t3_squash_tails

t3toolbox.backend.t3_operations.t3_squash_tails(data)

def t3_squash_tails(
        data: typ.Tuple[
            typ.Sequence[NDArray],  # tucker_cores. len=d, elm_shape=stack_shape+(ni,Ni)
            typ.Sequence[NDArray],  # tt_cores.     len=d, elm_shape=stack_shape+(rLi,ni,rR(i+1))
        ],
) -> typ.Tuple[
    typ.Tuple[NDArray, ...],  # tucker_cores, unchanged
    typ.Tuple[NDArray, ...],  # tt_cores with r0=rd=1
]:

Collapse the leading/trailing TT bonds of a T3 to one, without changing the represented tensor.

The T3-data-level twin of ut3_squash_tails() (the Tucker cores are untouched; the TT chain goes through tt_squash_tails()).

Parameters:

data (t3toolbox.backend.common.typ.Tuple[t3toolbox.backend.common.typ.Sequence[NDArray], t3toolbox.backend.common.typ.Sequence[NDArray]])

Return type:

t3toolbox.backend.common.typ.Tuple[t3toolbox.backend.common.typ.Tuple[NDArray, Ellipsis], t3toolbox.backend.common.typ.Tuple[NDArray, Ellipsis]]