2 Splitting and merging a MED file using MEDLoader's advanced API
3 ---------------------------------------------------------------
8 The aim of this exercise is to create a mesh with mixed geometrical type from scratch, and to associate two fields to it:
10 * a field on cells "CellField"
11 * a field on nodes "NodeField"
17 Create an unstructured mesh "m0" built from a 30x30 structured mesh (meshDim=2, spaceDim=2).
18 Each of the even cell of "m0" is "simplexized" (cut in triangles - method MEDCouplingUMesh.simplexize(0)) ::
20 from MEDLoader import *
22 arr=DataArrayDouble(31,1) ; arr.iota(0.)
24 m0=m0.buildUnstructured()
25 m00=m0[::2] ; m00.simplexize(0) ; m01=m0[1::2]
26 m0=MEDCouplingUMesh.MergeUMeshes([m00,m01])
27 m0.getCoords()[:]*=1/15.
30 .. note:: The call to setName() on "m0" is mandatory. Don't forget that the correct naming of the meshes is paramount in the MED file context.
32 Create the fields "CellField" and "NodeField" at the time-stamp (5,6) corresponding to 5.6s.
35 CellField=MEDCouplingFieldDouble(ON_CELLS,ONE_TIME) ; CellField.setTime(5.6,5,6) ; CellField.setMesh(m0)
36 CellField.setName("CellField")
37 CellField.fillFromAnalytic(1,"exp(-((x-1)*(x-1)+(y-1)*(y-1)))") ; CellField.getArray().setInfoOnComponent(0,"powercell [W]")
38 NodeField=MEDCouplingFieldDouble(ON_NODES,ONE_TIME) ; NodeField.setTime(5.6,5,6) ; NodeField.setMesh(m0)
39 NodeField.setName("NodeField")
40 NodeField.fillFromAnalytic(1,"exp(-((x-1)*(x-1)+(y-1)*(y-1)))") ; NodeField.getArray().setInfoOnComponent(0,"powernode [W]")
42 "CellField" looks like this:
44 .. image:: images/SplitAndMergeCell1.jpg
50 Cut "m0" into two distinct parts called "proc0" and "proc1". "proc0" will be contained in the bounding box [(0.,0.4),(0.,0.4)] (with a precision of 1e-10). Use the method MEDCouplingUMesh.getCellsInBoundingBox(). "proc1" is simply the complementary part of "proc0" (method DataArrayInt.buildComplement()). ::
52 proc0=m0.getCellsInBoundingBox([(0.,0.4),(0.,0.4)],1e-10)
53 proc1=proc0.buildComplement(m0.getNumberOfCells())
55 .. image:: images/SplitAndMerge2.jpg
57 Writing into two different MED files
58 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
60 Starting with the partition above ("proc0" and "proc1") create two MED files called "proc0.med" et "proc1.med". ::
62 NodeField0=NodeField[proc0] ; CellField0=CellField[proc0] ; CellField0.setMesh(NodeField0.getMesh())
63 NodeField1=NodeField[proc1] ; CellField1=CellField[proc1] ; CellField1.setMesh(NodeField1.getMesh())
65 proc0_fname="proc0.med"
66 MEDLoader.WriteField(proc0_fname,NodeField0,True)
67 MEDLoader.WriteFieldUsingAlreadyWrittenMesh(proc0_fname,CellField0)
69 proc1_fname="proc1.med"
70 MEDLoader.WriteField(proc1_fname,NodeField1,True)
71 MEDLoader.WriteFieldUsingAlreadyWrittenMesh(proc1_fname,CellField1)
73 Reading and merging 2 MED files - Easy (but non optimal) version
74 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
76 In the two files "proc0.med" and "proc1.med" read the respective "CellField" with the basic API. Aggregate the two and store the result in "CellField_read". ::
78 CellField0_read=MEDLoader.ReadFieldCell("proc0.med","mesh",0,"CellField",5,6)
79 CellField1_read=MEDLoader.ReadFieldCell("proc1.med","mesh",0,"CellField",5,6)
80 CellField_read=MEDCouplingFieldDouble.MergeFields([CellField0_read,CellField1_read])
82 .. note:: It might seem to the reader that the cell type information is repeated uselessly, but don't forget that the MED file norm doesn't forbid a field to be defined simultaneously on nodes and on Gauss points for example ...
84 Compare "CellField_read" and "CellField0". Problem: because of the constraint on the MED file numbering, the initial numbering has been lost. Or more exactly there is no standard way to retrieve it. This means that a call to MEDCouplingFieldDouble.isEqual() won't succeed. Let's use the method MEDCouplingFieldDouble.substractInPlaceDM() which operates a renumbering based on a given policy (see HTML doc).
