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

/***********************************

  Variable Elimination in Prolog

  How to do it


  Three steps:
  build the graph:
    - for all variables, find out
      all tables they connect to;
      multiply their size
      order by size
  
*********************************/

:- module(clpbn_ve, [ve/3,
		check_if_ve_done/1,
		init_ve_solver/4,
		run_ve_solver/3]).

:- attribute size/1, all_diffs/1.

:- use_module(library(ordsets),
	[ord_union/3, 
	 ord_member/2]).

:- use_module(library('clpbn/xbif'), [clpbn2xbif/3]).

:- use_module(library('clpbn/graphviz'), [clpbn2gviz/4]).

:- use_module(library('clpbn/dists'),
	      [
	       dist/4,
	       get_dist_domain_size/2,
	       get_dist_matrix/5]).

:- use_module(library('clpbn/utils'), [
	clpbn_not_var_member/2]).

:- use_module(library('clpbn/display'), [
	clpbn_bind_vals/3]).

:- use_module(library('clpbn/connected'),
	      [
	       init_influences/3,
	       influences/4
	      ]).

:- use_module(library('clpbn/matrix_cpt_utils'),
	      [project_from_CPT/3,
	       reorder_CPT/5,
	       multiply_CPTs/4,
	       normalise_CPT/2,
	       sum_out_from_CPT/4,
	       list_from_CPT/2]).

:- use_module(library(lists),
	      [
	       append/3
	      ]).

:- use_module(library('clpbn/aggregates'),
	      [check_for_agg_vars/2]).


check_if_ve_done(Var) :-
	get_atts(Var, [size(_)]), !.

%
% implementation of the well known variable elimination algorithm
%
ve([[]],_,_) :- !.
ve([LVs],Vs0,AllDiffs) :-
	init_ve_solver([LVs], Vs0, AllDiffs, State),
	% variable elimination proper
	run_ve_solver([LVs], [LPs], State),
	% bind Probs back to variables so that they can be output.
	clpbn_bind_vals([LVs],[LPs],AllDiffs).

init_ve_solver(Qs, Vs0, _, LVis) :-
	check_for_agg_vars(Vs0, Vs1),
	% LVi will have a  list of CLPBN variables
	% Tables0 will have the full data on each variable
	init_influences(Vs1, G, RG),
	init_ve_solver_for_questions(Qs, G, RG, _, LVis).

init_ve_solver_for_questions([], _, _, [], []).
init_ve_solver_for_questions([Vs|MVs], G, RG, [NVs|MNVs0], [NVs|LVis]) :-
	influences(Vs, G, RG, NVs0),
	sort(NVs0, NVs),
%clpbn_gviz:clpbn2gviz(user_error, test, NVs, Vs),
	init_ve_solver_for_questions(MVs, G, RG, MNVs0, LVis).

% use a findall to recover space without needing for GC
run_ve_solver(LVs, LPs, LNVs) :-
	findall(Ps, solve_ve(LVs, LNVs, Ps), LPs).

solve_ve([LVs|_], [NVs0|_], Ps) :-
%	length(NVs0, L), (L > 10 -> clpbn_gviz:clpbn2gviz(user_error,sort,NVs0,LVs) ; true ),
%	length(NVs0, L), writeln(+L),
	find_all_clpbn_vars(NVs0, NVs0, LV0, LVi, Tables0),
	sort(LV0, LV),
	% construct the graph
	find_all_table_deps(Tables0, LV),
	process(LVi, LVs, tab(Dist,_,_)),
%writeln(m:Dist),matrix:matrix_to_list(Dist,LD),writeln(LD),
%exps(LD,LDE),writeln(LDE),
	% move from potentials back to probabilities
	normalise_CPT(Dist,MPs),
	list_from_CPT(MPs, Ps).
solve_ve([_|MoreLVs], [_|MoreLVis], Ps) :-
	solve_ve(MoreLVs, MoreLVis, Ps).

exps([],[]).
exps([L|LD],[O|LDE]) :-
	O is exp(L),
	exps(LD,LDE).

keys([],[]).
keys([V|NVs0],[K:E|Ks]) :-
	clpbn:get_atts(V,[key(K),evidence(E)]), !,
	keys(NVs0,Ks).
keys([V|NVs0],[K|Ks]) :-
	clpbn:get_atts(V,[key(K)]),
	keys(NVs0,Ks).

