Questions tagged [search]

For questions involving search algorithms and their use in artificial intelligence

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30 views

How do the BFS and DFS search algorithms choose between nodes with the "same priority"?

I am currently taking an Artificial Intelligence course and learning about DFS and BFS. If we take the following example: From my understanding, the BFS algorithm will explore the first level ...
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2answers
112 views

What is the proof that the branch and bound algorithm always finds optimal path in a graph?

I've been studying Branch and Bound's graph algorithm and I hear it always finds the optimal path because it uses previously found solutions to find others However, I haven't been able to find a ...
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1answer
7k views

How does the uniform-cost search algorithm work?

What is the uniform-cost search (UCS) algorithm? How does it work? I would appreciate seeing a graphical execution of the algorithm. How does the frontier evolve in the case of UCS?
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1answer
2k views

How does best-first search differ from hill-climbing?

How does best-first search differ from hill-climbing?
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1answer
63 views

What does "unknown search spaces" mean in the context of Evolutionary Algorithms?

In the article Multi-Verse Optimizer: a nature-inspired algorithm for global optimization (DOI 10.1007/s00521-015-1870-7), it's written The results of the real case studies also demonstrate the ...
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0answers
14 views

What is an efficient way to implement an contextual search for a search engine?

So I am working on a search engine and want to implement a contextual search for my search engine but would like to get some advice before I start working on it. I have a basic knowledge of A.I. like ...
2
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1answer
52 views

Agents meeting in a directed connected graph

We have a directed connected graph, where nodes are places one can go to and edges are the "roads" between places. We have K agents whose goal is to meet in one node. Agents start in ...
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0answers
11 views

Are ranking models considered discriminative?

I'm developing a model that ranks entries based on cosine similarity to a query. Since it doesn't actually define a boundary between x and y I initially believed that such ranking models are not ...
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1answer
63 views

How do I create the search tree for DFS applied to a grid map?

I have been working through some search tree problems and came across this one: Assume that that the algorithm has a closed list and that nodes are added to the frontier in the following order: Up, ...
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2answers
3k views

What is the difference between search and planning?

I'm studying Artificial Intelligence. A Modern Approach, Stuart Russell, Peter Norvig, specifically about search and planning arguments. I don't understand the difference between the two terms. I was ...
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1answer
145 views

How does the MCTS tree look like?

I have come across the Monte Carlo tree search (MCTS) algorithm, but I can't find what the tree should look like. For example, does it still represent a minimax process, i.e. player 1 from the root ...
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1answer
109 views

Determining minimal state representation for maze game

I came across this question set. It asks following question: Let’s revisit our bug friends from assignment 2. To recap, you control one or more insects in a rectangular maze-like environment with ...
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1answer
296 views

Is this ExpectiMinimax Tree correctly drawn?

I need help with ExpectiMinimax problem: Start a game. The first player flips a coin. The second player flips a coin. The first player decides if he wants to flip another coin. The second player ...
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0answers
29 views

Fine tuning a BERT model for text classification

An article written by Jay Alammar (http://jalammar.github.io/a-visual-guide-to-using-bert-for-the-first-time/) on using a BERT transformer for text classification. The article mentions the following ...
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1answer
2k views

Why does the adversarial search minimax algorithm use Depth-First Search (DFS) instead of Breadth-First Search (BFS)?

I understand that the actual algorithm calls for using Depth-First Search, but is there a functionality reason for using it over another search algorithm like Breadth-First Search?
4
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1answer
194 views

How do we find the length (depth) of the game tic-tac-toe in adversarial search?

When we perform the tic-tac-toe game using adversarial search, I know how to make a tree. Is there a way to find the depth of the tree, and which level is the last level?
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1answer
23k views

What is the difference between tree search and graph search?

I have read various answers to this question at different places, but I am still missing something. What I have understood is that a graph search holds a closed list, with all expanded nodes, so ...
13
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1answer
15k views

Why is A* optimal if the heuristic function is admissible?

