# Copyright 2018 The Cirq Developers
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""An optimization pass that removes operations with tiny effects."""
from typing import TYPE_CHECKING
from cirq import protocols
from cirq.circuits import optimization_pass, circuit as _circuit
if TYPE_CHECKING:
# pylint: disable=unused-import
from typing import List, Tuple
from cirq import ops
[docs]class DropNegligible(optimization_pass.OptimizationPass):
"""An optimization pass that removes operations with tiny effects."""
[docs] def __init__(self, tolerance: float = 1e-8) -> None:
self.tolerance = tolerance
[docs] def optimize_circuit(self, circuit: _circuit.Circuit) -> None:
deletions = [] # type: List[Tuple[int, ops.Operation]]
for moment_index, moment in enumerate(circuit):
for op in moment.operations:
if (op is not None and
protocols.trace_distance_bound(op) <= self.tolerance):
deletions.append((moment_index, op))
circuit.batch_remove(deletions)