SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem...
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Transcript of SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem...
![Page 1: SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem formulation Breadth-first Uniform-cost Depth-first Depth-limited.](https://reader035.fdocuments.net/reader035/viewer/2022062713/56649ccf5503460f9499b519/html5/thumbnails/1.jpg)
SE 420 1
Last time: search strategies
Uninformed: Use only information available in the problem formulation• Breadth-first• Uniform-cost• Depth-first• Depth-limited• Iterative deepening
Informed: Use heuristics to guide the search• Best first:• Greedy search – queue first nodes that maximize heuristic “desirability”
based on estimated path cost from current node to goal;• A* search – queue first nodes that maximize sum of path cost so far and
estimated path cost to goal.
![Page 2: SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem formulation Breadth-first Uniform-cost Depth-first Depth-limited.](https://reader035.fdocuments.net/reader035/viewer/2022062713/56649ccf5503460f9499b519/html5/thumbnails/2.jpg)
SE 420 2
Exercise: Search Algorithms
The following figure shows a portion of a partially expanded search tree. Each arc between nodes is labeled with the cost of the corresponding operator, and the leaves are labeled with the value of the heuristic function, h.
Which node (use the node’s letter) will be expanded next by each of the following search algorithms?
(a) Depth-first search(b) Breadth-first search(c) Uniform-cost search(d) Greedy search
(e) A* search
5
D
5
A
C
54
19
6
3
h=15
B
F GE
h=8h=12h=10 h=10
h=18
H
h=20
h=14
![Page 3: SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem formulation Breadth-first Uniform-cost Depth-first Depth-limited.](https://reader035.fdocuments.net/reader035/viewer/2022062713/56649ccf5503460f9499b519/html5/thumbnails/3.jpg)
SE 420 3
Depth-first search
Node queue: initialization
# state depth path cost parent #
1 A 0 0 --
![Page 4: SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem formulation Breadth-first Uniform-cost Depth-first Depth-limited.](https://reader035.fdocuments.net/reader035/viewer/2022062713/56649ccf5503460f9499b519/html5/thumbnails/4.jpg)
SE 420 4
Depth-first search
Node queue: add successors to queue front; empty queue from top
# state depth path cost parent #
2 B 1 3 13 C 1 19 14 D 1 5 11 A 0 0 --
![Page 5: SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem formulation Breadth-first Uniform-cost Depth-first Depth-limited.](https://reader035.fdocuments.net/reader035/viewer/2022062713/56649ccf5503460f9499b519/html5/thumbnails/5.jpg)
SE 420 5
Depth-first search
Node queue: add successors to queue front; empty queue from top
# state depth path cost parent #
5 E 2 7 26 F 2 8 27 G 2 8 28 H 2 9 22 B 1 3 13 C 1 19 14 D 1 5 11 A 0 0 --
![Page 6: SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem formulation Breadth-first Uniform-cost Depth-first Depth-limited.](https://reader035.fdocuments.net/reader035/viewer/2022062713/56649ccf5503460f9499b519/html5/thumbnails/6.jpg)
SE 420 6
Depth-first search
Node queue: add successors to queue front; empty queue from top
# state depth path cost parent #
5 E 2 7 26 F 2 8 27 G 2 8 28 H 2 9 22 B 1 3 13 C 1 19 14 D 1 5 11 A 0 0 --
![Page 7: SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem formulation Breadth-first Uniform-cost Depth-first Depth-limited.](https://reader035.fdocuments.net/reader035/viewer/2022062713/56649ccf5503460f9499b519/html5/thumbnails/7.jpg)
SE 420 7
Exercise: Search Algorithms
The following figure shows a portion of a partially expanded search tree. Each arc between nodes is labeled with the cost of the corresponding operator, and the leaves are labeled with the value of the heuristic function, h.
Which node (use the node’s letter) will be expanded next by each of the following search algorithms?
(a) Depth-first search(b) Breadth-first search(c) Uniform-cost search(d) Greedy search
(e) A* search
5
D
5
A
C
54
19
6
3
h=15
B
F GE
h=8h=12h=10 h=10
h=18
H
h=20
h=14
![Page 8: SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem formulation Breadth-first Uniform-cost Depth-first Depth-limited.](https://reader035.fdocuments.net/reader035/viewer/2022062713/56649ccf5503460f9499b519/html5/thumbnails/8.jpg)
SE 420 8
Breadth-first search
Node queue: initialization
# state depth path cost parent #
1 A 0 0 --
![Page 9: SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem formulation Breadth-first Uniform-cost Depth-first Depth-limited.](https://reader035.fdocuments.net/reader035/viewer/2022062713/56649ccf5503460f9499b519/html5/thumbnails/9.jpg)
SE 420 9
Breadth-first search
Node queue: add successors to queue end; empty queue from top
# state depth path cost parent #
1 A 0 0 --2 B 1 3 13 C 1 19 14 D 1 5 1
![Page 10: SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem formulation Breadth-first Uniform-cost Depth-first Depth-limited.](https://reader035.fdocuments.net/reader035/viewer/2022062713/56649ccf5503460f9499b519/html5/thumbnails/10.jpg)
SE 420 10
Breadth-first search
Node queue: add successors to queue end; empty queue from top
# state depth path cost parent #
1 A 0 0 --2 B 1 3 13 C 1 19 14 D 1 5 15 E 2 7 26 F 2 8 27 G 2 8 28 H 2 9 2
![Page 11: SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem formulation Breadth-first Uniform-cost Depth-first Depth-limited.](https://reader035.fdocuments.net/reader035/viewer/2022062713/56649ccf5503460f9499b519/html5/thumbnails/11.jpg)
SE 420 11
Breadth-first search
Node queue: add successors to queue end; empty queue from top
# state depth path cost parent #
1 A 0 0 --2 B 1 3 13 C 1 19 14 D 1 5 15 E 2 7 26 F 2 8 27 G 2 8 28 H 2 9 2
![Page 12: SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem formulation Breadth-first Uniform-cost Depth-first Depth-limited.](https://reader035.fdocuments.net/reader035/viewer/2022062713/56649ccf5503460f9499b519/html5/thumbnails/12.jpg)
SE 420 12
Exercise: Search Algorithms
The following figure shows a portion of a partially expanded search tree. Each arc between nodes is labeled with the cost of the corresponding operator, and the leaves are labeled with the value of the heuristic function, h.
