//frees the SatState
void sat_state_free(SatState* sat_state) {
for (c2dSize i = 1; i <= sat_var_count(sat_state); i++) {
Var* var = sat_index2var(i, sat_state);
vector_free(&var->mentions);
vector_free(&var->mentions_lc);
free(var);
free(sat_index2literal(i, sat_state));
free(sat_index2literal(-i, sat_state));
}
for (c2dSize i = 1; i <= sat_clause_count(sat_state); i++) {
Clause* clause = sat_index2clause(i, sat_state);
vector_free(&clause->lits);
free(clause);
}
vector_free(&sat_state->vars);
vector_free(&sat_state->plits);
vector_free(&sat_state->nlits);
vector_free(&sat_state->kb);
vector_free(&sat_state->lc);
vector_free(&sat_state->ds);
vector_free(&sat_state->il);
vector_free(&sat_state->q);
vector_free(&sat_state->s);
free(sat_state);
}
/******************************************************************************
Two literal watch algorithm for unit resolution
The algorithm taken from the Class Notes for CS264A, UCLA
******************************************************************************/
BOOLEAN two_literal_watch(SatState* sat_state, Lit** literals_list, unsigned long num_elements, unsigned long type){
// Once I entered here I must have elements in the decision array
assert(sat_state->num_literals_in_decision > 0);
// initialize the list of watched clauses already initialized in ParseDIMACS
// if(!INIT_LITERAL_WATCH)
// intitialize_watching_clauses(sat_state);
BOOLEAN contradiction_flag = 0;
//TODO: Due to recursion of pending list we may need to consider more than one decided literal then we need a list that captures all literals of last decision
//loop on all decided literals
// Lit** literals_in_decision = literals_list;
// unsigned long max_size_decision_list = capacity;
// unsigned long num_decision_lit = num_elements;
// Create pending literal list
Lit** pending_list = (Lit**)malloc(sizeof(Lit*));
unsigned long max_size_pending_list = 1;
unsigned long num_pending_lit = 0;
unsigned long initial_num_elements = num_elements;
for(unsigned long i =0; i< num_elements; i++){
#ifdef DEBUG
printf("--------------------------------------\n");
printf("Decision list now in two literal watch: ");
for(unsigned long j =0; j< num_elements;j++){
printf("%ld\t", literals_list[j]->sindex );
}
printf("\n");
#endif
if(type == CASE1 && (sat_state->decisions[i]->decision_level != sat_state->current_decision_level)){
continue; // don't re-evaluate this literal
}else if(type == CASE2 && sat_state->decisions[i]->decision_level != sat_state->current_decision_level){
continue;
}else if(type == CASE2 && sat_state->decisions[i]->decision_level == sat_state->current_decision_level && i < initial_num_elements-1){
continue;
}
else{
//Lit* decided_literal = sat_state->decisions[sat_state->num_literals_in_decision -1];
Lit* decided_literal = literals_list[i];
Lit* resolved_literal = get_resolved_lit(decided_literal, sat_state);
#ifdef DEBUG
printf("Resolved Literal: %ld\n", resolved_literal->sindex);
#endif
//Update clauses state based on the decided literal
sat_update_clauses_state(decided_literal , sat_state);
//If no watching clauses on the resolved literal then do nothing and record the decision
if(resolved_literal->num_watched_clauses == 0){
// The decided literal is already in the decision list so no need to record it again
#ifdef DEBUG
printf("Number of watching clause on literal %ld is %ld\n",resolved_literal->sindex,resolved_literal->num_watched_clauses );
#endif
//wait for a new decision
continue;
}
else{
//Get the watched clauses for the resolved literal
