/**
\brief Small test for the at-most-one constraint.
*/
void tst_at_most_one()
{
Z3_context ctx = mk_context();
Z3_solver s = mk_solver(ctx);
Z3_ast k1 = mk_bool_var(ctx, "k1");
Z3_ast k2 = mk_bool_var(ctx, "k2");
Z3_ast k3 = mk_bool_var(ctx, "k3");
Z3_ast k4 = mk_bool_var(ctx, "k4");
Z3_ast k5 = mk_bool_var(ctx, "k5");
Z3_ast k6 = mk_bool_var(ctx, "k6");
Z3_ast args1[5] = { k1, k2, k3, k4, k5 };
Z3_ast args2[3] = { k4, k5, k6 };
Z3_model m = 0;
Z3_lbool result;
printf("testing at-most-one constraint\n");
assert_at_most_one(ctx, s, 5, args1);
assert_at_most_one(ctx, s, 3, args2);
printf("it must be sat...\n");
result = Z3_solver_check(ctx, s);
if (result != Z3_L_TRUE)
error("BUG");
m = Z3_solver_get_model(ctx, s);
Z3_model_inc_ref(ctx, m);
printf("model:\n%s\n", Z3_model_to_string(ctx, m));
Z3_model_dec_ref(ctx, m);
Z3_solver_assert(ctx, s, mk_binary_or(ctx, k2, k3));
Z3_solver_assert(ctx, s, mk_binary_or(ctx, k1, k6));
printf("it must be sat...\n");
result = Z3_solver_check(ctx, s);
if (result != Z3_L_TRUE)
error("BUG");
m = Z3_solver_get_model(ctx, s);
Z3_model_inc_ref(ctx, m);
printf("model:\n%s\n", Z3_model_to_string(ctx, m));
Z3_solver_assert(ctx, s, mk_binary_or(ctx, k4, k5));
printf("it must be unsat...\n");
result = Z3_solver_check(ctx, s);
if (result != Z3_L_FALSE)
error("BUG");
Z3_model_dec_ref(ctx, m);
Z3_solver_dec_ref(ctx, s);
Z3_del_context(ctx);
}
/**
\brief Naive maxsat procedure based on linear search and at-most-k
constraint. Return the number of soft-constraints that can be
satisfied. Return -1 if the hard-constraints cannot be
satisfied. That is, the formula cannot be satisfied even if all
soft-constraints are ignored.
Exercise: use binary search to implement MaxSAT.
Hint: you will need to use an answer literal to retract the at-most-k constraint.
*/
int naive_maxsat(Z3_context ctx, Z3_solver s, unsigned num_hard_cnstrs, Z3_ast * hard_cnstrs, unsigned num_soft_cnstrs, Z3_ast * soft_cnstrs)
{
Z3_ast * aux_vars;
Z3_lbool is_sat;
unsigned r, k;
assert_hard_constraints(ctx, s, num_hard_cnstrs, hard_cnstrs);
printf("checking whether hard constraints are satisfiable...\n");
is_sat = Z3_solver_check(ctx, s);
if (is_sat == Z3_L_FALSE) {
// It is not possible to make the formula satisfiable even when ignoring all soft constraints.
return -1;
}
if (num_soft_cnstrs == 0)
return 0; // nothing to be done...
aux_vars = assert_soft_constraints(ctx, s, num_soft_cnstrs, soft_cnstrs);
// Perform linear search.
r = 0;
k = num_soft_cnstrs - 1;
for (;;) {
Z3_model m;
unsigned num_disabled;
// at most k soft-constraints can be ignored.
printf("checking whether at-most %d soft-constraints can be ignored.\n", k);
assert_at_most_k(ctx, s, num_soft_cnstrs, aux_vars, k);
is_sat = Z3_solver_check(ctx, s);
if (is_sat == Z3_L_FALSE) {
printf("unsat\n");
return num_soft_cnstrs - k - 1;
}
m = Z3_solver_get_model(ctx, s);
Z3_model_inc_ref(ctx, m);
num_disabled = get_num_disabled_soft_constraints(ctx, m, num_soft_cnstrs, aux_vars);
Z3_model_dec_ref(ctx, m);
if (num_disabled > k) {
error("BUG");
}
printf("sat\n");
k = num_disabled;
if (k == 0) {
// it was possible to satisfy all soft-constraints.
