nm

11483 Reputation

20 Badges

13 years, 84 days

MaplePrimes Activity


These are questions asked by nm

What is the correct idiom in Maple to check that one number is greater than another or not?

For example if n=sqrt(3) and m=3 ?

Maple does not like to compare sqrt(3) with other number. It says 

   Error, cannot determine if this expression is true or false: 3 <= 3^(1/2)

I am doing this in code, so solution has to be such that it works for all cases of n and m, without the ability to look at screen and decide.

I found that using is works without the need to convert to float.  Should one then use is(n>=m) instead of evalb(n>=m) always?  

I can also always apply evalf() on each side before. But this seems like an overkill to me.

restart;

n:=sqrt(3);
m:=3;

3^(1/2)

3

if evalb(n>=m) then
   "yes";
else
   "no";
fi;

Error, cannot determine if this expression is true or false: 3 <= 3^(1/2)

if n>=m then
   "yes";
else
   "no";
fi;

Error, cannot determine if this expression is true or false: 3 <= 3^(1/2)

if evalb(evalf(n)>=m) then
   "yes";
else
   "no";
fi;

"no"

if is(n>=m) then
   "yes";
else
   "no";
fi;

"no"

 

 

Download checking_one_number_larger_than_another.mw

For reference, another software does compare these two numbers as is without the need to convert them to floating point;

But it looks the design of Maple in this aspect is different. Since the principal root of sqrt(3) is always the positive one, I did not think it will cause a problem.

Why Maple gives

           improper op or subscript selector

On this ode? I was not expecting to see steps for this, but was just trying to see what it will show.

restart;

interface(version);

`Standard Worksheet Interface, Maple 2024.1, Windows 10, June 25 2024 Build ID 1835466`

Physics:-Version();

`The "Physics Updates" version in the MapleCloud is 1810 and is the same as the version installed in this computer, created 2024, September 18, 18:16 hours Pacific Time.`

libname;

"C:\Users\Owner\maple\toolbox\2024\Physics Updates\lib", "C:\Program Files\Maple 2024\lib"

restart;

ode:=sin(x)*diff(y(x),x$2)+cos(x)*diff(y(x),x)+(sin(x)-cos(x))*y(x)=0;

sin(x)*(diff(diff(y(x), x), x))+cos(x)*(diff(y(x), x))+(sin(x)-cos(x))*y(x) = 0

dsolve(ode);

y(x) = c__1*(tan((1/2)*x)+I)^(1/2+(1/2)*(5-4*I)^(1/2))*(tan((1/2)*x)-I)^((1/2)*(5+4*I+(5+4*I)^(1/2))/(5+4*I)^(1/2))*HeunG(2, 2*(((3/4)*(5-4*I)^(1/2)+7/4-I)*(5+4*I)^(1/2)+5/4+I+(5/4+I)*(5-4*I)^(1/2))/(5+4*I)^(1/2), 1+(1/2)*(10+2*41^(1/2))^(1/2), (1/2)*((5+4*I)^(1/2)*(5-4*I)^(1/2)+5+4*I+2*(5+4*I)^(1/2))/(5+4*I)^(1/2), 1+(5-4*I)^(1/2), 1, 1-I*tan((1/2)*x))+c__2*(tan((1/2)*x)+I)^(1/2-(1/2)*(5-4*I)^(1/2))*(tan((1/2)*x)-I)^((1/2)*(5+4*I+(5+4*I)^(1/2))/(5+4*I)^(1/2))*HeunG(2, -2*(((3/4)*(5-4*I)^(1/2)+(-7/4+I))*(5+4*I)^(1/2)+(-5/4-I)+(5/4+I)*(5-4*I)^(1/2))/(5+4*I)^(1/2), -(1/2)*(5-4*I)^(1/2)+1+(1/2)*(5+4*I)^(1/2), (1/2)*(-(5+4*I)^(1/2)*(5-4*I)^(1/2)+5+4*I+2*(5+4*I)^(1/2))/(5+4*I)^(1/2), 1-(5-4*I)^(1/2), 1, 1-I*tan((1/2)*x))

Student:-ODEs:-ODESteps(ode)

Error, (in Student:-ODEs:-OdeSolveOrder2) improper op or subscript selector

 


 

Download internal_error_ODEsteps_sept_26_2024.mw

I thought I had post with collection showing timelimit still hangs in Maple. But can't find it searching. I wanted to add this to it.

