Why is torch.mm non deterministic?

Hi, sorry to open this issue again, but I am still not completely clear as to why torch.mm is non deterministic. I understand that there are some backend cuda operations that are non deterministic, but a matrix multiply must be deterministic right? Other wise if I do AB where A and B are matrices, and I do the same operation again, I will get 2 different results which does not make sense?
Am I missing some crucial point here? Please let me know and thanks again for your time.