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yap-6.3/packages/ProbLog/problog/variable_elimination.yap
2010-08-26 14:40:50 +02:00

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%%% -*- Mode: Prolog; -*-
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% $Date: 2010-08-24 15:23:06 +0200 (Tue, 24 Aug 2010) $
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:- module(variable_elimination, [trie_check_for_and_cluster/1, trie_replace_and_cluster/2, clean_up/0, variable_elimination_stats/3]).
:- ensure_loaded(library(lists)).
:- ensure_loaded(library(tries)).
:- use_module('flags', _, [problog_define_flag/5]).
:- nb_setval(prob_fact_count, 0).
:- problog_define_flag(variable_elimination, problog_flag_validate_boolean, 'enable variable elimination', false, variable_elimination).
bit_encode(L, ON):-
bit_encode(L, ON, 0).
bit_encode([], ON, ON):-!.
bit_encode([PF|T], ON, Acc):-
(recorded(variable_elimination, prob_fact(PF, ID), _) ->
true
;
nb_getval(prob_fact_count, ID),
NID is ID + 1,
nb_setval(prob_fact_count, NID),
recordz(variable_elimination, prob_fact(PF, ID), _)
),
NAcc is Acc \/ (1 << ID),
bit_encode(T, ON, NAcc).
bit_decode(ON, L):-
bit_decode(ON, 0, L).
bit_decode(_, ID, []):-
nb_getval(prob_fact_count, ID), !.
bit_decode(ON, ID, [PF|L]):-
0 < ON /\ (1 << ID),
recorded(variable_elimination, prob_fact(PF, ID), _),
NID is ID + 1,
bit_decode(ON, NID, L).
bit_decode(ON, ID, L):-
NID is ID + 1,
bit_decode(ON, NID, L).
update_table(T, ON, NT):-
update_table(T, ON, NT, 0).
update_table([], _ON, [], _).
update_table([H|T], ON, [NH|NT], Row):-
0 is ON /\ (1 << Row), !,
NH is H /\ \ ON, % this is an optional improvement
NRow is Row + 1,
update_table(T, ON, NT, NRow).
update_table([H|T], ON, [NH|NT], Row):-
NH is H /\ ON,
NRow is Row + 1,
update_table(T, ON, NT, NRow).
make_mask(FromBit, ToBit, Mask):-
Mask is (1 << (ToBit + 1) - 1) - (1 << FromBit - 1).
make_table(_, 0, []):-!.
make_table(ON, T, [ON|L]):-
NT is T - 1,
make_table(ON, NT, L).
modify_table(L, OT, NT):-
nb_getval(prob_fact_count, OLS),
bit_encode(L, ON),
nb_getval(prob_fact_count, NLS),
update_table(OT, ON, L1),
D is NLS - OLS,
make_mask(OLS, NLS, M),
NON is M /\ ON,
make_table(NON, D, L2),
append(L1, L2, NT).
examin(T):-
examin(T, 0).
examin([], _Row).
examin([H|T], Row):-
N is 1 << Row,
0 is H /\ (N - 1),
0 < H - N, !,
bit_decode(H, L),
calc_prob_AND_cluster(L, P),
make_prob_fact(L, P, ID),
recordz(variable_elimination, and_cluster(L, ID), _),
NRow is Row + 1,
examin(T, NRow).
examin([_H|T], Row):-
NRow is Row + 1,
examin(T, NRow).
trie_check_for_and_cluster(T):-
tries:trie_traverse_first(T, E), !,
trie_check_for_and_cluster(E, []).
trie_check_for_and_cluster(_T).
trie_check_for_and_cluster(E, T):-
tries:trie_traverse_next(E, N), !,
tries:trie_get_entry(E, L),
modify_table(L, T, NT),
trie_check_for_and_cluster(N, NT).
trie_check_for_and_cluster(E, T):-
tries:trie_get_entry(E, L),
modify_table(L, T, NT),
examin(NT), !.
