Hello everyone

I need help solving a system of equations as below. I'm looking for a way to do it, but I don't understand the general concept of how such an equation is calculated. So far I've been using a package in LabVIEW that worked similarly to Simulink and that was clear to me, whereas here I'm overwhelmed by the multitude of options and that's why I'm asking for help.

I need to solve these equations analogously to Matlab-Simulink, i.e., a time interval and integration step, and a numerical procedure in symbolic versions.

Help_me.mw

Hi MaplePrimes,

I have decided to look for an odd perfect number.  
I want Maple code to determine if there is a perfect number beween bounds on a factor.
For definitions of deficient and perfect and abundant numbers, see
https://mathworld.wolfram.com/DeficientNumber.html
https://mathworld.wolfram.com/PerfectNumber.html
https://mathworld.wolfram.com/AbundantNumber.html

I need some sort of loop that closes in on the edge of abundant/deficient numbers.

Specifically, an IF() statement is needed about wheather the function

sigma(a)-2*a is positive or negative.

Regards,

Matt

abundant_edge_30.mw

I see this question https://mathematica.stackexchange.com/questions/304317/how-to-draw-a-number-of-circles-inscribed-in-a-square-so-that-the-sum-of-the-rad

I have a square with length of side is $a$. How to draw a number of circles inscribed in a square so that the sum of the radii of the circle is greatest? In the below picture is twenty circles inscribed in a square. We can consider number of circles are 5, 6, ... We consider number of the circles is fixed.

How can I tell Maple to do that.

Have a list of four projective points. I need to check that they are colinear projectively. If one point is at infinity i.e. 0 in z position I can chech if combination of cross product and dot product is 0.
a)  What is a good way to find if one ot the four has zero in z position?

b) Having found that is there a neat way of piching the next two/three points by making the count wrap automatically. e.g 3  then 4,5,6 i.e. 3,4,1,2

Download 2024-06-18_Q_4_points_projective_colinear.mw

I was wondering if Maple could be setup in a way that no parallel processing is performed (as on a single core)?

I know, it's a poor way to test an algorithim/method for thread safety (i.e. deterministic behaviour). But it is better than nothing.

Are there other ways to test for thread safety?

I am getting Maple server crash each time running this solve command.

Could others reproduce it? I am using windows 10. Maple 2024.  Why does it happen?

Will report it to Maplesoft in case it is not known. Worksheet below.

Download maple_crash_calling_solve_june_18_2024.mw

This bug seems to have been introduced in Maple 2023 since it crashes there also.

But not in Maple 2022. No crash there. Same PC.

Download maple_NO_crash_calling_solve_june_18_maple_2022.mw

I want to solve for the intrinsic frequency of a structure by using the equation of the determinant of a matrix equal to 0. I don't know if this is the correct procedure. Also the result is too complicated, what does z mean? Is it possible to simplify the result?

odeadvisor says that this ode is _homogeneous, `class A`, but I am not able to verify this. Also when asking dsolve to solve it as 'homogeneous' it returns no solution. 

This type is described in https://www.maplesoft.com/support/help/maple/view.aspx?path=odeadvisor%2fhomogeneous

Here is worksheet with my tries.

Would someone be able to confirm if this is really an _homogeneous, `class A` ?

my own code checking says no.  But if it is, then why dsolve do not solve it when asking it to use homogeneous method? Is the method I asked it to use it do not apply to class A?

Download checking_homogo_ode_type_june_18_2024.mw

Hi everyone...
if f(x,y)=x+y
How can I calculate the following expressions for derivative of y(i) where i=1...n?

Hello guys, I am doing the numercial error analysis study, but now I meet such problem:
how to change the 2d dot plot to the 3d plot? I mean extending like the generatrix of a cylinder.
It can be understood as the inverse operation of projecting a three-dimensional xyz surface onto the xy plane. the code is attached. Welcome all you discuss.

Dear all, how can I plot the edge coordinates of a 2d plane?

using diff command to find  partial dervative of function g give zero in maple...it shouldn't be zero...how to fix itpartial_dervative.mw

Download partial_dervative.mw

if i want to solve non linear least square problem ..maple optimazation Interactive box show ..many option...but when it comes to least square default....what kind of algothrim does it used....and in maple ..NonLinear fit commad use what kind of algothrim?..Levenberg-Marquardt algorithm?

I use one engine per one worksheet. So one would expect that doing restart; command; to always behave the same way. Right?

Because each time, new or refreshed mserver.exe is used.  But here is a worksheet, where I run it few times (all with restart each time), where sometime the command timelimit hangs, and sometime does not. I do not mean it takes little longer sometime. I mean completely hang.

I've waited 10-20 minutes and nothing happens. And sometime I saw it return back in 2 or 3 minutes. But most of the time it hangs.

I wish someone could explain this to me. If it hangs each time, or not hang each time, I can understand. (ofcourse timelimit should never hang, as it was supposed to have been fixed in 2021, but this is separate issue).

But why it hangs sometimes and not other times? Does Maple use some sort of random number generator inside it to decide on things? For me, software should behave the same each time when run from same initial state.

It also depends on the amount of timeout given if it hangs or not.

What can cause this different behavior and most important, what can one do to make it behave same way each time? I thought that what restart supposed to do.

Any insight what can cause this is welcome.

I also found that closing the worksheet completely and opening it again, results in different behavior in the timing. It looks like restart does not clear everything, as what happens when closing the worksheet and reopeing it again.

i.e. Sometimes when it completes and not hang, then issuing restart again and running the int() command, it will also not hang most likely.

It seems Maple have remembered something. But closing the worksheet and opening it again, it will hang again most of the times.

The point of all this, is that Maple behaves differently each time. But why??

Download hangs_int_june_16_2024.mw

Here is one screen shot of one of those times where it returned back. Took little over one minute. Good.

Here is second screen shot where it took about1,800 real time seconds to return. (30 minutes, even though timelimit was one minute). Same exact code.

update

I tried the suggestion given below to use _EnvProbabilistic:=0 but it had no effect on making Maple behavior consistent each time.

Below worksheet shows this. I tried 6 trials, each with restart. 

First trial it timeout at 74 second. good. Second trial took 1403 seconds !  Third trial went back to 74 seconds again (good).  Trial 4 took also took about 74 seconds (good). trial 5 went back to being slow and took about 1400 seconds again. Trial 6 went back to being fast and took about 74 seconds.

So the pattern seems to be 

                     fast SLOW fast fast SLOW fast.....

But I also tried this whole test again, by closing the worksheet and opening. Now the pattern changed to

                     SLOW fast fast fast SLOW SLOW ....

I also attached the worksheet for the above below.

So Maple still behaves in random fashion in doing the integration above. sometimes it is slow, sometimes fast. All using same exact code and same integral. Extra points to anyone who could find out why and how to fix this.  

This worksheet have pattern    fast SLOW fast fast SLOW fast....

Download hangs_int_V2_june_16_2024.mw

This worksheet below have pattern      SLOW fast fast fast SLOW SLOW ....

Download hangs_int_V3_june_16_2024.mw

Observation: When it finishes fast, timeout is always in  PDEtools/NumerDenom.

When it takes long time, timeout is always in sdmp:-mull

Any other suggestions what to try are welcome.