contract¶
full name: tenpy.algorithms.network_contractor.contract
parent module:
tenpy.algorithms.network_contractor
type: function

tenpy.algorithms.network_contractor.
contract
(tensor_list, tensor_names=None, leg_contractions=None, open_legs=None, sequence=None)[source]¶ Contract a network of tensors.
Based on the MatLab function
ncon.m
as described in arXiv:1402.0939. Parameters
tensor_list (list of
Array
) – The tensors to be contracted.leg_contractions (list of
[n1, l1, n2, l2]
) – A list of contraction instructions. An entry of leg_contractions has the form[n1, l1, n2, l2]
, wheren1, n2
are entries of tensor_names and each identify anArray
in tensor_list.l1, l2
are leg labels of the correspondingArray
. The instruction implies to contract legl1
of tensorn1
with legl2
of tensorn2
.open_legs (list of
[n1, l1, l]
) – A list of instructions for “open” (uncontracted) legs.[n1, l1, l]
implies that legl1
of tensorn1
is not contracted and is labelledl
in the result.tensor_names (list of str) – A list of names for each tensor, to be used in leg_contractions and open_legs. The default value is list(range(len(tensor_list))), so that the tensor “names” are
0, 1, 2, ...
.sequence (list of int) – The order in which the leg_contractions are to be performed. An entry of network_contractor.outer_product indicates performing an outer product. This corresponds to the zeroinsequence convention of arXiv:1304.6112
 Returns
result – The number or tensor resulting from the contraction.
 Return type
Array
 complex