  We solve the Hubbard model with the exact diagonalization method on a
graphics processing unit (GPU). We benchmark our GPU program against a
sequential CPU code by using the Lanczos algorithm to solve the ground state
energy in two cases: a one-dimensional ring and a two-dimensional square
lattice. In the one-dimensional case, we obtain speedups of over 100 and 60 in
single and double precision arithmetic, respectively. In the two-dimensional
case, the corresponding speedups are over 110 and 70.
