yap-6.3/packages/CLPBN/clpbn/connected.yap

:- module(clpbn_connected,
	[influences/3,
	 factor_influences/4,
	 init_influences/3,
	 influences/4]
	 ).

:- use_module(library(maplist)).

:- use_module(library(dgraphs),
	[dgraph_new/1,
	dgraph_add_edges/3,
	dgraph_add_vertex/3,
	dgraph_neighbors/3,
	dgraph_edge/3,
	dgraph_transpose/2]).

:- use_module(library(rbtrees),
	[rb_new/1,
	rb_lookup/3,
	rb_insert/4,
	rb_visit/2]).

factor_influences(Vs, QVars, Ev, LV) :-
	init_factor_influences(Vs, G, RG),
	influences(QVars, Ev, G, RG, LV).

init_factor_influences(Vs, G, RG) :-
	dgraph_new(G0),
	foldl(factor_to_dgraph, Vs, G0, G),
	dgraph_transpose(G, RG).

influences(Vs, QVars, LV) :-
	init_influences(Vs, G, RG),
	influences(QVars, [], G, RG, LV).

init_influences(Vs, G, RG) :-
	dgraph_new(G0),
	to_dgraph(Vs, G0, G),
	dgraph_transpose(G, RG).

factor_to_dgraph(f([V|Parents],_,_,_), G0, G) :-
	dgraph_add_vertex(G0, V, G00),
	build_edges(Parents, V, Edges),
	dgraph_add_edges(G00, Edges, G).

to_dgraph([], G, G).
to_dgraph([V|Vs], G0, G) :-
	clpbn:get_atts(V, [dist(_,Parents)]), !,
	dgraph_add_vertex(G0, V, G00),
	build_edges(Parents, V, Edges),
	dgraph_add_edges(G00, Edges, G1),
	to_dgraph(Vs, G1, G).

build_edges([], _, []).
build_edges([P|Parents], V, [P-V|Edges]) :-
	build_edges(Parents, V, Edges).

% search for the set of variables that influence V
influences(Vs, G, RG, Vars) :-
    influences(Vs, [], G, RG, Vars).

% search for the set of variables that influence V
influences(Vs, Evs, G, RG, Vars) :-
    rb_new(Visited0),
    foldl(influence(Evs, G, RG), Vs, Visited0, Visited),
    all_top(Visited, Evs, Vars).

influence(_, _G, _RG, V, Vs, Vs) :-
	rb_lookup(V, [T|B], Vs), T == t, B == b, !.
influence(Ev, G, RG, V, Vs0, Vs) :-
	rb_insert(Vs0, V, [t|b], Vs1),
	process_new_variable(V, Ev, G, RG, Vs1, Vs).

process_new_variable(V, _Evs, _G, _RG, _Vs0, _Vs1) :-
	var(V),
	clpbn:get_atts(V,[evidence(Ev)]), !,
	throw(error(bound_to_evidence(V/Ev))).
process_new_variable(V, Evs, _G, _RG, _Vs0, _Vs1) :-
	rb_lookup(V, Ev, Evs), !,
	throw(error(bound_to_evidence(V/Ev))).
process_new_variable(V, Evs, G, RG, Vs0, Vs2) :-
	dgraph_neighbors(V, G, Children),
	foldl(throw_below(Evs, G, RG), Children, Vs0, Vs1),
	dgraph_neighbors(V, RG, Parents),
	foldl(throw_above(Evs, G, RG), Parents, Vs1, Vs2).

% visited
throw_below(Evs, G, RG, Child, Vs0, Vs1) :-
	rb_lookup(Child, [_|B], Vs0), !,
	( 
	    B == b ->
	  Vs0 = Vs1  % been there before
	    ;
	  B = b, % mark it
          handle_ball_from_above(Child, Evs, G, RG, Vs0, Vs1)
        ).
throw_below(Evs, G, RG, Child, Vs0, Vs2) :-
	rb_insert(Vs0, Child, [_|b], Vs1),
	handle_ball_from_above(Child, Evs, G, RG, Vs1, Vs2).

% share this with parents, if we have evidence
handle_ball_from_above(V, Evs, G, RG, Vs0, Vs1) :-
    var(V),
    clpbn:get_atts(V,[evidence(_)]), !,
    dgraph_neighbors(V, RG, Parents),
    foldl(throw_above(Evs, G, RG), Parents, Vs0, Vs1).
handle_ball_from_above(V, Evs, G, RG, Vs0, Vs1) :-
    nonvar(V),
    rb_lookup(V,_,Evs), !,
    dgraph_neighbors(V, RG, Parents),
    foldl(throw_above(Evs, G, RG), Parents, Vs0, Vs1).
% propagate to kids, if we do not
handle_ball_from_above(V, Evs, G, RG, Vs0, Vs1) :-
    dgraph_neighbors(V, G, Children),
    foldl(throw_below(Evs, G, RG), Children, Vs0, Vs1).
	
% visited
throw_above(Evs, G, RG, Parent, Vs0, Vs1) :-
	rb_lookup(Parent, [T|_], Vs0), !,
	( 
	    T == t ->
	  Vs1 = Vs0  % been there before
	    ;
	  T = t, % mark it
          handle_ball_from_below(Parent, Evs, G, RG, Vs0, Vs1)
        ).
throw_above(Evs, G, RG, Parent, Vs0, Vs2) :-
	rb_insert(Vs0, Parent, [t|_], Vs1),
	handle_ball_from_below(Parent, Evs, G, RG, Vs1, Vs2).

% share this with parents, if we have evidence
handle_ball_from_below(V, _Evs, _, _, Vs, Vs) :-
    var(V),
    clpbn:get_atts(V,[evidence(_)]), !.
handle_ball_from_below(V, Evs, _, _, Vs, Vs) :-
    nonvar(V),
    rb_lookup(V, _, Evs), !.
% propagate to kids, if we do not
handle_ball_from_below(V, Evs, G, RG, Vs0, Vs1) :-
    dgraph_neighbors(V, RG, Parents),
    propagate_ball_from_below(Parents, Evs, V, G, RG, Vs0, Vs1).

propagate_ball_from_below([], Evs, V, G, RG, Vs0, Vs1) :- !,
    dgraph_neighbors(V, G, Children),
    foldl(throw_below(Evs, G, RG), Children, Vs0, Vs1).
propagate_ball_from_below(Parents, Evs, _V, G, RG, Vs0, Vs1) :-
    foldl(throw_above(Evs, G, RG), Parents, Vs0, Vs1).

all_top(T, Evs, Vs) :-
    rb_visit(T, Pairs),
    foldl( get_top(Evs), Pairs, [], Vs).

get_top(_EVs, V-[T|_], Vs, [V|Vs]) :-
    T == t, !.
get_top(_EVs, V-_, Vs, [V|Vs]) :-
    var(V),
    clpbn:get_atts(V,[evidence(_)]), !.
get_top(EVs, V-_, Vs, [V|Vs]) :-
    nonvar(V),
    rb_lookup(V, _, EVs), !.
get_top(_, Vs, Vs).