z i=6SrSSKrSSKrSSKrSSKrSSKJr SSKJr SSK J r SSK J r SSK Jr SSKJr SS KJr \R&"\5r\R,"S S 5r\R,"S S SS9r"SS\5rSrSrSSjrSrSrSrSr Sr!g)zAMap input circuit onto a backend topology via insertion of SWAPs.N)SwapGate)TransformationPass)TranspilerError)Layout) DAGOpNode)Target)disjoint_utils_Step)state swaps_added gates_mappedgates_remaining _SystemState)layout coupling_mapregisterswapsN)defaultsc6^\rSrSrSrSU4SjjrSrSrU=r$) LookaheadSwap2aPMap input circuit onto a backend topology via insertion of SWAPs. Implementation of Sven Jandura's swap mapper submission for the 2018 Qiskit Developer Challenge, adapted to integrate into the transpiler architecture. The role of the swapper pass is to modify the starting circuit to be compatible with the target device's topology (the set of two-qubit gates available on the hardware.) To do this, the pass will insert SWAP gates to relocate the virtual qubits for each upcoming gate onto a set of coupled physical qubits. However, as SWAP gates are particularly lossy, the goal is to accomplish this remapping while introducing the fewest possible additional SWAPs. This algorithm searches through the available combinations of SWAP gates by means of a narrowed best first/beam search, described as follows: - Start with a layout of virtual qubits onto physical qubits. - Find any gates in the input circuit which can be performed with the current layout and mark them as mapped. - For all possible SWAP gates, calculate the layout that would result from their application and rank them according to the distance of the resulting layout over upcoming gates (see _calc_layout_distance.) - For the four (search_width) highest-ranking SWAPs, repeat the above process on the layout that would be generated if they were applied. - Repeat this process down to a depth of four (search_depth) SWAPs away from the initial layout, for a total of 256 (search_width^search_depth) prospective layouts. - Choose the layout which maximizes the number of two-qubit which could be performed. Add its mapped gates, including the SWAPs generated, to the output circuit. - Repeat the above until all gates from the initial circuit are mapped. For more details on the algorithm, see Sven's blog post: https://medium.com/qiskit/improving-a-quantum-compiler-48410d7a7084 c>[TU]5 [U[5(a&XlURR 5UlO SUlXlX lX0lX@l g)a|LookaheadSwap initializer. Args: coupling_map (Union[CouplingMap, Target]): CouplingMap of the target backend. search_depth (int): lookahead tree depth when ranking best SWAP options. search_width (int): lookahead tree width when ranking best SWAP options. fake_run (bool): if true, it will only pretend to do routing, i.e., no swap is effectively added. N) super__init__ isinstancertargetbuild_coupling_mapr search_depth search_widthfake_run)selfrrr r! __class__s i/home/james-whalen/.local/lib/python3.13/site-packages/qiskit/transpiler/passes/routing/lookahead_swap.pyrLookaheadSwap.__init__VsU  lF + +&K $ > > @D DK , (( cURc [S5e[UR5S:wdURR SS5c [S5e[URR 5n[UR 5U:a%[S[UR 5SUS35e[R"XRc URO UR5 URSn[[R"U5URU5n/n[UR55nU(a[R!S [U55 [#UUUR$UR&5nUc [S 5e[R!S [UR(5UR*5 UR,nUR(nUR.nUR1U5 U(aMUR2S cUR4UR2S 'O@UR2S R7UR4UR 5UR2S 'UR8(aU$UR;5n UH3n U R=U R>U R@U RBS S9 M5 U $)aTRun the LookaheadSwap 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 in the property_set. Raises: TranspilerError: if the coupling map or the layout are not compatible with the DAG, or if the coupling_map=None Nz/LookaheadSwap cannot run with coupling_map=Noneqz-Lookahead swap runs on physical circuits onlyzThe number of DAG qubits (z9) is greater than the number of available device qubits (z).z+Top-level routing step: %d gates remaining.zLLookahead failed to find a swap which mapped gates or improved layout score.z2Found best step: mapped %d gates. Added swaps: %s. final_layoutF)check)"rrlenqregsgetphysical_qubitsqubitsr $require_layout_isolated_to_componentrrrgenerate_trivial_layoutlist serial_layersloggerdebug_search_forward_n_swapsrr r r r rextend property_setrcomposer!copy_empty_likeapply_operation_backopqargscargs) r"dagnumber_of_available_qubitsr current_state mapped_gatesr best_stepr mapped_dagnodes r$runLookaheadSwap.runlsz    $!"ST T syy>Q #))--T":"B!"QR R%():):)J)J%K" szz?7 7!,S_,=>,,F+GrK  ;; kk&9""t{{ 99S>$  * *8 4d6G6G  s0023 LLFOH\ ]/!!!! I %b LLDI**+%%  &OOM$11L'77O    -3o6   ^ , 40=0D0DD  n - 150A0A.0Q0Y0Y$$cjj1D  n - ==J((*  D  + +DGGTZZSX + Y!r&)rr!rr r)rIF) __name__ __module__ __qualname____firstlineno____doc__rrG__static_attributes__ __classcell__)r#s@r$rr2s!F!,SSr&rc ^^TRcETRTRR5VVs1sHupEXE:aXE4OXT4iM snnS9m[ TT5upg[ T/Xg5nU(aUS:XaU$[ UU4SjTR5SS9n [RSUU SUS-V V V s/sH upoU 4PM sn n n 5 SS[R*pn [U 5Hunupn[UXrS - U5nUcM[U5nUU:a+[RS UU /UR-U5 U UUpn U[U[!U 5S - 5:dMxUcM}[!UR"5U:dR[!UR$5[!U5:d0['UR$UR(5['UU5:dM O g[+U T5n[ UR(U /UR-UU-UR"-UR$5n[RS UUR5 U$s snnfs sn n n f) abSearch for SWAPs which allow for application of largest number of gates. Args: state (_SystemState): The ``namedtuple`` collection containing the state of the physical system. This includes the current layout, the coupling map, the canonical register and the possible swaps available. gates (list): Gates to be mapped. depth (int): Number of SWAP layers to search before choosing a result. width (int): Number of SWAPs to consider at each layer. Returns: Optional(_Step): Describes the solution step found. If ``None``, no swaps leading to an improvement were found. N)rrc3>># UHn[UTT5v M g7fr)_score_state_with_swap).0swapgatesr s r$ *_search_forward_n_swaps..sL  eU 3 3 sc US$)Nr)xs r$)_search_forward_n_swaps..sadr&)keyz*At depth %d, ranked candidate swaps: %s...r(z0At depth %d, updating best step: %s (score: %f).zAt depth %d, best_swap set: %s.)r_replacer get_edges_map_free_gatesr sortedr5r6mathinf enumerater7 _score_stepr minr,r r_calc_layout_distancer _swap_ops_from_edge)r rVdepthwidthabr r base_step ranked_swapsscorerU_ best_swaprD best_scorerank new_state next_step next_scorebest_swap_gateouts`` r$r7r7sO {{=B=O=O=Y=Y=[\=[TQaeQF!/=[\ %4E5$A!LeR?I eqjL L L LL4 -9+EAI-FG-F>5-FG (,TDHH9*I&/ &=""q +IPQ SXY    +  " LLB...   04Y *I Cs<0145 5%I**+e3y001C4HH))*C*CY__U+OYGH C'>F(E:N   i+++~% (>(>>!!  C  LL2E3??K JA] Hs I <Ic[5n/n/nURRnUGH`nUS(dx[US5RnU(dM/UR U5(a#UR U5 URU5 O[X`5nURU5 MUSSnUR U5(a$UR U5 URU5 M[U5S:Xa[X`5nURU5 MURRXWSXWS5S:Xa[X`5nURU5 GM>UR U5 URU5 GMc X44$)aMap all gates that can be executed with the current layout. Args: state (_SystemState): The physical characteristics of the system, including its current layout and the coupling map. gates (list): Gates to be mapped. Returns: tuple: mapped_gates (list): ops for gates that can be executed, mapped onto layout. remaining_gates (list): gates that cannot be executed on the layout. partitiongraphrr() setr_v2p_first_op_noder> intersectionupdateappend_transform_gate_for_systemr,rdistance) r rVblocked_qubitsrCremaining_gates layout_mapgater0 mapped_gates r$rbrbseUNLO""JK #DM288F**622%%f-&&t,8E ##K0 k"1%  & &v . .  ! !& )  " "4 ( [A 4TAK    ,    ( (1I)> RS9@U VZ[ [4TAK    ,  ! !& )  " "4 (=@  ((r&c8Uc%SS[URR5--nURRnSnUSUHPnUS(dMUSSn[U5S:XdM(XARR X6SX6S5- nMR U$)zsReturn the sum of the distances of two-qubit pairs in each CNOT in gates according to the layout and the coupling. Nr rr|r_r()r,rr/rrr)rVr max_gatesrrzrr0s r$ririLsc%"4"4"D"DEEE ""J Cjy!K k"1% v;!  %%..z)/DjXYQZF[\ \C " Jr&cURR5nUR"U6 URUS9n[ X$5X4$)zCalculate the relative score for a given SWAP. Returns: float: the score of the given swap. Tuple[int, int]: the input swap that should be performed. _SystemState: an updated system state with the new layout contained. )r)rcopyrUr`ri)rUr rV trial_layoutrvs r$rSrS^sD<<$$&Ltl3I  2D CCr&c[URVs/sH n[UR5S:XdMUPM" sn5S[UR5-- $s snf)zACount the mapped two-qubit gates, less the number of added SWAPs.r_)r,r r>r )stepgs r$rgrglsM 4,,B,aAGG 0A,B Ca#dN^N^J_F_ __Bs AAc^^[R"[US55nURmURRm[ UU4SjUR 55UlU$)z6Return op implementing a virtual gate on given layout.r}c34># UH nTTUv M g7frrZ)rTrm device_qregrs r$rW-_transform_gate_for_system..xs ZEYZ]!;EYs)rrrrrtupler>)rr mapped_op_noderrs @@r$rrrsQYY~d7m<=N..K""J Z^EYEY ZZN r&cn^URm[U4SjU55n[[5USS9/$)zDGenerate list of ops to implement a SWAP gate along a coupling edge.c3.># UH nTUv M g7frrZ)rTirs r$rW&_swap_ops_from_edge..s3dk!ndsrZ)r=r>r?)rrrr)edger qreg_edgers @r$rjrj}s2..K3d33I 9B ? @@r&cB[SUR555$)z!Get the first op node from a DAG.c3T# UHn[U[5(dMUv M g7fr)rr)rTrFs r$rW!_first_op_node..sL 40Ks( ()nextnodes)r@s r$rrs LL LLr&)"rN collectionsrloggingrd%qiskit.circuit.library.standard_gatesrqiskit.transpiler.basepassesrqiskit.transpiler.exceptionsrqiskit.transpiler.layoutrqiskit.dagcircuitrqiskit.transpiler.targetrqiskit.transpiler.passes.layoutr getLoggerrJr5 namedtupler rrr7rbrirSrgrrjrrZr&r$rsH  :;8+'+:   8 $ w(cd%%3   M&M`Qh3)l$ D` AMr&