trí tuệ nhân tạo cao hoàng trứ chương ter2 problems and search sinhvienzone com

om nh Vi en Zo ne C Problems and Search Si Chapter SinhVienZone.com https://fb.com/sinhvienzonevn ne Zo Search strategies C State space search nh Vi en Problem characteristics Design of search programs Si • • • • om Outline Cao Hoang Tru CSE Faculty - HCMUT SinhVienZone.com 13 February, 2009 https://fb.com/sinhvienzonevn om State Space Search Si nh Vi en Zo ne C Problem solving = Searching for a goal state Cao Hoang Tru CSE Faculty - HCMUT SinhVienZone.com 13 February, 2009 https://fb.com/sinhvienzonevn om State Space Search: Playing Chess Zo ne C • Each position can be described by an 8-by-8 array • Initial position is the game opening position • Goal position is any position in which the opponent nh Vi en does not have a legal move and his or her king is under attack • Legal moves can be described by a set of rules: Si − Left sides are matched against the current state − Right sides describe the new resulting state Cao Hoang Tru CSE Faculty - HCMUT SinhVienZone.com 13 February, 2009 https://fb.com/sinhvienzonevn om State Space Search: Playing Chess Zo ne C • State space is a set of legal positions • Starting at the initial state another nh Vi en • Using the set of rules to move from one state to Si • Attempting to end up in a goal state Cao Hoang Tru CSE Faculty - HCMUT SinhVienZone.com 13 February, 2009 https://fb.com/sinhvienzonevn om State Space Search: Water Jug Problem Si nh Vi en Zo ne C “You are given two jugs, a 4-litre one and a 3-litre one Neither has any measuring markers on it There is a pump that can be used to fill the jugs with water How can you get exactly litres of water into 4-litre jug.” Cao Hoang Tru CSE Faculty - HCMUT SinhVienZone.com 13 February, 2009 https://fb.com/sinhvienzonevn om State Space Search: Water Jug Problem y = 0, 1, 2, nh Vi en • Start state: (0, 0) Zo x = 0, 1, 2, 3, or ne C • State: (x, y) Si • Goal state: (2, n) for any n • Attempting to end up in a goal state Cao Hoang Tru CSE Faculty - HCMUT SinhVienZone.com 13 February, 2009 https://fb.com/sinhvienzonevn (x, y) if x > Cao Hoang Tru CSE Faculty - HCMUT SinhVienZone.com C Zo Si (x, y) if y > → (x, 3) nh Vi en (x, y) if y < → (4, y) ne (x, y) if x < om State Space Search: Water Jug Problem → (x − d, y) → (x, y − d) 13 February, 2009 https://fb.com/sinhvienzonevn .C Zo → (x, 0) nh Vi en (x, y) if y > → (0, y) ne (x, y) if x > om State Space Search: Water Jug Problem (x, y) → (4, y − (4 − x)) if x + y ≥ 4, y > Si (x, y) → (x − (3 − y), 3) if x + y ≥ 3, x > Cao Hoang Tru CSE Faculty - HCMUT SinhVienZone.com 13 February, 2009 https://fb.com/sinhvienzonevn ne C (x, y) → (x + y, 0) if x + y ≤ 4, y > om State Space Search: Water Jug Problem nh Vi en Zo 10 (x, y) → (0, x + y) if x + y ≤ 3, x > 12 (2, y) → (2, 0) Si 11 (0, 2) Cao Hoang Tru CSE Faculty - HCMUT SinhVienZone.com → (0, y) 10 13 February, 2009 https://fb.com/sinhvienzonevn om Is the universe predictable? Si nh Vi en Certain outcome! Zo ne C The 8-Puzzle Every time we make a move, we know exactly what will happen Cao Hoang Tru CSE Faculty - HCMUT SinhVienZone.com 36 13 February, 2009 https://fb.com/sinhvienzonevn om Is the universe predictable? Si nh Vi en Uncertain outcome! Zo ne C Playing Bridge We cannot know exactly where all the cards are or what the other players will on their turns Cao Hoang Tru CSE Faculty - HCMUT SinhVienZone.com 37 13 February, 2009 https://fb.com/sinhvienzonevn om Is the universe predictable? Zo ne C • For certain-outcome problems, planning can be used to generate a sequence of operators that is guaranteed to lead to a solution nh Vi en • For uncertain-outcome problems, a sequence of generated operators can only have a good probability of leading to a solution Si Plan revision is made as the plan is carried out and the necessary feedback is provided Cao Hoang Tru CSE Faculty - HCMUT SinhVienZone.com 38 13 February, 2009 https://fb.com/sinhvienzonevn Marcus was a man ne Marcus was a Pompeian .C om Is a good solution absolute or relative? nh Vi en All men are mortal Zo Marcus was born in 40 A.D All Pompeians died when the volcano erupted in 79 A.D Si No mortal lives longer than 150 years It is now 2004 A.D Cao Hoang Tru CSE Faculty - HCMUT SinhVienZone.com 39 13 February, 2009 https://fb.com/sinhvienzonevn Zo ne C Marcus was a man Marcus was a Pompeian Marcus was born in 40 A.D