camir-aes2014: toolboxes/FullBNT-1.0.7/bnt/general/noisyORtoTable.m annotate

first hg version after svn

rev	line source
wolffd@0	1 function CPT = noisyORtoTable(inhibit, leak_inhibit)
wolffd@0	2 % NOISYORTOTABLE Convert noisyOR distribution to CPT
wolffd@0	3 % function CPT = noisyORtoTable(inhibit, leak_inhibit)
wolffd@0	4 %
wolffd@0	5 % inhibit(i) = prob i'th parent will be inhibited (flipped from 1 to 0)
wolffd@0	6 % leak_inhibit - optional suppression of leak
wolffd@0	7 % CPT(U1,...,Un, X) = Pr(X\|U1,...,Un) where the Us are the parents (excluding leak).
wolffd@0	8 % State 1 = off, 2 = on
wolffd@0	9
wolffd@0	10 if nargin < 2, leak_inhibit = 1; end
wolffd@0	11
wolffd@0	12 q = [leak_inhibit inhibit(:)'];
wolffd@0	13
wolffd@0	14 if length(q)==1
wolffd@0	15 CPT = [q 1-q];
wolffd@0	16 return;
wolffd@0	17 end
wolffd@0	18
wolffd@0	19 n = length(q);
wolffd@0	20 Bn = ind2subv(2*ones(1,n), 1:(2^n))-1; % all n bit vectors, with the left most column toggling fastest (LSB)
wolffd@0	21 CPT = zeros(2^n, 2);
wolffd@0	22 % Pr(X=0 \| U_1 .. U_n) = prod_{i: U_i = on} q_i = prod_i q_i ^ U_i = exp(u' * log(q_i))
wolffd@0	23 % This method is problematic when q contains zeros
wolffd@0	24
wolffd@0	25 Q = repmat(q(:)', 2^n, 1);
wolffd@0	26 Q(logical(~Bn)) = 1;
wolffd@0	27 CPT(:,1) = prod(Q,2);
wolffd@0	28 CPT(:,2) = 1-CPT(:,1);
wolffd@0	29
wolffd@0	30 CPT = reshape(CPT(2:2:end), 2*ones(1,n)); % skip cases in which the leak is off
wolffd@0	31
wolffd@0	32

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