for(unsigned long k = 0; k < resolved_literal->num_watched_clauses && contradiction_flag == 0; k++){
//check dirty flag
if(resolved_literal->list_of_dirty_watched_clauses[k] == 0) continue;
Clause* wclause = sat_index2clause( resolved_literal->list_of_watched_clauses[k], sat_state);
//TODO: Check if this actually works to skip the subsumed clauses
//TODO: Enhance: we can only get the watched clauses that are not subsumed to speed it up and to avoid checking the unit clause
if(wclause->is_subsumed)
continue;
unsigned long num_free_literals = 0;
// I have to check the other watched literal
Lit* the_other_watched_literal = NULL;
if(resolved_literal->sindex == wclause->L1->sindex)
the_other_watched_literal = wclause->L2;
else if(resolved_literal->sindex == wclause->L2->sindex)
the_other_watched_literal = wclause->L1;
// FIXME the_other_watched_literal is not always set by this point
// but is being dereferenced in the loop below
#ifdef DEBUG
printf("Current watching clause = %ld\n", wclause->cindex);
//printf("Before assertion, resolved literal %ld, wcluase 1 index=%ld, wclause 2 idx =%ld \n", resolved_literal->sindex, wclause->L1->sindex, wclause->L2->sindex );
//print_all_clauses(sat_state);
#endif
assert(the_other_watched_literal!=NULL);
for(unsigned long l = 0; l < wclause->num_literals_in_clause; l++){
//check for not resolved literal = free or asserted
if( !sat_is_resolved_literal(wclause->literals[l]) && wclause->literals[l]->sindex != the_other_watched_literal->sindex ) {
num_free_literals++;
}
}
if (num_free_literals == 0){ //3cases
//contradiction --> everything is resolved
//subsumed clause --> do nothing
//implication --> free literal
if(sat_is_resolved_literal(the_other_watched_literal)){
// all literal of the clause are resolved --> contradiction
contradiction_flag = 1;
#ifdef DEBUG
printf("-------------Contradiction happens with clause: %ld in level: %ld\n",wclause->cindex, sat_state->current_decision_level);
#endif
sat_state->conflict_clause = wclause;
break; //break from loop of watched clauses over this decided literal
}
else if(sat_is_asserted_literal(the_other_watched_literal)){
// we do nothing since this clause is subsumed
wclause->is_subsumed = 1;
contradiction_flag = 0; // just checking if I have to reassign the value in order to avoid the compilation optimization
continue;
}
else if (the_other_watched_literal->LitState == 0){
// implication
if(sat_literal_var(the_other_watched_literal)->antecedent == 0){
sat_literal_var(the_other_watched_literal)->antecedent = wclause->cindex; // remember the decision list is updated with the pending list so that's ok
#ifdef DEBUG
printf("free literal %ld\n",the_other_watched_literal->sindex);
//print_clause(wclause);
printf("Antecedent: \n");
print_clause(sat_index2clause(sat_literal_var(the_other_watched_literal)->antecedent, sat_state));
#endif
add_literal_to_list(&pending_list, the_other_watched_literal , &max_size_pending_list, &num_pending_lit);
#ifdef DEBUG
printf("Add the free literal %ld to the pending list with antecedent %ld\n",the_other_watched_literal->sindex, (sat_literal_var(the_other_watched_literal)->antecedent) );
#endif
continue; // go to the next clause
}
else { //this means I implied the opposite (contradiction) or the same literal again(redundancy) in another clause
//TODO: first check if pending list contains the same literal, if yes then just continue to the next clause else contradiction
BOOLEAN lit_is_already_in_pending = 0;
for(unsigned long pendelem =0; pendelem<num_pending_lit; pendelem ++){
if (pending_list[pendelem]->sindex == the_other_watched_literal->sindex)
