Questions tagged [a-star-search]

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Should your heuristic for an A* search algorithm be the same scale as your actual weights?

I'm a bit confused about the scale of heuristics for implementing A* search. $f(n)$ is the total cost of travelling to a node $n$. It is calculated by $f(n) = g(n) + h(n)$. $g(n)$ is the cost of the ...
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A* search tree version - Can a node be in the frontier multiple times

I took an exam today and it had a question on A* tree search version, we only briefly skimmed over this on the material, focusing more on the graph search version. In the example in the question text ...
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What's the best way to combine multiple A* searches?

I have a graph that looks like this The highlights nodes must be visited, and the blue node must be visited last, the stickman must be the start of the path. The weights are the Euclidean distance ...
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1answer
62 views

Using A* path finding is giving me inaccurate results

So i am using A* path finding to find a path from a person, to a node on a graph. This person has a few 'must pass' nodes that they must go through. So my solution was to run the algorithm for each of ...
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43 views

Pseudocode for A-star algorithm removes nodes from the currentList which are not in the list

I am trying to implement A star algorithm with Python. I am trying with this pseudocode found on Medium: ...
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1answer
93 views

Are there graphs for which A* cannot be admissible?

Wikipedia states that "On infinite graphs with a finite branching factor and edge costs that are bounded away from zero $ (d(x,y)>\varepsilon >0$ for some fixed $\varepsilon$), A* is guaranteed ...
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0answers
32 views

Finding multiple paths through a grid such that every grid square is equally used

Setup Here’s the setup: I have an $N$ x $N$ grid of tiles, and a list of $M$ agents that need to move across the grid. Each agent has its own start tile $S(a)$, end tile $E(a)$, and an exact number ...
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1answer
28 views

Why doesn't A* give the optimal path for navigating from A to R in this state space?

Well, I have heard that the A* algorithm is optimal and complete. However, when trying to navigate from A to R using A*, it outputs the path, A --> E --> R, although there is a shorter path, A --> M --...
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0answers
2k views

Comparing classical tree-search algorithms (BFS,DFS,A*,IDS) - when to use one or the other?

I have a question about classical tree-search algorithms as I will have an exam soon and this is the type of questions they might be asking. Although I know how to compare the complexities, optimality,...
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2answers
329 views

Coefficients in cost function in A-star

I'd like to expand on this question : https://stackoverflow.com/questions/52420788/why-does-the-a-star-algorithm-need-gn Dijkstra's algorithm uses cost function $f(n) = g(n)$ whereas A* uses cost ...
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1answer
109 views

Can Dijkstra's algorithm outperform A star, in terms of vertices checked?

I know Dijkstra's algorithm can be seen as a specific case of A star, when the estimation heuristic used simply returns 0, so I know that A star with this specific heuristic can not check more ...
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2answers
622 views

A* without heuristic more efficient than Dijkstra

I am using the module networkx to operate on graphs made from OpenStreetMap. I wanted to compare the shortest path algorithm to ...
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2answers
48 views

cheap multi agent path planning algorithms

I am trying to make a tower defence game where some critters are trying to make their ways through a 2D grid-like obstacle course. The idea is these critters cannot walk into the obstacles or into ...
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0answers
49 views

Heuristic for searching for solutions on an 8-puzzle variant with non-unique tiles

I'm trying to perform an A* search on a particular N-puzzle variant in which some tiles are identical. More specifically, assuming an $m \times m$ grid, there are m colors with m tiles of each. The ...
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358 views

How can an A* algorithm visit all nodes?

Is it possible to find the shortest path and visit all the nodes in a graph by A* algorithm? If yes, how?
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1answer
31 views

Term for an A*-like pathfinding strategy where only the heuristic goal distance matters

I am trying to find a proper term for the A*-like best-first pathfinding strategy where the node to expand next is the one with the least estimated distance from the goal, regardless of its distance ...
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2answers
227 views

Does an optimal path imply the heuristic is admissible?

If we are given an A$^*$ path search with some heuristic $h$ that yields an optimal path, without knowing that the heuristic is admissible beforehand, would this imply that $h$ is admissible?