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<p>Anton,</p>
<p> </p>
<p>I have some brief insight that I would like to share in addition to Marcello's excellent comments.</p>
<p> </p>
<p>First, please make sure that you have the "07-ProgrammersGuide.pdf" from the latest version of TRNSYS (17.01.0025). This piece of the documentation was completely re-written for version 17.1, so it may not make sense and lead to confusion if you have the documentation from 17.0.</p>
<p> </p>
<p>Second, you are more than welcome to send an email via your local TRNSYS distributor to send to the TRNSYS developers. This Trnsys-Users mailing list is a discussion forum, and the questions are answered voluntarily.</p>
<p> </p>
<p>Last, there is no "bomb" in the TRNSYS code. Most of the other simulation programs, as one of my colleagues mentioned, use fortran the same way (EnergyPlus, IES) and do not implement SAVE. It would be quite an extensive task as Marcello mentioned and not an efficient way to implement the code.</p>
<p> </p>
<p>Best regards,</p>
<p> </p>
<p>Matt Duffy</p>
<p> </p>
<p>On 2013-03-15 07:45, marcello.caciolo@cofelyaxima-gdfsuez.com wrote:</p>
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<p class="MsoNormal"><span style="color: #1f497d;">Dear Anton,<!-- o ignored --></span></p>
<p class="MsoNormal"><span style="color: #1f497d;"><!-- o ignored --> </span></p>
<p class="MsoNormal"><span style="color: #1f497d;">A quick answer to your questions :<!-- o ignored --></span></p>
<p class="MsoNormal"><span style="color: #1f497d;"><!-- o ignored --> </span></p>
<p class="MsoNormal"><span style="color: #1f497d;">1) and 2) During each time step, TRNSYS calls sequentially each type and update input variables of other types with calculated values from the current type, repeating this operation until output variables do not change anymore (successive substitutions algorithm). <!-- o ignored --></span></p>
<p class="MsoNormal"><span style="color: #1f497d;">The number of calls to a type in each time step is not limited to 3: I think you get confused by the table page 7-78 of the programmer’s guide, representing just un example assuming that convergence is reached for each time step at the second iteration.<!-- o ignored --></span></p>
<p class="MsoNormal"><span style="color: #1f497d;"><!-- o ignored --> </span></p>
<p class="MsoNormal"><span style="color: #1f497d;">3) I have never used the dTdt vector, than I cannot answer to you on this specific point <!-- o ignored --></span></p>
<p class="MsoNormal"><span style="color: #1f497d;"><!-- o ignored --> </span></p>
<p class="MsoNormal"><span style="color: #1f497d;">4) A TRNSYS Types is basically a procedure which computes an array of outputs knowing the following array:<!-- o ignored --></span></p>
<p class="MsoListParagraph" style="text-indent: -18.0pt; mso-list: l0 level1 lfo3;"><span style="font-family: Symbol; color: #1f497d;"><span style="mso-list: Ignore;">·<span style="font: 7.0pt 'Times New Roman';"> </span></span></span><span style="color: #1f497d;">An input array, provided by TRNSYS when calling the type.<!-- o ignored --></span></p>
<p class="MsoListParagraph" style="text-indent: -18.0pt; mso-list: l0 level1 lfo3;"><span style="font-family: Symbol; color: #1f497d;"><span style="mso-list: Ignore;">·<span style="font: 7.0pt 'Times New Roman';"> </span></span></span><span style="color: #1f497d;">A parameter array, which is constant (TRNSYS passes it to the type, but normally it should not change from call to call)<!-- o ignored --></span></p>
<p class="MsoListParagraph" style="text-indent: -18.0pt; mso-list: l0 level1 lfo3;"><span style="font-family: Symbol; color: #1f497d;"><span style="mso-list: Ignore;">·<span style="font: 7.0pt 'Times New Roman';"> </span></span></span><span style="color: #1f497d;">A static storage array, defined by the type during the initialization call, which is basically an additional parameter array<!-- o ignored --></span></p>
<p class="MsoListParagraph" style="text-indent: -18.0pt; mso-list: l0 level1 lfo3;"><span style="font-family: Symbol; color: #1f497d;"><span style="mso-list: Ignore;">·<span style="font: 7.0pt 'Times New Roman';"> </span></span></span><span style="color: #1f497d;">A dynamic storage array, which can be used to store variables between iterations and time steps (your state vector, I imagine?)<!-- o ignored --></span></p>
<p class="MsoNormal"><span style="color: #1f497d;"><!-- o ignored --> </span></p>
<p class="MsoNormal"><span style="color: #1f497d;">Derivative of variables can also be computed by TRNSYS and used by a type but, as I told before, I am not very familiar with this.<!-- o ignored --></span></p>
<p class="MsoNormal"><span style="color: #1f497d;"><!-- o ignored --> </span></p>