lit_is_already_in_pending =1;
}
if(lit_is_already_in_pending == 1)
continue; //go to the next clause
else{
contradiction_flag= 1;
#ifdef DEBUG
printf("free literal %ld\n",the_other_watched_literal->sindex);
printf("-------------Contradiction(opposite implication) happens with clause: %ld\n",wclause->cindex);
#endif
sat_state->conflict_clause = wclause;
break; //break from loop of watched clauses over this decided literal
}
}
} //end of the implication case
} // end of the three cases
else if (num_free_literals > 0) { // find another literal to watch that is free
for(unsigned long z = 0; z < wclause->num_literals_in_clause; z++){
if((!sat_is_resolved_literal(wclause->literals[z])) && wclause->literals[z] != wclause->L1 && wclause->literals[z] != wclause->L2){
Lit* new_watched_lit = wclause->literals[z];
//remove_watching_clause(k, resolved_literal);
resolved_literal->list_of_dirty_watched_clauses[k] = 0;
//add the watching clause to the free literal
add_watching_clause(wclause, new_watched_lit);
assert(resolved_literal->sindex == wclause->L1->sindex || resolved_literal->sindex == wclause->L2->sindex );
// remove the resolved literal from the watch and update the clause watch list
if(resolved_literal->sindex == wclause->L1->sindex)
wclause->L1 = new_watched_lit;
else if (resolved_literal->sindex == wclause->L2->sindex)
wclause->L2 = new_watched_lit;
break;
}
}
} //end of else number of free literals > 0
} //end of for for watched clauses over this decided literal
//SALMA removed and the contradiction !=1
if(num_pending_lit >0){
// Pass over the pending list and add the literals to the decision while maintaining the level
for(unsigned long i =0; i < num_pending_lit; i++){
//evaluate the pending list to make sure we didn't miss a chance of contraction // if the contradiction flag is raised then the conflict clause is already set in this function
//BOOLEAN fails = evaluate_delta(sat_state, pending_list, i+1); //up till this pending literal
// pending literal was an already watched clause so the associated list of watching clauses is already handled
// fix values of pending literal before putting in decision
Lit* pending_lit = pending_list[i];
//TODO: the decision level should be the same as the max level of the antecedent not the current level.
//pending_lit->decision_level = sat_state->current_decision_level; // this is so wrong ... this will affect the UIP learning at contradiction because of stopping condition
unsigned long pending_lit_decision =0;
Var* pending_var = sat_literal_var(pending_lit);
Clause* pending_antecedent = sat_index2clause(pending_var->antecedent, sat_state);
for(unsigned long indxant =0; indxant < pending_antecedent->num_literals_in_clause; indxant++ ){
Var* current_var = sat_literal_var(pending_antecedent->literals[indxant]);
if(current_var->index == pending_var->index)
continue; //skip the var
else if(pending_antecedent->literals[indxant]->decision_level > pending_lit_decision)
pending_lit_decision = pending_antecedent->literals[indxant]->decision_level;
}
pending_lit->decision_level = pending_lit_decision;
//TODO: this part is already done in evaluate delta
if(pending_lit->sindex <0){
pending_lit->LitValue = 0;
pending_lit->LitState = 1;
Lit* opposite_lit = sat_literal_var(pending_lit)->posLit;
opposite_lit->LitValue = 0;
opposite_lit->LitState = 1;
opposite_lit->decision_level = pending_lit->decision_level;
}
else if(pending_lit->sindex >0){
pending_lit->LitValue = 1;
pending_lit->LitState = 1;
Lit* opposite_lit = sat_literal_var(pending_lit)->negLit;
