  Saddle-point systems, i.e., structured linear systems with symmetric matrices
are considered. A modified implementation of (preconditioned) MINRES is derived
which allows to monitor the norms of the subvectors individually. Compared to
the implementation from the textbook of [Elman, Sylvester and Wathen, Oxford
University Press, 2014], our method requires one extra vector of storage and no
additional applications of the preconditioner. Numerical experiments are
included.
