Solving Problems by Searching 4 Problem solving agent

Solving Problems by Searching 제 4주 강의

Problem solving agent • What to do by finding sequences of actions that lead to desirable states • the current state (environment), applicable operations, nest states • Find a sequence of states maximizing the performance measure

Problem solving • Goal formulation • Problem formulation : : the process of deciding what actions and states to consider • Missionary-carnival problem, 청소하 는 로봇, 교육하는 시스템 등에 적용 • Sequence, solution

Formulating Problems • Amounts of knowledge that an agent can have concerning its actions and the state that it is in depends on the how the agent is connected to its environment through its percepts and actions

Knowledge and problem type (cont. ) • Contingency problem : : : Exact prediction is impossible Solving this problem requires sensing during the execution phase; Keep eyes open while walking or driving Agents need to act before founding a guaranteed plan Interleaving of search and execution

Knowledge and problem type (cont. ) • Exploration problem No information about the effects of its actions a strange country with no map The agent must experiment, gradually discovering what its action and what sorts of states exists Reinforcement learning

Well-defined problems and solutions operation new state Successor function Initial state operation select a state new state goal test state space path, solution, path cost (g)

Measuring problem-solving performance • Effectiveness of a search Does it find a solution ? Is it a good solution ? What is the search cost associated with the time and memory to find a solution ?

Example Problems • The 8(16)-puzzle problems 5 4 1 6 1 8 7 3 2 2 8 7 3 4 6 5

문제 정의(8 puzzle) • <States, Operators, Goal test, Path cost> • Solving as search : : : Breadth first, Depth-first • Heuristics • 16 puzzle

8 Queens problem • Goal test : : : 8 queens on board, none attacked • Path cost : : : zero • States : : : any arrangement of 0 to 8 queens on board • Operators : : : add a queen to any square • Branch and Bound, Dynamic Programming • AI techniques

Cryptarithmetic • FORTY 29785 + TEN 850 ------SIXTY 31418 (F=2, O=9, R=7, etc. )

Other toy problems • Missionary and cannibals • Water jug

Real world problems • • • Route finding Travelling salesperson problem VLSI design Robot navigation Assembly sequencing