[Scilab-users] ode, speed issue or tips to speed up ?

[Stéphane Mottelet]

Hi,

Le 02/09/2021 à 20:11, Jakub Kopac a écrit :
> Hello,
>
> In the past I solved the same issue.
> As Stephane points out, try to play with ODEOPTIONS.
> In my case (disretized PDE), I get massive speed up by setting
> %ODEOPTIONS(6)  =  0
> and selecting a stiff solver.
>
> If I understand it correctly, you are using function interp1 when 
> evaluating ODE function (many calls to interp1).
> If it is this case, I propose to make a copy of Scilab interp1 
> function and clean unecessary commands.
> I have also good experience with this aproach, but you are loosing 
> flexibility and is a ad hoc function.
>
> Best regards
>
> J.K.
>
> PS: it is great to hear that ODE solvers will be updated to more 
> recent versions.

The actual generic solvers of ode 
(https://computing.llnl.gov/projects/odepack) are still competitive but 
for large-scale stiff systems, odepack misses the versatileness of 
Sundials concerning linear solvers (e.g. odepack does not handle sparse 
Jacobians).

S.

>
>
> št 2. 9. 2021 o 18:32 Stéphane Mottelet <stephane.mottelet at utc.fr 
> <mailto:stephane.mottelet at utc.fr>> napísal(a):
>
>
>     Le 02/09/2021 à 18:03, CHEZE David 227480 a écrit :
>>
>>     Dear all,
>>
>>     In experimental work, I’m comparing dynamic model of a thermal
>>     system with measurements. I’m using function ode, “fix” solver
>>     (continuous time, lowest accuracy requirement is applying in my
>>     case at this stage) and Jacobian ( to try to speed up the
>>     calculation but not sensitive as for now) to get the solution of
>>     the equation,  a single temperature node, at 240 times (time
>>     vector), default rtol=1.d-3 and atol=1.d-4. The system inputs are
>>     available as vector of reals , size is 240 and inputs are passed
>>     to the ode function as inputs functions by interpolating
>>     (interp1) the inputs vectors. It is issuing correct temperature
>>     solutions but is very slow, ~40s for 240 times, while the
>>     variable inputs vector are actually not varying a lot and thus I
>>     would expect very short calculation time.
>>
>>     WIN10-64bits Intel i7 2,6GHz, Scilab 6.1.1
>>
>>     Is there any tips to speed up the calculation , advanced example
>>     documentation about ODEOPTIONS or ode_optional_output ? I guess
>>     it’s the same underlying code that is used in Xcos isn’t it ?
>>
>     No. Xcos uses the (more up-to-date) SUNDIALS solvers, they will be
>     made available at the user level in the next months.
>>
>>     Thank you for advising,
>>
>>     David
>>
>>
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>
>     -- 
>     Stéphane Mottelet
>     Ingénieur de recherche
>     EA 4297 Transformations Intégrées de la Matière Renouvelable
>     Département Génie des Procédés Industriels
>     Sorbonne Universités - Université de Technologie de Compiègne
>     CS 60319, 60203 Compiègne cedex
>     Tel : +33(0)344234688
>     http://www.utc.fr/~mottelet  <http://www.utc.fr/~mottelet>
>
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-- 
Stéphane Mottelet
Ingénieur de recherche
EA 4297 Transformations Intégrées de la Matière Renouvelable
Département Génie des Procédés Industriels
Sorbonne Universités - Université de Technologie de Compiègne
CS 60319, 60203 Compiègne cedex
Tel : +33(0)344234688
http://www.utc.fr/~mottelet

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