Pruned Dynamic Programming

Asked Feb 16 '14 at 07:15

Active Feb 16 '14 at 07:30

Viewed 954 times

Currently, I'm working a string alignment comparison. I'm confused on how to optimize DP by pruning.

DP can be represented as a matrix/table. The start point is (0, 0). For example, element at (3, 4) is pruned and its value marked as -1 or null. But when I compute location (4, 4), (3, 5) and (4, 5), I still need a if-statement to check whether the value of (3, 4) is invalid(pruned) or valid(not pruned). Can this implementation save time because pruning function brings extra running time???

edited Feb 16 '14 at 07:30

XiaoChuan Yu

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asked Feb 16 '14 at 07:15

happyWinner

Pruning is usually very important in order to save _memory_ and not time. For example - look into [SMA*](http://en.wikipedia.org/wiki/SMA*) – Benjamin Gruenbaum Feb 16 '14 at 07:19
You should try to fill only the valid parts of the table (for example using DFS/BFS) – Niklas B. Feb 17 '14 at 15:40
@BenjaminGruenbaum So I need use a tree instead of a 2D array? – happyWinner Feb 17 '14 at 19:20
@NiklasB. So I need a tree instead of a 2D array? – happyWinner Feb 17 '14 at 19:20
@happy: No, you probably need a sparse table (only store the valid entries) – Niklas B. Feb 17 '14 at 19:22
@NiklasB.thanks a lot. i'll try it – happyWinner Feb 19 '14 at 02:58

Pruned Dynamic Programming

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