Dear Jean-Paul, Thanks very much for your explanations. I managed to achieve my objective. You were right, one of the crucial points I had to take into account was the compatibility of data structures. Defining a new operator was another to the point advice, as some of the errors were laid on this ground. Thanks again.
Best, Behrooz On Friday, October 9, 2020 at 11:56:36 PM UTC+2 Jean-Paul Pelteret wrote: > Hi Behrooz, > > I must admit that I’ve not been able to follow why you want to store > Points when you’re interested in global vertex indices, but I’ll try to > give a little help where I can. > In case its of any help to you, I believe that you should be able to get > the coordinate of the vertex with a known global index with the help of the > Triangulation::get_vertices() > <https://dealii.org/current/doxygen/deal.II/classTriangulation.html#afb3059d54432e0d739534e5330bb7b3a> > function. > > By the way, to be more specific, a simple command like the following : > std::pair <Point<dim>, Point<dim>> mypair (vertices[v], vertices[v]); > (in conjunction with vertices[v] = cell->face(f)->vertex(v);) > makes a pair of coordinates of vertices. > > > In terms of the question “can I do this?”, what you’ve written here is > reasonable. If vertices[v] stores a Point<dim>, which is exactly what is > returned by cell->face(f)->vertex(v) ... > > However, when I modify it towards vertex_index(v), it doesn't work: > vertices[v] = cell->face(f)->vertex_index(v); > std::pair <Point<dim>, Point<dim>> mypair (vertices[v], vertices[v]); > Perhaps something according to Point<dim> needs be modified. > > > … but this doesn’t make sense. Specifically, this: > > vertices[v] = cell->face(f)->vertex_index(v); > > A call to cell->face(f)->vertex_index(v) returns the global index of a > vertex (so, effectively an integer) and unless the data type stored by > “vertices” has changed, you’re trying to assign an integer to a Point. This > cannot work. > > std::set <Point<dim>> set1; > > > This cannot work without a little work from your side. The problem is that > std::set <https://en.cppreference.com/w/cpp/container/set> orders its > entries, and to do this it requires a comparator. One way to do this is to > define operator < in the class that is to be stored in the set, but we do > not provide such an operator. Thankfully, you can create a custom > comparator for Points and declare that comparator as the one to be used by > the std::set to order the entries. There’s a somewhat comprehensive post on > the subject at this link <https://stackoverflow.com/a/46128321>. I wonder > though if you rather want to make this a vector of Points, because the > order in which you enter them into the set would not be preserved. That > means that if you somehow extract and store the global index at the same > time, then the entries in the containers are not stores in the same order. > > By the way could anyone kindly enlighten me about the Point<dim> and >>>> required steps to make a pair of and cast intended data into a set? >>>> Specially why Point<dim, double> is a preferred type (in the case of >>>> vertices) to other data types? >>> >>> > I guess that I answered half of this question, but to answer your question > on the relation of Points and vertices: Well, we choose to use the Point > class to describe the physical coordinates points in space, and the vector > that defines the coordinate has an end-point at the origin. The Tensor > class looks similar in structure (and has an overlap of functionality), but > represents other mathematical constructs such as a vector with both its > end-points being allowed to be anywhere in space. You can read more about > the conceptual difference in the introduction to the Point class > documentation <https://dealii.org/current/doxygen/deal.II/classPoint.html> > . > > I hope that this helps at least a bit, and that you manage to implement > what you’re trying to do here. > > Best, > Jean-Paul > > > > > > On Friday, October 9, 2020 at 6:11:11 AM UTC+2 Behrooz Karami wrote: > >> Dear Daniel, >> >> Thanks very much for your reply. Actually what I want to do is very >> simple. >> >> Consider that the above code gives me 3 nodal indices as: 1, 4 and 5. >> First, I need to be able to cast them into a set or vector. We can call >> it set1. >> Then assume that I have another set, e.g. set2, which is composed of >> those nodes (same coordinates), however consecutively renumbered to 101, >> 102 and 103. >> >> Second step I am trying to achieve is to create a pair between the >> components of those two sets (set1 and set2). The new set, e.g. set3, >> would be in fact a set of pairs which includes just three pairs namely >> (1,101) , (4, 102) and (5, 103). Pairs