<p class="MsoNormal"><span style="color: #1f497d;">For your second point you should consider an issue common to many old codes : TRNSYS was first developed in FORTRAN 77, which considers all variables with the attribute SAVE (static variables, in C/C++ terms). Modern FORTRAN compilers do not consider any more all variables as static (you should define a variable explicitly with SAVE attribute to define a static variable), but as there are many old codes written in FORTRAN, they practically <em><span style="text-decoration: underline;">always</span></em> give the possibility to use this old characteristics by a compiler directive (and I would be very surprised if next versions of Intel Visual FORTRAN would not give this possibility). <!-- o ignored --></span></p>
<p class="MsoNormal"><span style="color: #1f497d;"><!-- o ignored --> </span></p>
<p class="MsoNormal"><span style="color: #1f497d;">You are right, this is not a good programming practice, but the alternative would be to take all the code and insert the keyword SAVE to all variable definition. I understand that TRNSYS developers has better things to do...:-) By the way, the only problem with static variables is that you cannot optimize storage of data, but in my experience TRNSYS simulations are far from using much RAM.<!-- o ignored --></span></p>
<p class="MsoNormal"><span style="color: #1f497d;"><!-- o ignored --> </span></p>
<p class="MsoNormal"><span style="color: #1f497d;">Anyway, this feature explains the reason because, for example, if there is only one unit of the same type, you are not obliged to reread each time the parameters (which is the meaning of the code you sent to the forum).<!-- o ignored --></span></p>
<p class="MsoNormal"><span style="color: #1f497d;"><!-- o ignored --> </span></p>
<p class="MsoNormal"><span style="color: #1f497d;">Just a final note about INFO array : it is now possible (and even recommended) to use directly access functions to read inputs, parameters and storage arrays, for example in order to read the i-th input you can use the statement <em>var = getInputValue(i)</em>, to read the i-th parameter : <em>par = getParameterValue(i)</em>, etc…<!-- o ignored --></span></p>
<p class="MsoNormal"><span style="color: #1f497d;"><!-- o ignored --> </span></p>
<p class="MsoNormal"><span style="color: #1f497d;">I hope this helps.<!-- o ignored --></span></p>
<p class="MsoNormal"><span style="color: #1f497d;"><!-- o ignored --> </span></p>
<p class="MsoNormal"><span style="color: #1f497d;">Best regards,</span><span style="color: #1f497d;"><!-- o ignored --></span></p>
<p class="MsoNormal" style="mso-margin-top-alt: auto; mso-margin-bottom-alt: auto;"><strong><span style="font-family: 'Tahoma','sans-serif'; color: #58595b;">Marcello Caciolo</span></strong><span style="font-family: 'Tahoma','sans-serif'; color: #58595b;"><br /></span><span style="font-size: 9.0pt; font-family: 'Tahoma','sans-serif'; color: #58595b;">Responsable Outils et Méthodes d'Analyse Energétique</span><span style="font-family: 'Tahoma','sans-serif'; color: #58595b;"><!-- o ignored --></span></p>
<p class="MsoNormal" style="mso-margin-top-alt: auto; mso-margin-bottom-alt: auto;"><span style="font-size: 10.0pt; font-family: 'Arial','sans-serif'; color: gray;"><img id="Image_x0020_1" src="cid:4638b30197b6fe4b97af24c0b876ea5a@tess-inc.com" &_id=90498754751431b81156b6" alt="cid:image003.jpg@01CD4E08.954D04D0" width="170" height="62" /><br /><strong><br /></strong>Cellule Efficacité Energétique et Environnementale - Pôle Projets et Réalisations<br />46 Boulevard de la Prairie au Duc<br />BP 40119 - 44201 Nantes Cedex 02</span><span style="font-size: 9.0pt; font-family: 'Tahoma','sans-serif'; color: #1f497d;"><br /></span><span style="font-size: 10.0pt; font-family: 'Arial','sans-serif'; color: gray;">Tél.: +33 02 40 41 06 57</span><span style="font-size: 9.0pt; font-family: 'Tahoma','sans-serif'; color: #1f497d;"><br /><a href="mailto:prenom.nom@aximaseitha-gdfsuez.com"><span style="color: blue;">marcello.caciolo@cofelyaxima-gdfsuez.com</span></a></span><span style="font-size: 10.0pt; font-family: 'Arial','sans-serif'; color: gray;"><!-- o ignored --></span></p>
<p class="MsoNormal"><span style="font-family: Webdings; color: #339966;">P</span><span style="font-size: 10.0pt; font-family: Webdings; color: #339966;"> </span><strong><span style="font-size: 7.5pt; font-family: 'Arial','sans-serif'; color: #339966;">Pensez à l'environnement avant d'imprimer ce message</span></strong><span style="color: #1f497d;"><!-- o ignored --></span></p>
<p class="MsoNormal"><span style="color: #1f497d;"><!-- o ignored --> </span></p>
<p class="MsoNormal"><span style="color: #1f497d;"><!-- o ignored --> </span></p>
