ut3_sum_stack

t3toolbox.backend.ut3_linalg.ut3_sum_stack(x)

def ut3_sum_stack(x: UT3Data) -> UT3Data:  # sum over ALL stack axes -> unstacked UT3 (NOT squashed)

Sum the represented dense tensors over the whole stack (the genuine tensor sum, not a corewise sum): fold the stack S into the Tucker rank (merge) and into the TT ranks (block-diagonal over all three TT axes via three identities), and likewise reshape the masks. The frontend then squashes the tails, which performs the summation. S-fold generalization of ut3_add().

Parameters:

x (UT3Data)

Return type:

UT3Data