solve a PDE; instead, an analytic function to which we know the
values at time t is used, and the mesh points are updated with
the exact function values in each time instance. This approach
eliminates the impact of all exterior factors, such as interpolation
and rounding errors, but still exercises all the important aspects
of the mesh generation and adaptation. In each time step, the local
truncation error is estimated in each block (using the normalized
gradient [26]) and the mesh is updated from the existing mesh