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Offline uni  
#1 Posted : 19 January 2019 08:22:15(UTC)
uni


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OSLO - Open Solving Library for ODEs

SMath Studio compatibility SMath Viewer compatibility mono compatibility Extension page Sources


Functions list: RK547M(5), GearBDF(5)

RK547M(init, x1, x2, intvls, D) Implementation of Runge-Kutta algoritm with per-point accurancy control from Dormand and Prince article.
GearBDF(init, x1, x2, intvls, D) Implementation of Gear's BDF method with dynamically changed step size and order. Order changes between 1 and 3.

Arguments:

- init is either a vector of n real initial values, where n is the number of unknowns (or a single scalar initial value, in the case of a single ODE).
- x1 and x2 are real, scalar endpoints of the interval over which the solution to the ODE(s) is evaluated. Initial values in init are the values of the ODE function(s) evaluated at x1.
- intvls is the integer number of discretization intervals used to interpolate the solution function. The number of solution points is the number of intervals + 1.
- D is a vector function of the form D(x,y) specifying the right-hand side of the system

Options:

- AbsTol - absolute tolerance parameter, default value 10⁻⁷.
- RelTol - relative tolerance parameter, default value 10⁻⁴.
- MaxStep - maximal step value, default value ( x2- x1 ) / ( 2 * intvs ).

Links:

1. Open Solving Library for ODEs.
2. OSLO User Guide (pdf).

Open Solving Library for ODEs (OSLO) 1.0 User Guide.pdf (1,174kb) downloaded 8 time(s).

oslo.integrate.sm (11kb) downloaded 42 time(s).
oslo.kinetic1.sm (8kb) downloaded 36 time(s).
oslo.kinetic2.sm (12kb) downloaded 39 time(s).
oslo.kinetic3.sm (12kb) downloaded 34 time(s).
oslo.test1.sm (16kb) downloaded 31 time(s).
oslo.test2.sm (16kb) downloaded 34 time(s).
oslo.Amplitude detector.sm (21kb) downloaded 33 time(s).

oslo.integrate.pdf (89kb) downloaded 36 time(s).
oslo.kinetic1.pdf (76kb) downloaded 32 time(s).
oslo.kinetic2.pdf (92kb) downloaded 34 time(s).
oslo.kinetic3.pdf (86kb) downloaded 29 time(s).
oslo.test1.pdf (100kb) downloaded 30 time(s).
oslo.test2.pdf (102kb) downloaded 28 time(s).
oslo.Amplitude detector.pdf (150kb) downloaded 32 time(s).

Edited by user 04 December 2020 09:53:10(UTC)  | Reason: Not specified

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Viacheslav N. Mezentsev
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Offline omorr  
#2 Posted : 19 January 2019 12:49:32(UTC)
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Hello uni,

Thank you for some more ODE solvers. However, I could not resist to mention my favorite db_GearsBDF() which can escape the problem when y2 approaches zero. I mentioned this stiff example long time ago and you were using it often (kinetic2.sm example here). Unfortunately, it seams GearBDF() from this plugin can not overcome zero values and gets into the negative ones like most of the solvers.

kinetic2.PNG

Regards,
Radovan
When Sisyphus climbed to the top of a hill, they said: "Wrong boulder!"
Offline uni  
#3 Posted : 19 January 2019 13:03:21(UTC)
uni


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Yes, weak solvers. There are some settings there, but I was not able to select them correctly for this task. Another strange problem with accuracy. Unlike other solvers, a smaller step is needed here. In general, there are questions to the developers (Microsoft Research and Moscow State University).
Not only dn_GearsBDF() can solve your task. Some other solvers have also achieved success. Still looking for the best. Not all solvers are still implemented, the test suite is also still small.
Russia ☭ forever
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Offline Razonar  
#4 Posted : 20 January 2019 01:25:58(UTC)
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Originally Posted by: uni Go to Quoted Post
... the test suite is also still small.


Hi Viacheslav. Maybe you're interested in check this matlab ode's:

http://people.sc.fsu.edu...c/test_ode/test_ode.html .

At the end, there are also png images for the plots.

Best regards.

Alvaro.

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Offline uni  
#5 Posted : 20 January 2019 03:01:03(UTC)
uni


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And another one: TEST SET FOR IVP SOLVERS.
Russia ☭ forever
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Offline omorr  
#6 Posted : 20 January 2019 10:39:23(UTC)
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Originally Posted by: uni Go to Quoted Post
And another one: TEST SET FOR IVP SOLVERS.


In this link it was mentioned about the book and packages made in R (Karline Soetaert et al). I was exposing my students to the R and some of their packages (deSolve, bvpSolve, rootSolve etc.) for few years now. I am really impressed by them. There are solvers for IVP, BVP, DAE, PDE etc. All my credits to the authors and their efforts. Surprisingly, there are quite a lot numerical packages in R which is considered to be mainly a statistical environment.

Regards,
Radovan
When Sisyphus climbed to the top of a hill, they said: "Wrong boulder!"
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Online Jean Giraud  
#7 Posted : 20 January 2019 16:42:43(UTC)
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Originally Posted by: omorr Go to Quoted Post
In this link it was mentioned about the book and packages made in R (Karline Soetaert et al). I was exposing my students to the R and some of their packages (deSolve, bvpSolve, rootSolve etc.) for few years now. I am really impressed by them. There are solvers for IVP, BVP, DAE, PDE etc. All my credits to the authors and their efforts. Surprisingly, there are quite a lot numerical packages in R which is considered to be mainly a statistical environment.

Can't be more right Radovan: for using R, better be an R man
All those solvers fall in the category Lagrangian Methods quite evolved since CAS
Soon, there will be as many dedicated ODE solvers as they will be proved for
Physicals system to solve. dn_GearsBDF is a good companion for stiff systems,
and hyper fast [see comparison attached].


Jean

ODE HIRES.sm (58kb) downloaded 21 time(s).
Online Jean Giraud  
#8 Posted : 20 January 2019 17:15:14(UTC)
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... Legendre_Radau updated wrt local definition

ODE HIRES.sm (68kb) downloaded 27 time(s).
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Online Jean Giraud  
#9 Posted : 20 January 2019 23:44:58(UTC)
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... thanks Radovan for the undocumented

ODE GearsBDF Undocumented.sm (10kb) downloaded 36 time(s).
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Offline omorr  
#10 Posted : 21 January 2019 09:47:25(UTC)
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Originally Posted by: Jean Giraud Go to Quoted Post
... thanks Radovan for the undocumented

ODE GearsBDF Undocumented.sm (10kb) downloaded 36 time(s).


You are welcome Jean, and thank you. There is another one by uni - lsoda.

Regards,
Radovan
When Sisyphus climbed to the top of a hill, they said: "Wrong boulder!"
Online Jean Giraud  
#11 Posted : 21 January 2019 22:50:46(UTC)
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Originally Posted by: omorr Go to Quoted Post
You are welcome Jean, and thank you. There is another one by uni - lsoda.

Thanks Radovan,
As it looks, the previous 8 ODE from Viacheslav are all Isoda.
Do you feel comfortable to code Smath ?
An all version(s) compatible will enhance the native tiny Smath.
Naturally, Smath does not solve the "Pulse". Does not recognize F(t).

Cheers ... Jean

ODEpulse.PNG

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