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:
“Yet I doubt not through the ages one increasing purpose runs,
And the thoughts of men are widened with the process of the suns.”
—Alfred Tennyson (1809–1892)
“Science is a dynamic undertaking directed to lowering the degree of the empiricism involved in solving problems; or, if you prefer, science is a process of fabricating a web of interconnected concepts and conceptual schemes arising from experiments and observations and fruitful of further experiments and observations.”
—James Conant (1893–1978)
“Thinking is seeing.... Every human science is based on deduction, which is a slow process of seeing by which we work up from the effect to the cause; or, in a wider sense, all poetry like every work of art proceeds from a swift vision of things.”
—Honoré De Balzac (1799–1850)