Which node (use the node’s letter) will be expanded next by each of the following search algorithms?
(a) Depth-first search(b) Breadth-first search(c) Uniform-cost search(d) Greedy search
(e) A* search
5
D
5
A
C
54
19
6
3
h=15
B
F GE
h=8h=12h=10 h=10
h=18
H
h=20
h=14
![Page 13: SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem formulation Breadth-first Uniform-cost Depth-first Depth-limited.](https://reader035.fdocuments.net/reader035/viewer/2022062713/56649ccf5503460f9499b519/html5/thumbnails/13.jpg)
SE 420 13
Uniform-cost search
Node queue: initialization
# state depth path cost parent #
1 A 0 0 --
![Page 14: SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem formulation Breadth-first Uniform-cost Depth-first Depth-limited.](https://reader035.fdocuments.net/reader035/viewer/2022062713/56649ccf5503460f9499b519/html5/thumbnails/14.jpg)
SE 420 14
Uniform-cost search
Node queue: add successors to queue so that entire queue is sorted by path cost so far; empty queue from top
# state depth path cost parent #
1 A 0 0 --2 B 1 3 13 D 1 5 14 C 1 19 1
![Page 15: SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem formulation Breadth-first Uniform-cost Depth-first Depth-limited.](https://reader035.fdocuments.net/reader035/viewer/2022062713/56649ccf5503460f9499b519/html5/thumbnails/15.jpg)
SE 420 15
Uniform-cost search
Node queue: add successors to queue so that entire queue is sorted by path cost so far; empty queue from top
# state depth path cost parent #
1 A 0 0 --2 B 1 3 13 D 1 5 15 E 2 7 26 F 2 8 27 G 2 8 28 H 2 9 24 C 1 19 1
![Page 16: SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem formulation Breadth-first Uniform-cost Depth-first Depth-limited.](https://reader035.fdocuments.net/reader035/viewer/2022062713/56649ccf5503460f9499b519/html5/thumbnails/16.jpg)
SE 420 16
Uniform-cost search
Node queue: add successors to queue so that entire queue is sorted by path cost so far; empty queue from top
# state depth path cost parent #
1 A 0 0 --2 B 1 3 13 D 1 5 15 E 2 7 26 F 2 8 27 G 2 8 28 H 2 9 24 C 1 19 1
![Page 17: SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem formulation Breadth-first Uniform-cost Depth-first Depth-limited.](https://reader035.fdocuments.net/reader035/viewer/2022062713/56649ccf5503460f9499b519/html5/thumbnails/17.jpg)
SE 420 17
Exercise: Search Algorithms
The following figure shows a portion of a partially expanded search tree. Each arc between nodes is labeled with the cost of the corresponding operator, and the leaves are labeled with the value of the heuristic function, h.
Which node (use the node’s letter) will be expanded next by each of the following search algorithms?
(a) Depth-first search(b) Breadth-first search(c) Uniform-cost search(d) Greedy search
(e) A* search
5
D
5
A
C
54
19
6
3
h=15
B
F GE
h=8h=12h=10 h=10
h=18
H
h=20
h=14
![Page 18: SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem formulation Breadth-first Uniform-cost Depth-first Depth-limited.](https://reader035.fdocuments.net/reader035/viewer/2022062713/56649ccf5503460f9499b519/html5/thumbnails/18.jpg)
SE 420 18
Greedy search
Node queue: initialization
# state depth path cost total parent #cost to goalcost
1 A 0 0 20 20 --
![Page 19: SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem formulation Breadth-first Uniform-cost Depth-first Depth-limited.](https://reader035.fdocuments.net/reader035/viewer/2022062713/56649ccf5503460f9499b519/html5/thumbnails/19.jpg)
SE 420 19
Greedy search
Node queue: Add successors to queue, sorted by cost to goal.
