实现A *算法的正确方法是什么?我们是否更新closedSet中的节点?

问题描述

正如我在A *算法(A-star算法)中一样,我们将节点保留在两个列表中:一个优先级队列和一个规则数组。优先级队列称为openSet,另一个队列称为closedSet。

'openSet'包含我们要访问的节点,closedSet是我们已经访问过的节点。

这是实现A *算法的伪代码

openSet.add(startNode)
while not openSet.empty():
    currentNode = openSet.get()
  
    if currentNode == targetNode: # This is to stop searching when target is found
        break
    
    closedSet.add(currentNode)


    for neighborNode in currentNode.neighbors:
        if neighborNode not in openSet and not in closedSet:
            neighborNode.prevIoUsNode = currentNode   #building a path from currentNode to neighbor node
            neighborNode.g = currentNode.g + adjecentEdge.weight
            neighborNode.h = heuristic(neighborNode,targetNode)
            neighborNode.f = neighborNode.g + neighborNode.h
            openSet.add(neighborNode)
        else if neighborNode.g > currentNode.g + adjecentEdge.weight:
            neighborNode.prevIoUsNode = currentNode   #building a path from currentNode to neighbor node
            neighborNode.g = currentNode.g + adjecentEdge.weight
            neighborNode.h = heuristic(neighborNode,targetNode)
            neighborNode.f = neighborNode.g + neighborNode.h
                #Should I remove this part or not?
                if neighborNode in closedSet:
                    closedSet.remove(neighborNode)
                    openSet.add(neighborNode)


return getPath(startNode,targetNode)

在此代码中,我会更新节点以降低成本,更新是否是closedSet中的节点,如果它是closedSet中的节点,则将其从closedSet中删除并将其添加到openSet中。

我们是否使用A *算法更新closedSet中的节点?

我确实在Python中实现了这两种方法,但都找到了最短的路径。

当我不更新closedSet中的节点时,它会在我的图形中更快地找到路径,但这可能只是一些巧合。

这是另一个代码,根本不会更新closedSet中的节点:

这是实现A *算法的伪代码

openSet.add(startNode)
while not openSet.empty():
    currentNode = openSet.get()
  
    if currentNode == targetNode: # This is to stop searching when target is found
        break
    
    closedSet.add(currentNode)


    for neighborNode in currentNode.neighbors:
        if neighborNode not in openSet and not in closedSet:
            neighborNode.prevIoUsNode = currentNode   #building a path from currentNode to neighbor node
            neighborNode.g = currentNode.g + adjecentEdge.weight
            neighborNode.h = heuristic(neighborNode,targetNode)
            neighborNode.f = neighborNode.g + neighborNode.h
            openSet.add(neighborNode)
        else if neighborNode not in closedSet and neighborNode.g > currentNode.g + adjecentEdge.weight:
            neighborNode.prevIoUsNode = currentNode   #building a path from currentNode to neighbor node
            neighborNode.g = currentNode.g + adjecentEdge.weight
            neighborNode.h = heuristic(neighborNode,targetNode)
            neighborNode.f = neighborNode.g + neighborNode.h

return getPath(startNode,targetNode)

在实施A *算法时,我们是否更新closedSet中的节点?

如果我们更新closedSet中的节点,是否将它们再次添加到openSet中?

解决方法

如果启发式为consistent,则无需更新封闭集中的节点。如果试探法是admissible不一致一致,则可能需要更新封闭集中的节点。

大多数现实世界中的启发式方法是一致的,因此在实施A *的大部分时间中,该算法的那部分是不必要的,并且从速度上来说根本没有实现。