/*
* Compute an implicant for constraint i
* - we must have an assignment for the exists variable in solver->evalue
* and an assignment for the universal variables of constraints i in
* solver->uvalue_aux.
* - this builds and store the full model for constraint i in solver->full_model
* then construct and store the implicant in solver->implicant
*
* Error codes: set solver->status to EF_STATUS_ERROR
* - this may happen if yices_model_from_map or yices_implicant_for_fomuulas fail
*/
static void ef_build_implicant(ef_solver_t *solver, uint32_t i) {
model_t *mdl;
ef_cnstr_t *cnstr;
term_vector_t *v;
term_t a[2];
uint32_t n;
int32_t code;
assert(i < ef_prob_num_constraints(solver->prob));
// free the current full model if any
if (solver->full_model != NULL) {
yices_free_model(solver->full_model);
solver->full_model = NULL;
}
// build the full_map and the correspongin model.
ef_build_full_map(solver, i);
n = solver->all_vars.size;
assert(n == solver->all_values.size);
mdl = yices_model_from_map(n, solver->all_vars.data, solver->all_values.data);
if (mdl == NULL) {
// error in the model construction
solver->status = EF_STATUS_ERROR; // TODO: add another code
solver->error_code = yices_error_code();
return;
}
solver->full_model = mdl;
cnstr = solver->prob->cnstr + i;
a[0] = cnstr->assumption;
a[1] = opposite_term(cnstr->guarantee);
v = &solver->implicant;
v->size = 0;
code = yices_implicant_for_formulas(mdl, 2, a, v);
if (code < 0) {
solver->status = EF_STATUS_ERROR;
solver->error_code = yices_error_code();
}
#if 1
printf("Implicant\n");
yices_pp_term_array(stdout, v->size, v->data, 120, UINT32_MAX, 0, 0);
printf("(%"PRIu32" literals)\n", v->size);
#endif
}
/*
* Option 3: generalize by computing an implicant then
* applying projection.
*/
static term_t ef_generalize3(ef_solver_t *solver, uint32_t i) {
model_t *mdl;
ef_cnstr_t *cnstr;
ivector_t *v, *w;
term_t a[2];
uint32_t n;
int32_t code;
proj_flag_t pflag;
term_t result;
assert(i < ef_prob_num_constraints(solver->prob));
// free the current full model if any
if (solver->full_model != NULL) {
yices_free_model(solver->full_model);
solver->full_model = NULL;
}
// build the full_map and the corresponding model.
ef_build_full_map(solver, i);
n = solver->all_vars.size;
assert(n == solver->all_values.size);
mdl = yices_model_from_map(n, solver->all_vars.data, solver->all_values.data);
if (mdl == NULL) {
// error in the model construction
solver->status = EF_STATUS_MDL_ERROR;
solver->error_code = yices_error_code();
return NULL_TERM;
}
solver->full_model = mdl;
// Constraint
cnstr = solver->prob->cnstr + i;
a[0] = cnstr->assumption; // B(y)
a[1] = opposite_term(cnstr->guarantee); // not C(x, y)
#if EF_VERBOSE
printf("Constraint:\n");
yices_pp_term_array(stdout, 2, a, 120, UINT32_MAX, 0, 0);
printf("(%"PRIu32" literals)\n", 2);
#endif
// Compute the implicant
v = &solver->implicant;
ivector_reset(v);
code = get_implicant(mdl, solver->prob->manager, LIT_COLLECTOR_ALL_OPTIONS, 2, a, v);
if (code < 0) {
solver->status = EF_STATUS_IMPLICANT_ERROR;
solver->error_code = code;
return NULL_TERM;
}
#if EF_VERBOSE
printf("Implicant:\n");
yices_pp_term_array(stdout, v->size, v->data, 120, UINT32_MAX, 0, 0);
printf("(%"PRIu32" literals)\n", v->size);
#endif
// Projection
w = &solver->projection;
ivector_reset(w);
