KEMBAR78
State space search and Problem Solving techniques | PPTX
ARTIFICIAL INTELLIGENCE
PART #4
◊ Problem Spaces.
◊ State Space.
◊ Searching Techniques.
◊ Uninformed search technique.
◊ Informed search techniques.
◊ Some AI problems.
In This Video
Problem Space
Define the problem in detail is known as problem
space. There are 4 things concerned to solve a
particular problem.
 Define the problem precisely.
 Analyze the problem.
 Isolate and represent the task knowledge i.e.
required to solve the problem.
 Selection of the best problem solving technique
and apply it. Like Tower of Hanoi, 8 puzzle games.
 Set of states and the
connections between
them to represent the
problem.
 Graph is used represent
problem.
 States are represented
by nodes of the graph,
and the operators by
edges between nodes.
 For simplicity it is
represented as trees,
where the initial state
is the root of the tree.
State Space
S:{S,A,Action(s),Result(s,a),Cost(s,a)}
Where,
S: set of states like start state, goal state,
etc.
A :set of actions available.
s: an individual state from S.
Action(s): action performed on s .
a: any action from set A.
Result(s, a): An intermediate state obtain
by performing a on s.
Cost(s, a):cost of executing action a on s.
branching factor, should be minimum.
State Space Search
Problem Space of 8 puzzle
Search Strategy
A strategy is defined by picking the order of node
expansion.
 Completeness- does it always find a solution if
one exists?
 Time complexity- no. of nodes generated.
 Space complexity- max no. of nodes in memory.
 Optimality- does it always find least cost
solution?
Time and space is measured in
‘b’ – max branching factor of search tree.
‘d’- depth of least cost solution.
‘m’ – max depth of the state space may be
(infinite)
Searching
Techniques
Uninformed
/Blind search
Informed
/Heuristic search
Searching Techniques
Uninformed Search
 Also known as Blind search.
 Problems require no domain specific knowledge.
 No idea, how to obtain solution, we apply Brute
force technique (explore every possible step).
 Time consuming.
 Time/Space Complexity is more.
For e.g., Travelling salesman problem for 5 cities
needs (n-1)! Search.
 Non polynomial method.
 Provides optimal solution.
 Methods: Breath first search (BFS), Depth first
search(DFS)
Informed Search
• Also known as Heuristic
search(estimation).
• Search with information.
• Heuristic function is used to find steps of
the solution.
• Provides quick solution.
• Less Time and space complexity.
• Does not produce optimal solution.
• Perform search in exponential time.
• Methods: A*, Heuristic DFS, Best first
search.
AI PROBLEMS
• Games:Water Jug problem ,8 Queen problem, 8
Puzzle problem
• Missionaries and Cannibals ,The Monday &
Bananas problem.
• Route finding.(computer networks, airline
travel planning system)
• Layout problems (VLSI layout, furniture
layout, packaging)
• Assembly sequencing.(Assembly of electrical
motors)
• Task Scheduling.(Time tables, manufacturing)
State space search and Problem Solving techniques

State space search and Problem Solving techniques

  • 1.
  • 2.
    ◊ Problem Spaces. ◊State Space. ◊ Searching Techniques. ◊ Uninformed search technique. ◊ Informed search techniques. ◊ Some AI problems. In This Video
  • 3.
    Problem Space Define theproblem in detail is known as problem space. There are 4 things concerned to solve a particular problem.  Define the problem precisely.  Analyze the problem.  Isolate and represent the task knowledge i.e. required to solve the problem.  Selection of the best problem solving technique and apply it. Like Tower of Hanoi, 8 puzzle games.
  • 4.
     Set ofstates and the connections between them to represent the problem.  Graph is used represent problem.  States are represented by nodes of the graph, and the operators by edges between nodes.  For simplicity it is represented as trees, where the initial state is the root of the tree. State Space
  • 5.
    S:{S,A,Action(s),Result(s,a),Cost(s,a)} Where, S: set ofstates like start state, goal state, etc. A :set of actions available. s: an individual state from S. Action(s): action performed on s . a: any action from set A. Result(s, a): An intermediate state obtain by performing a on s. Cost(s, a):cost of executing action a on s. branching factor, should be minimum. State Space Search
  • 6.
  • 7.
    Search Strategy A strategyis defined by picking the order of node expansion.  Completeness- does it always find a solution if one exists?  Time complexity- no. of nodes generated.  Space complexity- max no. of nodes in memory.  Optimality- does it always find least cost solution? Time and space is measured in ‘b’ – max branching factor of search tree. ‘d’- depth of least cost solution. ‘m’ – max depth of the state space may be (infinite)
  • 8.
  • 9.
    Uninformed Search  Alsoknown as Blind search.  Problems require no domain specific knowledge.  No idea, how to obtain solution, we apply Brute force technique (explore every possible step).  Time consuming.  Time/Space Complexity is more. For e.g., Travelling salesman problem for 5 cities needs (n-1)! Search.  Non polynomial method.  Provides optimal solution.  Methods: Breath first search (BFS), Depth first search(DFS)
  • 10.
    Informed Search • Alsoknown as Heuristic search(estimation). • Search with information. • Heuristic function is used to find steps of the solution. • Provides quick solution. • Less Time and space complexity. • Does not produce optimal solution. • Perform search in exponential time. • Methods: A*, Heuristic DFS, Best first search.
  • 11.
    AI PROBLEMS • Games:WaterJug problem ,8 Queen problem, 8 Puzzle problem • Missionaries and Cannibals ,The Monday & Bananas problem. • Route finding.(computer networks, airline travel planning system) • Layout problems (VLSI layout, furniture layout, packaging) • Assembly sequencing.(Assembly of electrical motors) • Task Scheduling.(Time tables, manufacturing)