If someone finds such post, please let me know and I will append this to that post and delete this.

I just found another example where int() hangs all of Maple, using timelimit. I put timelimit of 30 seconds. After 2 hrs it is still running.

Maple 2024.1 on windows 10. This shows clearly that timelimit in Maple still does not work when It was supposed to have been fixed in Maple 2021?

For me, if there is anything that will make me stop using Maple for good, it is this timelimit issue.

Because with timelimit not working all the time, my program keeps hanging. It is not possible to do antything then. Having to keep checking if the program is still running or have hanged and restarting it is not a way to develop software.

Software that have been in development for almost 45 years now like Maple, should have figured by now how to implement timelimit that works. 

Note that, with smaller timelimit it is possible it will  not hang, because longer time limit makes it end in the code path which causes the hang. When I tried 5 seconds for example instead of 30 second, it did not hang With 30 it does. so if you try it and it does not hang, please increase the timelimit a little and it will surely hang. Just make sure to do restart each time, since Maple remembers last result.

maple's server.exe was running at full cpu also.

 

interface(version);

`Standard Worksheet Interface, Maple 2024.1, Windows 10, June 25 2024 Build ID 1835466`

Physics:-Version();

`The "Physics Updates" version in the MapleCloud is 1810 and is the same as the version installed in this computer, created 2024, September 18, 18:16 hours Pacific Time.`

libname;

"C:\Users\Owner\maple\toolbox\2024\Physics Updates\lib", "C:\Program Files\Maple 2024\lib"

restart;

M:=-6*(3^(1/2)*(27*R^2-4)^(1/2)-9*R)^(1/3)/(-6*(3^(1/2)*(27*R^2-4)^(1/2)-9*R)^(1/3)*R+(-6*I*3^(1/6)-2*3^(2/3))*2^(1/3)+2^(2/3)*(I*3^(5/6)-3^(1/3))*(3^(1/2)*(27*R^2-4)^(1/2)-9*R)^(2/3));
try #this hangs
    timelimit(40,int(M,R));
    print("finished with no timeout");
catch:
    print("waiting for timeout");
end try;

-6*(3^(1/2)*(27*R^2-4)^(1/2)-9*R)^(1/3)/(-6*(3^(1/2)*(27*R^2-4)^(1/2)-9*R)^(1/3)*R+(-(6*I)*3^(1/6)-2*3^(2/3))*2^(1/3)+2^(2/3)*(I*3^(5/6)-3^(1/3))*(3^(1/2)*(27*R^2-4)^(1/2)-9*R)^(2/3))

 

 

Download int_hangs_with_timelimit.mw

 

Update OCT 10, 2024

This is another example showing hang in Maple 2024.1 using timelimit. So adding it to this collection. I had large collection of such problems but not able to find it now.

I was trying to verify this solution (which could very well be wrong) on ode with IC. timelimit hangs when I added assumptions as shown. Used 10,20,30 seconds, and so on. all hang. Waited and waited. 

Does it hang on other systems? I am using Windows 10 and Maple 2024.1 with 128 GB RAM on fast CPU.


 

sol:=y(x) = -8/9*x-11/9+1/9*arcsin(1/103*2509^(1/2)*tan(1/5*(x+5/2509*2509^(1/2)*arctan(1/2509*2509^(1/2)*(103*tan(37)+90*sec(37)))-1)*2509^(1/2))*(90*2509^(1/2)*tan(1/5*(x+5/2509*2509^(1/2)*arctan(1/2509*2509^(1/2)*(103*tan(37)+90*sec(37)))-1)*2509^(1/2))-103*(2509*tan(1/5*(x+5/2509*2509^(1/2)*arctan(1/2509*2509^(1/2)*(103*tan(37)+90*sec(37)))-1)*2509^(1/2))^2+2509)^(1/2))/(2509*tan(1/5*(x+5/2509*2509^(1/2)*arctan(1/2509*2509^(1/2)*(103*tan(37)+90*sec(37)))-1)*2509^(1/2))^2+10609)-90/103):
ode:=5*diff(y(x),x) = 7+10*sin(8*x+9*y(x)+11):
IC:=y(1) = 2:
func:=y(x);

y(x)

try
    timelimit(30,`assuming`([odetest(sol,[ode, op(IC)],func)],[positive, func::positive]));
catch:
    print("timed out OK");
end try;
print("After try/catch");

 

Download time_limit_hang_example_oct_10_2024.mw

I would like to officially offer $1,000 prize for any one who can solve the timelimit hanging problem in Maple. Will send you personal check of this amount if you find why it hangs and provide fix to use that I can verify works.

