Implement greedy solution. Reaches 35/80, 56 needed to pass.
This commit is contained in:
204
facility/facility.py
Executable file
204
facility/facility.py
Executable file
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#!/usr/bin/env python3
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import math
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from collections import namedtuple
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Point = namedtuple("Point", ['x', 'y'])
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Facility = namedtuple("Facility", ['index', 'setup_cost', 'capacity', 'location'])
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Customer = namedtuple("Customer", ['index', 'demand', 'location'])
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class Solution(object):
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def __init__(self, facilities, customers):
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self.facilities = facilities
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self.customers = customers
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self.cost = 0
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self.facility_connected_customers = [set() for _ in facilities]
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self.facility_remaining_capacity = [f.capacity for f in facilities]
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self.customer_to_facility = [None for _ in customers]
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def connect(self, customer_index, facility_index):
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customer = self.customers[customer_index]
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facility = self.facilities[facility_index]
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# If customers is already connected handle disconnect properly.
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if (connected_facitlity_index := self.customer_to_facility[customer_index]):
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self.disconnect(customer_index, connected_facitlity_index)
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# If facility is currently not used we have to set it up.
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if not self.facility_connected_customers[facility_index]:
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self.cost += facility.setup_cost
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self.facility_connected_customers[facility_index].add(customer_index)
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if self.facility_remaining_capacity[facility_index] < customer.demand:
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raise Exception(f"Cannot connect {customer} to {facility}.")
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self.facility_remaining_capacity[facility_index] -= customer.demand
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self.customer_to_facility[customer_index] = facility_index
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self.cost += length(facility.location, customer.location)
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def disconnect(self, customer_index, facility_index):
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customer = self.customers[customer_index]
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facility = self.facilities[facility_index]
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self.cost -= length(facility.location, customer.location)
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self.facility_connected_customers[facility_index].remove(customer_index)
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self.facility_remaining_capacity[facility_index] += customer.demand
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self.customer_to_facility[customer_index] = None
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if not self.facility_connected_customers[facility_index]:
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self.cost -= self.facilities[facility_index].setup_cost
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def get_feasible_facilities(self, customer_index):
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customer = self.customers[customer_index]
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facility_indices = [f.index
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for f in self.facilities
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if self.facility_remaining_capacity[f.index] >= customer.demand]
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if not facility_indices:
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raise Exception("No feasible facilities.")
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def key(facility_index):
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cost = 0
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facility = self.facilities[facility_index]
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# If there are customers yet we have to open it.
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if not self.facility_connected_customers[facility_index]:
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cost += facility.setup_cost
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cost += length(customer.location, facility.location)
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return cost
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facility_indices.sort(key=key)
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return facility_indices
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def is_valid(self):
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for customer in self.customers:
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if self.customer_to_facility[customer.index] is None:
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raise Exception(f"{customer} not connected.")
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for facility in self.facilities:
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if self.facility_remaining_capacity[facility.index] < 0:
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raise Exception(f"{facility} exceeds capacity.")
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cost = sum([f.setup_cost
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for f in self.facilities
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if self.facility_connected_customers[f.index]])
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for customer in self.customers:
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facility = self.facilities[self.customer_to_facility[customer.index]]
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cost += length(facility.location, customer.location)
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if abs(cost - self.cost) > 0.00001:
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raise Exception(f"Running cost {self.cost} unequal to actual cost {cost}.")
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return True
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def plot_map(self):
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try:
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import matplotlib.pyplot as plt
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import matplotlib.lines as lines
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except ModuleNotFoundError:
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return
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figure = plt.figure()
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for f in self.facilities:
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x, y = f.location
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color = 'ro' if self.facility_connected_customers[f.index] else 'go'
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plt.plot(x, y, color)
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rem_cap = self.facility_remaining_capacity[f.index]
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plt.text(x, y, f" F({f.index}, {f.setup_cost}, {rem_cap}/{f.capacity})")
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for c in self.customers:
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x, y = c.location
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plt.plot(x, y, 'bx')
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plt.text(x, y, f" C({c.index}, {c.demand})")
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if (f_index := self.customer_to_facility[c.index]) is not None:
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f = self.facilities[f_index]
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x_f, y_f = f.location
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plt.plot([x, x_f], [y, y_f], 'b-')
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plt.show()
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def get_facilities_by_customers(self):
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facility_indices = [f.index for f in self.facilities
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if self.facility_connected_customers[f.index]]
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def key(facility_index):
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return len(self.facility_connected_customers[facility_index])
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facility_indices.sort(key=key)
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return facility_indices
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def to_output_data(self):
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# calculate the cost of the solution
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self.is_valid()
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obj = self.cost
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# prepare the solution in the specified output format
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output_data = '%.2f' % obj + ' ' + str(0) + '\n'
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output_data += ' '.join(map(str, self.customer_to_facility))
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return output_data
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def length(point1, point2):
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return math.sqrt((point1.x - point2.x)**2 + (point1.y - point2.y)**2)
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def build_trivial_solution(solution):
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# build a trivial solution
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# pack the facilities one by one until all the customers are served
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facility_index = 0
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for customer in solution.customers:
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if solution.facility_remaining_capacity[facility_index] >= customer.demand:
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solution.connect(customer.index, facility_index)
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else:
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facility_index += 1
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solution.connect(customer.index, facility_index)
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return solution
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def build_greedy_solution(solution):
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for customer in solution.customers:
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facility_index = solution.get_feasible_facilities(customer.index)[0]
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solution.connect(customer.index, facility_index)
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return solution
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def solve_it(input_data):
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facilities, customers = parse(input_data)
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solution = Solution(facilities, customers)
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build_greedy_solution(solution)
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solution.plot_map()
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output_data = solution.to_output_data()
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return output_data
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def main():
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file_location = "data/fl_3_1"
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with open(file_location, 'r') as input_data_file:
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input_data = input_data_file.read()
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print(solve_it(input_data))
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def parse(input_data):
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# parse the input
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lines = input_data.split('\n')
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parts = lines[0].split()
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facility_count = int(parts[0])
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customer_count = int(parts[1])
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facilities = []
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for i in range(1, facility_count+1):
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parts = lines[i].split()
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facilities.append(Facility(i-1, float(parts[0]), int(parts[1]),
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Point(float(parts[2]), float(parts[3])) ))
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customers = []
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for i in range(facility_count+1, facility_count+1+customer_count):
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parts = lines[i].split()
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customers.append(Customer(i-1-facility_count, int(parts[0]),
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Point(float(parts[1]), float(parts[2]))))
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return facilities, customers
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if __name__ == "__main__":
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main()
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