Greedy Best First Search, A* Search

1. Informed Search
Dr. J. Annrose
AP/IT
SXCCE

2. OVERVIEW
Greedy Best First Search
A* Search

3. Greedy Best First Search
SLD
1. h(S-G)=10
2. h(A-G)=7
3. h(D-G)=1
4. h(F-G)=1
5. h(B-G)=10
6. h(E-G)=8
7. h(C-G)=20
Evaluation Function
f(n)= g(n)

4. Greedy Best First Search
SLD
1. h(S-G)=10
2. h(A-G)=7
3. h(D-G)=1
4. h(F-G)=1
5. h(B-G)=10
6. h(E-G)=8
7. h(C-G)=20
Evaluation Function
f(n)= g(n)
S
C
B
A
f(n)= 7
f(n)= 10 f(n)= 20

5. Greedy Best First Search
SLD
1. h(S-G)=10
2. h(A-G)=7
3. h(D-G)=1
4. h(F-G)=1
5. h(B-G)=10
6. h(E-G)=8
7. h(C-G)=20
Evaluation Function
f(n)= g(n)
S
C
B
A
f(n)= 7
f(n)= 10 f(n)= 20
D
f(n)= 1 S
f(n)=10

6. Greedy Best First Search
SLD
1. h(S-G)=10
2. h(A-G)=7
3. h(D-G)=1
4. h(F-G)=1
5. h(B-G)=10
6. h(E-G)=8
7. h(C-G)=20
Evaluation Function
f(n)= g(n)
S
C
B
A
f(n)= 7
f(n)= 10 f(n)= 20
D
f(n)= 1 S
f(n)=10
F A
f(n)= 1
f(n)= 7

7. Greedy Best First Search
SLD
1. h(S-G)=10
2. h(A-G)=7
3. h(D-G)=1
4. h(F-G)=1
5. h(B-G)=10
6. h(E-G)=8
7. h(C-G)=20
Evaluation Function
f(n)= g(n)
S
C
B
A
f(n)= 7
f(n)= 10 f(n)= 20
D
f(n)= 1 S
f(n)=10
F A
G
f(n)= 7
f(n)= 1

8. Greedy Best First Search
SLD
1. h(S-G)=10
2. h(A-G)=7
3. h(D-G)=1
4. h(F-G)=1
5. h(B-G)=10
6. h(E-G)=8
7. h(C-G)=20
Evaluation Function
f(n)= g(n)
S
C
B
A
f(n)= 7
f(n)= 10 f(n)= 20
D
f(n)= 1 S
f(n)=10
F A
G
f(n)= 1
f(n)= 7 Total Cost
S-A-D-F-G = 3+6+1+1=11

9. A* Search
SLD
1. h(S-G)=10
2. h(A-G)=7
3. h(D-G)=1
4. h(F-G)=1
5. h(B-G)=10
6. h(E-G)=8
7. h(C-G)=20
Evaluation Function
f(n)= g(n) +h(n)

10. A* Search
SLD
1. h(S-G)=10
2. h(A-G)=7
3. h(D-G)=1
4. h(F-G)=1
5. h(B-G)=10
6. h(E-G)=8
7. h(C-G)=20
Evaluation Function
f(n)= g(n)+ h(n)
S
C
B
A
f(n)= 3+7=10
f(n)= 2+ 10 =12 f(n)= 1+ 20 =21

11. A* Search
SLD
1. h(S-G)=10
2. h(A-G)=7
3. h(D-G)=1
4. h(F-G)=1
5. h(B-G)=10
6. h(E-G)=8
7. h(C-G)=20
Evaluation Function
f(n)= g(n)+ h(n)
S
C
B
A
f(n)= 3+7=10
f(n)= 2+ 10 =12 f(n)= 1+ 20 =21
D
f(n)= 3+1+1=5 S
f(n)= 3+3+10=16

12. A* Search
SLD
1. h(S-G)=10
2. h(A-G)=7
3. h(D-G)=1
4. h(F-G)=1
5. h(B-G)=10
6. h(E-G)=8
7. h(C-G)=20
Evaluation Function
f(n)= g(n)+ h(n)
S
C
B
A
f(n)= 3+7=10
f(n)= 2+ 10 =12 f(n)= 1+ 20 =21
D
f(n)= 3+1+1=5 S
f(n)= 3+3+10=16
F
f(n)=3+1+1+ 1=6 A
f(n)= 3+1+1+7=12

13. A* Search
SLD
1. h(S-G)=10
2. h(A-G)=7
3. h(D-G)=1
4. h(F-G)=1
5. h(B-G)=10
6. h(E-G)=8
7. h(C-G)=20
Evaluation Function
f(n)= g(n)+ h(n)
S
C
B
A
f(n)= 3+7=10
f(n)= 2+ 10 =12 f(n)= 1+ 20 =21
D
f(n)= 3+1+1=5 S
f(n)= 3+3+10=16
F
f(n)=3+1+1+ 1=6 A
f(n)= 3+1+1+7=12
G

14. A* Search
SLD
1. h(S-G)=10
2. h(A-G)=7
3. h(D-G)=1
4. h(F-G)=1
5. h(B-G)=10
6. h(E-G)=8
7. h(C-G)=20
Evaluation Function
f(n)= g(n)+ h(n)
S
C
B
A
f(n)= 3+7=10
f(n)= 2+ 10 =12 f(n)= 1+ 20 =21
D
f(n)= 3+1+1=5 S
f(n)= 3+3+10=16
F
f(n)=3+1+1+ 1=6 A
f(n)= 3+1+1+7=12
G
Total Cost
S-A-D-F-G = 3+6+1+1=11