function h = etaijX(P,m,n,i,j,X)
P0 = getcondP(P,m,n,[j:n],[1:i  ],[X(1:i  )])
P1 = getcondP(P,m,n,[j:n],[1:i-1],[X(1:i-1)])
h = .5*sum(abs(P0-P1));
%keyboard
return

pmargx = getPX(P,m,n,X,1:i)
pmargx1 = getPX(P,m,n,X(1:i-1),1:i-1)

%return
for zi = 1:m^(n-j+1)
  z = ind2coord(zi,repmat(m,1,(n-j+1)));
  pmargu = getPX0(P,m,n,[X z],[1:i,j:n]);
  pmargu1 = getPX0(P,m,n,[X(1:i-1) z],[1:i-1,j:n]);
  %fprintf('pmargu = %1.5f  pmargu1 = %1.5f \n',pmargu,pmargu1);
end
return


%function Pjj = getcondP(P,m,n,jj,ii,y)
% Pjj(x) = P{ X[jj]=x | X[ii]=y }