85 To this end, create a deep copy of "CellField" into "CellFieldCpy" and invoke substractInPlaceDM() on it (DM stands for "Different Meshes", contrarily to substract() which only succeeds if the fields share the same mesh). ::
87 CellFieldCpy=CellField.deepCpy()
88 CellFieldCpy.substractInPlaceDM(CellField_read,10,1e-12)
89 CellFieldCpy.getArray().abs()
90 print CellFieldCpy.getArray().isUniform(0.,1e-12)
92 Let's do the same on "NodeField". The main difference here is that redundant information is created at the boundary. ::
94 NodeField0_read=MEDLoader.ReadFieldNode("proc0.med","mesh",0,"NodeField",5,6)
95 NodeField1_read=MEDLoader.ReadFieldNode("proc1.med","mesh",0,"NodeField",5,6)
96 NodeField_read=MEDCouplingFieldDouble.MergeFields([NodeField0_read,NodeField1_read])
98 .. note:: The mesh is read a second time here, which can be damaging in terms of performance.
100 Invoke MEDCouplingUMesh.mergeNodes() on "NodeField_read" to remove duplicate nodes.
101 Make a deep copy called "NodeFieldCpy" from "NodeField" and call MEDCouplingUMesh.mergeNodes(). ::
103 NodeField_read.mergeNodes(1e-10)
104 NodeFieldCpy=NodeField.deepCpy()
105 NodeFieldCpy.mergeNodes(1e-10)
107 .. note:: mergeNodes() takes two epsilons: the first classical one on the absolute distance between nodes, and the second expressing a tolerance on the values. If the field value of two nodes to be merged is bigger than this an exception is raised.
109 Compare "NodeFieldCpy" and "NodeField_read" still using MEDCouplingFieldDouble.substractInPlaceDM(). ::
111 NodeFieldCpy.substractInPlaceDM(NodeField_read,10,1e-12)
112 print NodeFieldCpy.getArray().isUniform(0.,1e-12)
115 Read/write of two separated MED files - More complex but more efficient version
116 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
118 We show a more systematic and more general method to merge files.
119 This is the preferred route when dealing with big files .
120 This method adds performance but also allows to add extra information.
122 Using the advanced API read the meshes of two files "proc0.med" and "proc1.med" and aggregate the result in an MEDFileUMesh instance "mergeMLMesh".
123 Handle all the levels (even if there is only one in the present case) using the method
124 MEDFileUMesh.getNonEmptyLevels() on the instance coming from "proc0.med". ::
126 fileNames=["proc0.med","proc1.med"]
127 msML=[MEDFileMesh.New(fname) for fname in fileNames]
128 fsML=[MEDFileFields.New(fname) for fname in fileNames]
129 mergeMLMesh=MEDFileUMesh()
130 mergeMLFields=MEDFileFields()
131 for lev in msML[0].getNonEmptyLevels():
132 o2nML=len(msML[0].getNonEmptyLevels())*[None]
133 cs=[mML.getCoords() for mML in msML]
134 mergeMLMesh.setCoords(DataArrayDouble.Aggregate(cs))
135 ms=[mML.getMeshAtLevel(lev) for mML in msML]
136 m=MEDCouplingUMesh.MergeUMeshes(ms) ; m.setCoords(mergeMLMesh.getCoords())
137 o2nML[lev]=m.sortCellsInMEDFileFrmt()
138 mergeMLMesh.setMeshAtLevel(lev,m)
141 for fieldName in fsML[0].getFieldsNames():
142 fmts=[fML[fieldName] for fML in fsML]
143 mergeField=MEDFileFieldMultiTS()
144 for dt,it,tim in fmts[0].getTimeSteps():
145 fts=[fmt[dt,it] for fmt in fmts]
147 for typp in fts[0].getTypesOfFieldAvailable():
151 for geoTyp,smth in ft.getFieldSplitedByType():
152 if geoTyp!=NORM_ERROR:
153 smth1=filter(lambda x:x[0]==ON_CELLS,smth)
154 arr2s=[ft.getUndergroundDataArray()[elt[1][0]:elt[1][1]] for elt in smth1]
155 arr1s.append(DataArrayDouble.Aggregate(arr2s))
162 smth=filter(lambda x:x[0]==NORM_ERROR,ft.getFieldSplitedByType())
163 arr2=DataArrayDouble.Aggregate([ft.getUndergroundDataArray()[elt[1][0][1][0]:elt[1][0][1][1]] for elt in smth])
167 arr=DataArrayDouble.Aggregate(arr1s)
169 arr.renumberInPlace(o2nML[lev])
170 mcf=MEDCouplingFieldDouble(typp,ONE_TIME) ; mcf.setName(fieldName) ; mcf.setTime(tim,dt,it) ; mcf.setArray(arr)
171 mcf.setMesh(mergeMLMesh.getMeshAtLevel(lev)) ; mcf.checkCoherency()
172 mergeField.appendFieldNoProfileSBT(mcf)
175 mergeMLFields.pushField(mergeField)
177 mergeMLMesh.write("merge.med",2)
178 mergeMLFields.write("merge.med",0)
184 :ref:`python_testMEDLoaderSplitAndMerge1_solution`