I would assume Dave has some good ideas around how to implement this in a video game.

In the real world price dynamics emerge because people are agreeing on prices before anything actually changes hands. In other words, oil is sold before it's even pumped from the ground. When you are told that 'the price of oil is $xxx a barrel' what you're getting is an estimate based on contractual agreements for a future delivery. Think of it as an auction for something that might not actually exist.


In terms of a video game: If you have shop keepers, you might want to keep a global commodities index running, and have the shop keeper essentially act as a broker that gets him/her a premium (a function of the index price * volatility/risk * profit expectation). If you assigned production of certain regions of the world, and adjust output/cost based on how much combat (or other type of events) occures in those areas then you provide a way for player dynamics to indirectly affect global prices.

That's a great point. People in the real world bitch about how gas prices at the pump increase immediately when the price of oil increases. "But you didn't pay that much for this gasoline! How come you won't sell it at the price you paid for it?" The simple answer is, "because I need to be able to afford to buy more to replace it."

Therefore, in the shopkeeper example, you should not use of what the shopkeeper paid for it. You need to calculate what he would have to pay for it if he wanted to replace his supply. Doing it the other way punishes him for buying a huge inventory when the price is low... which is economics rule #1 (#2 being "sell high").

However, there is a reason to keep track of what the shopkeeper paid... and that is that he may not want to sell at a certain price. For example, if he has an inventory of A, and the price of A drops below what he paid (in cost, effort, etc.) he may find it beneficial to sit on his inventory and hope the price goes back up. Why sell at a loss? (Of course, then you get into a classic situation where the price continues to drop and he must decide to cut his losses by selling... but that's why economics is so much fun!)

sorry about the multiple posts...

DaveMark, I just ordered your book (mainly because I went ahead and just finished reading the first chapter available on Amazon, and secondly, I read an interaction between you and another somewhere else in this forum and I appreciated the advice you gave (understanding their particular programming/AI ability: novice) and how you dealt with an adversarial poster that considered your advice 'wrong' - which it wasn't.

Now I gotta wait 5 days for the book to get here...
That part I can't help with. :-(

meanwhile, are there any other books you might recommend? What about Steve Rabin "AI Wisdom" et al?

See the pinned topic on this forum. Note that the AI Wisdom books are a collection of articles between 10-18 pages from various authors. (Full disclosure, I wrote for #4.) Therefore, it isn't as good a foundation but more tips and tricks. Same with the Gems books (I wrote for #8).

'LorenzoGatti' said:

Of course there might be different available jobs; hunting and cooking one rabbit might be less unpleasant than 4 hours of rabbit hunting, but more unpleasant than a 2% quota of a quick $1000 armed robbery.

Remember to include the potential for success and failure – and the ramifications of each. For example, what is the risk-reward ratio of the armed robbery? If the penalty is negligible, then give it a shot. If the penalty far outweighs the gain, then pause. But what is the potential for getting caught? If the penalty is death, but you have a 0.001% of getting caught, it doesn't matter. Fun with math, folks!