Dear Zaim Yassine It would be useful to know which version of GetFEM++ you are currently using. If you are using version 5.1 or later I can help you at least regarding the use of global basis functions. The standard way I am using them is by deriving a class from getfem::global_function_simple, lets call it global_function_custom, where I redefine the following methods
virtual scalar_type val(const base_node &pt) const virtual void grad(const base_node &pt, base_small_vector &g) const virtual void hess(const base_node &pt, base_matrix &h) const virtual bool is_in_support(const base_node &pt) const virtual void bounding_box(base_node &bmin, base_node &bmax) const where the coordinates of the point pt are global coordinates. Then I save all instances of my derived class, in a vector of shared pointers std::vector<getfem::pglobal_function> basis_funcs; for (...) basis_funcs.push_back(std::make_shared<global_function_custom>(...)); Then I define my mesh_fem as getfem::mesh_fem_global_function mf(m,1); mf.set_functions(basis_funcs, mim); and I am ready to use mf. The difference between global fem and standard fem is that the basis functions in the latter case are defined in terms of the local/element coordinates and there is an additional geometric transformation between global and local coordinates. I hope this helps you a bit. Best regards Kostas On Sun, Nov 20, 2016 at 6:38 PM, Yassine ZAIM <[email protected]> wrote: > Hello dear GetFEM users, > I am trying to add a new FEM with some global functions in addition to > some polynomial functions. I found this discussion about how I can do it: > https://mail.gna.org/public/getfem-users/2014-04/msg00034.html#content > However when I look in the file "getfem_mesh_fem_global_function.cc/h" > to inspire. I don't found where the basis functions are defined? as the > functions: > std::stringstream s > for (int i = 0; i<size_basis; ++i) p->base()[i] > =bgeot::read_base_poly(dim,s); > for the polynomial case; And also where the name of FEM is defined? as the > function: add_suffix("Name", fem_element); in the polynomial case. > > I tried to add my element by programming a similar class of > template <class FUNC> class fem : public virtual_fem {...}; > in which I have determined explicitly the value of base_value, > grad_base_value and hess_base_value. I inherited from this class to define > my element in the file getfem_fem.cc. I define the basis and DOF by the > functions: > //############# code to add the basis and DOF ###############// > base_[i] = polynomial or global basis function;//like base_value in annex > add_node(DOF, Point);// corresponding to each basis function > > I know that for this method I could program a class with the functions > eval() and derivative(). But in my case I defined the functions base_value, > grad_base_value and hess_base_value explicitly without need of these > methods (I think). You can see my class in the annex. By this way I get a > bad result. > > I hope that I was clear, and I will be thankful for your help of how I can > add my element correctly. > > > > ///########## Annex ##############/// > class MyFUNC : public virtual_fem { > protected : > std::vector<opt_long_scalar_type> base_; > > public : > /// Gives the array of basic functions (components). > const std::vector<opt_long_scalar_type> &base(void) const { return > base_; } > std::vector<opt_long_scalar_type> &base(void) { return base_; } > > /** Evaluates at point x, all base functions and returns the result in > t(nb_base,target_dim) */ > void base_value(const base_node &z, base_tensor &t) const { > //scalar_type res = 0; > bgeot::multi_index mi(2); > mi[1] = target_dim(); mi[0] = short_type(nb_base(0)); > t.adjust_sizes(mi); > base_tensor::iterator it = t.begin(); > scalar_type x = *z.begin();//z[0]; > scalar_type y = *z.end(); > *it = bgeot::to_scalar(x*y); ++it; > *it = bgeot::to_scalar((1-x)*y); ++it; > *it = bgeot::to_scalar((1-x)*(1-y)); ++it; > *it = bgeot::to_scalar(x*(1-y)); ++it; > *it = > bgeot::to_scalar((32/1281)*sqrt(2)*(1-x)*sqrt(1-x)*(12*x-66*x*x+(143/2)*x*x*x)); > ++it; > *it = bgeot::to_scalar((32/1281)*sqrt(2)*(1-y)*sqrt(1-y)*(12*y+ > 66*y*y+(143/2)*y*y*y)); > } > /** Evaluates at point x, the gradient of all base functions w.r.t. the > reference element directions 0,..,dim-1 and returns the result in > t(nb_base,target_dim,dim) */ > void grad_base_value(const base_node &z, base_tensor &t) const { > bgeot::multi_index mi(3); > dim_type n = dim(); > mi[2] = n; mi[1] = target_dim(); mi[0] = short_type(nb_base(0)); > t.adjust_sizes(mi); > base_tensor::iterator it = t.begin(); > scalar_type x = *z.begin(); > scalar_type y = *z.end(); > *it = bgeot::to_scalar(y); ++it; > *it = bgeot::to_scalar(-y); ++it; > *it = bgeot::to_scalar(-(1-y) ); ++it; > *it = bgeot::to_scalar((1-y)); ++it; > *it = bgeot::to_scalar((32/1281)*sqrt(2)*(-3/2*sqrt(1-x)*(12*x- > 66*x*x+(143/2)*x*x*x)+(1-x)*sqrt(1-x)*(12-132*x+(429/2)*x*x))); ++it; > *it = bgeot::to_scalar(0); ++it; > > *it = bgeot::to_scalar(x); ++it; > *it = bgeot::to_scalar((1-x)); ++it; > *it = bgeot::to_scalar(-(1-x)); ++it; > *it = bgeot::to_scalar(-x); ++it; > *it = bgeot::to_scalar(0); ++it; > *it = bgeot::to_scalar((32/1281)*sqrt(2)*(-3/2*sqrt(1-y)*(12*y- > 66*y*y+(143/2)*y*y*y)+(1-y)*sqrt(1-y)*(12-132*y+(429/2)*y*y))); > } > /** Evaluates at point x, the hessian of all base functions w.r.t. the > reference element directions 0,..,dim-1 and returns the result in > t(nb_base,target_dim,dim,dim) */ > void hess_base_value(const base_node &z, base_tensor &t) const { > bgeot::multi_index mi(4); > dim_type n = dim(); > mi[3] = n; mi[2] = n; mi[1] = target_dim(); > mi[0] = short_type(nb_base(0)); > t.adjust_sizes(mi); > base_tensor::iterator it = t.begin(); > scalar_type x = *z.begin(); > scalar_type y = *z.end(); > > *it = bgeot::to_scalar(0); ++it; > *it = bgeot::to_scalar(0); ++it; > *it = bgeot::to_scalar(0); ++it; > *it = bgeot::to_scalar(0); ++it; > *it = bgeot::to_scalar((32/1281)*sqrt(2)*(3/4*(1/sqrt(1-x))*( > 12*x-66*x*x+(143/2)*x*x*x)-3*sqrt(1-x)*(12-132*x+(429/2)*x* > x)+(1-x)*sqrt(1-x)*(-132+429*x))); ++it; > *it = bgeot::to_scalar(0); ++it; > > *it = bgeot::to_scalar(1); ++it; > *it = bgeot::to_scalar(-1); ++it; > *it = bgeot::to_scalar(1); ++it; > *it = bgeot::to_scalar(-1); ++it; > *it = bgeot::to_scalar(0); ++it; > *it = bgeot::to_scalar(0); ++it; > > *it = bgeot::to_scalar(1); ++it; > *it = bgeot::to_scalar(-1); ++it; > *it = bgeot::to_scalar(1); ++it; > *it = bgeot::to_scalar(-1); ++it; > *it = bgeot::to_scalar(0); ++it; > *it = bgeot::to_scalar(0); ++it; > > *it = bgeot::to_scalar(0); ++it; > *it = bgeot::to_scalar(0); ++it; > *it = bgeot::to_scalar(0); ++it; > *it = bgeot::to_scalar(0); ++it; > *it = bgeot::to_scalar(0); ++it; > *it = bgeot::to_scalar((32/1281)*sqrt(2)*(3/4*(1/sqrt(1-y))*( > 12*y-66*y*y+(143/2)*y*y*y)-3*sqrt(1-y)*(12-132*y+(429/2)*y* > y)+(1-y)*sqrt(1-y)*(-132+429*y))); > } > }; > > > -- > *ZAIM Yassine * > *PhD Student in Applied Mathematics* > > > _______________________________________________ > Getfem-users mailing list > [email protected] > https://mail.gna.org/listinfo/getfem-users > >
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