%
% just get a list of variables plus associated tables
%
find_all_clpbn_vars([], _, [], [], []) :- !.
find_all_clpbn_vars([V|Vs], NVs0, [Var|LV], ProcessedVars, [table(I,Table,Parents,Sizes)|Tables]) :-
	var_with_deps(V, NVs0, Table, Parents, Sizes, Ev, Vals), !,
	% variables with evidence should not be processed.
	(var(Ev) ->
	    Var = var(V,I,Sz,Vals,Parents,Ev,_,_),
	    ve_get_dist_size(V,Sz),
	    ProcessedVars = [Var|ProcessedVars0]
	;
	    ProcessedVars = ProcessedVars0
	),
	find_all_clpbn_vars(Vs, NVs0, LV, ProcessedVars0, Tables).

var_with_deps(V, NVs0, Table, Deps, Sizes, Ev, Vals) :-
	clpbn:get_atts(V, [dist(Id,Parents)]),
	get_dist_matrix(Id,Parents,_,Vals,TAB0),
	( 
	    clpbn:get_atts(V, [evidence(Ev)])
	->
	    true
	;
	    true
	), !,
	% set CPT in canonical form
	reorder_CPT([V|Parents],TAB0,Deps0,TAB1,Sizes1),
	% remove evidence.
	simplify_evidence(Deps0, NVs0, TAB1, Deps0, Sizes1, Table, Deps, Sizes).

find_all_table_deps(Tables0, LV) :-
	find_dep_graph(Tables0, DepGraph0),
	sort(DepGraph0, DepGraph),
	add_table_deps_to_variables(LV, DepGraph).

find_dep_graph([], []) :- !.
find_dep_graph([table(I,Tab,Deps,Sizes)|Tables], DepGraph) :-
	add_table_deps(Deps, I, Deps, Tab, Sizes, DepGraph0, DepGraph),
	find_dep_graph(Tables, DepGraph0).

add_table_deps([], _, _, _, _, DepGraph, DepGraph).
add_table_deps([V|Deps], I, Deps0, Table, Sizes, DepGraph0, [V-tab(Table,Deps0,Sizes)|DepGraph]) :-
	add_table_deps(Deps, I, Deps0, Table, Sizes, DepGraph0, DepGraph).

add_table_deps_to_variables([], []).
add_table_deps_to_variables([var(V,_,_,_,_,_,Deps,K)|LV], DepGraph) :-
	steal_deps_for_variable(DepGraph, V, NDepGraph, Deps),
	compute_size(Deps,[],K),
%	( clpbn:get_atts(V,[key(Key)]) -> format('~w:~w~n',[Key,K]) ; true),
	add_table_deps_to_variables(LV, NDepGraph).
	
steal_deps_for_variable([V-Info|DepGraph], V0, NDepGraph, [Info|Deps]) :-
	V == V0, !,
	steal_deps_for_variable(DepGraph, V0, NDepGraph, Deps).
steal_deps_for_variable(DepGraph, _, DepGraph, []).

compute_size([],Vs,K) :-
	% use sizes now
%	length(Vs,K).
	multiply_sizes(Vs,1,K).
compute_size([tab(_,Vs,_)|Tabs],Vs0,K) :-
	ord_union(Vs,Vs0,VsI),
	compute_size(Tabs,VsI,K).

multiply_sizes([],K,K).
multiply_sizes([V|Vs],K0,K) :-
	ve_get_dist_size(V, Sz),
	KI is K0*Sz,
	multiply_sizes(Vs,KI,K).

process(LV0, InputVs, Out) :-
	find_best(LV0, V0, -1, V, WorkTables, LVI, InputVs),
	V \== V0, !,
%	clpbn:get_atts(V,[key(K)]), writeln(chosen:K),
% format('1 ~w: ~w~n',[V,WorkTables]), write_tables(WorkTables),
	multiply_tables(WorkTables, tab(Tab0,Deps0,_)),
	reorder_CPT(Deps0,Tab0,Deps,Tab,Sizes),
	Table = tab(Tab,Deps,Sizes),
% format('2 ~w: ~w~n',[V,Table]),
	project_from_CPT(V,Table,NewTable),
% format('3 ~w: ~w~n',[V,NewTable]), write_tables([NewTable]),
	include(LVI,NewTable,V,LV2),
	process(LV2, InputVs, Out).
process(LV0, _, Out) :-
	fetch_tables(LV0, WorkTables0),
	sort(WorkTables0, WorkTables),
% format('4 ~w: ~w~n',[LV0,WorkTables]), write_tables(WorkTables),
	multiply_tables(WorkTables, Out).