A heuristic is admissible if it never overestimates the true cost to reach the goal node from $n$. If a heuristic is consistent, then the heuristic value of $n$ is never greater than the cost of its ...
2
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1answer
49 views

Is $\min(h_1(s),\ h_2(s))$ consistent?

If $h_1(s)$ is a consistent heuristic and $h_2(s)$ is a admissible heuristic, is $\min(h_1(s),\ h_2(s))$ consistent?
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2answers
4k views

If an heuristic is not admissible, can it be consistent?

I am solving a problem in which, according to the given values, the heuristic is not admissible. According to my calculation from other similar problems, it should be consistent, as well as keeping in ...
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0answers
16 views

Why is that the heuristic is not admissible, then it is not consistent [duplicate]

I don't understand why if the heuristic is not admissible then it is not consistent?
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0answers
33 views

What would happen if we set the evaluation function in the best-first search algorithm as the cost of paths taken to new nodes?

I am reading AI: A Modern Approach. In Chapter 3, Section 3.3.1, The best-first search algorithm is introduced. We learn that in each iteration, this algorithm chooses which node to expand based on ...
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1answer
59 views

Does a differential evolution algorithm mutate its population during a generation?

I'm implementing a differential evolution algorithm and when it comes to evolving a population, the page I am referencing is vague on how the new population is generated. https://en.wikipedia.org/wiki/...
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1answer
76 views

Are hill climbing variations always optimal and complete?

Are hill climbing variations (like steepest ascent hill climbing, stochastic hill climbing, random restart hill climbing, local beam search) always optimal and complete?
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2answers
128 views

Is there any situation in which breadth-first search is preferable over A*?

Is there any situation in which breadth-first search is preferable over A*?
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1answer
5k views

What is a successor function (in CSPs)?

In Constraint Satisfaction Problems (CSPs), a state is any data structure that supports a successor function, a heuristic function, and a goal test. In this context, what is a successor function?
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0answers
1k views

How to improve the efficiency of the backtracking search in CSPs?

Backtracking search is the basic uninformed search algorithm for constraint satisfaction problems (CSPs). How could we improve the efficiency of the backtracking search in CSPs?
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1answer
53 views

What are the common techniques one could use to deal with collisions in a transposition table?

Consider an iterative deepening search using a transposition table. Whenever the transposition table is full, what are common strategies applied to replace entries in the table? I'm aware of two ...
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0answers
29 views

Incorrect node expansion in game board with A* search

I have the following game board below, and we're using A* search to find the optimal path from the agent to the key. There are 8 directions. Up, down, left, right have a cost of 1, and diagonal ...
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0answers
25 views

Can an inadmissable heuristic be consistent? [duplicate]

If something is inadmissible, can we just assume it's also inconsistent? Also, I understand how to check if a heuristic is inadmissible, but I'm still a bit confused on checking consistency. If I have ...
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1answer
440 views

What is the difference between the heuristic function and the evaluation function in A*?

I am reading college notes on state search space. The notes (which are not publicly available) say: To do state-search space, the strategy involves two parts: defining a heuristic function, and ...
5
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1answer
250 views

Given an image and two points $A$ and $B$ on that image, how could we find a path from $A$ to $B$?

If we have a search or path-finding problem, A* and Dijkstra's algorithm require that we formulate it as a search in a graph with nodes and connections between these nodes. If there are obstacles, we ...
2
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1answer
193 views

How to transform a PDDL to search?

I have a question about search and planning: I still haven't understood the difference from the two, but they seem very similar to me; here is a question I am struggling with: "Having formulated a ...
5
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1answer
735 views

How do we determine whether a heuristic function is better than another?

