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@@ -5,6 +5,7 @@ Bidirectional_a_star 2D
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import os
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import sys
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+import math
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sys.path.append(os.path.dirname(os.path.abspath(__file__)) +
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"/../../Search-based Planning/")
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@@ -15,50 +16,51 @@ from Search_2D import env
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class BidirectionalAstar:
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- def __init__(self, x_start, x_goal, heuristic_type):
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- self.xI, self.xG = x_start, x_goal
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+ def __init__(self, s_start, s_goal, heuristic_type):
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+ self.s_start, self.s_goal = s_start, s_goal
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self.heuristic_type = heuristic_type
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- self.Env = env.Env() # class Env
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+ self.Env = env.Env() # class Env
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- self.u_set = self.Env.motions # feasible input set
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- self.obs = self.Env.obs # position of obstacles
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+ self.u_set = self.Env.motions # feasible input set
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+ self.obs = self.Env.obs # position of obstacles
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- self.g_fore = {self.xI: 0, self.xG: float("inf")} # cost to come: from x_start
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- self.g_back = {self.xG: 0, self.xI: float("inf")} # cost to come: form x_goal
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+ self.g_fore = {self.s_start: 0, self.s_goal: float("inf")} # cost to come: from s_start
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+ self.g_back = {self.s_goal: 0, self.s_start: float("inf")} # cost to come: form s_goal
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- self.OPEN_fore = queue.QueuePrior() # U set for foreward searching
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- self.OPEN_fore.put(self.xI, self.g_fore[self.xI] + self.h(self.xI, self.xG))
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- self.OPEN_back = queue.QueuePrior() # U set for backward searching
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- self.OPEN_back.put(self.xG, self.g_back[self.xG] + self.h(self.xG, self.xI))
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+ self.OPEN_fore = queue.QueuePrior() # U set for foreward searching
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+ self.OPEN_fore.put(self.s_start,
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+ self.g_fore[self.s_start] + self.h(self.s_start, self.s_goal))
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+ self.OPEN_back = queue.QueuePrior() # U set for backward searching
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+ self.OPEN_back.put(self.s_goal,
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+ self.g_back[self.s_goal] + self.h(self.s_goal, self.s_start))
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- self.CLOSED_fore = [] # CLOSED set for foreward
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- self.CLOSED_back = [] # CLOSED set for backward
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+ self.CLOSED_fore = [] # CLOSED set for foreward
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+ self.CLOSED_back = [] # CLOSED set for backward
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- self.PARENT_fore = {self.xI: self.xI}
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- self.PARENT_back = {self.xG: self.xG}
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+ self.PARENT_fore = {self.s_start: self.s_start}
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+ self.PARENT_back = {self.s_goal: self.s_goal}
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def searching(self):
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- s_meet = self.xI
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+ s_meet = self.s_start
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- while not self.OPEN_fore.empty() and not self.OPEN_back.empty():
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+ while self.OPEN_fore and self.OPEN_back:
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# solve foreward-search
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s_fore = self.OPEN_fore.get()
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+
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if s_fore in self.PARENT_back:
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s_meet = s_fore
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break
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self.CLOSED_fore.append(s_fore)
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- for u in self.u_set:
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- s_next = tuple([s_fore[i] + u[i] for i in range(2)])
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- if s_next not in self.obs:
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- new_cost = self.g_fore[s_fore] + self.get_cost(s_fore, u)
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- if s_next not in self.g_fore:
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- self.g_fore[s_next] = float("inf")
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- if new_cost < self.g_fore[s_next]:
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- self.g_fore[s_next] = new_cost
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- self.PARENT_fore[s_next] = s_fore
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- self.OPEN_fore.put(s_next, new_cost + self.h(s_next, self.xG))
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+ for s_n in self.get_neighbor(s_fore):
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+ new_cost = self.g_fore[s_fore] + self.cost(s_fore, s_n)
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+ if s_n not in self.g_fore:
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+ self.g_fore[s_n] = float("inf")
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+ if new_cost < self.g_fore[s_n]:
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+ self.g_fore[s_n] = new_cost
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+ self.PARENT_fore[s_n] = s_fore
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+ self.OPEN_fore.put(s_n, new_cost + self.h(s_n, self.s_goal))
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# solve backward-search
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s_back = self.OPEN_back.get()
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@@ -67,20 +69,40 @@ class BidirectionalAstar:
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break
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self.CLOSED_back.append(s_back)
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- for u in self.u_set:
