def find_rows(a, b):
    dt = np.dtype((np.void, a.dtype.itemsize * a.shape[1]))

    a_view = np.ascontiguousarray(a).view(dt).ravel()
    b_view = np.ascontiguousarray(b).view(dt).ravel()

    sort_b = np.argsort(b_view)
    where_in_b = np.searchsorted(b_view, a_view,
                                 sorter=sort_b)
    where_in_b = np.take(sort_b, where_in_b)
    which_in_a = np.take(b_view, where_in_b) == a_view
    where_in_b = where_in_b[which_in_a]
    which_in_a = np.nonzero(which_in_a)[0]
    return np.column_stack((which_in_a, where_in_b))