I am trying to solve a maze puzzle using the A* algorithm. I am trying to analyze the algorithm based on different applicable heuristic functions. Currently, I explored the Manhattan and Euclidean ...
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0answers
24 views

Satisficing searches - how does speedy search compensate for higher execution costs

While reading AI: A Modern Approach (4th ed), I have some difficulty in coming to terms with the usefulness of a satisficing search. Generally speaking, I understand that in real life situations we ...
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2answers
293 views

Is a good evaluation function as good as any of the extensions of alpha-beta pruning?

I would like to know if having a really good evaluation function is as good as using any of the extensions of alpha-beta pruning, such as killer moves or quiescence search?
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1answer
114 views

How can I calculate the shortest path between two 2d vector points in an environment with obstacles?

I have a 2D plane, with a fixed height and width of 10M. The plane has an agent (or robot) in the point $(1, 2.2)$, and an electric outlet in the point $(8.2, 9.1)$. The plane has a series of ...
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0answers
27 views

How to interpret the output of alpha-beta pruning in terms of which position to play next in a game

I'm trying to understand question 4 of this paper. This is a tree pruned with alpha-beta pruning: I understand technically how this pruning worked (i.e. calculating mix/max/alpha/beta values). My ...
6
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1answer
218 views

To deal with infinite loops, should I do a deeper search of the best moves with the same value, in alpha-beta pruning?

I have implemented minimax with alpha-beta pruning to play checkers. As my value heuristic, I am using only the summation of material value on the board regardless of the position. My main issue lays ...
7
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1answer
169 views

A* is similar to Dijkstra with reduced cost

According to this Wikipedia article If the heuristic $h$ satisfies the additional condition $h(x) \leq d(x, y) + h(y)$ for every edge $(x, y)$ of the graph (where $d$ denotes the length of that edge),...
6
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1answer
3k views

What are the state space and the state transition function in AI?

I'm studying for my AI final exam, and I'm stuck in the state space representation. I understand initial and goal states, but what I don't understand is the state space and state transition function. ...
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1answer
38 views

Which "assumptions" made about the state space are Russell and Norvig referring to in their book?

I am reading the cornerstone book, "Artificial Intelligence, A Modern Approach" by Stuart Russel, and Peter Norvig, and there is a passage in the book on page 98: The complexity results ...
3
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1answer
369 views

Why does the hill climbing algorithm only produce a local maximum?

Apparently, the hill climbing algorithm just produces a local maximum, and not necessarily a global optimum. It's stuck on a local maximum. Why does hill climbing algorithm only produce a local ...
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1answer
751 views

How could we solve the TSP using a hill-climbing approach?

How could we solve the TSP using a hill-climbing approach?
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4answers
4k views

When to choose Stochastic Hill Climbing over Steepest Hill Climbing?

Stochastic Hill Climbing generally performs worse than Steepest Hill Climbing, but what are the cases in which the former performs better?
2
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1answer
95 views

When does IDA* consider the goal has been found?

I was reading about IDA* and I found this link explaining IDA* and providing an animation for it. Here is a picture of the solution. I know what is the cutoff condition (it depends on F), and the ...
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2answers
1k views

If uniform cost search is used for bidirectional search, is it guaranteed the solution is optimal?

If uniform cost search is used for both the forward and backward search in bidirectional search, is it guaranteed the solution is optimal?
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3answers
5k views

What heuristic to use when doing A* search with multiple targets? [closed]

Usually, using the Manhattan distance as a heuristic function is enough when we do an A* search with one target. However, it seems like for multiple goals, this is not the most useful way. Which ...
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0answers
54 views

Why do we use the tree-search version of breadth-first search or A*?

In Artificial Intelligence A Modern Approach, search algorithms are divided into tree-search version and graph-search version, where the graph-search version keeps an extra explored set to avoid ...
2
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1answer
566 views

What is the difference between the uniform-cost search and Dijkstra's algorithm?

Every computer science student (including myself, when I was doing my bachelor's in CS) probably encountered the famous single-source shortest path Dijkstra's algorithm (DA). If you also took an ...