Wednesday, July 25, 2007

Harry Potter and the Game Theory

Warning: possible spoiler

Call it what you want, but yes, I am a Harry Potter reader. I am now reading the seventh book (which I got it exactly on July 21st). I have halfway through so I can't tell whether Harry's going to die or, is he marrying Ginny, or else. But there are some passages from the book that, I think, make good examples of game theoretical concepts and situation.

So the Order plans to move Harry from the Dursleys' to the Wesleys'. But with Death Eaters patrolling, ready to intercept, they need to set a plan. The success would depend on what the Death Eaters' move when they choose one strategy. Similarly, the Death Eaters' strategy would depend on the Order's strategy. And so forth.

By the way, the initial strategy was to duplicate Harry into seven. This way, they hoped to split the Death Eaters' attention and efforts. Well, to make the story short, here are some quotes:
'We think the Death Eaters will expect you to be on a broom,' said Moody, who seemed to guess how Harry was feeling. 'Snape's had plenty of time to tell them everything about you h's never mentioned before, so if we do run into any Death Eaters, we're betting they'll choose one of the Potters who look at home on a broomstick..."
This was before they separated. So Moody was doing forward induction analysis.

Then, after they -- well, not all of them -- reached the Wesleys':
'You-Know-Who acted exactly as Mad-Eye expected him to,' sniffed Tonk.s 'Mad-Eye said he'd expect the real Harry to be with the toughest, most skilled Aurors. He chased Mad-Eye first, and when Mundungus gave them away he switched to Kingsley...'
Here we can see two things. Moody's another forward induction before they went, and a backward induction analysis on You-Know-Who's move.

Somehow, Voldemort and the Death Eaters were finally able to identify the real Harry. How?
'...Expelliarmus is a useful spell, Harry, but the Death Eaters seem to think it is your signature move, and I urge you not to let it become so.' [said Lupin].
This is an example of a strictly dominated strategy.

1 comment:

  1. there's one strange thing on this seventh book, when hermione said she only know theory about memory spell and never use it in practice, yet before... have been mentioned that hermione said of using the spell to her parent