@Edmund CUDA, OpenCL.

The Arduino interface and the code for SQL as well.

Can someone else confirm this problem which has been marked as a bug? I can't reproduce it.

ok, it's been cleared up. It started in a newer version than I was using.

Excuse me.I make a custom function with default and conditon like this

randomColor[n_, threshold_: 0.8?(Between[{0, 1}])]

But it not work..help..

Wow,I get it,just by randomColor[n_, threshold : (_?(Between[{0, 1}])) : .8]

@yode Also, see this.

@C.E. Thanks.It's hard to find those related post for me.

I'm so sad for this.

@C.E. Can I search those post contain some string in my own answer in this site?

Just in my answer,but not in my question post

@yode I don't think we can restrict it to only answers unfortunately.

@yode I sometimes find that Google is much better than the built in search engine at finding what I'm looking for.

Anyway,thank. :)

@C.E.

@C.E. You looked at FEM stuff in detail, right? Perhaps also got that internship? Maybe you can answer this question:

I have a region like this: reg = RegionDifference[Disk[{0, 0}, 10], Disk[{0, 0}, 2]]. I want an ElementMesh from it. It has the "MaxBoundaryCellMeasure" option to control the discretization at the boundaries. I want a fine resolution on the inner boundary, but a coarse one on the outer boundary. What is the best way to achieve this?

Currently I do the following:

domain = BoundaryDiscretizeRegion[Disk[{0, 0}, 10], MaxCellMeasure -> 5, PrecisionGoal -> 1];
hole = BoundaryDiscretizeRegion[Disk[{0, 0}, 2], MaxCellMeasure -> .1];
ToElementMesh[RegionDifference[domain, hole]]["Wireframe"]

So, if I may be allowed to brag, I've written a paper on something of relevance to Mathematica: arxiv.org/abs/1702.08114 :D

Although of course it is unlikely to be a topic most people care about :)

@Szabolcs Yes, I did :) I'll look into this later, I'll let you know if I come up with anything better.

@BenNiehoff Working on xAct?

I may be in the future

@BenNiehoff wasn't the xact author hired by WRI? I always assumed that was where the v9 tensor stuff came from

Yes, that is exactly what happened

But i may be mistaken

I emailed with him a bit, he's very interested in the paper of course :)

@C.E. Here's what I'm trying to do. I want to solve the Poisson equation with an inner boundary, and an outer boundary at "infinity". Then I want to see the magnitude of the solution's gradient on the inner boundary. I am not sure how to make the solution more precise, as I am not experienced with FEM. In fact using a finer discretization leads to some strange artefacts in the solution.

Does anyone have experience with Dynamics / FrontEnd hanging during/after fetching files via URLFetch/Save?

@Kuba I encountered hangs with URLSaveAsynchronous when I set a callback function for progress tracking. WRI said it was a bug in 11.0.

The front end did not lock up though. The symptom was that the evaluation never finished (even though the progress indicator showed that the download was complete).

I see. In 11.0.1 too?

I'm using synchronous methods so far but was about to change couple of procedures so good to know @Szabolcs

@Kuba As I remember, yes. But only with URLFetchAsynchronous, not with URLFetch. And the GUI was still responsive, only the evaluation didn't return.

Also, it wasn't consistent. It happened randomly. Probably some race condition ...

@Szabolcs I have URLSave called from queued Initialization which works fine but sometimes it just hangs, asks whether to wait or abort and if you pick abort (wait does not help) then the Initialization is started again and then URLSave works.

Not major because fetched file isn't big but quite annoying.

Does anyone know how to exactly write coefficents to InitializePDECoefficients for our differencial equations? mathematica.stackexchange.com/questions/138840/…

@Szabolcs If your problem is not more complicated than what you have exposed in your notebook (in particular no dielectric), it can be better solved by the virtual charge method (very basic method also known in the literature as : charge simulation method, superposition method, ...). This method is well suited to infinity boundaries.

Here is the code :

hole=BoundaryDiscretizeRegion[
RegionUnion@{Disk[{-3,0},1/2],Rectangle[{-3,-1/2},{3,1/2}],Disk[{3,0},1/2]},
MaxCellMeasure->0.01/2,
MeshCellStyle->{0->Red}
]
pointsTestPositions=hole //MeshPrimitives[#,0]& //(First /@ # &);
pointsTestPositions //Length
pointsTestPositions //Take[#,3]&

contractionRatio=0.8;
chargesPositions=BoundaryDiscretizeRegion[
RegionUnion@{
Disk[contractionRatio {-3,0},contractionRatio 1/2],
Rectangle[contractionRatio {-3,-1/2},contractionRatio {3,1/2}],
Disk[contractionRatio {3,0},contractionRatio 1/2]},

The result is very precise (0.3 % at the boundary).I can give explanations if you are interested.

@yode is:question restricts the search results to questions only and can be combined with user:me.

@Karsten7. Wow,I have to say this help me a lot...Thanks

A further question,can we find those post,whose title have word "function","option" and "value" meanwhile?

@andre Could you elaborate a bit?

@andre Thanks, I read the code and I think I understand how it works now.

You put the charges at a somewhat arbitrary positions and found their magnitude so the potential would add up to the desired value on the points taken on the boundary.

Yes Exactly

The location of the charges are arbitrary, but it is not difficult to find these locations. One thing important is to have many more test points than charge points. Having to much tests point can't be bad.

The charge locations are fixed because this permits to have a linear arithmetic problem.

@Szabolcs FWIW I did not come up with anything, but I'm still learning so that doesn't say anything about whether there are solutions to the problem or not.

Anyone else having trouble uploading images to the site? I get SETools`SEUploader`Private`stackImage::err: Server returner error: Failed to upload image; imgur is rejecting the request with the uploader and with the SE's own image upload button.

@yode Yes, for example try user:21532 is:question title:built-in function.

See Search Help for more info.

Do others agree that this is a bug? I don't think I should bugs-tag my own post, by convention.