Questions tagged [search]

For questions involving search algorithms and their use in artificial intelligence

Filter by
Sorted by
Tagged with
28
votes
4answers
895 views

How to find the optimal number of neurons per layer?

When you're writing your algorithm, how do you know how many neurons you need per single layer? Are there any methods for finding the optimal number of them, or is it a rule of thumb?
12
votes
6answers
464 views

Are methods of exhaustive search considered to be AI?

Some programs do exhaustive searches for a solution while others do heuristic searches for a similar answer. For example, in chess, the search for the best next move tends to be more exhaustive in ...
9
votes
3answers
454 views

Why teaching only search algorithms in a short introductory AI course?

I understood that the concept of search is important in AI. There's a question on this website regarding this topic, but one could also intuitively understand why. I've had an introductory course on ...
9
votes
2answers
6k views

What are the limitations of the hill climbing algorithm and how to overcome them?

What are the limitations of the hill climbing algorithm? How can we overcome these limitations?
9
votes
3answers
7k 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 ...
9
votes
4answers
2k 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?
8
votes
8answers
2k views

Why is search important in AI?

Why is search important in AI? What kinds of search algorithms are used in AI? How do they improve the result of an AI?
8
votes
2answers
132 views

What is the difference between search and learning?

I came across an article, The Bitter Truth, via the Two Minute Papers YouTube Channel. Rich Sutton says... One thing that should be learned from the bitter lesson is the great power of general ...
8
votes
2answers
106 views

Memory intensive local search methods

I have been studying local search algorithms such as greedy hill climbing, stochastic hill climbing, simulated annealing etc. I have noticed that most of these methods take up very little memory as ...
7
votes
1answer
6k 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 ...
6
votes
1answer
53 views

Can two admissable heuristics not dominate each other?

I am working on a project for my artificial intelligence class. I was wondering if I have 2 admissible heuristics, A and B, is it possible that A does not dominate B and B does not dominate A? I am ...
6
votes
2answers
559 views

Why is the larger value, as opposed to the smaller one, chosen, in the hill climbing algorithm?

In the hill climbing algorithm, the greater value, compared to the current value, is selected, but I cannot understand why it takes the larger value instead of the smaller one. Why is that? I greatly ...
6
votes
3answers
887 views

Why does Monte Carlo work when a real opponent's behavior may not be random

I am learning about Monte Carlo algorithms and struggling to understand the following: If simulations are based on random moves, how can the modeling of the opponent's behavior work well? For ...
5
votes
1answer
5k views

What is the fringe in the context of search algorithms?

What is the fringe in the context of search algorithms?
5
votes
2answers
179 views

How does A* search work given there are multiple goal states?

When I have read through the fundamentals of AI, I saw a situation (i.e., a search space) which is illustrated in the following picture. These are the heuristic estimates: ...
5
votes
1answer
567 views

Is the 'direction' considered, when determining the branching factor in bidirectional search?

If I am correct, the branching factor is the maximum number of successors of any node. When I am applying bidirectional search to a transition graph like this one below If 11 is the goal state and I ...
5
votes
3answers
738 views

Can someone help me to understand the alpha-beta pruning algorithm?

I understand the minimax algorithm, but I am unable to understand deeply the minimax algorithm with alpha-beta pruning, even after having looked up several sources (on the web) and having tried to ...
5
votes
2answers
373 views

More effective way to improve the heuristics of an AI… evolution or testing between thousands of pre-determined sets of heuristics?

I'm making a Connect Four game where my engine uses Minimax with Alpha-Beta pruning to search. Since Alpha-Beta pruning is much more effective when it looks at the best moves first (since then it can ...
5
votes
2answers
742 views

Are leaf nodes included in the calculation of average branching factor for search trees?

In the search tree below, there are 11 nodes, 5 of which are leaves. There are 10 branches. Is the average branching factor given by 10/6, or 10/11? Are leaves included in the calculation? ...
5
votes
1answer
135 views

Illustration of Von Neumann's Minimax theorem in games?

The Von Neumann's Minimax theorem gives the conditions that make the max-min inequality an equality. I understand the max-min inequality, basically ...
4
votes
2answers
1k views

How can I formulate the map colouring problem as a hill climbing search problem?

I have a map. I need to colour it with $k$ colours, such that two adjacent regions do not share a colour. How can I formulate the map colouring problem as a hill climbing search problem?
4
votes
1answer
2k views

How do I show that uniform-cost search is a special case of A*?

How do I show that uniform-cost search is a special case of A*? How do I prove this?
4
votes
1answer
2k views

How is iterative deepening A* better than A*?

The iterative deepening A* search is an algorithm that can find the shortest path between a designated start node and any member of a set of goals. The A* algorithm evaluates nodes by combining the ...
4
votes
1answer
1k views

What is the difference between local search and global search algorithms?

What is the difference between local search and global (or complete) search algorithms?
4
votes
1answer
226 views

How to create an AI to solve a word search?

