48 lines
901 B
Plaintext
48 lines
901 B
Plaintext
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type rank(node, int, float).
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type reachable(node, node).
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type calcRank(node, int, sum float).
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% type persistent numPages(node, int).
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type persistent numPages(node, sum int).
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type numLinks(node, sum int).
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type path(node, node).
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const damping = 0.85.
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const num_iterations = 4.
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% extern float to_float(int).
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% extern float float_abs(float).
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rank(A, 0, 1.0 / to_float(T)) :- numPages(A,T).
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rank(A, I, V) :-
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numPages(A, Ps),
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calcRank(A, I, T),
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Before = I - 1,
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rank(A, Before, VOld),
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V = (damping + (1.0 - damping) * T)/to_float(Ps),
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I =< num_iterations.
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% //float_abs((damping + (1.0 - damping) * T) - VOld) > 0.001.
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calcRank(A, I + 1, O / to_float(C)) :-
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edge(B, A),
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rank(B, I, O),
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numLinks(B, C).
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numLinks(A, 1) :-
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edge(A,B).
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numPages(A, 1) :- path(A,_).
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path(A, B) :-
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edge(A,B).
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path(A, B) :-
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edge(B,A).
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path(A, B) :-
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edge(A,C),
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path(C,B).
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path(A, B) :-
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edge(C,A),
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path(C,B).
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