multi_hueristic_astar.py

import heapq
import numpy as np


class PriorityQueue:
	def __init__(self):
		self.elements = []
		self.set = set()

	def minkey(self):
		if not self.empty():
			return self.elements[0][0]
		else:
			return float('inf')

	def empty(self):
		return len(self.elements) == 0

	def put(self, item, priority):
		if item not in self.set:
			heapq.heappush(self.elements, (priority, item))
			self.set.add(item)
		else:
			# update
			# print("update", item)
			temp = []
			(pri, x) = heapq.heappop(self.elements)
			while x != item:
				temp.append((pri, x))
				(pri, x) = heapq.heappop(self.elements)
			temp.append((priority, item))
			for (pro, xxx) in temp:
				heapq.heappush(self.elements, (pro, xxx))

	def remove_element(self, item):
		if item in self.set:
			self.set.remove(item)
			temp = []
			(pro, x) = heapq.heappop(self.elements)
			while x != item:
				temp.append((pro, x))
				(pro, x) = heapq.heappop(self.elements)
			for (prito, yyy) in temp:
				heapq.heappush(self.elements, (prito, yyy))

	def top_show(self):
		return self.elements[0][1]

	def get(self):
		(priority, item) = heapq.heappop(self.elements)
		self.set.remove(item)
		return (priority, item)

def consistent_hueristic(P, goal):
	# euclidean distance
	a = np.array(P)
	b = np.array(goal)
	return np.linalg.norm(a - b)

def hueristic_2(P, goal):
	# integer division by time variable
	return consistent_hueristic(P, goal) // t

def hueristic_1(P, goal):
	# manhattan distance
	return abs(P[0] - goal[0]) + abs(P[1] - goal[1])

def key(start, i, goal, g_function):
	ans = g_function[start] + W1 * hueristics[i](start, goal)
	return ans

def do_something(back_pointer, goal, start):
	grid = np.chararray((n, n))
	for i in range(n):
		for j in range(n):
			grid[i][j] = '*'

	for i in range(n):
		for j in range(n):
			if (j, (n-1)-i) in blocks:
				grid[i][j] = "#"

	grid[0][(n-1)] = "-"
	x = back_pointer[goal]
	while x != start:
		(x_c, y_c) = x
		# print(x)
		grid[(n-1)-y_c][x_c] = "-"
		x = back_pointer[x]
	grid[(n-1)][0] = "-"


	for i in range(n):
		for j in range(n):
			if (i, j) == (0, n-1):
				print(grid[i][j], end=' ')
				print("<-- End position", end=' ')
			else:
				print(grid[i][j], end=' ')
		print()
	print("^")
	print("Start position")
	print()
	print("# is an obstacle")
	print("- is the path taken by algorithm")
	print("PATH TAKEN BY THE ALGORITHM IS:-")
	x = back_pointer[goal]
	while x != start:
		print(x, end=' ')
		x = back_pointer[x]
	print(x)
	quit()

def valid(p):
	if p[0] < 0 or p[0] > n-1:
		return False
	if p[1] < 0 or p[1] > n-1:
		return False
	return True

def expand_state(s, j, visited, g_function, close_list_anchor, close_list_inad,  open_list, back_pointer):
	for itera in range(n_hueristic):
		open_list[itera].remove_element(s)
	# print("s", s)
	# print("j", j)
	(x, y) = s
	left = (x-1, y)
	right = (x+1, y)
	up = (x, y+1)
	down = (x, y-1)

	for neighbours in [left, right, up, down]:
		if neighbours not in blocks:
			if valid(neighbours) and neighbours not in visited:
				# print("neighbour", neighbours)
				visited.add(neighbours)
				back_pointer[neighbours] = -1
				g_function[neighbours] = float('inf')

			if valid(neighbours) and g_function[neighbours] > g_function[s] + 1:
				g_function[neighbours] = g_function[s] + 1
				back_pointer[neighbours] = s
				if neighbours not in close_list_anchor:
					open_list[0].put(neighbours, key(neighbours, 0, goal, g_function))
					if neighbours not in close_list_inad:
						for var in range(1,n_hueristic):
							if key(neighbours, var, goal, g_function) <= W2 * key(neighbours, 0, goal, g_function):
								# print("why not plssssssssss")
								open_list[j].put(neighbours, key(neighbours, var, goal, g_function))


