function benchmark_minpoly_integers()
  print("benchmark_minpoly_integers ... ")
  M = matrix_space(ZZ, 80, 80)()

  for i in 1:40
    for j in 1:40
      r = rand(-20:20)
      M[i, j] = r
      M[40 + i, 40 + j] = deepcopy(r)
    end
  end

  for i in 1:10
    similarity!(M, rand(1:80), ZZRingElem(rand(-3:3)))
  end

  tt = @elapsed minpoly(polynomial_ring(ZZ, "x")[1], M)
  println("$tt")
end