Bernoulli first order ode has form as show in wikipedia  and also on Maple own site as

Notice that it is P(x)*y above and not P(x)* y^(-1) so the y(x) must be linear in that term.   But when I give Maple this ode

ode:=diff(y(x),x) + x*y(x)^(-1)= y(x)^(-1);

Which is clearly not of the form above, it solves it as Bernoulli.  In the above ode, P(x) is x and Q(x) is 1 and n is -1.

The ode advisor correctly said it is separable. But trace shows it used Bernoulli. Also when asking it to solve it as Bernoulli, it does.

What Am I missing here?  Is it not wrong for Maple to use Bernoulli method on this ode which is not Bernoulli?

Worksheet below

interface(version);

`Standard Worksheet Interface, Maple 2024.1, Windows 10, June 25 2024 Build ID 1835466`

Physics:-Version();

`The "Physics Updates" version in the MapleCloud is 1805 and is the same as the version installed in this computer, created 2024, September 3, 11:35 hours Pacific Time.`

libname;

"C:\Users\Owner\maple\toolbox\2024\Physics Updates\lib", "C:\Program Files\Maple 2024\lib"

restart;

ode:=diff(y(x),x) + x*y(x)^(-1)= y(x)^(-1);
IC:=y(1) = 0;
DEtools:-odeadvisor(ode);

diff(y(x), x)+x/y(x) = 1/y(x)

y(1) = 0

[_separable]

infolevel[dsolve]:=5;

5

dsolve(ode,y(x));  #why this says it solved it as Bernoulli ?

Methods for first order ODEs:

--- Trying classification methods ---

trying a quadrature

trying 1st order linear

trying Bernoulli

<- Bernoulli successful

y(x) = (-x^2+c__1+2*x)^(1/2), y(x) = -(-x^2+c__1+2*x)^(1/2)

dsolve(ode,y(x),[Bernoulli])

Classification methods on request

Methods to be used are: [Bernoulli]

----------------------------

* Tackling ODE using method: Bernoulli

--- Trying classification methods ---

trying Bernoulli

<- Bernoulli successful

y(x) = (-x^2+c__1+2*x)^(1/2), y(x) = -(-x^2+c__1+2*x)^(1/2)

 

 

Download why_this_ode_bernullli_sept_15_2024.mw

I wanted to change  eq:= 1/2 * sqrt(-2*lambda)  to 1/2 %* sqrt(-2*lambda)  using a rule.

It works outside of rule ofcourse. But when I put %* in the RHS of the rule, maple hangs. It seems it is going into infinite loop.

I tried the trick of using '%*' but this gives syntax error.

Same problem happens when using %. and not just %*

Is there a workaround?

Attached worksheet. Make sure to save all work before trying it.
 

interface(version);

`Standard Worksheet Interface, Maple 2024.1, Windows 10, June 25 2024 Build ID 1835466`

Physics:-Version()

`The "Physics Updates" version in the MapleCloud is 1804. The version installed in this computer is 1802 created 2024, September 3, 11:35 hours Pacific Time, found in the directory C:\Users\Owner\maple\toolbox\2024\Physics Updates\lib\`

libname;

"C:\Users\Owner\maple\toolbox\2024\Physics Updates\lib", "C:\Program Files\Maple 2024\lib"

restart;

eq:= 1/2 * sqrt(-2*lambda)

(1/2)*(-2*lambda)^(1/2)

eq:= 1/2 %. sqrt(-2*lambda); #no problem

`%.`(1/2, (-2*lambda)^(1/2))

eq:= 1/2 %* sqrt(-2*lambda); #no problem

`%*`(1/2, (-2*lambda)^(1/2))

restart;

eq:= 1/2 * sqrt(-2*lambda)

(1/2)*(-2*lambda)^(1/2)

applyrule(sqrt(x::anything)/y::anything = 1/y %. sqrt(x),eq); #why this hangs?

 

restart;

eq:= 1/2 * sqrt(-2*lambda)

(1/2)*(-2*lambda)^(1/2)

applyrule(sqrt(x::anything)/y::anything = 1/y %* sqrt(x),eq); #why this hangs?

 


 

Download maples_hangs_applyrule_sept_10_2024.mw

First 19 20 21 22 23 24 25 Last Page 21 of 202