All men are mortal All Pompeians died when the volcano erupted in 79 A.D No mortal lives longer than 150 years It is now 2004 A.D nh Vi en om Is a good solution absolute or relative? Si Is Marcus alive? Cao Hoang Tru CSE Faculty - HCMUT SinhVienZone.com 40 13 February, 2009 https://fb.com/sinhvienzonevn Zo ne C Marcus was a man Marcus was a Pompeian Marcus was born in 40 A.D All men are mortal All Pompeians died when the volcano erupted in 79 A.D No mortal lives longer than 150 years It is now 2004 A.D nh Vi en om Is a good solution absolute or relative? Si Is Marcus alive? Different reasoning paths lead to the answer It does not matter which path we follow Cao Hoang Tru CSE Faculty - HCMUT SinhVienZone.com 41 13 February, 2009 https://fb.com/sinhvienzonevn om Is a good solution absolute or relative? Si nh Vi en Zo ne C The Travelling Salesman Problem We have to try all paths to find the shortest one Cao Hoang Tru CSE Faculty - HCMUT SinhVienZone.com 42 13 February, 2009 https://fb.com/sinhvienzonevn om Is a good solution absolute or relative? ne C • Any-path problems can be solved using heuristics that suggest good paths to explore Si nh Vi en Zo • For best-path problems, much more exhaustive search will be performed Cao Hoang Tru CSE Faculty - HCMUT SinhVienZone.com 43 13 February, 2009 https://fb.com/sinhvienzonevn om Is the solution a state or a path? Zo ne C Finding a consistent intepretation “The bank president ate a dish of pasta salad with the fork” Si nh Vi en – “bank” refers to a financial situation or to a side of a river? – “dish” or “pasta salad” was eaten? – Does “pasta salad” contain pasta, as “dog food” does not contain “dog”? – Which part of the sentence does “with the fork” modify? What if “with vegetables” is there? No record of the processing is necessary Cao Hoang Tru CSE Faculty - HCMUT SinhVienZone.com 44 13 February, 2009 https://fb.com/sinhvienzonevn om Is the solution a state or a path? Si nh Vi en Zo ne C The Water Jug Problem The path that leads to the goal must be reported Cao Hoang Tru CSE Faculty - HCMUT SinhVienZone.com 45 13 February, 2009 https://fb.com/sinhvienzonevn om Is the solution a state or a path? Zo ne C • A path-solution problem can be reformulated as a state-solution problem by describing a state as a partial path to a solution Si nh Vi en • The question is whether that is natural or not Cao Hoang Tru CSE Faculty - HCMUT SinhVienZone.com 46 13 February, 2009 https://fb.com/sinhvienzonevn om What is the role of knowledge Zo ne C Playing Chess Knowledge is important only to constrain the search for a solution Si nh Vi en Reading Newspaper Knowledge is required even to be able to recognize a solution Cao Hoang Tru CSE Faculty - HCMUT SinhVienZone.com 47 13 February, 2009 https://fb.com/sinhvienzonevn om Does the task require human-interaction? Zo ne C • Solitary problem, in which there is no intermediate communication and no demand for an explanation of the reasoning process Si nh Vi en • Conversational problem, in which intermediate communication is to provide either additional assistance to the computer or additional information to the user Cao Hoang Tru CSE Faculty - HCMUT SinhVienZone.com 48 13 February, 2009 https://fb.com/sinhvienzonevn om Problem Classification ne C • There is a variety of problem-solving methods, but there is no one single way of solving all problems Si nh Vi en Zo • Not all new problems should be considered as totally new Solutions of similar problems can be exploited Cao Hoang Tru CSE Faculty - HCMUT SinhVienZone.com 49 13 February, 2009 https://fb.com/sinhvienzonevn om Homework 1-7 (Chapter – AI Rich & Knight) Si nh Vi en Zo ne C Exercises Cao Hoang Tru CSE Faculty - HCMUT SinhVienZone.com 50 13 February, 2009 https://fb.com/sinhvienzonevn ... https://fb .com/ sinhvienzonevn om State Space Search Si nh Vi en Zo ne C Problem solving = Searching for a goal state Cao Hoang Tru CSE Faculty - HCMUT SinhVienZone. com 13 February, 2009 https://fb .com/ sinhvienzonevn... (4, 3) C om Search Strategies Cao Hoang Tru CSE Faculty - HCMUT SinhVienZone. com 17 13 February, 2009 https://fb .com/ sinhvienzonevn om Search Strategies: Blind Search ne nh Vi en Zo Expand all the... necessarily the best, answer Cao Hoang Tru CSE Faculty - HCMUT SinhVienZone. com 15 13 February, 2009 https://fb .com/ sinhvienzonevn om Search Strategies C Uninformed search (blind search) Zo ne Having