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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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.
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2023/2024
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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)
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!
b
Cost-Sensitive Search
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Uniform Cost Search
Uniform Cost Search
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q c G
a
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