Release 3.0.0 (#67)

* Module name changes, update notebooks and readme

* Black code formatting

* Add black to GH Actions workflow

.github/workflows/alns.yml

@@ -26,11 +26,11 @@ jobs:
           pip install poetry
           poetry install
       - name: Run tests
-        run: |
-          poetry run pytest
+        run: poetry run pytest
+      - name: Black
+        uses: psf/black@stable
       - name: Run static analysis
-        run: |
-          poetry run mypy alns
+        run: poetry run mypy alns
       - uses: codecov/codecov-action@v2
   deploy:
     needs: build

LICENSE.md

@@ -1,6 +1,6 @@
 The MIT License (MIT)
 
-Copyright (c) 2019 Niels Wouda
+Copyright (c) 2019 Niels Wouda and contributors
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

README.md

@@ -25,11 +25,11 @@ showing how the ALNS library may be used. These include:
   using a number of different operators and enhancement techniques from the 
   literature.
 
-Finally, the weight schemes and acceptance criteria notebook gives an overview
-of various options available in the `alns` package (explained below). In the
-notebook we use these different options to solve a toy 0/1-knapsack problem. The
-notebook is a good starting point for when you want to use the different schemes
-and criteria yourself. It is available [here][5].
+Finally, the features notebook gives an overview of various options available 
+in the `alns` package (explained below). In the notebook we use these different
+options to solve a toy 0/1-knapsack problem. The notebook is a good starting
+point for when you want to use different schemes, acceptance or stopping criteria 
+yourself. It is available [here][5].
 
 ## How to use
 The `alns` package exposes two classes, `ALNS` and `State`. The first
@@ -43,7 +43,7 @@ criterion_.
 ### Weight scheme
 The weight scheme determines how to select destroy and repair operators in each
 iteration of the ALNS algorithm. Several have already been implemented for you,
-in `alns.weight_schemes`:
+in `alns.weights`:
 
 - `SimpleWeights`. This weight scheme applies a convex combination of the 
    existing weight vector, and a reward given for the current candidate 
@@ -60,7 +60,7 @@ your own.
 The acceptance criterion determines the acceptance of a new solution state at
 each iteration. An overview of common acceptance criteria is given in
 [Santini et al. (2018)][3]. Several have already been implemented for you, in
-`alns.criteria`:
+`alns.accept`:
 
 - `HillClimbing`. The simplest acceptance criterion, hill-climbing solely
   accepts solutions improving the objective value.
@@ -70,8 +70,21 @@ each iteration. An overview of common acceptance criteria is given in
   scaled probability is bigger than some random number, using an
   updating temperature.
 
-Each acceptance criterion inherits from `AcceptanceCriterion`, which may
-be used to write your own.
+Each acceptance criterion inherits from `AcceptanceCriterion`, which may be used
+to write your own.
+
+### Stoppping criterion
+The stopping criterion determines when ALNS should stop iterating. Several 
+commonly used stopping criteria have already been implemented for you, in
+`alns.stop`:
+
+- `MaxIterations`. This stopping criterion stops the heuristic search after a
+  given number of iterations.
+- `MaxRuntime`. This stopping criterion stops the heuristic search after a given
+  number of seconds.
+
+Each stopping criterion inherits from `StoppingCriterion`, which may be used to
+write your own.
 
 ## References
 - Pisinger, D., and Ropke, S. (2010). Large Neighborhood Search. In M.
@@ -85,5 +98,5 @@ be used to write your own.
 [2]: https://github.com/N-Wouda/ALNS/blob/master/examples/travelling_salesman_problem.ipynb
 [3]: https://link.springer.com/article/10.1007%2Fs10732-018-9377-x
 [4]: https://github.com/N-Wouda/ALNS/blob/master/examples/cutting_stock_problem.ipynb
-[5]: https://github.com/N-Wouda/ALNS/blob/master/examples/weight_schemes_acceptance_criteria.ipynb
+[5]: https://github.com/N-Wouda/ALNS/blob/master/examples/alns_features.ipynb
 [6]: https://github.com/N-Wouda/ALNS/blob/master/examples/resource_constrained_project_scheduling_problem.ipynb

alns/ALNS.py

@@ -6,9 +6,9 @@
 from alns.Result import Result
 from alns.State import State
 from alns.Statistics import Statistics
-from alns.criteria import AcceptanceCriterion
-from alns.weight_schemes import WeightScheme
-from alns.stopping_criteria import StoppingCriterion
+from alns.accept import AcceptanceCriterion
+from alns.stop import StoppingCriterion
+from alns.weights import WeightScheme
 
