5 .. index:: single: YACS
7 Using a YACS scheme allows the coupling between a computation and an adaptation as described into :doc:`intro`. This coupling can be repeated inside a loop as long as a criteria for the convergence is reached for instance. Many ways are available to program a YACS scheme. The solution that is shown here is correct but many others are too!
9 In this part, an extensive description of a schema YACS is available.
12 The module HOMARD proposes an automatic creation of a schema YASC starting from a defined case. To do that, see :doc:`gui_create_yacs`
17 Here is the description of a scheme for a computation in which a value is to be stabilized. The computation starts over an initial mesh, then HOMARD makes an adaptation. A new computation is done over this new mesh and its result is analyzed. Depending on this analysis, the coupling goes on or does not. The general look of the scheme is this one:
19 .. image:: ./images/yacs_01.png
21 :alt: yacs - global view
26 Among all the treated data, certain are unchanging: the name of the directory of calculation, the name of the case, the name of the hypothesis of adaptation, etc. It was chosen to impose them 'hard' in the various parameters of service or within the scripts python. We could also define them a priori in a node PresetNode and then pass on them by links. We did not hold this solution because it increases strongly the number of parameters and links attached to every node. It is very penalizing for the legibility of the scheme. The only data which are going to circulate are the ones been imperative by the description of the service and those that evolve during the execution of the scheme.
33 - DataInit : initialisation of the initial mesh
34 - Study_Initialisation : launching of the module HOMARD inside SALOME
35 - Convergence_Loop : gestion of the loop computation/adaptation
36 - Results : final information
40 .. image:: ./images/yacs_a_01.png
46 This box is type PresetNode's elementary node. Its only function is to initialize the variable MeshFile that contains the name of the file of the initial mesh.
48 .. literalinclude:: ../files/yacs_01.en.xml
54 The box Study_Initialisation launches the component HOMARD inside SALOME. It is a block consisted of two parts, that are invariable whatever is the envisaged application:
56 - StudyCreation : python node
57 - UpdateStudy : service of the component HOMARD
59 .. image:: ./images/yacs_b_01.png
61 :alt: Study_Initialisation
65 The python node StudyCreation initialize the SALOME study that is given through the output:
67 .. literalinclude:: ../files/yacs_01.en.xml
71 The service UpdateStudy connects this study to an instance of HOMARD.
73 .. literalinclude:: ../files/yacs_01.en.xml
80 The box Convergence_Loop is type WhileLoop. The condition is initialized with 1: the internal block Alternation_Computation_HOMARD is executed. Within this block, we calculate and we adapt the mesh; when the process has to stop either as a result of error, or by convergence, the condition passes to 0. The loop ends and we pass in the following box, Results.
82 .. image:: ./images/yacs_c_01.png
90 .. image:: ./images/yacs_d_01.png
96 This box is a node python that takes in input a character string, MessInfo. If everything passed well, this message is empty. A window QT appears to confirm the convergence. If there was a problem, the message contains messages emitted during the calculations. The window QT shows this message.
98 .. literalinclude:: ../files/yacs_01.en.xml
103 Loop for the calculations
104 *************************
105 .. image:: ./images/yacs_c_02.png
111 This box is a block that manages the computation, the adaptation and the analysis.
115 .. image:: ./images/yacs_c_03.png
121 This box is a node python that is going to drive the calculation. In input, we find the number of the calculation (0 at first) and the name of the file which contains the mesh on which to calculate. In output, we find an integer which represents the error on this calculation (0 so everything goes well) and a dictionary python gathering the results of the calculation. The body of the node is established by the launch of a script python that activates the calculation.
123 .. literalinclude:: ../files/yacs_01.en.xml
127 In this example, we must define:
129 - rep_calc : the directory in which will be executed the calculation.
130 - rep_script : the directory in which is the python that will launch the calculation. This directory is to be added to the PATH. From this directory, we shall import Script from the file ScriptAster.py
132 The python Script is programmed as the user wishes it so that the calculation can be made on the current mesh. According to the mode of launch of the code of calculation, we can need other information, as the number of the calculation or the directory of the calculation for example. The freedom is total. In our case, the arguments of input are the name of the file of mesh, the number of the calculation and the directory of calculation. They are given in a list python: ["--rep_calc=rep_calc", "--num=numCalc", "--mesh_file=MeshFile"]
135 On the other hand the output of the script has to obey the following rule. We get back a code of error, an error message and a dictionary. This dictionary contains necessarily the following keys:
137 - "FileName" : the name of the file that contains the results of the calculation
138 - "V_TEST" : the value the convergence of which we want to test
142 .. image:: ./images/yacs_c_04.png
148 The box Adaptation is a Switch node driven by the code of error of the previous calculation. If this code is nil, YACS will activate the box Adaptation_HOMARD that will launch the adaptation. If the code is not nil, we pass directly in the box Loop_Stop.
