tensor([[ 0.2847,  0.0000,  0.0000],
          [ 0.0000, -0.7805,  0.0000],
          [ 0.0000,  0.0000, -0.1900]], device='cuda:0')
      >>> torch.sparse.sampled_addmm(input, mat1, mat2, beta=0.5, alpha=0.5)
      tensor(crow_indices=tensor([0, 1, 2, 3]),
          col_indices=tensor([0, 1, 2]),
          values=tensor([ 0.1423, -0.3903, -0.0950]), device='cuda:0',
          size=(3, 3), nnz=3, layout=torch.sparse_csr)