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Pengantar Kecerdasan Buatan

Pengantar Kecerdasan Buatan. INFORMED SEARCH. Informed Search. Uninformed searches easy but very inefficient in most cases of huge search tree Informed searches uses problem-specific information to reduce the search tree into a small one resolve time and memory complexities.

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Pengantar Kecerdasan Buatan

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  1. Pengantar Kecerdasan Buatan INFORMED SEARCH

  2. Informed Search • Uninformed searches • easy • but very inefficient in most cases of huge search tree • Informed searches • uses problem-specific information to reduce the search tree into a small one • resolve time and memory complexities

  3. Informed Search • Greedy best-first search • A* search • Uniform Cost Search Another method : • Heuristics • Local search algorithms • Hill-climbing search • Simulated annealing search • Local beam search • Genetic algorithms

  4. Romania with Straight-Line dist.

  5. Greedy best-first search • f(n) = estimate of cost from n to goal • e.g., fSLD(n) = straight-line distance from n to Bucharest • Greedy best-first search expands the node that appears to be closest to goal.

  6. Greedy best-first search example

  7. Greedy best-first search example

  8. Greedy best-first search example

  9. Greedy best-first search example

  10. Properties of greedy best-first search • Complete? No – can get stuck in loops. • Time?O(bm), but a good heuristic can give dramatic improvement • Space?O(bm) - keeps all nodes in memory • Optimal? No e.g. AradSibiuRimnicu VireaPitestiBucharest is shorter!

  11. A* search • Idea: avoid expanding paths that are already expensive • Evaluation function f(n) = g(n) + h(n) • g(n) = cost so far to reach n • h(n) = estimated cost from n to goal • f(n) = estimated total cost of path through n to goal • Best First search has f(n)=h(n)

  12. A* search example

  13. A* search example

  14. A* search example

  15. A* search example

  16. A* search example

  17. A* search example

  18. Uniform Cost Search • Prinsip : Lakukan node expansion terhadap node yang path cost-nya paling kecil • Jika semua step costnya sama, uniform cost sama dengan BFS

  19. Contoh UCS

  20. Arad ke Bucharest menggunakan UCS

  21. 8 Puzzle, using A* Search

  22. Water Jug using UCS • Mengisi wadah 3 L s.d. Penuh • Membuang isi wadah 3 L • Menuangkan isi wadah 3 L ke 4 L s.d 4 L penuh • Menuangkan isi wadah 3 L ke 4 L s.d 3 L kosong • Mengisi wadah 4 L s.d. Penuh • Membuang isi wadah 4 L • Menuangkan isi wadah 4 L ke 3 L s.d 3 L penuh • Menuangkan isi wadah 4 L ke 3 L s.d 4 L kosong

  23. Cost • Cost is 1 point per gallon used when filling, 1 point to make a transfer, 5 points per gallon emptied (since it makes a mess) • How to get 2 L ?

  24. Water Jug using UCS (Cont)

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