opposite_lit->LitValue = 1;
opposite_lit->LitState = 1;
opposite_lit->decision_level = pending_lit->decision_level;
}
// for(unsigned long i = 0; i< sat_literal_var(pending_lit)->num_of_clauses_of_variables; i++){
// Clause* clause = sat_literal_var(pending_lit)->list_clause_of_variables[i];
//
// }
//update the decision list
sat_state->decisions[sat_state->num_literals_in_decision++] = pending_lit;
//update list of literals in last decision because this is the main loop
literals_list[num_elements++] = pending_lit;
// if (fails == 1){
// contradiction_flag = 1;
// break;
// }
}
// //free pending list for the next round
// if(pending_list != NULL && num_pending_lit != 0)
// FREE(pending_list);
} // pending_list > 1
}//Get the watched clauses for the resolved literal
//free pending list for the next round
//--> pending list is related to each decided literal. so before taking a new decision clear the pending list
//double free or corruption (out):
if(pending_list != NULL && num_pending_lit != 0){
//FREE(pending_list);
// TODO: free pending list
num_pending_lit = 0;
}
if(contradiction_flag == 1) // no need to go for another literal in the decided literal list
break;
}//end of for for decide literal
}
//TODO: This is so bad ... need to figure out why this sentence is executed even if I have a return when the contradiction happens
//TODO: needs to find a way to clear the literals in last_decision
// if(literals_in_last_decision != NULL && num_last_decision_lit !=0)
// FREE(literals_in_last_decision);
if(contradiction_flag == 1)
return 0;
else
return 1;
}
static BOOLEAN evaluate_current_assignment(SatState* sat_state, Lit** pending_list, unsigned long num_pending_lit){
#ifdef DEBUG
printf("Evaluate the current assignment\n");
#endif
BOOLEAN fails = 0;
// just for the sake of this function but will be reset if contradiction happens
for(unsigned long i =0; i<num_pending_lit; i++){
Lit* pending_lit = pending_list[i];
if(pending_lit->sindex <0){
pending_lit->LitValue = 0;
pending_lit->LitState = 1;
}
else if(pending_lit->sindex >0){
pending_lit->LitValue = 1;
pending_lit->LitState = 1;
}
}
Lit** decisions = sat_state->decisions;
//now I have the current decision and the pending list
// instead of merging the two list in one list just pass by each one
for(unsigned long i =0; i<sat_state->num_literals_in_decision; i++){
#ifdef DEBUG
printf("In the decision literals loop: current literal %ld \n", decisions[i]->sindex);
#endif
Var* corresponding_var = sat_literal_var(decisions[i]);
unsigned long* decision_clause_list = corresponding_var->list_clause_of_variables;
for(unsigned long j=0; j<corresponding_var->num_of_clauses_of_variables; j++){
Clause* clause = sat_index2clause(decision_clause_list[j], sat_state);
//check clause
for(unsigned long k = 0; k<clause->num_literals_in_clause;k++){
//check if the literal is asserted or not yet set
if(sat_is_asserted_literal(clause->literals[k]) || (!sat_implied_literal(clause->literals[k]) )){
break; //don't check the other literals of the clause
}
else if(k== clause->num_literals_in_clause-1){ // I reached the end of the loop with no break (contradicted clause)
fails = 1;
sat_state->conflict_clause = clause;
// reset the pending list
for(unsigned long i =0; i<num_pending_lit; i++){
Lit* pending_lit = pending_list[i];
pending_lit->LitValue = 'u';
pending_lit->LitState = 0;
}
return fails;
}
} // for all literals in a clause
} // for all clauses for this variable
}// for all variables in decision list
//repeat the same for pending list
for(unsigned long i =0; i< num_pending_lit; i++){