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<p class="MsoNormal"><strong><span style="font-size: 10.0pt; font-family: 'Tahoma','sans-serif';">De :</span></strong><span style="font-size: 10.0pt; font-family: 'Tahoma','sans-serif';"> trnsys-users-bounces@cae.wisc.edu [mailto:trnsys-users-bounces@cae.wisc.edu] <strong>De la part de</strong> Soppelsa Anton<br /><strong>Envoyé :</strong> vendredi 15 mars 2013 11:34<br /><strong>À :</strong> trnsys-users@cae.wisc.edu<br /><strong>Objet :</strong> [TRNSYS-users] Types programming: Types-Kernel interface explanation<!-- o ignored --></span></p>
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<p class="MsoNormal"><!-- o ignored --> </p>
<p class="MsoNormal"><span>Dear TRNSYS users,<!-- o ignored --></span></p>
<p class="MsoNormal"><span><!-- o ignored --> </span></p>
<p class="MsoNormal"><span>I have been looking for a while to the seventh section of the TRNSYS 17 manual in order to understand how and why the kernel calls a type in the way it does.<!-- o ignored --></span></p>
<p class="MsoNormal"><span><!-- o ignored --> </span></p>
<p class="MsoNormal"><span>Notwithstanding my experience with simulation software like Matlab/Simulink, Scilab/XCos, Ptolemy II, I still have difficulties in understanding some aspects of the TRNSYS callbacks interface, e.g.:<!-- o ignored --></span></p>
<p class="MsoNormal"><span><!-- o ignored --> </span></p>
<p class="MsoListParagraph" style="margin-left: 20.25pt; text-indent: -18.0pt; mso-list: l2 level1 lfo2;"><span><span style="mso-list: Ignore;">1)<span style="font: 7.0pt 'Times New Roman';"> </span></span></span><span>What’s the purpose of the inter-step calls (iterations)<!-- o ignored --></span></p>
<p class="MsoListParagraph" style="margin-left: 20.25pt; text-indent: -18.0pt; mso-list: l2 level1 lfo2;"><span><span style="mso-list: Ignore;">2)<span style="font: 7.0pt 'Times New Roman';"> </span></span></span><span>Why they need to be exactly 3 (as I understood from the manual).<!-- o ignored --></span></p>
<p class="MsoListParagraph" style="margin-left: 20.25pt; text-indent: -18.0pt; mso-list: l2 level1 lfo2;"><span><span style="mso-list: Ignore;">3)<span style="font: 7.0pt 'Times New Roman';"> </span></span></span><span>How the kernel make use of the vector dTdt (which I would have called dxdt).<!-- o ignored --></span></p>
<p class="MsoListParagraph" style="margin-left: 20.25pt; text-indent: -18.0pt; mso-list: l2 level1 lfo2;"><span><span style="mso-list: Ignore;">4)<span style="font: 7.0pt 'Times New Roman';"> </span></span></span><span>Whether my understanding that Types can be used to implement the following mathematical models: y = g(x, u, t), dxdt = fc(x, u, t) (or x(t+1) = fd(x(t), u(t), t) in case of discrete systems), where t is the time, u is the input vector, x is the state vector and y is the output vector is correct.<!-- o ignored --></span></p>
<p class="MsoNormal"><span><!-- o ignored --> </span></p>
<p class="MsoNormal"><span>Can anybody suggest me what is the right section of the manual to find an answer to these questions? I had no luck reading the programmer´s guide section of the manual.<!-- o ignored --></span></p>
<p class="MsoNormal"><span><!-- o ignored --> </span></p>
<p class="MsoNormal"><span>A second point is that I found puzzling the code example published therein. In the first time I though that my doubts where related to my scarce knowledge of the Fortran language (I am a C/C++ programmer) so I raised a point in a programmer community <a href="http://stackoverflow.com/questions/15414277/where-does-fortran-store-local-variables">http://stackoverflow.com/questions/15414277/where-does-fortran-store-local-variables</a> . It turned out that the code published in the manual (which contains a pattern which I noticed has widespread to many other types) seems to rely on a Fortran language “feature” which is considered “bad programming practice”, is compiler-dependent and may not be supported any more in the future.<!-- o ignored --></span></p>
<p class="MsoNormal"><span><!-- o ignored --> </span></p>
<p class="MsoNormal"><span>As it seem to me impossible that such a “bomb” is present in the program without affecting the TRNSYS community I kindly ask the help of a TRNSYS expert to clarify this point.<!-- o ignored --></span></p>
<p class="MsoNormal"><span><!-- o ignored --> </span></p>
<p class="MsoNormal"><span>Does anybody know if there a trnsys-devel mailing list?<!-- o ignored --></span></p>
<p class="MsoNormal"><span><!-- o ignored --> </span></p>
<p class="MsoNormal"><span>Sincerely,<!-- o ignored --></span></p>
<p class="MsoNormal"><span> AS<!-- o ignored --></span></p>
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