[Libmesh-users] Initialize DenseSubMatrix with m x n (non-const) size

[edgar <edg...@cr...>]

Hello!

I am trying to do something like this (systems of equations, example 6):

     DenseSubMatrix<Number> Ke_var[3][3] =
       {
         {DenseSubMatrix<Number>(Ke), DenseSubMatrix<Number>(Ke), 
DenseSubMatrix<Number>(Ke)},
         {DenseSubMatrix<Number>(Ke), DenseSubMatrix<Number>(Ke), 
DenseSubMatrix<Number>(Ke)},
         {DenseSubMatrix<Number>(Ke), DenseSubMatrix<Number>(Ke), 
DenseSubMatrix<Number>(Ke)}
       };

Except that I would like to do it like this (does not work):

     const unsigned int mesh_dim = mesh.mesh_dimension ();
     DenseSubMatrix<Number> Ke_var[mesh_dim][mesh_dim];
     for (unsigned int i=0; i<mesh_dim; i++)
         for (unsigned int j=0; j<mesh_dim; i++)
             Ke_var[i][j] = DenseSubMatrix<Number>(Ke);

- One of the reasons for which this does not work is that there is no 
empty constructor defined for =DenseSubMatrix<T>=. In other words, the 
second line in the above code requires parametrized initialization.
- I considered using double pointers (**) and =new= (dynamic 
allocation), but that would be a bomb for memory.
- Since =mesh_dim= is =const=, I think that even the ISO C++ would be 
fine with =Ke_var[mesh_dim][mesh_dim]=.
- I also thought of playing with =new_m= and =new_n= from the definition 
of the constructor (something like =DenseSubMatrix<Number> Ke_var (Ke, 
0, 0, mesh_dim, mesh_dim)=), but I don't know how I would do that.

The point is to be able to generate the matrix with specific dimensions. 
Can you help me, please? Thanks!