apt – System update misses things

Why is it that if you run a system update or use dist-upgrade you’re still left with things needing updating?

For example if you run a full system update and than open software updater it says “your system is up to date.”

But if you open the software center and check for updates, there are still packages listed requiring update.

These sometimes include:

  • shared gnome ubuntu stack
  • gtk common theme
  • snapd
  • snap store
  • core 18

Why are these not covered by the the system update?

Anybody else misses emails in gmail?

Anybody else misses emails in gmail?

Lots of times gmail just won’t accept an email.
Those emails just do not get delivered, nor do they get bounced back.
They just disappear. They are in none of the folders in gmail.
I used to think that this is only from servers where mail servers are not configured properly, or from black listed IPS.
But recently gmail even rejected emails from facebook.
Has this happened to anyone else?

I had a secondary fb account, and I login to that once a week or so.
My windows install got corrupted, so I got a new one installed. OS version changed.
When I logged to this secondary account on fb, they asked me to verify, they sent a code in email (gmail email)
Never got that email, even after trying multiple times, on different days.

Similar thing happened in the primary account as well.
Surprisingly, I got that email, a different gmail id.
But I lost that other secondary account…

Anyone else experiences this?
Emails which used to come to inbox, suddenly started going to spam, and some get completely rejected.
Support ticket emails, forgot password emails, etc important emails…


equation solving – Solve misses positive solutions

Why Solve returns only negative solutions?

Solve((x + 1)^(2 n) + (x - 1)^(2 n) == 0, x)

$left{left{xto frac{1+e^{frac{i pi }{2 n}}}{-1+e^{frac{i pi }{2 n}}}right}right}$

But we know conjugates are also a solution i.e.

$left{left{xto -frac{1+e^{frac{i pi }{2 n}}}{-1+e^{frac{i pi }{2 n}}}right}right}$

are also solutions.

We see that

With({n = 1}, Solve((x + 1)^(2 n) + (x - 1)^(2 n) == 0, x))


${{xto -i},{xto i}}$

$ left{left{xto frac{1+e^{frac{i pi }{2 n}}}{-1+e^{frac{i pi }{2 n}}}right}right} /. n -> 1$



air travel – Does Qatar Airways have a no-show fee in case a passenger misses a flight (assuming the passenger only purchased a flight ticket and nothing else)?

https://www.qatarairways.com/tradepartner/en/bookingnticketing/Penalties-and-Charges.html states:

No-Show Charge: The charge made by reason of the failure of a passenger to use reserved accommodation, either through failure to arrive at the airport at the time fixed by the carrier, or through arriving improperly documented or otherwise not ready to travel on flight.

From my understanding, this means that Qatar Airways may charge a no-show fee in case a passenger misses a flight (even if the passenger only purchased a flight ticket and nothing else, i.e. didn’t book any hotel).

However I read some comments that contradict my understanding:

  • To me, it is quite clear that the hotel will want to be paid for accomodation you reserved, but did not pay for, because it could have been used by someone else. The flight has been paid for in advance, but the room was only reserved. So it is no-show as applicable to the accomodation, not the flight. – Weather Vane 10 mins ago 

Does Qatar Airways have a no-show fee in case a passenger misses a flight (assuming the a passenger only purchased a flight ticket and nothing else)?

rds – What is the best practice when MYSQL Slabe misses data?

We have a huge database running into a TB plus running on AWS RDS. We have a MYSQL slave set up on premises basically for compliance and statutory needs. We have a big audit coming up in weeks. And I notice that why data seems to be syncing perfectly there are number of rows missing across many tables. There is no pattern which is emerging.

In such cases, what is the best recommended practice to trouble shoot? To set up everything again is not an option.

computer architecture – Memory Invalidation and Misses

Assume this particular architecture of a machine. Say we have 4 processors and each processor has its private L1 cache and shared L2 cache. Now if we write to an address in one of the private cache’s of the L1 cache then we Invalidate the blocks in the other private cache which contains the same address. Say P0(processor 0) reads an address 100 and so the block containing it say B0 gets stored in the private cache of P0 and as well as in the shared L2 cache. Now say P2 writes to the location 100. So we need to invalidate the block B0 from the private cache of P0. Now if P0 wants to read from address 100 again it will suffer a miss in its private cache, but will it get HIT or MISS in the L2 cache?