 # Potential candidate solution consideration outcomes.
 _BEST = 0
@@ -22,26 +22,27 @@
 
 
 class ALNS:
-    def __init__(self, rnd_state: rnd.RandomState = rnd.RandomState()):
-        """
-        Implements the adaptive large neighbourhood search (ALNS) algorithm.
-        The implementation optimises for a minimisation problem, as explained
-        in the text by Pisinger and Røpke (2010).
-
-        Parameters
-        ----------
-        rnd_state
-            Optional random state to use for random number generation. When
-            passed, this state is used for operator selection and general
-            computations requiring random numbers. It is also passed to the
-            destroy and repair operators, as a second argument.
+    """
+    Implements the adaptive large neighbourhood search (ALNS) algorithm.
+    The implementation optimises for a minimisation problem, as explained
+    in the text by Pisinger and Røpke (2010).
+
+    Parameters
+    ----------
+    rnd_state
+        Optional random state to use for random number generation. When
+        passed, this state is used for operator selection and general
+        computations requiring random numbers. It is also passed to the
+        destroy and repair operators, as a second argument.
+
+    References
+    ----------
+    [1]: Pisinger, D., and Røpke, S. (2010). Large Neighborhood Search. In
+         M. Gendreau (Ed.), *Handbook of Metaheuristics* (2 ed., pp. 399
+         - 420). Springer.
+    """
 
-        References
-        ----------
-        [1]: Pisinger, D., and Røpke, S. (2010). Large Neighborhood Search. In
-             M. Gendreau (Ed.), *Handbook of Metaheuristics* (2 ed., pp. 399
-             - 420). Springer.
-        """
+    def __init__(self, rnd_state: rnd.RandomState = rnd.RandomState()):
         self._destroy_operators: Dict[str, _OperatorType] = {}
         self._repair_operators: Dict[str, _OperatorType] = {}
 

alns/Result.py

@@ -9,19 +9,19 @@
 
 
 class Result:
+    """
+    Stores ALNS results. An instance of this class is returned once the
+    algorithm completes.
 
-    def __init__(self, best: State, statistics: Statistics):
-        """
-        Stores ALNS results. An instance of this class is returned once the
-        algorithm completes.
+    Parameters
+    ----------
+    best
+        The best state observed during the entire iteration.
+    statistics
+        Statistics collected during iteration.
+    """
 
-        Parameters
-        ----------
-        best
-            The best state observed during the entire iteration.
-        statistics
-            Statistics collected during iteration.
-        """
+    def __init__(self, best: State, statistics: Statistics):
         self._best = best
         self._statistics = statistics
 
@@ -39,10 +39,12 @@ def statistics(self) -> Statistics:
         """
         return self._statistics
 
-    def plot_objectives(self,
-                        ax: Optional[Axes] = None,
-                        title: Optional[str] = None,
-                        **kwargs: Dict[str, Any]):
+    def plot_objectives(
+        self,
+        ax: Optional[Axes] = None,
+        title: Optional[str] = None,
+        **kwargs: Dict[str, Any]
+    ):
         """
         Plots the collected objective values at each iteration.
 
@@ -75,11 +77,13 @@ def plot_objectives(self,
 
         plt.draw_if_interactive()
 
-    def plot_operator_counts(self,
-                             fig: Optional[Figure] = None,
-                             title: Optional[str] = None,
-                             legend: Optional[List[str]] = None,
-                             **kwargs: Dict[str, Any]):
+    def plot_operator_counts(
+        self,
+        fig: Optional[Figure] = None,
+        title: Optional[str] = None,
+        legend: Optional[List[str]] = None,
+        **kwargs: Dict[str, Any]
+    ):
         """
         Plots an overview of the destroy and repair operators' performance.
 
@@ -114,17 +118,21 @@ def plot_operator_counts(self,
         if legend is None:
             legend = ["Best", "Better", "Accepted", "Rejected"]
 
-        self._plot_op_counts(d_ax,
-                             self.statistics.destroy_operator_counts,
-                             "Destroy operators",
-                             min(len(legend), 4),
-                             **kwargs)
-
-        self._plot_op_counts(r_ax,
-                             self.statistics.repair_operator_counts,
-                             "Repair operators",
-                             min(len(legend), 4),
-                             **kwargs)
+        self._plot_op_counts(
+            d_ax,
+            self.statistics.destroy_operator_counts,
+            "Destroy operators",
+            min(len(legend), 4),
+            **kwargs
+        )
+
+        self._plot_op_counts(
+            r_ax,
+            self.statistics.repair_operator_counts,
+            "Repair operators",
+            min(len(legend), 4),
+            **kwargs
+        )
 
         fig.legend(legend[:4], ncol=len(legend), loc="lower center")
 
