neural net and CPU simulation](https://discourse.julialang.org/t/back-and-forth-transfer-of-data-between-gpu-neural-net-and-cpu-simulation/24328)

<div class="topic-metadata">

**Author:** [@HenriDeh](https://discourse.julialang.org/u/HenriDeh)\
**Replies:** 0\
**Last updated:** [May 17, 2019, 2:51pm UTC](https://discourse.julialang.org/t/back-and-forth-transfer-of-data-between-gpu-neural-net-and-cpu-simulation/24328 "2019-05-17T14:51:13Z")

</div>

Hello, I have a neural network that interacts with a simulation. To accelerate its training, the network is transfered to my GPU. I implemented my simulation as a structure that handles other structures. In my toy exam…

---

## [Directed Graph With Specific Locations](https://discourse.julialang.org/t/directed-graph-with-specific-locations/24304)

<div class="topic-metadata">

**Author:** [@samslam](https://discourse.julialang.org/u/samslam)\
**Replies:** 1\
**Last updated:** [May 17, 2019, 6:17am UTC](https://discourse.julialang.org/t/directed-graph-with-specific-locations/24304 "2019-05-17T06:17:47Z")

</div>

Hello As part of a university project I am solving a version of the Vehicle routing problem. I hope to illustrate the results with a directed graph. I have managed to generate such graphs using LightGraphs, but am havin…

---

## [SOS use on multidimensional arrays](https://discourse.julialang.org/t/sos-use-on-multidimensional-arrays/24282)

<div class="topic-metadata">

**Author:** [@iharjunk](https://discourse.julialang.org/u/iharjunk)\
**Replies:** 5\
**Last updated:** [May 17, 2019, 4:48am UTC](https://discourse.julialang.org/t/sos-use-on-multidimensional-arrays/24282 "2019-05-17T04:48:23Z")

</div>

Hello all! I am trying to use the new way of SOS2 constraints (MOI.SOS2) but since I have a 3-dimensional variable (the last dimension should be part of the SOS2 set), existing examples are not sufficient. Any hints how…

---

## [Graph construction performance](https://discourse.julialang.org/t/graph-construction-performance/24288)

<div class="topic-metadata">

**Author:** [@Azamat](https://discourse.julialang.org/u/Azamat)\
**Replies:** 2\
**Last updated:** [May 16, 2019, 6:15pm UTC](https://discourse.julialang.org/t/graph-construction-performance/24288 "2019-05-16T18:15:15Z")

</div>

I need to construct a dense weighted undirected graph with ~20,000 vertices. Currently, I have the following code using LightGraphs, SimpleWeightedGraphs function main(n) g = SimpleWeightedGraph(n) for u ∈ verti…

---

## [Find gradient of a posterior](https://discourse.julialang.org/t/find-gradient-of-a-posterior/24254)

<div class="topic-metadata">

**Author:** [@Uche](https://discourse.julialang.org/u/Uche)\
**Replies:** 12\
**Last updated:** [May 16, 2019, 5:25pm UTC](https://discourse.julialang.org/t/find-gradient-of-a-posterior/24254 "2019-05-16T17:25:45Z")

</div>

Please can anyone help me with this. I have been trying to use ForwardDiff or Flux.Tracker or Zygote to get the gradient of this posterior but has not had any success yet: using AltDistributions, Distributions using L…

---

## [Resetting the canvas within Cairo.jl and Gtk.jl for an image selection viewing gui](https://discourse.julialang.org/t/resetting-the-canvas-within-cairo-jl-and-gtk-jl-for-an-image-selection-viewing-gui/24251)

<div class="topic-metadata">

**Author:** [@mantzaris](https://discourse.julialang.org/u/mantzaris)\
**Replies:** 7\
**Last updated:** [May 16, 2019, 5:18am UTC](https://discourse.julialang.org/t/resetting-the-canvas-within-cairo-jl-and-gtk-jl-for-an-image-selection-viewing-gui/24251 "2019-05-16T05:18:58Z")

