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Artificial Intelligence: Search Algorithms, Lecture notes of Refrigeration and Air Conditioning

An overview of various search algorithms used in artificial intelligence, including depth-first search (dfs), breadth-first search (bfs), uniform cost search (ucs), and a* search. It covers the key concepts, strategies, and properties of these algorithms, as well as their implementation details. The document also discusses the importance of heuristics in informed search algorithms like a* and the optimality guarantees of a* under certain conditions. The content is suitable for university-level courses in artificial intelligence, computer science, or related fields, and could be useful for students as study notes, lecture notes, or exam preparation material.

Typology: Lecture notes

2023/2024

Uploaded on 03/21/2024

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CSS 382: Artificial Intelligence!
Search Continued
Instructor: Roger Stanev, Ph.D.
University of Washington Bothell
(slides adapted from Anca Dragan, Dan Klein, Pieter Abbeel and others from Berkeley)
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Download Artificial Intelligence: Search Algorithms and more Lecture notes Refrigeration and Air Conditioning in PDF only on Docsity!

CSS 382: Artificial Intelligence!

Search Continued

Instructor: Roger Stanev, Ph.D.

University of Washington Bothell

(slides adapted from Anca Dragan, Dan Klein, Pieter Abbeel and others from Berkeley)

Recap: Search

Depth-First Search

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Strategy: expand a

deepest node first

Implementation:

Fringe is a LIFO stack

Breadth-First (Tree) Search

Iterative Deepening

o Idea: get DFS’s space advantage with

BFS’s time / shallow-solution

advantages

o Run a DFS with depth limit 1. If no

solution…

o Run a DFS with depth limit 2. If no

solution…

o Run a DFS with depth limit 3. …..

o Isn’t that wastefully redundant?

o Generally most work happens in the lowest

level searched, so not so bad!

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Cost-Sensitive Search

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Uniform Cost Search

Uniform Cost Search

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Strategy: expand a

cheapest node first:

Fringe is a priority queue

(priority: cumulative cost)

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Cost

contours

Uniform Cost Issues

o Remember: UCS explores increasing

cost contours

o The good: UCS is complete and

optimal!

o The bad:

o Explores options in every “direction”

o No information about goal location

o We’ll fix that soon!

Start Goal

c ≤ 3

c ≤ 2

c ≤ 1

[Demo: empty grid UCS (L2D5)]

[Demo: maze with deep/shallow

water DFS/BFS/UCS (L2D7)]

Video of Demo Empty UCS

Video of Demo Maze with Deep/Shallow Water --- DFS, BFS, or UCS? (part

Video of Demo Maze with Deep/Shallow Water --- DFS, BFS, or UCS? (part

The One Queue

o All these search algorithms are

the same except for fringe

strategies

o Conceptually, all fringes are priority

queues (i.e. collections of nodes

with attached priorities)

o Practically, for DFS and BFS, you

can avoid overhead from an actual

priority queue, by using stacks and

queues

o Can even code one implementation

that takes a variable queuing object

Up next: Informed Search

o Uninformed Search

o DFS

o BFS

o UCS

▪ Informed Search

▪ Heuristics

▪ Greedy Search

▪ A* Search

▪ Graph Search