should be constructed in a >> one-to-one manner, for example we do not want to have something like (1, >> 102). >> >> So basically to me it seems that I need first to make a set of points, >> very roughly like: >> std::set <Point<dim>> set1; >> std::set <Point<dim>> set2; >> >> and then making a pair of sets: >> std::pair <set1, set2> pairs; >> >> and finally making a set of pairs: >> std::set <pairs> set3; >> >> However, I haven't yet been able to figure out a proper and correct >> method to do that. I get various errors (some notably related to >> Point<dim>) and I do not understand what is missing or what is misdefined. >> Hope I could have been able to clarify it a bit more. >> >> Thanks again, >> Behrooz >> >> On Thursday, October 8, 2020 at 2:39:25 PM UTC+2 d.arnd...@gmail.com >> wrote: >> >>> Behrooz, >>> >>> Can you elaborate some more on what you are trying to achieve? >>> The (pseudo-)code you posted looks OK apart from vertices being declared >>> in the innermost loop. >>> You probably want it to be outside the loop over the vertices of a face. >>> >>> The API for Point can be found at >>> https://www.dealii.org/current/doxygen/deal.II/classPoint.html. In >>> particular, it is derived from Tensor. >>> >>> In the end, it should not be a problem to create a std::vector of >>> storage type Point (if you are interested in the position of vertices) >>> or unsigned int (if you are interested in the index of the vertices) and >>> push_back into it. >>> >>> Best, >>> Daniel >>> >>> >>> Am Do., 8. Okt. 2020 um 04:48 Uhr schrieb Behrooz Karami < >>> be.k...@gmail.com>: >>> >>>> Hi everyone, >>>> >>>> I am trying to cast extracted vertex_indices into a set (or vector). >>>> Before that it is needed to make a pair of those indices (just doubling) >>>> and to cast the pairs into a set for further manipulations. >>>> >>>> I get the vertex information mainly through following lines of code: >>>> >>>> for (auto cell : triangulation.active_cell_iterators()) >>>> for (unsigned int f=0; f<GeometryInfo<dim>::faces_per_cell; >>>> ++f) >>>> if (...) >>>> for (unsigned int v=0; v < >>>> GeometryInfo<dim>::vertices_per_face; ++v) >>>> { >>>> if (...) >>>> { >>>> Point<dim> >>>> vertices[GeometryInfo<dim>::vertices_per_face]; >>>> >>>> //vertices[v] = >>>> cell->face(f)->vertex(v); >>>> std::cout<<" vertex_id: >>>> "<<cell->face(f)->vertex_index(v)<<std::endl; >>>> //std::cout<<" coords: "<< >>>> cell->face(f)->vertex(v)<<std::endl; >>>> } >>>> } >>>> >>>> However I have not yet been able to construct the required data >>>> structure to get that. >>>> Specially the nature of Point<dim> is not yet clear to me. It looks to >>>> have some similarities with vectors. >>>> >>>> Though std::cout yields vertex IDs, I am not sure how to store them (as >>>> well as vertex coords., face IDs, etc) into a set or vector. >>>> Having a look on GeometryInfo<dim>, my new guess is that I probably >>>> need to loop over vertex_indices(), i.e. >>>> vertices[GeometryInfo<dim>::vertex_indices()]. >>>> >>>> By the way could anyone kindly enlighten me about the Point<dim> and >>>> required steps to make a pair of and cast intended data into a set? >>>> Specially why Point<dim, double> is a preferred type (in the case of >>>> vertices) to other data types? >>>> >>>> Thanks very much, >>>> Behrooz >>>> >>>> -- >>>> The deal.II project is located at http://www.dealii.org/ >>>> For mailing list/forum options, see >>>> https://groups.google.com/d/forum/dealii?hl=en >>>> --- >>>> You received this message because you are subscribed to the Google >>>> Groups "deal.II User Group" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to dealii+un...@googlegroups.com. >>>> To view this discussion on the web visit >>>> https://groups.google.com/d/msgid/dealii/b192e1e9-4905-4e40-9e32-17d8a4a3ee62n%40googlegroups.com >>>> >>>> <https://groups.google.com/d/msgid/dealii/b192e1e9-4905-4e40-9e32-17d8a4a3ee62n%40googlegroups.com?utm_medium=email&utm_source=footer> >>>> . >>>> >>> > -- > The deal.II project is located at http://www.dealii.org/ > For mailing list/forum options, see > https://groups.google.com/d/forum/dealii?hl=en > --- > You received this message because you are subscribed to the Google Groups > "deal.II User Group" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to dealii+un...@googlegroups.com. > > To view this discussion on the web visit > https://groups.google.com/d/msgid/dealii/c0a31673-5f54-41d7-8350-4accc6e54984n%40googlegroups.com > > <https://groups.google.com/d/msgid/dealii/c0a31673-5f54-41d7-8350-4accc6e54984n%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > > -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. 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