I think it will get HIT. Can anyone confirm.

database design – MS ACCESS : On a subject form, how can I highlight a required control IF AND ONLY IF the user misses it (an error is thrown)

I have built a subject form and would like to find a way to highlight a textbox control that is required (it is paired to a required field) IF AND ONLY IF the user fails to enter it. I know that there are validation rules that are built as part of the subject table that will give the user an indication of an error when they fail to enter required data. But, I am looking for a more “colorful” or “visual” indication, so to speak. I have seen people simply give a colorful border to a required field. This is fine, but I am trying to find a way to either highlight or make a colorful border on the required control IF AND ONLY IF an error is thrown.

I hope my question is clear. This is my first question on here so I apologize if it’s messy. I am using ACCESS 2016

differential equations – PeriodicBoundaryConditions misses points with coarse mesh?

I’m noticing that some boundary points are “missed” by PeriodicBoundaryCondition in the case below. This points qualify in the sense that they satisfy the prescribed condition (predicate), but are nevertheless not identified by NDSolveValue.

The issue becomes a real problem only when I use a coarse mesh, and then no boundary points at all are found that satisfy the given condition.

To motivate this question, note that using a mesh with only a few points in one independent variable is useful for example when solving test cases with symmetries, or problems where the solution is believed to vary slowly in one dimension.

For the example, we solve Laplace’s equation in a cylinder. Using the command ToElementMesh(Cylinder()) is not useful here because the mesh is not coarse enough. So I turn to the package MeshTools. This can be installed in Mathematica 12.0+ with ResourceFunction("GitHubInstall")("c3m-labs", "MeshTools"). An “extruded” mesh is nice for my purposes, because I know exactly where all the mesh points are and can really precise control of my boundary conditions — or so I thought! Here’s a coarse cylindrical mesh:

N1 = 8;
DMesh = DiskMesh({0, 0}, 1, N1);
N2 = 4;
mesh = ExtrudeMesh(DMesh, 2 Pi, N2);

cylindrical mesh using MeshTools

Then I solve Laplace’s equation with Dirichlet boundary conditions.. The problem occurs when I do this using PeriodicBoundaryCondition to target the points with phi > Pi (using the fact that our solution will be symmetric about phi == Pi):

ReflectPhi = Function({#((1)), #((2)), 2 Pi - #((3))});
{uf} = NDSolveValue({Laplacian(u(x, y, phi), {x, y, phi}) == 0, 
   DirichletCondition(u(x, y, phi) == Cos(phi) y^2, Or(0 <= phi <= Pi, phi == 2 Pi)), 
   PeriodicBoundaryCondition(u(x, y, phi), Pi < phi < 2 Pi, ReflectPhi)}, {u}, Element({x, y, phi}, mesh))

The error produced is

NDSolveValue: No places were found on the boundary where (Pi)<phi<2
(Pi) was True, so PeriodicBoundaryCondition… will effectively be

And NDSolveValue fails. This example is a bit artificial because I could just do the whole boundary condition with a single DirichletCondition but it reveals the issue. As mentioned, the error is not encountered when I increase the resolution, e.g. N2 = 8. In that case, places were found where the predicate is satisfied — but now I wonder if Mathematica still “missing” some boundary points..?

To finish, let us just demonstrate there are points that satisfy the condition for N2 = 4. These are points with phi == 3 Pi/2.

bCoords = Map(mesh("Coordinates")((#)) &, DeleteDuplicates@Flatten@mesh("BoundaryElements")((1, 1)));
Cases(bCoords, _?(Pi < #((3)) < 2 Pi &)) // Length


Indeed there are 32 points corresponding to the boundary points of DMesh, which have been “extruded” to the phi == 3 Pi/2 location.

dnd 5e – Plan to hit a second target with an arrow if it misses the first target

I've read a lot about how to "shoot the other enemy" and how enemies don't occupy the entire 5-foot field. However, what I can't find is the following scenario:

two orcs an arrow

I deliberately position my character so that it has a straight line with two enemies. I aim at the first one, but if it misses, I want my arrow to continue and possibly hit the next enemy. My understanding is that I can miss for two reasons.

  1. I'm shooting something in the wrong direction
  2. I'm shooting right, but the enemy is evading.

It is the situation (2) that I want to take advantage of and basically want to roll again for the second enemy, perhaps even with advantage, since he did not expect to be shot. Would you let that happen? What would you ask to roll?