def test_lookahead_swap_higher_depth_width_is_better(self):
"""Test that lookahead swap finds better circuit with increasing search space.
Increasing the tree width and depth is expected to yield a better (or same) quality
circuit, in the form of fewer SWAPs.
"""
qr = QuantumRegister(8, name='q')
circuit = QuantumCircuit(qr)
circuit.cx(qr[0], qr[1])
circuit.cx(qr[1], qr[2])
circuit.cx(qr[2], qr[3])
circuit.cx(qr[3], qr[4])
circuit.cx(qr[4], qr[5])
circuit.cx(qr[5], qr[6])
circuit.cx(qr[6], qr[7])
circuit.cx(qr[0], qr[3])
circuit.cx(qr[6], qr[4])
circuit.cx(qr[7], qr[1])
circuit.cx(qr[4], qr[2])
circuit.cx(qr[3], qr[7])
circuit.cx(qr[5], qr[3])
circuit.cx(qr[6], qr[2])
circuit.cx(qr[2], qr[7])
circuit.cx(qr[0], qr[6])
circuit.cx(qr[5], qr[7])
original_dag = circuit_to_dag(circuit)
# Create a ring of 8 connected qubits
coupling_map = CouplingMap.from_grid(num_rows=2, num_columns=4)
mapped_dag_1 = LookaheadSwap(coupling_map,
search_depth=3,
search_width=3).run(original_dag)
mapped_dag_2 = LookaheadSwap(coupling_map,
search_depth=5,
search_width=5).run(original_dag)
num_swaps_1 = mapped_dag_1.count_ops().get('swap', 0)
num_swaps_2 = mapped_dag_2.count_ops().get('swap', 0)
self.assertLessEqual(num_swaps_2, num_swaps_1)
def test_grid_factory(self):
coupling = CouplingMap.from_grid(2, 3)
edges = coupling.get_edges()
expected = [
(0, 3),
(0, 1),
(3, 0),
(3, 4),
(1, 0),
(1, 4),
(1, 2),
(4, 1),
(4, 3),
(4, 5),
(2, 1),
(2, 5),
(5, 2),
(5, 4),
]
self.assertEqual(set(edges), set(expected))
def test_grid_factory_unidirectional(self):
coupling = CouplingMap.from_grid(2, 3, bidirectional=False)
edges = coupling.get_edges()
expected = [(0, 3), (0, 1), (3, 4), (1, 4), (1, 2), (4, 5), (2, 5)]
self.assertEqual(set(edges), set(expected))
def setup(self, size, _):
edge_len = int((2 * size + 2)**0.5) + 1
self.coupling_map = CouplingMap.from_grid(edge_len, edge_len)
self.sim_backend = QasmSimulatorPy()
self.circuit = build_ripple_adder_circuit(size)
def test_lookahead_swap_higher_depth_width_is_better(self):
"""Test that lookahead swap finds better circuit with increasing search space.
Increasing the tree width and depth is expected to yield a better (or same) quality
circuit, in the form of fewer SWAPs.
"""
# q_0: ──■───────────────────■───────────────────────────────────────────────»
# ┌─┴─┐ │ ┌───┐ »
# q_1: ┤ X ├──■──────────────┼─────────────────┤ X ├─────────────────────────»
# └───┘┌─┴─┐ │ └─┬─┘┌───┐ ┌───┐ »
# q_2: ─────┤ X ├──■─────────┼───────────────────┼──┤ X ├──────────┤ X ├──■──»
# └───┘┌─┴─┐ ┌─┴─┐ │ └─┬─┘ ┌───┐└─┬─┘ │ »
# q_3: ──────────┤ X ├──■──┤ X ├─────────────────┼────┼────■──┤ X ├──┼────┼──»
# └───┘┌─┴─┐└───┘ ┌───┐ │ │ │ └─┬─┘ │ │ »
# q_4: ───────────────┤ X ├──■────────────┤ X ├──┼────■────┼────┼────┼────┼──»
# └───┘┌─┴─┐ └─┬─┘ │ │ │ │ │ »
# q_5: ────────────────────┤ X ├──■─────────┼────┼─────────┼────■────┼────┼──»
# └───┘┌─┴─┐ │ │ │ │ │ »
# q_6: ─────────────────────────┤ X ├──■────■────┼─────────┼─────────■────┼──»
# └───┘┌─┴─┐ │ ┌─┴─┐ ┌─┴─┐»
# q_7: ──────────────────────────────┤ X ├───────■───────┤ X ├──────────┤ X ├»
# └───┘ └───┘ └───┘»
# «q_0: ──■───────
# « │
# «q_1: ──┼───────
# « │
# «q_2: ──┼───────
# « │
# «q_3: ──┼───────
# « │
# «q_4: ──┼───────
# « │
# «q_5: ──┼────■──
# « ┌─┴─┐ │
# «q_6: ┤ X ├──┼──
# « └───┘┌─┴─┐
# «q_7: ─────┤ X ├
# « └───┘
qr = QuantumRegister(8, name="q")
circuit = QuantumCircuit(qr)
circuit.cx(qr[0], qr[1])
circuit.cx(qr[1], qr[2])
circuit.cx(qr[2], qr[3])
circuit.cx(qr[3], qr[4])
circuit.cx(qr[4], qr[5])
circuit.cx(qr[5], qr[6])
circuit.cx(qr[6], qr[7])
circuit.cx(qr[0], qr[3])
circuit.cx(qr[6], qr[4])
circuit.cx(qr[7], qr[1])
circuit.cx(qr[4], qr[2])
circuit.cx(qr[3], qr[7])
circuit.cx(qr[5], qr[3])
circuit.cx(qr[6], qr[2])
circuit.cx(qr[2], qr[7])
circuit.cx(qr[0], qr[6])
circuit.cx(qr[5], qr[7])
original_dag = circuit_to_dag(circuit)
# Create a ring of 8 connected qubits
coupling_map = CouplingMap.from_grid(num_rows=2, num_columns=4)
mapped_dag_1 = LookaheadSwap(coupling_map,
search_depth=3,
search_width=3).run(original_dag)
mapped_dag_2 = LookaheadSwap(coupling_map,
search_depth=5,
search_width=5).run(original_dag)
num_swaps_1 = mapped_dag_1.count_ops().get("swap", 0)
num_swaps_2 = mapped_dag_2.count_ops().get("swap", 0)
self.assertLessEqual(num_swaps_2, num_swaps_1)
