113 lines
3.4 KiB
Plaintext
113 lines
3.4 KiB
Plaintext
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abolish_table_info :- at(compress/2).
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time :- statistics(runtime,_), benchmark, fail;
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statistics(runtime,[_,T]), write(T).
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benchmark :- data(Data), compress(Data, _C).
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test :-
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data(Data), reinit,
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cputime(T0),
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compress(Data, C), write(C), write(' '),
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cputime(T1), T is T1-T0, write(T), write(' msecs'), nl, fail.
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test.
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%% data([a,a,b,a,a,b]).
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%% data([a,a,b,a,a,b,a,a,b]).
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%% data([a,a,a,a,a,a,a,a,a,a,a,a]).
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%% data([a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a]).
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%% data([a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a]).
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%% data(D) :- bigdata(D).
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%% data(D2) :- bigdata(D), append(D,D,D2).
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data(D4) :- bigdata(D), append(D,D,D2), append(D2,D2,D4).
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%% data(D8) :- bigdata(D), append(D,D,D2), append(D2,D2,D4), append(D4,D4,D8).
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%% data(D16) :- bigdata(D), append(D,D,D2), append(D2,D2,D4), append(D4,D4,D8), append(D8,D8,D16).
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bigdata([x,c,a,a,b,a,a,b,a,a,b,c,c,a,d,a,d,c,a,a,b,a,a,b,a,a,b,c,c,a,d,a,d,y]).
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%% ==================== VERSION USING ASSERT FOR TABLES ======================
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%% reinit :-
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%% retractall(memo_compress(_, _)),
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%% assert(memo_compress([C1], [C1])),
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%% assert(memo_compress([C1,C2], [C1,C2])).
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%%
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%% compress(Initial, Compressed) :-
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%% ( memo_compress(Initial, Compressed) -> true
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%% mlength(Initial, LenInitial),
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%% CurrentBest = Initial,
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%% LenCurrentBest = LenInitial,
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%% compress4(Initial, CurrentBest, LenCurrentBest, Compressed)
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%% assert(memo_compress(Initial, Compressed))
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%% ).
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%% ===========================================================================
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reinit :- abolish_all_tables.
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:- table compress/2.
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compress(Initial, Compressed) :-
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mlength(Initial, LenInitial),
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CurrentBest = Initial,
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LenCurrentBest = LenInitial,
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compress4(Initial, CurrentBest, LenCurrentBest, Compressed).
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compress4(Initial, CurrentBest, LenCurrentBest, Compressed) :-
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( compress_with_bound(Initial, LenCurrentBest, NewBest) ->
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mlength(NewBest, NewLenBest),
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compress4(Initial, NewBest, NewLenBest, Compressed)
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; Compressed = CurrentBest
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).
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compress_with_bound(Initial, LenBound, Better) :-
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repetition_compress(Initial, LenBound, Better).
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compress_with_bound(Initial, LenBound, Better) :-
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two_price_compress(Initial, LenBound, Better).
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repetition_compress(Initial, LenBound, Better) :-
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chopup(Initial, Piece, Repeated),
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( Piece = [C] ->
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Better = [C,Repeated]
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; compress(Piece, CompressedPiece),
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append(['('|CompressedPiece], [')',Repeated], Better)
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),
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mlength(Better, LenBetter),
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LenBetter < LenBound.
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two_price_compress(Initial, LenBound, Better) :-
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append(Piece1, Piece2, Initial),
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Piece1 \== [],
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Piece2 \== [],
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compress(Piece1, Compressed1),
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mlength(Compressed1, LenCompressed1),
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LenCompressed1 < LenBound,
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compress(Piece2, Compressed2),
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mlength(Compressed2, LenCompressed2),
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LenCompressed1 + LenCompressed2 < LenBound,
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append(Compressed1, Compressed2, Better).
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chopup(List, Part, Repeated) :-
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append(Part, Rest, List),
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Part \== [],
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Rest \== [],
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count_parts(Rest, Part, 1, Repeated).
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count_parts(Rest, Part, I, O) :-
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( Rest == [] -> I = O
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; append(Part, Rest1, Rest),
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I1 is I+1,
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count_parts(Rest1, Part, I1, O)
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).
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%%----------------------------------------------------------------------------
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%% Utilities below
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%%----------------------------------------------------------------------------
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append([],L,L).
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append([H|L1],L2,[H|L3]) :- append(L1,L2,L3).
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mlength(L,N) :- mlength(L,0,N).
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mlength([],N,N).
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mlength([_|R],N0,N) :- N1 is N0+1, mlength(R,N1,N).
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