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- s_next = tuple([s_back[i] + u[i] for i in range(len(s_back))])
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- if s_next not in self.obs:
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- new_cost = self.g_back[s_back] + self.get_cost(s_back, u)
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- if s_next not in self.g_back:
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- self.g_back[s_next] = float("inf")
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- if new_cost < self.g_back[s_next]:
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- self.g_back[s_next] = new_cost
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- self.PARENT_back[s_next] = s_back
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- self.OPEN_back.put(s_next, new_cost + self.h(s_next, self.xI))
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+ for s_n in self.get_neighbor(s_back):
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+ new_cost = self.g_back[s_back] + self.cost(s_back, s_n)
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+ if s_n not in self.g_back:
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+ self.g_back[s_n] = float("inf")
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+ if new_cost < self.g_back[s_n]:
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+ self.g_back[s_n] = new_cost
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+ self.PARENT_back[s_n] = s_back
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+ self.OPEN_back.put(s_n, new_cost + self.h(s_n, self.s_start))
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return self.extract_path(s_meet), self.CLOSED_fore, self.CLOSED_back
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+ def get_neighbor(self, s):
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+ """
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+ find neighbors of state s that not in obstacles.
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+ :param s: state
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+ :return: neighbors
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+ """
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+
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+ s_list = set()
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+
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+ for u in self.u_set:
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+ s_next = tuple([s[i] + u[i] for i in range(2)])
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+ if s_next not in self.obs:
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+ s_list.add(s_next)
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+
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+ return s_list
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+
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def extract_path(self, s_meet):
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+ """
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+ extract path from start and goal
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+ :param s_meet: meet point of bi-direction a*
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+ :return: path
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+ """
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+
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# extract path for foreward part
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path_fore = [s_meet]
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s = s_meet
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@@ -88,7 +110,7 @@ class BidirectionalAstar:
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while True:
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s = self.PARENT_fore[s]
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path_fore.append(s)
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- if s == self.xI:
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+ if s == self.s_start:
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break
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# extract path for backward part
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@@ -98,7 +120,7 @@ class BidirectionalAstar:
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while True:
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s = self.PARENT_back[s]
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path_back.append(s)
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- if s == self.xG:
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+ if s == self.s_goal:
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break
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return list(reversed(path_fore)) + list(path_back)
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@@ -115,17 +137,15 @@ class BidirectionalAstar:
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if heuristic_type == "manhattan":
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return abs(goal[0] - s[0]) + abs(goal[1] - s[1])
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- elif heuristic_type == "euclidean":
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- return ((goal[0] - s[0]) ** 2 + (goal[1] - s[1]) ** 2) ** (1 / 2)
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else:
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- print("Please choose right heuristic type!")
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+ return math.hypot(goal[0] - s[0], goal[1] - s[1])
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@staticmethod
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- def get_cost(x, u):
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+ def cost(s_start, s_goal):
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"""
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Calculate cost for this motion
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- :param x: current node
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- :param u: input
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+ :param s_start: starting node
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+ :param s_goal: end node
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:return: cost for this motion
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:note: cost function could be more complicate!
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"""
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@@ -139,10 +159,9 @@ def main():
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bastar = BidirectionalAstar(x_start, x_goal, "euclidean")
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plot = plotting.Plotting(x_start, x_goal)
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- fig_name = "Bidirectional-A*"
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path, visited_fore, visited_back = bastar.searching()
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- plot.animation_bi_astar(path, visited_fore, visited_back, fig_name) # animation
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+ plot.animation_bi_astar(path, visited_fore, visited_back, "Bidirectional-A*") # animation
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if __name__ == '__main__':
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