137 lines
5.3 KiB
Python
137 lines
5.3 KiB
Python
# Copyright 2010-2025 Google LLC
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""Python interrupter for solves."""
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from collections.abc import Callable, Iterator
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import contextlib
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from typing import Optional
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from absl import logging
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from ortools.util.python import pybind_solve_interrupter
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class CallbackError(Exception):
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"""Exception raised when an interrupter callback fails.
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When using SolveInterrupter.interruption_callback(), this exception is raised
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when exiting the context manager if the callback failed. The error in the
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callback is the cause of this exception.
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"""
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class SolveInterrupter:
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"""Interrupter used by solvers to know when they should interrupt the solve.
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Once triggered with interrupt(), an interrupter can't be reset. It can be
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triggered from any thread.
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Thread-safety: APIs on this class are safe to call concurrently from multiple
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threads.
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Attributes:
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pybind_interrupter: The pybind wrapper around PySolveInterrupter.
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"""
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def __init__(self) -> None:
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self.pybind_interrupter = pybind_solve_interrupter.PySolveInterrupter()
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def interrupt(self) -> None:
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"""Interrupts the solve as soon as possible.
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Once requested the interruption can't be reset. The user should use a new
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SolveInterrupter for later solves.
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It is safe to call this function multiple times. Only the first call will
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have visible effects; other calls will be ignored.
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"""
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self.pybind_interrupter.interrupt()
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@property
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def interrupted(self) -> bool:
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"""True if the solve interruption has been requested."""
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return self.pybind_interrupter.interrupted
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def add_trigger_target(self, target: "SolveInterrupter") -> None:
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"""Triggers the target when this interrupter is triggered."""
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self.pybind_interrupter.add_trigger_target(target.pybind_interrupter)
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def remove_trigger_target(self, target: "SolveInterrupter") -> None:
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"""Removes the target if not null and present, else do nothing."""
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self.pybind_interrupter.remove_trigger_target(target.pybind_interrupter)
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@contextlib.contextmanager
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def interruption_callback(self, callback: Callable[[], None]) -> Iterator[None]:
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"""Returns a context manager that (un)register the provided callback.
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The callback is immediately called if the interrupter has already been
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triggered or if it is triggered during the registration. This is typically
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useful for a solver implementation so that it does not have to test
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`interrupted` to do the same thing it does in the callback. Simply
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registering the callback is enough.
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The callback function can't make calls to interruption_callback(), and
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interrupt(). This would result is a deadlock. Reading `interrupted` is fine
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though.
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Exceptions raised in the callback are raised on exit from the context
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manager if no other error happens within the context. Else the exception is
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logged.
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Args:
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callback: The callback.
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Returns:
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A context manager.
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Raises:
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CallbackError: When exiting the context manager if an exception was raised
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in the callback.
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"""
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callback_error: Optional[Exception] = None
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def protetected_callback():
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"""Calls callback() storing any exception in callback_error."""
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nonlocal callback_error
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try:
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callback()
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except Exception as e: # pylint: disable=broad-exception-caught
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# It is fine to set callback_error without any threading protection as
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# the SolveInterrupter guarantees it will only call it at most once.
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callback_error = e
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callback_id = self.pybind_interrupter.add_interruption_callback(
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protetected_callback
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)
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no_exception_in_context = False
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try:
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yield
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no_exception_in_context = True
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finally:
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self.pybind_interrupter.remove_interruption_callback(callback_id)
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# It is fine to access callback_error without threading protection after
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# remove_interruption_callback() has returned as the SolveInterrupter
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# guarantees any pending call is done and no future call can happen.
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if callback_error is not None:
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if no_exception_in_context:
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raise CallbackError() from callback_error
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# We don't want the error in the context to be masked by an error in the
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# callback. We log it instead.
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logging.error(
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"An exception occurred in callback but is masked by another"
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" exception: %s",
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repr(callback_error),
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)
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