/**
\brief Finds the maximal number of assumptions that can be satisfied.
An assumption is any formula preceeded with the :assumption keyword.
"Hard" constraints can be supported by using the :formula keyword.
Input: file in SMT-LIB format, and MaxSAT algorithm to be used: 0 - Naive, 1 - Fu&Malik's algo.
Output: the maximum number of assumptions that can be satisfied.
*/
int smtlib_maxsat(char * file_name, int approach)
{
Z3_context ctx;
Z3_solver s;
unsigned num_hard_cnstrs, num_soft_cnstrs;
Z3_ast * hard_cnstrs, * soft_cnstrs;
unsigned result = 0;
ctx = mk_context();
s = Z3_mk_solver(ctx);
Z3_parse_smtlib_file(ctx, file_name, 0, 0, 0, 0, 0, 0);
hard_cnstrs = get_hard_constraints(ctx, &num_hard_cnstrs);
soft_cnstrs = get_soft_constraints(ctx, &num_soft_cnstrs);
switch (approach) {
case NAIVE_MAXSAT:
result = naive_maxsat(ctx, s, num_hard_cnstrs, hard_cnstrs, num_soft_cnstrs, soft_cnstrs);
break;
case FU_MALIK_MAXSAT:
result = fu_malik_maxsat(ctx, s, num_hard_cnstrs, hard_cnstrs, num_soft_cnstrs, soft_cnstrs);
break;
default:
/* Exercise: implement your own MaxSAT algorithm.*/
error("Not implemented yet.");
break;
}
free_cnstr_array(hard_cnstrs);
free_cnstr_array(soft_cnstrs);
return result;
}
/**
\brief Finds the maximal number of assumptions that can be satisfied.
An assumption is any formula preceded with the :assumption keyword.
"Hard" constraints can be supported by using the :formula keyword.
Input: file in SMT-LIB format, and MaxSAT algorithm to be used: 0 - Naive, 1 - Fu&Malik's algo.
Output: the maximum number of assumptions that can be satisfied.
*/
int smtlib_maxsat(char * file_name, int approach)
{
Z3_context ctx;
Z3_solver s;
unsigned i;
Z3_optimize opt;
unsigned num_hard_cnstrs, num_soft_cnstrs;
Z3_ast * hard_cnstrs, * soft_cnstrs;
Z3_ast_vector hard, objs;
Z3_app soft;
unsigned result = 0;
ctx = mk_context();
s = mk_solver(ctx);
opt = Z3_mk_optimize(ctx);
Z3_optimize_inc_ref(ctx, opt);
Z3_optimize_from_file(ctx, opt, file_name);
hard = Z3_optimize_get_assertions(ctx, opt);
Z3_ast_vector_inc_ref(ctx, hard);
num_hard_cnstrs = Z3_ast_vector_size(ctx, hard);
hard_cnstrs = (Z3_ast *) malloc(sizeof(Z3_ast) * (num_hard_cnstrs));
for (i = 0; i < num_hard_cnstrs; i++) {
hard_cnstrs[i] = Z3_ast_vector_get(ctx, hard, i);
}
objs = Z3_optimize_get_objectives(ctx, opt);
Z3_ast_vector_inc_ref(ctx, objs);
// soft constraints are stored in a single objective which is a sum
// of if-then-else expressions.
soft = Z3_to_app(ctx, Z3_ast_vector_get(ctx, objs, 0));
num_soft_cnstrs = Z3_get_app_num_args(ctx, soft);
soft_cnstrs = (Z3_ast *) malloc(sizeof(Z3_ast) * (num_soft_cnstrs));
for (i = 0; i < num_soft_cnstrs; ++i) {
soft_cnstrs[i] = Z3_get_app_arg(ctx, Z3_to_app(ctx, Z3_get_app_arg(ctx, soft, i)), 0);
}
switch (approach) {
case NAIVE_MAXSAT:
result = naive_maxsat(ctx, s, num_hard_cnstrs, hard_cnstrs, num_soft_cnstrs, soft_cnstrs);
break;
case FU_MALIK_MAXSAT:
result = fu_malik_maxsat(ctx, s, num_hard_cnstrs, hard_cnstrs, num_soft_cnstrs, soft_cnstrs);
break;
default:
/* Exercise: implement your own MaxSAT algorithm.*/
error("Not implemented yet.");
break;
}
free_cnstr_array(hard_cnstrs);
free_cnstr_array(soft_cnstrs);
Z3_solver_dec_ref(ctx, s);
Z3_optimize_dec_ref(ctx, opt);
return result;
}
/**
\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);
}