This at first sounds ridiculous. Of course there is an easy way to write a program to solve a wordsearch. But what I would like to do is write a program that solves a word-search like a human. That ...
4
votes
1answer
7k views

What are the differences between A* and greedy best-first search?

What are the differences between the A* algorithm and the greedy best-first search algorithm? Which one should I use? Which algorithm is the better one, and why?
4
votes
1answer
138 views

Transposition table is only used for roughly 17% of the nodes - is this expected?

I'm making a Connect Four game using the typical minimax + alpha-beta pruning algorithms. I just implemented a Transposition Table, but my tests tell me the TT only helps 17% of the time. By this I ...
4
votes
2answers
105 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 ...
4
votes
2answers
710 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 ...
4
votes
1answer
171 views

Why is breadth search only optimal when the cost solution is a non-decreasing function?

I am learning about searching strategies in AI and I was reading that Breadth first search is only optimal when the cost solution is a non-decreasing function? I am not really sure what this refer to, ...
4
votes
1answer
1k views

How do I solve the knapsack problem using the hill climbing algorithm?

I need to solve the knapsack problem using hill climbing algorithm (I need to write a program). But I'm clueless about how to do it. My code should contain a method called ...
4
votes
1answer
74 views

How do we determine whether a heuristic 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 heuristics. Currently, I explored the Manhattan and Euclidean distances. ...
4
votes
1answer
60 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 make a tree. Is there a way to find the depth of the tree; which level is the last level?
4
votes
1answer
88 views

What is the basic purpose of local search methods?

I read about the hill climbing algorithms, the simulating annealing algorithm, but I am confused. What is the basic purpose of local search methods?
4
votes
2answers
4k 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?
4
votes
1answer
543 views

Exploration Strategies for Reinforcement Learning w/ Continuous Action Space

I'm building a deep neural network to serve as the policy estimator in an Actor-Critic reinforcement learning algorithm for a continuing (not episodic) case. I'm trying to determine how to explore ...
3
votes
2answers
2k views

What is an objective function?

Local search algorithms are useful for solving pure optimization problems, in which the aim is to find the best state according to an objective function. My question is what is the objective function ?...
3
votes
1answer
302 views

How does a google choose it's autocomplete solution

While writing a paper yesterday this strange thing happened to me. I was wrtiting it in Word, and wasn't satisfied with the repeated usage of word "relesase" in last few senteces. So I've decided to ...
3
votes
1answer
136 views

How do I find whether this heuristic is or not admissible and consistent?

I was given the following problem to solve. Given a circular trail divided by $n> 2$ segments labeled $0 \dots n-1$. In the beginning, an agent is at the start of segment number $0$ (the edge ...
3
votes
1answer
33 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 ...
3
votes
1answer
77 views

In the implementation of AI programming, does DFS always stop when it has found the leftmost solution?

I'm a fresh learner of AI. I was told that depth-first search is not an optimal searching algorithm since "it finds the 'leftmost' solution, regardless of depth or cost". Therefore, does it mean that ...
3
votes
1answer
103 views

Using graph searching to solve peg solitaire?

Problem: I've been reading research papers on how to solve a peg solitaire using graph searching, but all the papers kind of assume you know how to do the reduction(polynomial time conversion) from ...
3
votes
1answer
127 views

Why does 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 ...
3
votes
1answer
137 views

Minimax with only max

If both the players want to increase their score (by selecting the highest/best cost path) can this be done using Minimax Algorithm and not other algorithms?
3
votes
1answer
277 views

How many iterations are required for iterative-lengthening search when step costs are drawing from a continuos range [ϵ, 1]?

This is AI: A Modern Approach, 3.17c. The solution manual gives the answer as $\frac{d}{\epsilon}$, where $d$ is the depth of the shallowest goal node. Iterative lengthening search uses a path cost ...
3
votes
0answers
27 views

How to choose the weights for a linear combination of heuristic functions?

I need to write a minimax algorithm with alpha-beta pruning in limited time for the 2048 game. I know expectimax is better for this work. Assume I wrote different heuristic functions. If I want to ...
3
votes
1answer
26 views

Proof Branch and Bound 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, but I haven't been able to find a proof on ...
3
votes
2answers
476 views

What is the difference between graph search and tree search? [duplicate]

First of all, there is a lot of misunderstanding about the graph search and tree search. The difference between these two is not about graphs and trees. They have two different algorithms. You can ...
2
votes
2answers
527 views

What are examples of daily life applications that use simulated annealing?

In AIMA, 3rd Edition on Page 125, Simulated Annealing is described as: Hill-climbing algorithm that never makes “downhill” moves toward states with lower value (or higher cost) is guaranteed to be ...
2
votes
1answer
67 views

How is the cost of the path to each node computed in A*?

How is the cost of the path to each node $n$ computed in the A* algorithm? Do we need to add the cost of the path to the parent node $p$ to the cost of the path of the child node $n$?