Building of the matrix and right hand side

With respect to the building of matrix and right hand side we start by computing all contributions in the integration points. This is done by looping over the various integration points. Since the contribution of point (0,1) in cell $(i,j)$ is equal to that of point (0, -1) in cell $(i-1,j)$ it is sufficient to loop over two sets of integration points only.


Once we have computed the coefficients in a set of integration points we must add these contributions, multiplied by some factor, to the matrix elements. This process is known as distribution.