  We study the two-dimensional Edwards-Anderson spin-glass model using a
parallel tempering Monte Carlo algorithm. The ground-state energy and entropy
are calculated for different bond distributions. In particular, the entropy is
obtained by using a thermodynamic integration technique and an appropriate
reference state, which is determined with the method of high-temperature
expansion. This strategy provide accurate values of this quantity for
finite-size lattices. By extrapolating to the thermodynamic limit, the
ground-state energy and entropy of the different versions of the spin-glass
model are determined.