trie_replace_and_cluster(To, Tn):-
tries:trie_open(Tn),
trie_replace_and_cluster_do(To, Tn).
trie_replace_and_cluster_do(To, Tn):-
trie_traverse(To, E),
trie_get_entry(E, L),
findall(Cluster/VarName, recorded(variable_elimination, and_cluster(Cluster, VarName), _), Clusters),
foreach(Clusters, NewL, L),
trie_put_entry(Tn, NewL, _),
fail.
trie_replace_and_cluster_do(_To, _Tn).
foreach([], L, L).
foreach([Cluster/VarName|Rest], L, Acc):-
check_replace_cluster(Cluster, VarName, Acc, NL),
foreach(Rest, L, NL).
check_replace_cluster(Cluster, _VarName, L, L):-
nocluster(Cluster, L), !.
check_replace_cluster(Cluster, VarName, L, NewL):-
replace_cluster(Cluster, VarName, L, NewL).
replace_cluster(Cluster, VarName, L, Res):-
first_cluster_element(L, Cluster, First),
replace(L, First, VarName, NL),
delete(Cluster, First, RestCluster),
eliminate_list(RestCluster, NL, Res),
!.
replace_cluster(Cluster, VarName, _L, _Res):-
throw(error(Cluster, VarName)).
replace_cluster2(Cluster, VarName, L, Res):-
eliminate_list(Cluster, L, NL),
append(NL, [VarName], Res),
!.
replace_cluster2(Cluster, VarName, _L, _Res):-
throw(error(Cluster, VarName)).
replace_cluster3(Cluster, VarName, L, Res):-
last_cluster_element(L, Cluster, Last),
replace(L, Last, VarName, NL),
delete(Cluster, Last, RestCluster),
eliminate_list(RestCluster, NL, Res),
!.
replace_cluster3(Cluster, VarName, _L, _Res):-
throw(error(Cluster, VarName)).
first_cluster_element([], _, _).
first_cluster_element([H|_T], Cluster, H):-
memberchk(H, Cluster), !.
first_cluster_element([_H|T], Cluster, R):-
first_cluster_element(T, Cluster, R).
last_cluster_element(L, Cluster, R):-
reverse(L, RL),
first_cluster_element(RL, Cluster, R).
nocluster([], _).
nocluster([H|T], L):-
not(memberchk(H, L)),
nocluster(T, L).
eliminate_list([], L, L).
eliminate_list([H|T], L, Res):-
memberchk(H, L),
delete(L, H, NL),
eliminate_list(T, NL, Res).
replace([], _, _, []).
replace([H|T], H, NH, [NH|NT]):-
replace(T, H, NH, NT).
replace([H|T], R, NR, [H|NT]):-
\+ H == R,
replace(T, R, NR, NT).
clean_up:-
eraseall(variable_elimination),
nb_setval(prob_fact_count, 0).
variable_elimination_stats(Clusters, OrigPF, CompPF):-
nb_getval(prob_fact_count, OrigPF),
findall(L, (recorded(variable_elimination, and_cluster(Cluster, _), _), length(Cluster, L)), LL),
sum_list(LL, EliminatedPF),
length(LL, Clusters),
CompPF is OrigPF - EliminatedPF + Clusters.
calc_prob_AND_cluster(L, P):-
multiply_list(L, P, 1.0).
multiply_list([], P, P).
multiply_list([H|T], Pr, A):-
problog:get_fact_probability(H, P),
number(P),
NA is A * P,
multiply_list(T, Pr, NA).
make_prob_fact(L, P, ID):-
(clause(problog:problog_var_elimination(ID, L, _), true) ->
true
;
problog:probclause_id(ID),
assert_static(problog:prob_for_id(ID, P, _)),
(clause(problog:problog_predicate(var_elimination, 1), true) ->
true
;
assert(problog:problog_predicate(var_elimination, 1))
),
assert(problog:problog_var_elimination(ID, L, P))
).