@rlopez @Carl Love @Ronan 

After a week of careful observing in total 3 Maple sessions on two notebooks I see a strong pattern.

This is the process tree from above. (What changed (which is probably irrelevant) is that the two Maple session are now not sub tasks of explorer.exe any more. I assume something restarted the explorer.)

The pattern:

Each time the system hibernates or goes to energy saving the submenus are gone. After a while (~5-10 minutes) working with the system, submenus are back. Applications running in parallel were Outlook, Word, Excel, Teams, Foxit reader, Signal, Firefox and Edge.

Since the moment when the menus came back was not clear, I positioned the Maple 2023 session in the upper right corner of my screen and the Maple 2024 session in the lower right corner (using the Windows key and cursor arrows). In the left half of the screen, I ran the other applications. This permitted me to check the Maple sessions more frequently without opening and closing windows (which might have an impact on the recovery).

Subsequently I closed the applications (I had to kill Teams and Edge in the task manager) up to the point that only Firefox was running in parallel. This did not change the recovery pattern (I.e., this leaves Firefox as one potential reason for recovery).

I also observed that the Maple 2023 session recovered earlier. A reason could be that I configured the system in a way that javaw.exe of Maple 2023 was only running on the internal graphic adapter whereas for Maple 2024 the system was free to choose between internal and external (Nividia) graphics adapter.

Often the context panel was empty when the submenus were gone but not always.

On both notebooks I opened and closed plenty of Maple documents from other authors in the sessions.

The other system only running Maple 2024 without hibernation (only energy saving) showed the same behavior.

Both systems turned on screen saver after 5 min and energy saving after 10 min. Hibernation was activated on one system after 30 min.

There is not much left that I can do to identify an event that triggers recovery.

To further narrow down the root cause, it would now be good,

• that someone can confirm whether there are installations where submenus never come back
• that someone can tell if Linux or Apple systems also show the effect
• if there are Windows 10 installations with a non NVIDIA graphic adapter showing the effect

What Maplesoft could do now: Try to reproduce the above and run a screen recorder while working. It is almost impossible to capture the moment of recovery (context panel of a newly opened document (I open in document mode) showing suddenly context) while doing something in parallel. The screen recording could narrow down the moment of recovery to a few seconds which would allow identifying system events and/or processes triggering the recovery.

I hope that the management will allow a few working days to be sacrificed for this. Submenus that do not work are really annoying and hardly acceptable for a commercial product.

@Alfred_F 

The argument of IsDefine is corrupted. You get the same error message without IsDefine. I managed to recover it, but you might want to enter it again.

IsDefinite(Matrix(2, 2, [[-1/4*(2*u + 10)^2/(81 + (u + 5)^2)^(3/2) + 1/sqrt(81 + (u + 5)^2) - 1/4*(-2*v + 2*u - 2)^2/(4 + (v - u + 1)^2)^(3/2) + 1/sqrt(4 + (v - u + 1)^2), -1/4*(-2*v + 2*u - 2)*(2*v - 2*u + 2)/(4 + (v - u + 1)^2)^(3/2) - 1/sqrt(4 + (v - u + 1)^2)], [-1/4*(-2*v + 2*u - 2)*(2*v - 2*u + 2)/(4 + (v - u + 1)^2)^(3/2) - 1/sqrt(4 + (v - u + 1)^2), -1/4*(2*v - 6)^2/(49 + (v - 3)^2)^(3/2) + 1/sqrt(49 + (v - 3)^2) - 1/4*(2*v - 2*u + 2)^2/(4 + (v - u + 1)^2)^(3/2) + 1/sqrt(4 + (v - u + 1)^2)]]));

@Paras31 I like the idea of color coding. Below it a quick attempt where the color alternates every 50 "seconds". (frem is not the best choice because the first period is only 25 s seconds long).

@WD0HHU 

You are welcome. The whole topic is facinating.

I would be interested if you can make events work and if it makes a difference. If I was in the spaceship, I would in any case halt calculations at an event and restart with modified odes.
That's what I did in an answer that I posted here (which I cannot find straight away). I remember also a pro user posting an event version to the same problem in the same thread.

If I had more time I would try so simulate spaceflight with MapleSim just for curiosity. (I would start with Apollo 8, if data is available). MapleSim uses allot of Maple with one difference that scaling methods are provided.

I have not found out what it is and what it is good for. Scaling might be applicable to such problems.

I am still facinated what is possible today and what people did by hand not so long ago. Luckly, today calculations run faster than real time ;-). The film hidden figures shows it nicely how difficult it was at the time. And by the way, the story of Apollo 11 is boring compared to Apollo 8.
 

@Axel Vogt The link is not working

@Carl Love This exactly what I was looking for. Thank you

@Carl Love mods does not work on real numbers ("analog")

mods(11.5, 10);
Error, invalid argument for modp or mods
NULL;

I object using frem because it took quite a while to figure out how to get a MapleSim (or other languages) style mod. Next time I need it I will probably not remember straight away (for compatibilty and code exchange reasons I have stopped making custom commands).

Therefore fmod would be a nice extension to Maple commands. I will suggest this

@dharr 

I was not clear. Imagine you have some code to review. Somewhere in the code

sol:=dsolve({odes,ics},numeric,...)

If sol was a module I could ask for the exports. Since sol is a procedure I cannot ask which variables are returned.

Take for example this code from one man 1.mw
and enter

sln(0.1);
interface(verboseproc = 2);
print(sln);
showstat(sln);

after execution of the worksheet

@WD0HHU 

I do not think that this is a bug. It is a general weakness of variable step solvers.

There is an option that should enforce an event with variable step solvers. Have a look here

?dsolve,numeric,Events

I had to abandon rewriting the mass equation with events because I could not immediately spot an example/description that fitted your case.

Could you share a screen shot of the final trajectory?

By the way, I was wondering if such simulations could not profit from the Physics package which allows for a vectorial description of the problem which could save some lines of code.

@GFY 

This question is often asked.
I have only read the programming guide that comes with Maple. It's not really a book for learning.

Try searching here on MaplePrimes, and if you don't find anything, ask here, with topics that interest you.

@Scot Gould @Carl Love
Thank you for the clarification.

I overlooked that mod works on more than numbers. I also did not pay attention to the fact that mod works for "digital clocks" only but not for "analog clocks". I could not find an equivalent command that works on floats. Do I really have to do something like this

fmod := (t, modul) -> frem(t - 1/2*modul, 10) + 1/2*modul;
plot(fmod(t, 10), t = 0 .. 100);

One example, where this is extensively used is phase wrapping in signal processing. (I could use arctanxy for this, but that is also not straight forward).

By the way MapleSim does not restrict mod to integers

Looks like an infinite loop

@one man 

Thank you. I have to study this. What I learnd so far:

It's about common solutions of a system of equations.

Already the bivariate case can be non-trivial

@Thomas Richard 

The example from vv nicely shows how a parameter (velocity, acceleration, jerk,...) could be overlayed on a path. A usefull addition if it can be combined with a color bar.

vv example also shows that only expert users can do such things at the moment.

@mmcdara 
Intersting: I did not know that the color option accepts the plot structure COLOR. Is that an undocumented feature?