implement the first version of the ACO algorithm

aman/sys/aco/Ant.py

@@ -1,7 +1,123 @@
 #!/usr/bin/env python
 
-from aman.sys.aco.Colony import Colony
+from datetime import datetime, timedelta
+import math
+import numpy as np
+import random
+import bisect
+import itertools
 
+from aman.sys.aco.Configuration import Configuration
+from aman.sys.aco.RunwayManager import RunwayManager
+from aman.types.Inbound import Inbound
+
+# This class implements a single ant of the following paper:
+# https://sci-hub.mksa.top/10.1109/cec.2019.8790135
 class Ant:
-    def __init__(self, colony : Colony):
-        self.Colony = colony
+    def __init__(self, pheromoneTable : np.array, configuration : Configuration):
+        self.Configuration = configuration
+        self.RunwayManager = RunwayManager(self.Configuration)
+        self.InboundSelected = [ False ] * len(self.Configuration.Inbounds)
+        self.PheromoneMatrix = pheromoneTable
+        self.SequenceDelay = timedelta(seconds = 0)
+        self.Sequence = None
+
+    # Implements function (5), but adapted to the following logic:
+    # An adaption of the heuristic function is used:
+    #   - Calculates the unused runway time (time between two consecutive landings)
+    #   - Calculates a ratio between the inbound delay and the unused runway time
+    #   - Adds the current overal sequence delay to the heuristic function
+    def heuristicInformation(self, preceeding : int, current : int):
+        rwy, eta, unusedRunwayTime = self.RunwayManager.selectArrivalRunway(self.Configuration.Inbounds[current], True, self.Configuration.EarliestArrivalTime)
+        inboundDelay = eta - self.Configuration.Inbounds[current].ArrivalCandidates[rwy.Name].InitialArrivalTime
+        if 0.0 > inboundDelay.total_seconds():
+            inboundDelay = timedelta(seconds = 0)
+
+        # calculate the fraction with a mix of the unused runway time and the delay of single aircrafts
+        fraction = self.Configuration.RunwayOccupasionRatio * unusedRunwayTime.total_seconds()
+        fraction += (1.0 - self.Configuration.RunwayOccupasionRatio) * inboundDelay.total_seconds()
+        fraction += self.SequenceDelay.total_seconds()
+        fraction /= 60.0
+
+        return self.PheromoneMatrix[preceeding, current] * ((1.0 / (fraction or 1)) ** self.Configuration.Beta)
+
+    # Implements functions (3), (6)
+    def selectNextLandingIndex(self, preceedingIndex : int):
+        q = float(random.randint(0, 100)) / 100
+        weights = []
+
+        if q <= self.Configuration.PseudoRandomSelectionRate:
+            for i in range(0, len(self.InboundSelected)):
+                if False == self.InboundSelected[i]:
+                    weights.append(self.heuristicInformation(preceedingIndex, i))
+        else:
+            # roulette selection strategy
+            pheromoneScale = 0.0
+            for i in range(0, len(self.InboundSelected)):
+                if False == self.InboundSelected[i]:
+                    pheromoneScale += self.heuristicInformation(preceedingIndex, i)
+
+            # fallback
+            if 0.0 >= pheromoneScale:
+                pheromoneScale = 1.0
+
+            for i in range(0, len(self.InboundSelected)):
+                if False == self.InboundSelected[i]:
+                    weights.append(self.heuristicInformation(preceedingIndex, i) / pheromoneScale)
+
+        total = sum(weights)
+        cumdist = list(itertools.accumulate(weights)) + [total]
+        candidateIndex = bisect.bisect(cumdist, random.random() * total)
+
+        for i in range(0, len(self.InboundSelected)):
+            if False == self.InboundSelected[i]:
+                if 0 == candidateIndex:
+                    return i
+                else:
+                    candidateIndex -= 1
+
+        return None
+
+    def associateInbound(self, inbound : Inbound, earliestArrivalTime : datetime):
+        # prepare the statistics
+        rwy, eta, _ = self.RunwayManager.selectArrivalRunway(inbound, True, self.Configuration.EarliestArrivalTime)
+        eta = max(earliestArrivalTime, eta)
+
+        inbound.PlannedRunway = rwy
+        inbound.PlannedStar = inbound.ArrivalCandidates[rwy.Name].Star
+        inbound.PlannedArrivalTime = eta
+        inbound.InitialArrivalTime = inbound.ArrivalCandidates[rwy.Name].InitialArrivalTime
+        self.RunwayManager.RunwayInbounds[rwy.Name] = inbound
+
+        delay = inbound.PlannedArrivalTime - inbound.InitialArrivalTime 
+        if 0.0 < delay.total_seconds():
+            return delay
+        else:
+            return timedelta(seconds = 0)
+
+    def findSolution(self, first : int):
+        self.Sequence = []
+
+        # select the first inbound
+        self.InboundSelected[first] = True
+        self.Sequence.append(first)
+        self.SequenceDelay += self.associateInbound(self.Configuration.Inbounds[first], self.Configuration.EarliestArrivalTime)
+
+        while True:
+            index = self.selectNextLandingIndex(self.Sequence[-1])
+            if None == index:
+                break
+
+            self.InboundSelected[index] = True
+            self.SequenceDelay += self.associateInbound(self.Configuration.Inbounds[index], self.Configuration.EarliestArrivalTime)
+            self.Sequence.append(index)
+
+            # update the local pheromone
+            update = (1.0 - self.Configuration.propagationRatio) * self.PheromoneMatrix[self.Sequence[-2], self.Sequence[-1]]
+            update += self.Configuration.propagationRatio * self.Configuration.ThetaZero
+            self.PheromoneMatrix[self.Sequence[-2], self.Sequence[-1]] = max(self.Configuration.ThetaZero, update)
+
+        # validate that nothing went wrong
+        if len(self.Sequence) != len(self.Configuration.Inbounds):
+            self.SequenceDelay = None
+            self.Sequence = None