programming-for-dummies

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Adversarial Search
Figure 2-8:
Clustered
indexes
physically
rearrange
data
whereas
unclustered
indexes
point to
data.
555-0147
555-1462
555-7001
555-8163
555-8772
555-9604
Unclustered index
Adams
Gullins
Hall
Perkins
Smith
Wiggins
Clustered index
Mary 555-7001
Travis 555-0147
Gail 555-8772
Sam 555-8136
John 555-1462
Nancy 555-9604
Problems with indexes
A single clustered index makes sense because it rearranges data in a specific
way. Multiple, unclustered indexes can help search data in different ways.
Although indexes make searching faster, they make inserting and deleting
slower because every time you add or delete data, you must update and
organize the index at the same time.
If you’ve created multiple indexes, adding or deleting data means having to
update every multiple index. If you have a small amount of data, creating
and using an index may be more trouble than it’s worth. Only when you have
large amounts of data is an index (or multiple indexes) worth using.
Adversarial Search
One of the most popular uses for searching is an adversarial search. This
type of search is often used to create artificial intelligence in video games.
Essentially, the computer analyzes the current game situation, such as a tictac-toe
game, and calculates its list of possible moves. For each possible
move, the computer creates a tree where the root node represents one of the
computer’s possible moves and each alternating level represents the human
opponent’s possible counter-moves, as shown in Figure 2-9.
Each possible move is given a specific value:
✦ A high value signifies a good move.
✦ A negative value signifies a bad move.
Assuming the human opponent chooses one possible counter-move, the
next level of the tree displays the computer’s possible responses and so on.