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<p>Hi,</p>
<p>The "fix" solver is the classical Runge-Kutta-Fehlberg scheme,
hence an *explicit* scheme. So, your Jacobian is just ignored in
the computations. If you guessed that some stiffness may occur,
e.g. if you ode is a discretized pde, then you should force the
"stiff" solver instead. In that case the Jacobian will be used. If
you want to speed up things and if your Jacobian is banded, using
%ODEOPTIONS allows to do so. <br>
</p>
<p>S.<br>
</p>
<div class="moz-cite-prefix">Le 02/09/2021 à 18:03, CHEZE David
227480 a écrit :<br>
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<p class="MsoNormal">Dear all,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span lang="EN-GB">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. <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">WIN10-64bits Intel i7
2,6GHz, Scilab 6.1.1<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">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 ?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Thank you for advising,<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:FR"
lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial",sans-serif;mso-fareast-language:FR">David
</span><span style="mso-fareast-language:FR"><o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<br>
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<pre class="moz-signature" cols="72">--
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
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