Download presentation

Presentation is loading. Please wait.

Published byMalcolm Walton Modified over 2 years ago

1
Properties of breadth-first search Complete? Yes (if b is finite) Time? 1+b+b 2 +b 3 +… +b d + b(b d -1) = O(b d+1 ) Space? O(b d+1 ) (keeps every node in memory) Optimal? Yes (if cost = 1 per step) Space is the bigger problem (more than time)

2
Uniform-cost search Expand least-cost unexpanded node Implementation: –fringe = queue ordered by path cost Equivalent to breadth-first if step costs all equal Complete? Yes, if step cost ≥ ε Time? # of nodes with g ≤ cost of optimal solution, O(b ceiling(C*/ ε) ) where C * is the cost of the optimal solution Space? # of nodes with g ≤ cost of optimal solution, O(b ceiling(C*/ ε) ) Optimal? Yes – nodes expanded in increasing order of g(n)

3
Properties of depth-first search Complete? No: fails in infinite-depth spaces, spaces with loops –Modify to avoid repeated states along path complete in finite spaces Time? O(b m ): terrible if m is much larger than d – but if solutions are dense, may be much faster than breadth-first Space? O(bm), i.e., linear space! Optimal? No

4
Summary of algorithms

5
Properties of greedy best-first search Complete? No – can get stuck in loops, e.g., Iasi Neamt Iasi Neamt Time? O(b m ), but a good heuristic can give dramatic improvement Space? O(b m ) -- keeps all nodes in memory Optimal? No

6
Properties of A* Complete? Yes (unless there are infinitely many nodes with f ≤ f(G) ) Time? Exponential Space? Keeps all nodes in memory Optimal? Yes

Similar presentations

OK

Uninformed search strategies A search strategy is defined by picking the order of node expansion Uninformed search strategies use only the information.

Uninformed search strategies A search strategy is defined by picking the order of node expansion Uninformed search strategies use only the information.

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on self awareness theory Ppt on physical features of india for class 9th Ppt on operator overloading in c++ Ppt on earthquake for class 10 Ppt on mammals and egg laying animals called Ppt on biped robots Ppt on unemployment in india free download Ppt on asian continent pictures Ppt on arunachal pradesh cultured Free ppt on brain machine interface invasive