	# print

def make_common_ground():
	some_list = []
	# block 1
	for x in range(1, 5):
		for y in range(1, 6):
			some_list.append((x, y))

	# line
	for x in range(15, 20):
		some_list.append((x, 17))

	# block 2 big
	for x in range(10, 19):
		for y in range(1, 15):
			some_list.append((x, y))

	# L block
	for x in range(1, 4):
		for y in range(12, 19):
			some_list.append((x, y))
	for x in range(3, 13):
		for y in range(16, 19):
			some_list.append((x, y))
	return some_list

hueristics = {0: consistent_hueristic, 1: hueristic_1, 2: hueristic_2}

blocks_blk = [(0, 1),(1, 1),(2, 1),(3, 1),(4, 1),(5, 1),(6, 1),(7, 1),(8, 1),(9, 1),(10, 1),(11, 1),(12, 1),(13, 1),(14, 1),(15, 1),(16, 1),(17, 1),(18, 1), (19, 1)]
blocks_no = []
blocks_all = make_common_ground()




blocks = blocks_blk
# hyper parameters
W1 = 1
W2 = 1
n = 20
n_hueristic = 3 # one consistent and two other inconsistent

# start and end destination
start = (0, 0)
goal = (n-1, n-1)

t = 1
def multi_a_star(start, goal, n_hueristic):
	g_function = {start: 0, goal: float('inf')}
	back_pointer = {start:-1, goal:-1}
	open_list = []
	visited = set()

	for i in range(n_hueristic):
		open_list.append(PriorityQueue())
		open_list[i].put(start, key(start, i, goal, g_function))

	close_list_anchor = []
	close_list_inad = []
	while open_list[0].minkey() < float('inf'):
		for i in range(1, n_hueristic):
			# print("i", i)
			# print(open_list[0].minkey(), open_list[i].minkey())
			if open_list[i].minkey() <= W2 * open_list[0].minkey():
				global t
				t += 1
				# print("less prio")
				if g_function[goal] <= open_list[i].minkey():
					if g_function[goal] < float('inf'):
						do_something(back_pointer, goal, start)
				else:
					_, get_s = open_list[i].top_show()
					visited.add(get_s)
					expand_state(get_s, i, visited, g_function, close_list_anchor, close_list_inad, open_list, back_pointer)
					close_list_inad.append(get_s)
			else:
				# print("more prio")
				if g_function[goal] <= open_list[0].minkey():
					if g_function[goal] < float('inf'):
						do_something(back_pointer, goal, start)
				else:
					# print("hoolla")
					get_s = open_list[0].top_show()
					visited.add(get_s)
					expand_state(get_s, 0, visited, g_function, close_list_anchor, close_list_inad, open_list, back_pointer)
					close_list_anchor.append(get_s)
	print("No path found to goal")
	print()
	for i in range(n-1,-1, -1):
		for j in range(n):
			if (j, i) in blocks:
				print('#', end=' ')
			elif (j, i) in back_pointer:
				if (j, i) == (n-1, n-1):
					print('*', end=' ')
				else:
					print('-', end=' ')
			else:
				print('*', end=' ')
			if (j, i) == (n-1, n-1):
				print('<-- End position', end=' ')
		print()
	print("^")
	print("Start position")
	print()
	print("# is an obstacle")
	print("- is the path taken by algorithm")


if __name__ == "__main__":
    multi_a_star(start, goal, n_hueristic)