z i.SrSSKrSSKrSSKrSSKJr SSKJr SSKJ r SSK J r J r SSK Jr SSKJr SS KJr SS KJrJrJrJr SS KJr \R4"\5r"S S \5rg)z@Routing via SWAP insertion using the SABRE method from Li et al.N)TransformationPass)TranspilerError)Layout)Target _FakeTarget) CouplingMap)disjoint_utils)default_num_processes) sabre_routing Heuristic SetScaling RoutingTarget)NLayoutc~^\rSrSrSrSU4Sjjr\RS5r\RS5r Sr Sr U=r $) SabreSwap!aMap input circuit onto a backend topology via insertion of SWAPs. Implementation of the SWAP-based heuristic search from the SABRE qubit mapping paper [2] (Algorithm 1) with the modifications from the LightSABRE paper [1]. The heuristic aims to minimize the number of lossy SWAPs inserted and the depth of the circuit. This algorithm starts from an initial layout of virtual qubits onto physical qubits, and iterates over the circuit DAG until all gates are exhausted, inserting SWAPs along the way. It only considers 2-qubit gates as only those are germane for the mapping problem (it is assumed that 3+ qubit gates are already decomposed). In each iteration, it will first check if there are any gates in the ``front_layer`` that can be directly applied. If so, it will apply them and remove them from ``front_layer``, and replenish that layer with new gates if possible. Otherwise, it will try to search for SWAPs, insert the SWAPs, and update the mapping. The search for SWAPs is restricted, in the sense that we only consider physical qubits in the neighborhood of those qubits involved in ``front_layer``. These give rise to a ``swap_candidate_list`` which is scored according to some heuristic cost function. The best SWAP is implemented and ``current_layout`` updated. This transpiler pass adds onto the SABRE algorithm in that it will run multiple trials of the algorithm with different seeds. The best output, determined by the trial with the least amount of SWAPed inserted, will be selected from the random trials. **References:** [1] Henry Zou and Matthew Treinish and Kevin Hartman and Alexander Ivrii and Jake Lishman. "LightSABRE: A Lightweight and Enhanced SABRE Algorithm" `arXiv:2409.08368 `__ [2] Li, Gushu, Yufei Ding, and Yuan Xie. "Tackling the qubit mapping problem for NISQ-era quantum devices." ASPLOS 2019. `arXiv:1809.02573 `_ cz>[TU]5 SUl[U[5(a[U[ 5(dXlONUcSUlOC[U[ 5(aUR5OUn[R"SS/US9UlX l X0l Uc [5OUUl X@l g)a SabreSwap initializer. Args: coupling_map (Union[CouplingMap, Target]): CouplingMap of the target backend. heuristic (str): The type of heuristic to use when deciding best swap strategy ('basic' or 'lookahead' or 'decay'). seed (int): random seed used to tie-break among candidate swaps. fake_run (bool): if true, it only pretend to do routing, i.e., no swap is effectively added. trials (int): The number of seed trials to run sabre with. These will be run in parallel (unless the PassManager is already running in parallel). If not specified this defaults to the number of physical CPUs on the local system. For reproducible results it is recommended that you set this explicitly, as the output will be deterministic for a fixed number of trials. Raises: TranspilerError: If the specified heuristic is not valid. Additional Information: The search space of possible SWAPs on physical qubits is explored by assigning a score to the layout that would result from each SWAP. The goodness of a layout is evaluated based on how viable it makes the remaining virtual gates that must be applied. A few heuristic cost functions are supported - 'basic': The sum of distances for corresponding physical qubits of interacting virtual qubits in the front_layer. .. math:: H_{basic} = \sum_{gate \in F} D[\pi(gate.q_1)][\pi(gate.q2)] - 'lookahead': This is the sum of two