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yap-6.3/packages/prism/exs/noisy_or/noisy_or.psm
2011-11-10 12:24:47 +00:00

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%%%%
%%%% Library for generic noisy OR predicates --- noisy_or.psm
%%%%
%%%% Copyright (C) 2007,2008
%%%% Sato Laboratory, Dept. of Computer Science,
%%%% Tokyo Institute of Technology
%% When this file included, the following predicates will be available:
%%
%% - cpt(X,PaVs,V) represents a probabilistic choice where a
%% random variable X given instantiations PaVs of parents
%% takes a value V. If X is an ordinary node, a random
%% switch bn(X,PaVs) will be used. On the other hand, if
%% X is a noisy-OR node, switch cause(X,Y) will be used,
%% where Y is one of parents of X.
%%
%% - set_nor_params/0 sets inhibition probabilisties (i.e.
%% the parameters of switches cause(X,Y)) according to
%% the specifications for noisy-OR nodes with noisy_or/3.
%%---------------------------------------
%% Declarations:
% added just for making the results of probabilistic inference
% simple and readable:
:- p_not_table choose_noisy_or/4, choose_noisy_or/6.
%%---------------------------------------
%% Modeling part:
cpt(X,PaVs,V):-
( noisy_or(X,Pa,_) -> choose_noisy_or(X,Pa,PaVs,V) % for noisy OR nodes
; msw(bn(X,PaVs),V) % for ordinary nodes
).
choose_noisy_or(X,Pa,PaVs,V):- choose_noisy_or(X,Pa,PaVs,no,no,V).
choose_noisy_or(_,[],[],yes,V,V).
choose_noisy_or(_,[],[],no,_,no).
choose_noisy_or(X,[Y|Pa],[PaV|PaVs],PaHasYes0,ValHasYes0,V):-
( PaV=yes ->
msw(cause(X,Y),V0),
PaHasYes=yes,
( ValHasYes0=no, V0=no -> ValHasYes=no
; ValHasYes=yes
)
; PaHasYes=PaHasYes0,
ValHasYes=ValHasYes0
), % do not insert the cut symbol here
choose_noisy_or(X,Pa,PaVs,PaHasYes,ValHasYes,V).
%%---------------------------------------
%% Utility part:
set_nor_params:-
( noisy_or(X,Pa,DistList), % spec for a noisy OR node
set_nor_params(X,Pa,DistList),
fail
; true
).
set_nor_params(_,[],[]).
set_nor_params(X,[Y|Pa],[Dist|DistList]):-
set_sw(cause(X,Y),Dist),!,
set_nor_params(X,Pa,DistList).