[Getfem-users] Problems with sparse vectors in assembly routines

[Roman Putanowicz]

Hi All, 

First of all my appologies if this is duplicated message
(I messed with e-mail adresses).

I would be very grateful for help with the following issue.
I am using GetFEM++ 2.0 on a GNU/Linux box with gcc 3.3.5

I have encountered a problem with using sparse vectors in assembly
routines (for dense vectors everything works OK):

In the following code I am trying to assembly Neumann boundary
condition for 1D problem. I have created regions with identifiers
0 and 1 for each domain end, respectively. Neuman boundary conditions
can be set on either end:

//-----------------8<-----------------

  typedef gmm::wsvector<bgeot::scalar_type> SparseVector;
  getfem::mesh_fem mf_u;

  // skip some code

  SparseVector R;
  gmm::resize(R,mf_u.nb_dof()); gmm::clear(R);

  for (int i=0; i<2; i++) {
    for (dal::bv_visitor d(mf_u.dof_on_set(i)); !d.finished(); ++d) {
      R[d] = bc_value[i];
    }
  }
  for (int i=0; i<2; i++) {
    if (bc_type[i] == NEUMANN_BC) {
      getfem::asm_source_term(F, im_u, mf_u, mf_u, R, i);
    }
  }
//-----------------8<-----------------

The problem is with routine asm_source_term. Somewhere under the hood
calling this routine requires the usage of operator+= on the sparse
vector iterator. The symptoms is the following error message:

-------------------8<-------------------
g++ -c  -g  -I/home/putanowr/include -I. rod7.cxx -o rod7.o
/home/putanowr/include/getfem_assembling_tensors.h: In member function `void
   getfem::asm_data<VEC>::copy_with_mti(const
   std::vector<bgeot::tensor_strides, std::allocator<bgeot::tensor_strides> >&,
   bgeot::multi_tensor_iterator&) const [with VEC = gmm::wsvector<scalar_type>]
   ':
/usr/include/c++/3.3/bits/stl_map.h:120:   instantiated from here
/home/putanowr/include/getfem_assembling_tensors.h:278: error: no match for
   'operator+=' in 'it += (+(+str)->std::vector<_Tp, _Alloc>::operator[] [with
   _Tp = bgeot::tensor_strides, _Alloc =
   std::allocator<bgeot::tensor_strides>](i))->std::vector<_Tp,
   _Alloc>::operator[] [with _Tp = int, _Alloc =
   std::allocator<int>]((+mti)->bgeot::multi_tensor_iterator::index(i))'
make: *** [rod7.o] Error 1
make: Leaving directory `/home/putanowr/programming/c++/getfem/tutorials/tut1'
-------------------8<-------------------

If I substitute dense vector for a sparse one then the whole code works OK.
However I imagine that here is the place where sparse vector should be
used as otherwise it is a waste of space. Am I right?

I know that the error message shown above is caused by the fact that
sparse wsvector is based on std::map container for which iterators
does not provide operator+=, as in general case that would make no sense.

Could you please advise me? I would like to avoid creation of dense vector
for the situation where I use only two of its elements. I imagine I could
write appropriate container myself but I wonder what is the right way of
dealing with such situations in GetFEM++

Thank you in advance for your help

Regards

Roman
-- 
Roman Putanowicz  < address@hidden  >
Institute for Computational Civil Engng (L-5)
Dept. of Civil Engng, Cracow Univ. of Technology
www.l5.pk.edu.pl, tel. +48 12 628 2569, fax 2034

-- 
Roman Putanowicz  < address@hidden  >
Institute for Computational Civil Engng (L-5)
Dept. of Civil Engng, Cracow Univ. of Technology
www.l5.pk.edu.pl, tel. +48 12 628 2569, fax 2034