odesolve
12-09-2016, 03:54 PM
Post: #1
 roadrunner Senior Member Posts: 446 Joined: Jun 2015
odesolve
odesolve(sin(x),[x,y],[0,-1],0.01) returns [−0.999950000417]
odesolve(sin(x),[x,y],[0,-1],0.0001) returns [−0.999999995]
odesolve(sin(x),[x,y],[0,-1],0.00000001) returns [-1.]

but

odesolve(sin(x),[x,y],[0,-1],0.) returns [0]

perhaps a bug?

12-10-2016, 07:17 AM
Post: #2
 parisse Senior Member Posts: 1,320 Joined: Dec 2013
RE: odesolve
Indeed, fixed in source.
11-13-2021, 10:20 AM
Post: #3
 GeJo Junior Member Posts: 1 Joined: Nov 2021
RE: odesolve
Hi,
I have another issue with odesolve:

Entering a simple differential equation does not seem to lead to proper results, e.g
odesolve(t,[t,y],[0,0],3) should give 4.5

The following expression gives a correct result:
odesolve(y,[t,y],[0,0],3)
Gives the correct result 20.0855...

It holds true for a hardware Prime with latest software as well as for the Prime Virtual Calculator:
Prime Software Version 2.1.14596 (2021 10 1)
The same ho[0.,[1.005]]lds true for the virtual calculator Build: 2.1.14593 (2021 10 1)

I found an older thread in The HP Support forum where it is said tha it got fixed in version 11586, but for the latest version, it still or again seems to be the same.
https://h30434.www3.hp.com/t5/Calculator...-p/6515319

https://h30434.www3.hp.com/t5/Calculator...319/page/2

11-14-2021, 07:08 PM
Post: #4
 parisse Senior Member Posts: 1,320 Joined: Dec 2013
RE: odesolve
The answer form [0.0,[0.005]] shows that the numerical algorithm fails. The reason is that the algorithm is unable to estimate the step by comparing errors with 2 different methods, because it's not really a differential equation and error is 0 for both methods.
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