Help Creating Arbitray States

major
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Posts: 2

Help Creating Arbitray States Dec 4, 2014 19:49:04 GMT -8

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Post by major on Dec 4, 2014 19:49:04 GMT -8

Hi all,

I'm very new at this and would be willing to bet this is probably a stupid question. I don't normally ask for help on forums but I'm stuck so here goes.

Say that in a game of Tic Tac Toe I have a terminal state with the following contents:

[( true ( cell 3 1 o ) ), ( true ( cell 2 2 o ) ), ( true ( cell 3 3 x ) ), ( true ( cell 1 2 o ) ), ( true ( cell 1 3 x ) ), ( true ( cell 1 1 o ) ), ( true ( cell 3 2 x ) ), ( true ( cell 2 1 x ) ), ( true ( cell 2 3 x ) )]

And the previous state was (difference bolded):

[( true ( cell 3 1 o ) ), ( true ( cell 2 2 b ) ), ( true ( cell 3 3 x ) ), ( true ( cell 1 2 o ) ), ( true ( cell 1 3 x ) ), ( true ( cell 1 1 o ) ), ( true ( cell 3 2 x ) ), ( true ( cell 2 1 x ) ), ( true ( cell 2 3 x ) )]

What I want to do is change values in the prior to terminal state and see if the terminal state can still be achieved. For example if ( false ( cell 3 2 x) ) the move ( mark ( cell 2, 2, o ) ) would still lead to the end of the game. What I am hoping to ultimately achieve is to have my player learn the conditions for a given move to create a terminal state and thereby try to achieve them/defend against them depending on the whether or not it is a winning terminal state.

How should I go about doing this? I know I can access a set of GdlSentences with MachineState.getContents() and from there I can convert them to strings, iterate over them, change the ones I want and create new Gdl objects with GdlFactory.create but that seems like a roundabout way of doing things and I am unsure of how to create a GdlSentence object from a Gdl object anyway.

Is this the kind of thing that makes more sense with propnets? If so I would appreciate any advice on using OptimizingPropNetFactory to achieve this.

Hopefully I phrased that in a way that was comprehensible. Thanks in advance for any help/advice, and apologies again if it is a stupid question.

Andrew Rose
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Posts: 100

Help Creating Arbitray States Dec 5, 2014 6:35:41 GMT -8

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Post by Andrew Rose on Dec 5, 2014 6:35:41 GMT -8

Hi "major",

Welcome to the world of GGP. Out of interest, how did you get involved in this field?

It sounds like you've got a novel approach there. Let me try to answer your questions...

- Firstly, note that anything which isn't explicitly true in a state is automatically false. Therefore, you don't need (and shouldn't use) sentences like "(false(cell 3 2 x))".

- Secondly, beware that meddling with the state in the way you suggest could well leave you in an invalid state. Or, to put it another way, picking arbitrary propositions and making them true/false, is going to leave you with some additional problems. If you do this, you need to be aware that you may end up with, for example, (a) states where there are no legal moves for one or more of the players, (b) terminal states in which there are either 0 or >1 goal propositions set for one of the players, (c) states from which the game can't ever become terminal (and therefore risks looping endlessly), etc..

- There's nothing about propnets that will make what you're doing easier/harder. Both the ProverStateMachine and the PropNetStateMachine present the same StateMachine interface. In either case, you'd need to enhance the machine with the ability to get the underlying propositions and then set them to true/false as your player saw fit.

If you're at an early stage of GGP, I would advise you to instead get a basic MCTS player working first. That's likely to be a better first with the codebase, be a better introduction to GGP and lead you down a better-trodden path. Once you've got the hang of things, then you could revisit ideas like this. Just a suggestion though - I certainly don't want to put you off. Novel ideas always have the chance of producing interesting results.

All the best,

Andrew

Steve Draper
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Posts: 143

Help Creating Arbitray States Dec 5, 2014 6:39:00 GMT -8

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Post by Steve Draper on Dec 5, 2014 6:39:00 GMT -8

The state is a collection of sentences, and I think you're over (or under!) thinking a bit to believe you need to MODIFY sentences in that state. In fact I think you just want to remove them (turn them from true to false), which you can do directly since it's just removal of a member of a collection.

The thing to worry about is whether removal (alone) is semantically meaningful (which will actually depend on the game). In TicTacToe for example ONE of:

(cell 3 2 x), (cell 3 2 o), (cell 3 2 b)

is always true, so just removing (cell 3 2 x) without replacing it with either (cell 3 2 o) or (cell 3 2 b) will create an invalid (unreachable) state, so analysis based on this **may** not be useful (in your example it still is I think, but it's unclear how generic that is). This may be why you started from a supposition that you need to MODIFY rather than just REMOVE (?). However, it would take considerable analysis of the rules to decide what modifications are meaningful (it's inobvious without significant analysis that one of the above three propositions has to be true), and that is (I believe) untenable as game complexity rises (note - this is closely related to things like detecting boards and pieces in board games - essentially you're looking for invariants on the state).

Propnets won't help you much apart from (as a side effect really) generating a complete list of ground base propositions, which are the members of the set of sentences which can appear in the state collection. The only valid operations on the state are then exactly addition and removal of each of those ground propositions (which is another way of saying that the set of valid states is the power set of the set of ground base props). Note however that 'valid' in this sense does not imply reachable (in a game, starting with the initial state).

alandau
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Posts: 159

Help Creating Arbitray States Dec 5, 2014 11:39:03 GMT -8

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Post by alandau on Dec 5, 2014 11:39:03 GMT -8

To answer the low-level question of how to create GdlSentence objects to put in a state, you'll want to use the static method GdlPool#getRelation (or, if the sentence is just one literal like "terminal", GdlPool#getProposition). Note that GdlSentences and other Gdl language types are immutable -- you can't change their contents. You may also want to treat MachineStates as immutable, to avoid bugs around having stored states (e.g. in game tree nodes) suddenly change.

What you'd generally want to do is create a new HashSet<GdlSentence> with the GdlSentences you want and pass it into the StateMachine#getMachineStateFromSentenceList method to get the modified MachineState.

major New Member Posts: 2	Help Creating Arbitray States Dec 11, 2014 3:25:41 GMT -8 Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by major on Dec 11, 2014 3:25:41 GMT -8 Thanks for your help everyone. I am now able to achieve what I set out to do. I appreciate how quickly you all got back to me. Sorry it took me so long to thank you!

Post by major on Dec 4, 2014 19:49:04 GMT -8

Post by Andrew Rose on Dec 5, 2014 6:35:41 GMT -8

Post by Steve Draper on Dec 5, 2014 6:39:00 GMT -8

Post by alandau on Dec 5, 2014 11:39:03 GMT -8

Post by major on Dec 11, 2014 3:25:41 GMT -8

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