#ifdef DEBUG
printf("In the pending literals loop: current literal %ld \n", pending_list[i]->sindex);
#endif
Var* corresponding_var = sat_literal_var(pending_list[i]);
unsigned long* pending_clause_list = corresponding_var->list_clause_of_variables;
for(unsigned long j=0; j<corresponding_var->num_of_clauses_of_variables; j++){
Clause* clause = sat_index2clause(pending_clause_list[j], sat_state);
//check clause
for(unsigned long k = 0; k<clause->num_literals_in_clause;k++){
//check if the literal is asserted or not yet set
if(sat_is_asserted_literal(clause->literals[k]) || (!sat_implied_literal(clause->literals[k]) )){
break; //don't check the other literals of the clause
}
else if(k== clause->num_literals_in_clause-1){ // I reached the end of the loop with no break (contradicted clause)
fails = 1;
sat_state->conflict_clause = clause;
// reset the pending list
for(unsigned long i =0; i<num_pending_lit; i++){
Lit* pending_lit = pending_list[i];
pending_lit->LitValue = 'u';
pending_lit->LitState = 0;
}
return fails;
}
} // for all literals in a clause
} // for all clauses for this variable
}// for all variables in pending list
//TODO: check do i have to unset all the literals in the pending list
#ifdef DEBUG
if(fails == 1){
printf("Contradiction happens in evaluating clauses in the pending list\n");
}
#endif
return fails;
}
//constructs a SatState from an input cnf file
SatState* sat_state_new(const char* file_name) {
FILE *file;
if (!(file = fopen(file_name, "r")))
return NULL;
SatState *sat_state = malloc(sizeof(SatState));
while (!feof(file)) {
if (fgetc(file) == 'p')
break;
while (fgetc(file) != '\n')
continue;
}
fscanf(file, " cnf %lu %lu", &sat_state->varnum, &sat_state->clausenum);
vector_init(&sat_state->vars);
vector_init(&sat_state->plits);
vector_init(&sat_state->nlits);
vector_init(&sat_state->kb);
vector_init(&sat_state->lc);
vector_init(&sat_state->ds);
vector_init(&sat_state->il);
vector_init(&sat_state->q);
vector_init(&sat_state->s);
sat_state->ac = NULL;
for (c2dSize i = 1; i <= sat_var_count(sat_state); i++) {
Var* var = malloc(sizeof(Var));
var->index = i;
var->mark = 0;
vector_init(&var->mentions);
vector_init(&var->mentions_lc);
Lit* plit = malloc(sizeof(Lit));
plit->index = i;
plit->implied = 0;
plit->var = var;
Lit* nlit = malloc(sizeof(Lit));
nlit->index = -i;
nlit->implied = 0;
nlit->var = var;
vector_push(&sat_state->plits, plit);
vector_push(&sat_state->nlits, nlit);
var->plit = plit;
var->nlit = nlit;
vector_push(&sat_state->vars, var);
}
for (c2dSize i = 1; i <= sat_clause_count(sat_state); i++) {
Clause* clause = malloc(sizeof(Clause));
clause->index = i;
clause->subsumed = 0;
clause->mark = 0;
vector_init(&clause->lits);
while (1) {
c2dLiteral index;
while (!fscanf(file, "%ld", &index) || (index == 0 && vector_size(&clause->lits) == 0)) {
while (fgetc(file) != '\n')
continue;
}
if (index == 0)
break;
vector_push(&clause->lits, sat_index2literal(index, sat_state));
}
vector_push(&sat_state->kb, clause);
vector_push(&sat_state->q, clause);
}
for (c2dSize i = 1; i <= sat_clause_count(sat_state); i++) {
Clause* clause = sat_index2clause(i, sat_state);
for (c2dSize j = 0; j < sat_clause_size(clause); j++) {
Lit* lit = vector_get(&clause->lits, j);
Var* var = sat_literal_var(lit);
if (vector_size(&var->mentions) == 0 || vector_top(&var->mentions) != clause)
vector_push(&var->mentions, clause);
}
}
fclose(file);
return sat_state;
}
//applies unit resolution to the cnf of sat state
//returns 1 if unit resolution succeeds, 0 if it finds a contradiction
