Source code for qiskit.transpiler.passes.optimization.commutation_analysis

# This code is part of Qiskit.
# (C) Copyright IBM 2017, 2018.
# This code is licensed under the Apache License, Version 2.0. You may
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"""Analysis pass to find commutation relations between DAG nodes."""

from collections import defaultdict

from qiskit.dagcircuit import DAGOpNode
from qiskit.transpiler.basepasses import AnalysisPass
from qiskit.circuit.commutation_checker import CommutationChecker

[docs]class CommutationAnalysis(AnalysisPass): """Analysis pass to find commutation relations between DAG nodes. Property_set['commutation_set'] is a dictionary that describes the commutation relations on a given wire, all the gates on a wire are grouped into a set of gates that commute. TODO: the current pass determines commutativity through matrix multiplication. A rule-based analysis would be potentially faster, but more limited. """ def __init__(self): super().__init__() self.comm_checker = CommutationChecker()
[docs] def run(self, dag): """Run the CommutationAnalysis pass on `dag`. Run the pass on the DAG, and write the discovered commutation relations into the property_set. """ # Initiate the commutation set self.property_set["commutation_set"] = defaultdict(list) # Build a dictionary to keep track of the gates on each qubit # The key with format (wire) will store the lists of commutation sets # The key with format (node, wire) will store the index of the commutation set # on the specified wire, thus, for example: # self.property_set['commutation_set'][wire][(node, wire)] will give the # commutation set that contains node. for wire in dag.wires: self.property_set["commutation_set"][wire] = [] # Add edges to the dictionary for each qubit for node in dag.topological_op_nodes(): for (_, _, edge_wire) in dag.edges(node): self.property_set["commutation_set"][(node, edge_wire)] = -1 # Construct the commutation set for wire in dag.wires: for current_gate in dag.nodes_on_wire(wire): current_comm_set = self.property_set["commutation_set"][wire] if not current_comm_set: current_comm_set.append([current_gate]) if current_gate not in current_comm_set[-1]: prev_gate = current_comm_set[-1][-1] does_commute = False if isinstance(current_gate, DAGOpNode) and isinstance(prev_gate, DAGOpNode): does_commute = self.comm_checker.commute( current_gate.op, current_gate.qargs, current_gate.cargs, prev_gate.op, prev_gate.qargs, prev_gate.cargs, ) if does_commute: current_comm_set[-1].append(current_gate) else: current_comm_set.append([current_gate]) temp_len = len(current_comm_set) self.property_set["commutation_set"][(current_gate, wire)] = temp_len - 1