Seems to work for me:
import torch
from torch.autograd import Variable
i = torch.LongTensor([[0, 1, 1],
                      [2, 0, 2]])
v = torch.FloatTensor([3, 4, 5])
x = torch.sparse.FloatTensor(i, v, torch.Size([2,3])).cuda()
y = x.to_dense().t()
torch.mm(x, y)

What version of pytorch are you using?