b77427df89
git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@211 b08c6af1-5177-4d33-ba66-4b1c6b8b522a
43 lines
1.0 KiB
Plaintext
43 lines
1.0 KiB
Plaintext
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:- object(hill_climbing(Threshold),
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instantiates(heuristic_search(Threshold))).
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:- info([
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version is 1.0,
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authors is 'Paulo Moura',
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date is 1998/3/23,
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comment is 'Hill climbing heuristic state space search strategy.',
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parnames is ['Threshold']]).
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:- uses(list).
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:- private(hill/7).
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search(Space, State, Threshold, Solution, Cost) :-
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hill(Space, State, Threshold, [], Path, 0, Cost),
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list::reverse(Path, Solution).
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hill(Space, State, _, Path, [State| Path], Cost, Cost) :-
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Space::goal_state(State).
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hill(Space, State, Threshold, Path, Solution, SoFar, Total) :-
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findall(
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(Estimate, Cost, Next),
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(Space::next_state(State, Next, Cost),
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\+ list::member(Next, [State| Path]),
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Space::heuristic(Next, Guess),
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Estimate is Guess + Cost),
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States),
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list::sort(States, SortedStates),
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list::member((_, Cost2, Next2), SortedStates),
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SoFar2 is SoFar + Cost2,
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SoFar2 =< Threshold,
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hill(Space, Next2, Threshold, [State| Path], Solution, SoFar2, Total).
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:- end_object.
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