152 The first task tries to execute concern the initialization of the data necessary for HOMARD in the box HOMARD_Initialisation. This box is a switch node driven by the number of the calculation. In the starting up, the number is nil and YACS activates the box Iter_1.
156 .. image:: ./images/yacs_c_06.png
162 This box begins by creating the case HOMARD by calling the CreateCase service.
164 .. literalinclude:: ../files/yacs_01.en.xml
168 The name of the case CaseName is imposed on "Computation". The name of the case MeshName is imposed on "BOX". The parameters of input FileName arise from the output of the previous calculation. The parameter of output is an instance of case.
170 .. literalinclude:: ../files/yacs_01.en.xml
174 .. literalinclude:: ../files/yacs_01.en.xml
178 The options of this case must be now given. It is made by the node python CaseOptions. It is imperative to give the directory of calculation. We shall look at the description of the functions in :doc:`tui_create_case`. In output, we get back the instance of the iteration corresponding to the initial state of the case.
180 .. literalinclude:: ../files/yacs_01.en.xml
184 Finally, a hypothesis is created by calling the CreateHypothese service. The parameter of output is an instance of hypothese.
188 Once initialized, the adaptation can be calculated. It is the goal of the Homard_Exec box, in the form of a script python.
190 .. image:: ./images/yacs_c_09.png
196 The directory of calculation is recovered. The name of the mesh is given.
198 .. literalinclude:: ../files/yacs_01.en.xml
204 .. literalinclude:: ../files/yacs_01.en.xml
208 The hypothesis transmitted in input parameter characterized (look :doc:`tui_create_hypothese`) :
210 .. literalinclude:: ../files/yacs_01.en.xml
214 It is necessary to establish a name for the future iteration. To make sure that the name was never used, one installs a mechanism of incremental naming starting from the name of the initial iteration. As this initial name is the name of the initial mesh, one obtains a succession of names in the form: M_001, M_002, M_003, etc
216 .. literalinclude:: ../files/yacs_01.en.xml
220 The iteration is supplemented : hypothesis, future mesh, field (look :doc:`tui_create_iteration`) :
222 .. literalinclude:: ../files/yacs_01.en.xml
226 The iteration is calculated. If it were correct, variable OK equals 1: one will be able to continue the execution of the scheme. If there were a problem, variable OK equals 0 to mean that calculation must stop; an error message then is given.
228 .. literalinclude:: ../files/yacs_01.en.xml
232 After this execution, the process leaves the Adaptation_HOMARD node, then Adaptation node. One arrives then at the node of analysis.
236 .. image:: ./images/yacs_c_07.png
242 For the following passing in the block of adaptation, it is necessary to recover:
244 - the last created iteration: service LastIteration (look :doc:`tui_create_iteration`)
245 - the created hypothesis: service GetHypothesis (look :doc:`tui_create_hypothese`)
247 One passes then in the Homard_Exec node to calculate the new mesh.
251 .. image:: ./images/yacs_c_08.png
257 The Loop_Stop block is present to only make forward variables because the input parameters of the nodes must always be filled. It is a very simple python:
259 .. literalinclude:: ../files/yacs_01.en.xml
265 .. image:: ./images/yacs_c_05.png
271 The Analysis block is a script python which ensures the complete control of the process by examining the causes of possible error successively.
273 .. literalinclude:: ../files/yacs_01.en.xml
279 .. literalinclude:: ../files/yacs_01.en.xml
283 One starts by analyzing the return of the computer code:
285 .. literalinclude:: ../files/yacs_01.en.xml
289 Checking of the presence of the name of the result file in the dictionary of the results:
291 .. literalinclude:: ../files/yacs_01.en.xml
295 Checking of convergence. That supposes that the value to be tested is present in the dictionary under the key 'V_TEST'. Here, one set up a test on the variation of the value of one calculation at the other. With the first passage, nothing is tested. In the following passing, one tests if the relative variation is lower than 1 thousandths. One could have set up an absolute test if one had recovered a total level of error for example.
297 .. literalinclude:: ../files/yacs_01.en.xml
301 Lastly, it is checked that a maximum nomber of adaptations is not exceeded:
303 .. literalinclude:: ../files/yacs_01.en.xml
310 To reproduce this example, download:
311 * :download:`the scheme <../files/yacs_01.en.xml>`
312 * :download:`an example of python script <../files/yacs_script.py>`
313 * :download:`an example of python script ... for nothing <../files/yacs_script_test.py>`
315 It should be adapted to simulation considered. In particular, it is necessary:
317 - to adjust the names of the files and the directories
318 - to provide a script of launching of calculation respecting the instructions evoked herebefore
319 - to choose the hypothesis of driving of the adaptation
320 - to set up the test of stop