Question: timelimit hangs calling DEtools:-odeadvisor

The following example shows clearly that timelimit is still broken in Maple.

I tried this 10 times, and it hangs each time. I could wait 30 minutes and it still hangs. timelimit simply does not work. I set timelimit to 20 or 30 seconds.  This really makes developing software in Maple very difficult when timelimit itself hangs as it means the whole program comes to halt and becomes frozen and I see no workaround this problem.

 

interface(version);

`Standard Worksheet Interface, Maple 2022.2, Windows 10, October 23 2022 Build ID 1657361`

restart;

ode:=1/2*sqrt((diff(y(x), x) - sqrt(-a^2*(a - b)*(a + b))/a^2)^2 + 2*sqrt(-a^2*(a - b)*(a + b))*(diff(y(x), x) - sqrt(-a^2*(a - b)*(a + b))/a^2)/a^2 + b^2/a^2)/a - 1/2*b^2*ln((2*b^2/a^2 + 2*sqrt(-a^2*(a - b)*(a + b))*(diff(y(x), x) - sqrt(-a^2*(a - b)*(a + b))/a^2)/a^2 + 2*sqrt(b^2/a^2)*sqrt((diff(y(x), x) - sqrt(-a^2*(a - b)*(a + b))/a^2)^2 + 2*sqrt(-a^2*(a - b)*(a + b))*(diff(y(x), x) - sqrt(-a^2*(a - b)*(a + b))/a^2)/a^2 + b^2/a^2))/(diff(y(x), x) - sqrt(-a^2*(a - b)*(a + b))/a^2))/(a^3*sqrt(b^2/a^2)) + 1/2*sqrt((diff(y(x), x) + sqrt(-a^2*(a - b)*(a + b))/a^2)^2 - 2*sqrt(-a^2*(a - b)*(a + b))*(diff(y(x), x) + sqrt(-a^2*(a - b)*(a + b))/a^2)/a^2 + b^2/a^2)/a - 1/2*b^2*ln((2*b^2/a^2 - 2*sqrt(-a^2*(a - b)*(a + b))*(diff(y(x), x) + sqrt(-a^2*(a - b)*(a + b))/a^2)/a^2 + 2*sqrt(b^2/a^2)*sqrt((diff(y(x), x) + sqrt(-a^2*(a - b)*(a + b))/a^2)^2 - 2*sqrt(-a^2*(a - b)*(a + b))*(diff(y(x), x) + sqrt(-a^2*(a - b)*(a + b))/a^2)/a^2 + b^2/a^2))/(diff(y(x), x) + sqrt(-a^2*(a - b)*(a + b))/a^2))/(a^3*sqrt(b^2/a^2)) - 1/2*b*ln(a^2*diff(y(x), x)^2 + a^2 - b^2)/a^2 - y(x) - _C1 = 0:

try
  print("Before calling timelimt on odeadvisor");
  timelimit(20,DEtools:-odeadvisor(ode,y(x)));
  print("Did not time out");
catch:
  print("TIMED OUT");
end try;

"Before calling timelimt on odeadvisor"

 


 

Does this hang on your version of Maple? I am using 2022.2 on windows 10.

I was hoping this problem with timelimit has finally been fixed in Maple 2022.2. From this post almost 2 years ago!  it says

"You will also be pleased to know that Maple 2021 addresses the timelimit() issue that you mentioned."

But it is clearly not yet fixed.

 

Some important observations

1) sometimes I noticed if timelimit is small (say 5 or 10), it does not hang. So it the above does timeout for you, please try with larger time out, say 40 or 60 seconds. Since it depens on how fast the PC is.

2)sometimes I  noticed if I close Maple and start new sesstion, the very first time it could timeout OK, but the second time it is called, it hangs. May be because the server caches something to cause this.

All this means, it is completely not predictable what wil happen when starting the maple run. I have no idea how long it will take from one time to another, or even if it will hang or not. For all the years I used Maple, I never had one single time where one run completed without having to restart it at least 2 or 3 times in order to reach the finish line.  This is in addition to all those server.exe crashing on its own many times in between. I noticed more and more of these in Maple 2022.2.  But that is for another topic.

The following screen shot showing one instance when I run the above timelimit (been wainting now for 15 minutes, using timeout of 30 second)., It shows Maple server taking 81% of the CPU

 

And the following is screen shot of the worksheet itself when I took the above screen shot

 

Download timelimit_hangs_on_odeadvisor.mw

 

 

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