Thanks for the tips  If my sparse matrices are in a list, do you mean something like this? :
import torch
import torch.autograd as ann


mat2 = ann.Variable(torch.rand(4, 5, 6), requires_grad=True)
mats = [ann.Variable(torch.zeros(4, 3, 5), requires_grad=True) for _ in range(3)]
for i in range(len(mats)):
    result = torch.bmm(mats[i], mat2)
    print result.size()