  We present an algorithmic study for the simulation of two massless flavors of
O(a) improved Wilson quarks with Schroedinger functional boundary conditions.
The algorithm used is Hybrid Monte Carlo with two pseudo-fermion fields as
proposed by M. Hasenbusch. A gain in CPU cost of a factor two is reached when
compared to one pseudo-fermion field due to the larger possible step-size. This
study is integrated in the ALPHA project for the computation of the running of
the renormalized quark mass. We include an update on these physics results.
