EN
The quantum Hall ferromagnets at the half-filling of a pair of degenerate electron or composite fermion Landau levels are studied by exact numerical diagonalization. The results obtained using open and closed geometries (rectangular - with periodic boundary conditions and spherical) are compared. The ferro- and paramagnetic ground states are identified in finite-size energy spectra, and the pair-correlation functions are used in search of the domain structure at half-polarization.