@@ -155,7 +163,7 @@ def _plot_op_counts(ax, operator_counts, title, num_types, **kwargs):
             ax.barh(operator_names, widths, left=starts, height=0.5, **kwargs)
 
             for y, (x, label) in enumerate(zip(starts + widths / 2, widths)):
-                ax.text(x, y, str(label), ha='center', va='center')
+                ax.text(x, y, str(label), ha="center", va="center")
 
         ax.set_title(title)
         ax.set_xlabel("Iterations where operator resulted in this outcome (#)")

alns/Statistics.py

@@ -5,12 +5,12 @@
 
 
 class Statistics:
+    """
+    Statistics object that stores some iteration results. Populated by the ALNS
+    algorithm.
+    """
 
     def __init__(self):
-        """
-        Statistics object that stores some iteration results, which is
-        optionally populated by the ALNS algorithm.
-        """
         self._objectives = []
         self._runtimes = []
 

alns/criteria/AcceptanceCriterion.py → alns/accept/AcceptanceCriterion.py

@@ -11,11 +11,9 @@ class AcceptanceCriterion(ABC):
     """
 
     @abstractmethod
-    def __call__(self,
-                 rnd: RandomState,
-                 best: State,
-                 current: State,
-                 candidate: State) -> bool:
+    def __call__(
+        self, rnd: RandomState, best: State, current: State, candidate: State
+    ) -> bool:
         """
         Determines whether to accept the proposed, candidate solution based on
         this acceptance criterion and the other solution states.

alns/criteria/HillClimbing.py → alns/accept/HillClimbing.py

@@ -1,4 +1,4 @@
-from alns.criteria.AcceptanceCriterion import AcceptanceCriterion
+from alns.accept.AcceptanceCriterion import AcceptanceCriterion
 
 
 class HillClimbing(AcceptanceCriterion):

alns/accept/RecordToRecordTravel.py

@@ -0,0 +1,89 @@
+from alns.accept.AcceptanceCriterion import AcceptanceCriterion
+from alns.accept.update import update
+
+
+class RecordToRecordTravel(AcceptanceCriterion):
+    """
+    Record-to-record travel, using an updating threshold. The threshold is
+    updated as,
+
+    ``threshold = max(end_threshold, threshold - step)`` (linear)
+
+    ``threshold = max(end_threshold, step * threshold)`` (exponential)
+
+    where the initial threshold is set to ``start_threshold``.
+
+    Parameters
+    ----------
+    start_threshold
+        The initial threshold.
+    end_threshold
+        The final threshold.
+    step
+        The updating step.
+    method
+        The updating method, one of {'linear', 'exponential'}. Default
+        'linear'.
+
+    References
+    ----------
+    [1]: Santini, A., Ropke, S. & Hvattum, L.M. A comparison of acceptance
+         criteria for the adaptive large neighbourhood search metaheuristic.
+         *Journal of Heuristics* (2018) 24 (5): 783–815.
+    [2]: Dueck, G., Scheuer, T. Threshold accepting: A general purpose
+         optimization algorithm appearing superior to simulated annealing.
+         *Journal of Computational Physics* (1990) 90 (1): 161-175.
+    """
+
+    def __init__(
+        self,
+        start_threshold: float,
+        end_threshold: float,
+        step: float,
+        method: str = "linear",
+    ):
+        if start_threshold < 0 or end_threshold < 0 or step < 0:
+            raise ValueError("Thresholds must be positive.")
+
+        if start_threshold < end_threshold:
+            raise ValueError(
+                "End threshold must be bigger than start threshold."
+            )
+
+        if method == "exponential" and step > 1:
+            raise ValueError(
+                "Exponential updating cannot have explosive step parameter."
+            )
+
+        self._start_threshold = start_threshold
+        self._end_threshold = end_threshold
+        self._step = step
+        self._method = method
+
+        self._threshold = start_threshold
+
+    @property
+    def start_threshold(self) -> float:
+        return self._start_threshold
+
+    @property
+    def end_threshold(self) -> float:
+        return self._end_threshold
+
+    @property
+    def step(self) -> float:
+        return self._step
+
+    @property
+    def method(self) -> str:
+        return self._method
+
+    def __call__(self, rnd, best, current, candidate):
+        # This follows from the paper by Dueck and Scheueur (1990), p. 162.
+        result = (candidate.objective() - best.objective()) <= self._threshold
+
+        self._threshold = max(
+            self.end_threshold, update(self._threshold, self.step, self.method)
+        )
+
+        return result