void UpdateProblem(Mesh &mesh, FiniteElementSpace &fespace,
GridFunction &x, BilinearForm &a, LinearForm &b)
{
// Update the space: recalculate the number of DOFs and construct a matrix
// that will adjust any GridFunctions to the new mesh state.
fespace.Update();
// Interpolate the solution on the new mesh by applying the transformation
// matrix computed in the finite element space. Multiple GridFunctions could
// be updated here.
x.Update();
// Free any transformation matrices to save memory.
fespace.UpdatesFinished();
// Inform the linear and bilinear forms that the space has changed.
a.Update();
b.Update();
}