n = ef_constraint_num_uvars(cnstr);
#if EF_VERBOSE
printf("(%"PRIu32" universals)\n", n);
yices_pp_term_array(stdout, n, cnstr->uvars, 120, UINT32_MAX, 0, 0);
#endif
pflag = project_literals(mdl, solver->prob->manager, v->size, v->data, n, cnstr->uvars, w);
if (pflag != PROJ_NO_ERROR) {
solver->status = EF_STATUS_PROJECTION_ERROR;
solver->error_code = pflag;
return NULL_TERM;
}
#if EF_VERBOSE
printf("Projection:\n");
yices_pp_term_array(stdout, w->size, w->data, 120, UINT32_MAX, 0, 0);
printf("(%"PRIu32" literals)\n", w->size);
#endif
switch (w->size) {
case 0:
result = true_term;
break;
case 1:
result = w->data[0];
break;
default:
result = mk_and(solver->prob->manager, w->size, w->data);
break;
}
return opposite_term(result);
}
/*
* Sample exists models
* - stop when we find one that's not refuted by the forall constraints
* - or when we reach the iteration bound
*
* Result:
* - solver->status = EF_STATUS_ERROR if something goes wrong
* - solver->status = EF_STATUS_INTERRUPTED if one of the calls to
* check_context is interrupted
* - solver->status = EF_STATUS_UNSAT if all efmodels have been tried and none
* of them worked
* - solver->status = EF_STATUS_UNKNOWN if the iteration limit is reached
* - solver->status = EF_STATUS_SAT if a good model is found
*
* In the later case,
* - the model is stored in solver->exists_model
* - also it's available as a mapping form solver->prob->evars to solver->evalues
*
* Also solver->iters stores the number of iterations used.
*/
static void ef_solver_search(ef_solver_t *solver) {
smt_status_t stat;
uint32_t i, max;
max = solver->max_iters;
i = 0;
assert(max > 0);
tprintf(solver->trace, 2,
"(EF search: %"PRIu32" constraints, %"PRIu32" exists vars, %"PRIu32" forall vars)\n",
ef_prob_num_constraints(solver->prob),
ef_prob_num_evars(solver->prob),
ef_prob_num_uvars(solver->prob));
#if EF_VERBOSE
printf("\nConditions on the exists variables:\n");
yices_pp_term_array(stdout, ef_prob_num_conditions(solver->prob), solver->prob->conditions, 120, UINT32_MAX, 0, 0);
#endif
ef_solver_start(solver);
while (solver->status == EF_STATUS_SEARCHING && i < max) {
tprintf(solver->trace, 3, "(EF Iteration %"PRIu32", scan_idx = %"PRIu32")\n", i, solver->scan_idx);
stat = ef_solver_check_exists(solver);
switch (stat) {
case STATUS_SAT:
case STATUS_UNKNOWN:
// we have a candidate exists model
// check it and learn what we can
#if EF_VERBOSE
// FOR DEBUGGING
printf("Candidate exists model:\n");
print_ef_solution(stdout, solver);
printf("\n");
#endif
tputs(solver->trace, 4, "(EF: Found candidate model)\n");
ef_solver_check_exists_model(solver);
break;
case STATUS_UNSAT:
tputs(solver->trace, 4, "(EF: No candidate model)\n");
solver->status = EF_STATUS_UNSAT;
break;
case STATUS_INTERRUPTED:
tputs(solver->trace, 4, "(EF: Interrupted)\n");
solver->status = EF_STATUS_INTERRUPTED;
break;
default:
solver->status = EF_STATUS_CHECK_ERROR;
solver->error_code = stat;
break;
}
i ++;
}
/*
* Cleanup and set status if i == max
*/
if (solver->status != EF_STATUS_SAT && solver->exists_model != NULL) {
yices_free_model(solver->exists_model);
solver->exists_model = NULL;
if (solver->status == EF_STATUS_SEARCHING) {
assert(i == max);
solver->status = EF_STATUS_UNKNOWN;
}
}
solver->iters = i;
tputs(solver->trace, 3, "(EF: done)\n\n");
}