</div>

I have here a MWE for what is a Gtk window (Gkt.jl) that uses Cairo to draw on the canvas some png image files. There is a ‘button’ that changes a counter for the selection of which image is drawn, but the images are ove…

---

## [Joining two DataFrames with same columns](https://discourse.julialang.org/t/joining-two-dataframes-with-same-columns/5671)

<div class="topic-metadata">

**Author:** [@IljaK91](https://discourse.julialang.org/u/IljaK91)\
**Replies:** 2\
**Last updated:** [May 15, 2019, 5:49pm UTC](https://discourse.julialang.org/t/joining-two-dataframes-with-same-columns/5671 "2019-05-15T17:49:34Z")

</div>

Hi there, I would like to join two DataFrames that have the same column, let’s say: DataFrameA: country GDP Germany 1 DataFrameB: country GDP USA 2 The resulting DataFrame should be: country GDP …

---

## [How to load URDF files with .dae models into MeshCat?](https://discourse.julialang.org/t/how-to-load-urdf-files-with-dae-models-into-meshcat/19509)

<div class="topic-metadata">

**Author:** [@cserteGT3](https://discourse.julialang.org/u/cserteGT3)\
**Replies:** 11\
**Last updated:** [May 15, 2019, 6:54am UTC](https://discourse.julialang.org/t/how-to-load-urdf-files-with-dae-models-into-meshcat/19509 "2019-05-15T06:54:13Z")

</div>

I’m trying to use the JuliaRobotics ecosystem with UR robotic arms and can not find a way to open the official URDF-s. My problem is, that .dae files are not supported, and if I convert those files to .obj, then the mode…

---

## [HN comment on Julia vs Swift type checking and auto diff](https://discourse.julialang.org/t/hn-comment-on-julia-vs-swift-type-checking-and-auto-diff/24178)

<div class="topic-metadata">

**Author:** [@datnamer](https://discourse.julialang.org/u/datnamer)\
**Replies:** 24\
**Last updated:** [May 14, 2019, 6:55pm UTC](https://discourse.julialang.org/t/hn-comment-on-julia-vs-swift-type-checking-and-auto-diff/24178 "2019-05-14T18:55:42Z")

</div>

Anyone know if this is accurate? https://news.ycombinator.com/item?id=19897585 “I don’t think static type checking is a matter of tooling, getting Julia to perform well amounts to either a lot of trust in the compiler …

---

## [Getting constraint matrix and bound from JuMP model (JuMP 0.19)](https://discourse.julialang.org/t/getting-constraint-matrix-and-bound-from-jump-model-jump-0-19/24197)

<div class="topic-metadata">

**Author:** [@Jonathan\_Droxler](https://discourse.julialang.org/u/Jonathan_Droxler)\
**Replies:** 7\
**Last updated:** [May 14, 2019, 6:20pm UTC](https://discourse.julialang.org/t/getting-constraint-matrix-and-bound-from-jump-model-jump-0-19/24197 "2019-05-14T18:20:28Z")

</div>

Hi everyone, I just change to JuMP 0.19 and I get some problem with my code. I construct a big JuMP model with a lot of specific variables and constraints, and I want to extract constraint matrix and vectors from the m…

---

## [Find k-cliques in a graph](https://discourse.julialang.org/t/find-k-cliques-in-a-graph/24022)

<div class="topic-metadata">

**Author:** [@pablosanjose](https://discourse.julialang.org/u/pablosanjose)\
**Replies:** 15\
**Last updated:** [May 14, 2019, 6:07pm UTC](https://discourse.julialang.org/t/find-k-cliques-in-a-graph/24022 "2019-05-14T18:07:28Z")

</div>

I have an undirected graph, given for the sake of simplicity as a list of edges (n,m), where n and m are integers corresponding to nodes. I need to find all possible k-cliques (groups of k nodes wherein all members are c…

[Previous page](https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=495)

[Next page](https://discourse.julialang.org/c/domain/10.md?no_subcategories=false&page=497)