Process
Like all informed search algorithms, it first searches the routes that appear to be most likely to lead towards the goal. What sets A* apart from a greedy best-first search is that it also takes the distance already traveled into account; the part of the heuristic is the cost from the starting point, not simply the local cost from the previously expanded node.
Starting with the initial node, it maintains a priority queue of nodes to be traversed, known as the open set. The lower for a given node, the higher its priority. At each step of the algorithm, the node with the lowest value is removed from the queue, the and values of its neighbors are updated accordingly, and these neighbors are added to the queue. The algorithm continues until a goal node has a lower value than any node in the queue (or until the queue is empty). (Goal nodes may be passed over multiple times if there remain other nodes with lower values, as they may lead to a shorter path to a goal.) The value of the goal is then the length of the shortest path, since at the goal is zero in an admissible heuristic. If the actual shortest path is desired, the algorithm may also update each neighbor with its immediate predecessor in the best path found so far; this information can then be used to reconstruct the path by working backwards from the goal node. Additionally, if the heuristic is monotonic (or consistent, see below), a closed set of nodes already traversed may be used to make the search more efficient.
Read more about this topic: A* Search Algorithm
Famous quotes containing the word process:
“... geometry became a symbol for human relations, except that it was better, because in geometry things never go bad. If certain things occur, if certain lines meet, an angle is born. You cannot fail. It’s not going to fail; it is eternal. I found in rules of mathematics a peace and a trust that I could not place in human beings. This sublimation was total and remained total. Thus, I’m able to avoid or manipulate or process pain.”
—Louise Bourgeois (b. 1911)
“A man had better starve at once than lose his innocence in the process of getting his bread.”
—Henry David Thoreau (1817–1862)
“The moralist and the revolutionary are constantly undermining one another. Marx exploded a hundred tons of dynamite beneath the moralist position, and we are still living in the echo of that tremendous crash. But already, somewhere or other, the sappers are at work and fresh dynamite is being tamped in place to blow Marx at the moon. Then Marx, or somebody like him, will come back with yet more dynamite, and so the process continues, to an end we cannot foresee.”
—George Orwell (1903–1950)