/*
* Pushes a clause to a list depending on its evaluation
*
* If it is fixed to be satisfied, push to sat_clauses
* If it is satisfied, push to the corresponding watched list
* If it is unsatisified, push to unsat_clauses
*/
void insert_live_clause(samp_clause_t *clause, samp_table_t *table) {
rule_inst_table_t *rule_inst_table = &table->rule_inst_table;
atom_table_t *atom_table = &table->atom_table;
int32_t i, fixable;
samp_literal_t lit;
/* See if the clause is fixed-unit propagating */
fixable = get_fixable_literal(atom_table->assignment,
rule_inst_table->assignment, clause);
if (fixable == -2) {
/* fixed unsat */
mcsat_err("There is a fixed unsat clause, no model exists.");
return;
}
else if (fixable == -1) { /* more than one unfixed lits */
i = get_true_literal(atom_table->assignment,
rule_inst_table->assignment, clause);
if (i < 0) {
/* currently unsat, put back to the unsat list */
clause_list_insert_head(clause,
&rule_inst_table->unsat_clauses);
} else if (i == clause->num_lits) {
/* currently sat, put to the rule_watched list */
clause_list_insert_head(clause,
&rule_inst_table->rule_watched[clause->rule_index]);
} else {
/* currently sat, put to the watched list */
clause_list_insert_head(clause,
&rule_inst_table->watched[clause->disjunct[i]]);
}
} else {
/* fix a soft rule to unsat, because one of its clauses is fixed unsat */
if (fixable == clause->num_lits) {
rule_inst_t *rinst = rule_inst_table->rule_insts[clause->rule_index];
if (assigned_true(rule_inst_table->assignment[clause->rule_index])) {
rule_inst_table->unsat_weight += rinst->weight;
} else {
rule_inst_table->sat_weight += rinst->weight;
}
if (get_verbosity_level() >= 3) {
printf("[insert_live_clause] Fix rule %d: \n", clause->rule_index);
print_rule_instance(rinst, table);
printf(" to false\n");
}
rule_inst_table->assignment[clause->rule_index] = v_up_false;
} else {
/* fixed sat if we fix the 'fixable' literal */
lit = clause->disjunct[fixable];
if (unfixed_tval(atom_table->assignment[var_of(lit)])) {
/* unit propagation */
fix_lit_true(table, lit);
} else {
// already fixed sat
}
assert(assigned_fixed_true_lit(atom_table->assignment, lit));
}
clause_list_insert_head(clause, &rule_inst_table->sat_clauses);
}
}
/*
* Returns if a clause contains a literal that is fixed to true
*/
static bool clause_contains_fixed_true_lit(samp_clause_t *clause,
samp_truth_value_t *assignment) {
int32_t i;
for (i = 0; i < clause->num_lits; i++) {
if (assigned_fixed_true_lit(assignment, clause->disjunct[i]))
return true;
}
return false;
}
/*
* Checks the satisfiability of a clause
*
* if fixable, i.e., a fixed true literal or a unique non-fixed literal exists,
* returns the index of the literal;
* if unfixable, i.e., has at least two unfixed literals, returns -1;
* if fixed unsat, returns -2.
*/
static int32_t get_fixable_literal(
samp_truth_value_t *atom_assignment,
samp_truth_value_t *rule_assignment,
samp_clause_t *clause) {
samp_literal_t *disjunct = clause->disjunct;
int32_t num_lits = clause->num_lits;
int32_t i, j;
/* case 0: fixed sat */
/* if a rule is fixed false, its clauses should not be in the clause lists */
assert(!assigned_fixed_false(rule_assignment[clause->rule_index]));
for (i = 0; i < num_lits; i++) {
if (assigned_fixed_true_lit(atom_assignment, disjunct[i]))
return i;
}
for (i = 0; i < num_lits; i++) {
if (!assigned_fixed_false_lit(atom_assignment, disjunct[i]))
break;
}
if (i == num_lits) {
if (assigned_fixed_true(rule_assignment[clause->rule_index]))
return -2; /* case 4: fixed unsat */
else
return num_lits; /* the rule delegate literal is fixable */
}
/* i is the first unfixed literal, now check if there is a second one */
for (j = i + 1; j < num_lits; j++) {
if (!assigned_fixed_false_lit(atom_assignment, disjunct[j]))
break;
}
/* there are at least two unfixed literals */
if (j < num_lits) {
return -1;
} else if (!fixed_tval(rule_assignment[clause->rule_index])) {
return -1;
} else { /* i is uniquely fixable */
return i;
}
}