return num_soft_cnstrs;
}
k--;
}
}
Z3Model& Z3Model::operator = (const Z3Model& Other)
{
if(&Other == this) {
return *this;
}
// Do the destructor
if(Model != nullptr && Ctx != nullptr) {
Z3_model_dec_ref(Ctx, Model);
}
// Assign
Ctx = Other.Ctx;
Model = Other.Model;
if(Model != nullptr && Ctx != nullptr) {
Z3_model_inc_ref(Ctx, Model);
}
return *this;
}
void get_function(z3_wrapper *z3, Z3_func_decl fun, uint32_t fun_arity, struct fun *kfun) {
Z3_model m = Z3_solver_get_model(z3->ctx, z3->solver);
assert(m);
/* printf("------\n%s\n------\n", Z3_model_to_string(z3->ctx, m)); */
Z3_model_inc_ref(z3->ctx, m);
fun_init(kfun, fun_arity);
for(size_t xs = 0; xs < int_pow(K, fun_arity); ++xs) {
/* represent `xs` in the K-ary form,
* with digits[0] being the highest digit. */
uint32_t digits[fun_arity];
get_K_digits(digits, fun_arity, xs);
Z3_ast args[fun_arity];
for(size_t i = 0; i < fun_arity; ++i) {
args[i] = z3->Ek_consts[digits[i]];
}
/* eval func on given args */
Z3_ast t = Z3_mk_app(z3->ctx, fun, fun_arity, args);
Z3_ast res;
assert(Z3_model_eval(z3->ctx, m, t, 1, &res) == Z3_TRUE);
/* printf("%s == %s\n", Z3_ast_to_string(z3->ctx, t), Z3_ast_to_string(z3->ctx, res)); */
/* interpret the result of function application */
uint64_t y;
sscanf(Z3_ast_to_string(z3->ctx, res), "V%lu", &y);
fun_set_val(kfun, xs, y);
}
Z3_model_dec_ref(z3->ctx, m);
}
SolverImpl::SolverRunStatus Z3SolverImpl::handleSolverResponse(
::Z3_solver theSolver, ::Z3_lbool satisfiable,
const std::vector<const Array *> *objects,
std::vector<std::vector<unsigned char> > *values, bool &hasSolution) {
switch (satisfiable) {
case Z3_L_TRUE: {
hasSolution = true;
if (!objects) {
// No assignment is needed
assert(values == NULL);
return SolverImpl::SOLVER_RUN_STATUS_SUCCESS_SOLVABLE;
}
assert(values && "values cannot be nullptr");
::Z3_model theModel = Z3_solver_get_model(builder->ctx, theSolver);
assert(theModel && "Failed to retrieve model");
Z3_model_inc_ref(builder->ctx, theModel);
values->reserve(objects->size());
for (std::vector<const Array *>::const_iterator it = objects->begin(),
ie = objects->end();
it != ie; ++it) {
const Array *array = *it;
std::vector<unsigned char> data;
data.reserve(array->size);
for (unsigned offset = 0; offset < array->size; offset++) {
// We can't use Z3ASTHandle here so have to do ref counting manually
::Z3_ast arrayElementExpr;
Z3ASTHandle initial_read = builder->getInitialRead(array, offset);
bool successfulEval =
Z3_model_eval(builder->ctx, theModel, initial_read,
/*model_completion=*/Z3_TRUE, &arrayElementExpr);
assert(successfulEval && "Failed to evaluate model");
Z3_inc_ref(builder->ctx, arrayElementExpr);
assert(Z3_get_ast_kind(builder->ctx, arrayElementExpr) ==
Z3_NUMERAL_AST &&
"Evaluated expression has wrong sort");
int arrayElementValue = 0;
bool successGet = Z3_get_numeral_int(builder->ctx, arrayElementExpr,
&arrayElementValue);
assert(successGet && "failed to get value back");
assert(arrayElementValue >= 0 && arrayElementValue <= 255 &&
"Integer from model is out of range");
data.push_back(arrayElementValue);
Z3_dec_ref(builder->ctx, arrayElementExpr);
}
values->push_back(data);
}
Z3_model_dec_ref(builder->ctx, theModel);
return SolverImpl::SOLVER_RUN_STATUS_SUCCESS_SOLVABLE;
}
case Z3_L_FALSE:
hasSolution = false;
return SolverImpl::SOLVER_RUN_STATUS_SUCCESS_UNSOLVABLE;
case Z3_L_UNDEF: {
::Z3_string reason =
::Z3_solver_get_reason_unknown(builder->ctx, theSolver);
if (strcmp(reason, "timeout") == 0 || strcmp(reason, "canceled") == 0) {
return SolverImpl::SOLVER_RUN_STATUS_TIMEOUT;
}
if (strcmp(reason, "unknown") == 0) {
return SolverImpl::SOLVER_RUN_STATUS_FAILURE;
}
llvm::errs() << "Unexpected solver failure. Reason is \"" << reason
<< "\"\n";
abort();
}
default:
llvm_unreachable("unhandled Z3 result");
}
}
Z3Model::~Z3Model()
{
if (Ctx != Z3Ctx::NullPtr && Model != nullptr) {
Z3_model_dec_ref(*Ctx, Model);
}
}
void Z3_API Z3_del_model(Z3_context c, Z3_model m) {
Z3_model_dec_ref(c, m);
}
Z3Model::~Z3Model()
{
if(Model != nullptr && Ctx != nullptr) {
Z3_model_dec_ref(Ctx, Model);
}
}