# state depth path cost total parent #cost to goalcost
1 A 0 0 20 20 --2 B 1 3 14 17 13 D 1 5 15 20 14 C 1 19 18 37 1
Sort key
![Page 20: SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem formulation Breadth-first Uniform-cost Depth-first Depth-limited.](https://reader035.fdocuments.net/reader035/viewer/2022062713/56649ccf5503460f9499b519/html5/thumbnails/20.jpg)
SE 420 20
Greedy search
Node queue: Add successors to queue, sorted by cost to goal.
# state depth path cost total parent #cost to goalcost
1 A 0 0 20 20 --2 B 1 3 14 17 15 G 2 8 8 16 27 E 2 7 10 17 26 H 2 9 10 19 28 F 2 8 12 20 23 D 1 5 15 20 14 C 1 19 18 37 1
![Page 21: SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem formulation Breadth-first Uniform-cost Depth-first Depth-limited.](https://reader035.fdocuments.net/reader035/viewer/2022062713/56649ccf5503460f9499b519/html5/thumbnails/21.jpg)
SE 420 21
Greedy search
Node queue: Add successors to queue, sorted by cost to goal.
# state depth path cost total parent #cost to goalcost
1 A 0 0 20 20 --2 B 1 3 14 17 15 G 2 8 8 16 27 E 2 7 10 17 26 H 2 9 10 19 28 F 2 8 12 20 23 D 1 5 15 20 14 C 1 19 18 37 1
![Page 22: SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem formulation Breadth-first Uniform-cost Depth-first Depth-limited.](https://reader035.fdocuments.net/reader035/viewer/2022062713/56649ccf5503460f9499b519/html5/thumbnails/22.jpg)
SE 420 22
Exercise: Search Algorithms
The following figure shows a portion of a partially expanded search tree. Each arc between nodes is labeled with the cost of the corresponding operator, and the leaves are labeled with the value of the heuristic function, h.
Which node (use the node’s letter) will be expanded next by each of the following search algorithms?
(a) Depth-first search(b) Breadth-first search(c) Uniform-cost search(d) Greedy search
(e) A* search
5
D
5
A
C
54
19
6
3
h=15
B
F GE
h=8h=12h=10 h=10
h=18
H
h=20
h=14
![Page 23: SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem formulation Breadth-first Uniform-cost Depth-first Depth-limited.](https://reader035.fdocuments.net/reader035/viewer/2022062713/56649ccf5503460f9499b519/html5/thumbnails/23.jpg)
SE 420 23
A* search
Node queue: initialization
# state depth path cost total parent #cost to goalcost
1 A 0 0 20 20 --
![Page 24: SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem formulation Breadth-first Uniform-cost Depth-first Depth-limited.](https://reader035.fdocuments.net/reader035/viewer/2022062713/56649ccf5503460f9499b519/html5/thumbnails/24.jpg)
SE 420 24
A* search
Node queue: Add successors to queue, sorted by total cost.
# state depth path cost total parent #cost to goalcost
1 A 0 0 20 20 --2 B 1 3 14 17 13 D 1 5 15 20 14 C 1 19 18 37 1
Sort key
![Page 25: SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem formulation Breadth-first Uniform-cost Depth-first Depth-limited.](https://reader035.fdocuments.net/reader035/viewer/2022062713/56649ccf5503460f9499b519/html5/thumbnails/25.jpg)
SE 420 25
A* search
Node queue: Add successors to queue front, sorted by total cost.
# state depth path cost total parent #cost to goalcost
1 A 0 0 20 20 --2 B 1 3 14 17 15 G 2 8 8 16 26 E 2 7 10 17 27 H 2 9 10 19 23 D 1 5 15 20 18 F 2 8 12 20 24 C 1 19 18 37 1
![Page 26: SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem formulation Breadth-first Uniform-cost Depth-first Depth-limited.](https://reader035.fdocuments.net/reader035/viewer/2022062713/56649ccf5503460f9499b519/html5/thumbnails/26.jpg)
SE 420 26
A* search
Node queue: Add successors to queue front, sorted by total cost.
# state depth path cost total parent #cost to goalcost
1 A 0 0 20 20 --2 B 1 3 14 17 15 G 2 8 8 16 26 E 2 7 10 17 27 H 2 9 10 19 23 D 1 5 15 20 18 F 2 8 12 20 24 C 1 19 18 37 1
![Page 27: SE 420 1 Last time: search strategies Uninformed: Use only information available in the problem formulation Breadth-first Uniform-cost Depth-first Depth-limited.](https://reader035.fdocuments.net/reader035/viewer/2022062713/56649ccf5503460f9499b519/html5/thumbnails/27.jpg)
SE 420 27
Exercise: Search Algorithms
The following figure shows a portion of a partially expanded search tree. Each arc between nodes is labeled with the cost of the corresponding operator, and the leaves are labeled with the value of the heuristic function, h.
Which node (use the node’s letter) will be expanded next by each of the following search algorithms?
(a) Depth-first search(b) Breadth-first search(c) Uniform-cost search(d) Greedy search
(e) A* search
5
D
5
A
C
54
19
6
3
h=15
B
F GE
h=8h=12h=10 h=10
h=18
H
h=20
h=14