#cumulative-sum

a @ t returns the cumulative sum tensor([1, 3, 6, 10]) (Tensor Puzzle 7). What does t @ a return?

def arange(i):
    return torch.tensor(range(i))

a = torch.tensor([1, 2, 3, 4])
t = 1 * (arange(4)[:, None] <= arange(4))   # t[r, c] = 1 if r <= c
print(a @ t)
print(t @ a)