BOOLEAN sat_unit_resolution(SatState* sat_state) {
Lit* ret_lit;
Var* var;
c2dLiteral tmp_value;
Clause* conflict_clause = NULL;
c2dSize f = 0, r = 0;
Lit** tmp_lit_list = sat_state->tmp_lit_list;
// Push the new decided literal
if (sat_state->unit_resolution_s == UNIT_RESOLUTION_AFTER_DECIDING_LITERAL) {
if (sat_state->num_decided_literals > 0) {
tmp_lit_list[++r] = sat_state->decided_literals[sat_state->num_decided_literals-1];
}
if (sat_state->num_implied_literals > 0) {
c2dSize i = sat_state->num_implied_literals - 1;
while (sat_state->implied_literals[i]->decision_level == sat_state->cur_level) {
tmp_lit_list[++r] = sat_state->implied_literals[i];
if (i == 0) break;
i--;
}
}
}
// Check whether has unit clause
c2dSize start_clauses = 1;
if (sat_state->unit_resolution_s == UNIT_RESOLUTION_AFTER_ASSERTING_CLAUSE)
start_clauses = sat_state->num_cnf_clauses + sat_state->num_learned_clauses;
if (sat_state->unit_resolution_s == UNIT_RESOLUTION_AFTER_DECIDING_LITERAL)
start_clauses = sat_state->num_cnf_clauses + sat_state->num_learned_clauses + 1;
for (c2dSize i = start_clauses; i <= sat_state->num_cnf_clauses + sat_state->num_learned_clauses; i++) {
Clause* clause = sat_index2clause(i, sat_state);
tmp_value = check_clause(clause, &ret_lit);
if (tmp_value == -1) {
conflict_clause = clause;
break;
}
if (tmp_value == 2) {
instantiate_literal(ret_lit, sat_state->cur_level, clause);
sat_state->implied_literals[sat_state->num_implied_literals++] = ret_lit;
tmp_lit_list[++r] = ret_lit;
}
}
if (conflict_clause == NULL) {
// BFS, expands the implied literals
while (f < r) {
var = sat_literal_var(tmp_lit_list[++f]);
for (c2dSize i = 0; i < var->num_clauses; i++) {
tmp_value = check_clause(var->clauses[i], &ret_lit);
if (tmp_value == -1) {
conflict_clause = var->clauses[i];
break;
}
if (tmp_value == 2) {
instantiate_literal(ret_lit, sat_state->cur_level, var->clauses[i]);
sat_state->implied_literals[sat_state->num_implied_literals++] = ret_lit;
tmp_lit_list[++r] = ret_lit;
}
}
}
}
if (conflict_clause == NULL) {
// No conflict
sat_state->asserted_clause = NULL;
return 1;
}
// Has conflict, derives asserted clause
//
// It follows the algorithm:
//
// In implication graph, if the contradition happended at node n.
// then
// { {n} if n is root
// C(n) = {
// { ePa(n) \union \union_{m \in Pa(n)} C(m)
// where Pa(n) are the parents of node n which are set at the same level as n
// ePa(n) are the parents of ndoe n set at earlier levels
//
BOOLEAN* seen = sat_state->seen;
for (c2dSize i = 1; i <= sat_state->num_vars; i++) seen[i] = 0;
Lit** lit_list = sat_state->lit_list;
c2dSize lit_list_sz = 0;
f = 0, r = 0;
for (c2dSize i = 0; i < conflict_clause->size; i++) {
if (!seen[conflict_clause->literals[i]->var->index]) {
tmp_lit_list[++r] = conflict_clause->literals[i]->op_lit;
seen[conflict_clause->literals[i]->var->index] = 1;
}
}
c2dSize assertion_level = 1;
c2dSize dl;
while (f < r) {
Lit* lit = tmp_lit_list[++f];
if (lit->decision_level < sat_state->cur_level ||
lit->decision_clause == NULL) {
lit_list[lit_list_sz++] = lit->op_lit;
dl = lit->decision_level;
if (dl < sat_state->cur_level && dl > assertion_level) {
assertion_level = dl;
}
} else {
for (c2dSize i = 0; i < lit->decision_clause->size; i++) {
if (!seen[lit->decision_clause->literals[i]->var->index]) {
tmp_lit_list[++r] = lit->decision_clause->literals[i]->op_lit;
seen[lit->decision_clause->literals[i]->var->index] = 1;
}
}
}
}
sat_state->asserted_clause = new_clause(0, lit_list_sz, lit_list);
sat_state->asserted_clause->assertion_level = assertion_level;
return 0;
}
