/
trivial_layout.py
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/
trivial_layout.py
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# -*- coding: utf-8 -*-
# This code is part of Qiskit.
#
# (C) Copyright IBM 2017, 2018.
#
# This code is licensed under the Apache License, Version 2.0. You may
# obtain a copy of this license in the LICENSE.txt file in the root directory
# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
#
# Any modifications or derivative works of this code must retain this
# copyright notice, and modified files need to carry a notice indicating
# that they have been altered from the originals.
"""Choose a Layout by assigning ``n`` circuit qubits to device qubits ``0, .., n-1``."""
from qiskit.transpiler.layout import Layout
from qiskit.transpiler.basepasses import AnalysisPass
from qiskit.transpiler.exceptions import TranspilerError
class TrivialLayout(AnalysisPass):
"""Choose a Layout by assigning ``n`` circuit qubits to device qubits ``0, .., n-1``.
A pass for choosing a Layout of a circuit onto a Coupling graph, using a simple
round-robin order.
This pass associates a physical qubit (int) to each virtual qubit
of the circuit (Qubit) in increasing order.
Does not assume any ancilla.
"""
def __init__(self, coupling_map):
"""TrivialLayout initializer.
Args:
coupling_map (Coupling): directed graph representing a coupling map.
Raises:
TranspilerError: if invalid options
"""
super().__init__()
self.coupling_map = coupling_map
def run(self, dag):
"""Run the TrivialLayout pass on `dag`.
Args:
dag (DAGCircuit): DAG to find layout for.
Raises:
TranspilerError: if dag wider than self.coupling_map
"""
num_dag_qubits = sum([qreg.size for qreg in dag.qregs.values()])
if num_dag_qubits > self.coupling_map.size():
raise TranspilerError('Number of qubits greater than device.')
self.property_set['layout'] = Layout.generate_trivial_layout(*dag.qregs.values())