costs: first is the same as the basic cost. Second is the basic cost but now evaluated for the extended set as well (i.e. :math:`|E|` number of upcoming successors to gates in front_layer F). This is weighted by some amount EXTENDED_SET_WEIGHT (W) to signify that upcoming gates are less important that the front_layer. .. math:: H_{decay}=\frac{1}{\left|{F}\right|}\sum_{gate \in F} D[\pi(gate.q_1)][\pi(gate.q2)] + W*\frac{1}{\left|{E}\right|} \sum_{gate \in E} D[\pi(gate.q_1)][\pi(gate.q2)] - 'decay': This is the same as 'lookahead', but the whole cost is multiplied by a decay factor. This increases the cost if the SWAP that generated the trial layout was recently used (i.e. it penalizes increase in depth). .. math:: H_{decay} = max(decay(SWAP.q_1), decay(SWAP.q_2)) { \frac{1}{\left|{F}\right|} \sum_{gate \in F} D[\pi(gate.q_1)][\pi(gate.q2)]\\ + W *\frac{1}{\left|{E}\right|} \sum_{gate \in E} D[\pi(gate.q_1)][\pi(gate.q2)] } Nucx) basis_gates coupling_map)super__init___routing_target isinstancerrtargetbuild_coupling_mapfrom_configuration heuristicseedr trialsfake_run)selfrrr r"r! __class__s e/home/james-whalen/.local/lib/python3.13/site-packages/qiskit/transpiler/passes/routing/sabre_swap.pyrSabreSwap.__init__Js~ # lF + +J|[4Y4Y&K  !DKlK88//1!  !33 $KlDK# 17+-V  cTURcS$URR5$N)rdistance_matrixr#s r% dist_matrixSabreSwap.dist_matrixs)++3t_9M9M9]9]9__r'cfURcS$[URR55$r))rr coupling_listr+s r%rSabreSwap.coupling_maps8 ##+  T11??AB r'cURc [S5eURc%[R"UR5Ul[ UR 5S:wdUR RSS5c [S5e[ UR5nURRnX#:a[SUSUS35eX#:a[S US US 35e[UR[5(aURnGOURS :Xa+[S U-S9RS[R5nOURS:XaJ[S U-S9RS[R 5R#SS[R5nOURS:XaZ[S U-S9RS[R 5R#SS[R5R%SS5nO[SURS35e[&R("XR5 [*R,"U5n[.R0"5n[3XRXEUR4UR65up[.R0"5n[8R;SX- 5 [=U5V s/sH#n UR?URAU 55PM% n n [C[E[GURU 555n URHS=n cU OU RKXR5URHS'U$s sn f)a5Run the SabreSwap pass on `dag`. Args: dag (DAGCircuit): the directed acyclic graph to be mapped. Returns: DAGCircuit: A dag mapped to be compatible with the coupling_map. Raises: TranspilerError: if the coupling map or the layout are not compatible with the DAG, or if the coupling_map=None Nz+SabreSwap cannot run with coupling_map=Noneqz*Sabre swap runs on physical circuits only.zFewer qubits in the circuit (z) than the coupling map (z). Have you run a layout pass and then expanded your DAG with ancillas? See `FullAncillaAllocation`, `EnlargeWithAncilla` and `ApplyLayout`.zMore qubits in the circuit (z&) than available in the coupling map (z0). This circuit cannot be routed to this device.basic ) attempt_limitg? lookaheadg?decaygMbP?z Heuristic z not recognized.z.Sabre swap algorithm execution complete in: %s final_layout)&rrrr from_targetlenqregsgetqubits num_qubitsrrr with_basicr SizeConstantwith_lookahead with_decayr $require_layout_isolated_to_componentrgenerate_trivial_layouttime perf_counterr r!r LOGdebugrangevirtual_to_physicalphysical_to_virtualrdictzip property_setcompose) r#dagnum_dag_qubitsnum_coupling_qubitsrinitial_layout sabre_startr; sabre_stopi permutationlayoutprevs r%run SabreSwap.runs ;; !"OP P    '#0#<#Q #))--T":"B!"NO OSZZ"kk44  /!//?@()*XX   /!.~.>?()*AA  dnni 0 0I ^^w &!^0CDOOZ__I^^{ *^(;<C!4!45R9  ^^w &^(;<C!4!45R9E1% "Jt~~.>>N"OP P;;CM 88H'') ) %%y$++tyy &&(  BJD\]>* *  , ,^-O-OPQ-R S*  S[9:;)).99B  fjj1 .)  s*M/)rr"rr rr!)r4NFN) __name__ __module__ __qualname____firstlineno____doc__r functoolscached_propertyr,rr^__static_attributes__ __classcell__)r$s@r%rr!sR&PU!n``  OOr'r)rdreloggingrIqiskit.transpiler.basepassesrqiskit.transpiler.exceptionsrqiskit.transpiler.layoutrqiskit.transpiler.targetrrqiskit.transpiler.couplingrqiskit.transpiler.passes.layoutr qiskit.utilsr qiskit._accelerate.sabrer r r rqiskit._accelerate.nlayoutr getLoggerr`rKrr'r%rusQG ;8+82:.XX. !]"]r'