write_tables([]).
write_tables([tab(Mat,_,_)|WorkTables]) :-
	matrix:matrix_to_list(Mat,L),
	writeln(L),
	write_tables(WorkTables).


find_best([], V, _TF, V, _, [], _).
%:-
%	clpbn:get_atts(V,[key(K)]), writeln(chosen:K:_TF).
% root_with_single_child
%find_best([var(V,I,_,_,[],Ev,[Dep],K)|LV], _, _, V, [Dep], LVF, Inputs) :- !.	
find_best([var(V,I,Sz,Vals,Parents,Ev,Deps,K)|LV], _, Threshold, VF, NWorktables, LVF, Inputs) :-
	( K < Threshold ; Threshold < 0),
	clpbn_not_var_member(Inputs, V), !,
	find_best(LV, V, K, VF, WorkTables,LV0, Inputs),
	(V == VF ->
	    LVF = LV0, Deps = NWorktables
	;
	    LVF = [var(V,I,Sz,Vals,Parents,Ev,Deps,K)|LV0], WorkTables = NWorktables
	).
find_best([V|LV], V0, Threshold, VF, WorkTables, [V|LVF], Inputs) :-
	find_best(LV, V0, Threshold, VF, WorkTables, LVF, Inputs).

multiply_tables([Table], Table) :- !. %, Table = tab(T,D,S),matrix:matrix_to_list(T,L),writeln(D:S:L).
multiply_tables([TAB1, TAB2| Tables], Out) :-
%TAB1 = tab(T,_,_),matrix:matrix_to_list(T,L),writeln(doing:L),
	multiply_CPTs(TAB1, TAB2, TAB, _),
	multiply_tables([TAB| Tables], Out).


simplify_evidence([], _, Table, Deps, Sizes, Table, Deps, Sizes).
simplify_evidence([V|VDeps], NVs0, Table0, Deps0, Sizes0, Table, Deps, Sizes) :-
	clpbn:get_atts(V, [evidence(_)]), !,
	project_from_CPT(V,tab(Table0,Deps0,Sizes0),tab(NewTable,Deps1,Sizes1)),
	simplify_evidence(VDeps, NVs0, NewTable, Deps1, Sizes1, Table, Deps, Sizes).
simplify_evidence([V|VDeps], NVs0, Table0, Deps0, Sizes0, Table, Deps, Sizes) :-
	ord_member(V, NVs0), !,
	simplify_evidence(VDeps, NVs0, Table0, Deps0, Sizes0, Table, Deps, Sizes).
simplify_evidence([V|VDeps], NVs0, Table0, Deps0, Sizes0, Table, Deps, Sizes) :-
	project_from_CPT(V,tab(Table0,Deps0,Sizes0),tab(NewTable,Deps1,Sizes1)),
	simplify_evidence(VDeps, NVs0, NewTable, Deps1, Sizes1, Table, Deps, Sizes).

fetch_tables([], []).
fetch_tables([var(_,_,_,_,_,_,Deps,_)|LV0], Tables) :-
	append(Deps,Tables0,Tables),
	fetch_tables(LV0, Tables0).

 
include([],_,_,[]).
include([var(V,P,VSz,D,Parents,Ev,Tabs,Est)|LV],tab(T,Vs,Sz),V1,[var(V,P,VSz,D,Parents,Ev,Tabs,Est)|NLV]) :-
	clpbn_not_var_member(Vs,V), !,
	include(LV,tab(T,Vs,Sz),V1,NLV).
include([var(V,P,VSz,D,Parents,Ev,Tabs,_)|LV],Table,NV,[var(V,P,VSz,D,Parents,Ev,NTabs,NEst)|NLV]) :-
	update_tables(Tabs,NTabs,Table,NV),
	compute_size(NTabs, [], NEst),
	include(LV,Table,NV,NLV).

update_tables([],[Table],Table,_).
update_tables([tab(Tab0,Vs,Sz)|Tabs],[tab(Tab0,Vs,Sz)|NTabs],Table,V) :-
	clpbn_not_var_member(Vs,V), !,
	update_tables(Tabs,NTabs,Table,V).
update_tables([_|Tabs],NTabs,Table,V) :-
	update_tables(Tabs,NTabs,Table,V).

ve_get_dist_size(V,Sz) :-
	get_atts(V, [size(Sz)]), !.
ve_get_dist_size(V,Sz) :-
	clpbn:get_atts(V,dist(Id,_)), !,
	get_dist_domain_size(Id,Sz),
	put_atts(V, [size(Sz)]).