simplifybysat.cpp

/*****************************************************************************
Copyright (C) 2016  Security Research Labs
Copyright (C) 2018  Mate Soos, Davin Choo, Kian Ming A. Chai, DSO National Laboratories

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#include "simplifybysat.hpp"
#include "cryptominisat5/cryptominisat.h"
#include "time_mem.h"

using std::cout;
using std::endl;

using namespace BLib;

inline bool testSolution(const ANF& anf, const vector<lbool>& solution)
{
    bool goodSol = anf.evaluate(solution);
    if (!goodSol) {
        cout << "ERROR! Solution found is incorrect!" << endl;
        exit(-1);
    }
    return goodSol;
}

SimplifyBySat::SimplifyBySat(const CNF& _cnf, const ConfigData& _config)
    : config(_config), cnf(_cnf)
{
    // Create SAT solver
    solver = new CMSat::SATSolver();
    solver->set_verbosity(config.verbosity >= 5 ? 1 : 0);
    solver->set_num_threads(config.numThreads);
}

SimplifyBySat::~SimplifyBySat()
{
    delete solver;
}

void SimplifyBySat::addClausesToSolver(size_t beg)
{
    const auto& csets = cnf.getClauses();
    for (auto it = csets.begin() + beg; it != csets.end(); ++it) {
        for (const Clause& c : it->first) {
            vector<Lit> lits = c.getClause();
            vector<CMSat::Lit>* lits2 = (vector<CMSat::Lit>*)&lits;
            solver->add_clause(*lits2);
        }
    }
}

int SimplifyBySat::extractUnitaries(vector<BoolePolynomial>& loop_learnt)
{
    vector<CMSat::Lit> units = solver->get_zero_assigned_lits();
    if (config.verbosity >= 3) {
        cout << units.size(); // "c Number of unit learnt clauses: " << << endl;
    }

    uint64_t numVarLearnt = 0;
    for (const CMSat::Lit& unit : units) {
        //If var represents a partial XOR clause, skip it
        if (!cnf.varRepresentsMonomial(unit.var())) {
            continue;
        }

        BooleMonomial m = cnf.getMonomForVar(unit.var());
        assert(m.deg() > 0);

        // Monomial is high degree, and FALSE. That doesn't help much
        if (m.deg() > 1 && unit.sign() == true) {
            continue;
        }

        // If DEG is 1, then this will set the variable
        // If DEG is >0 and setting is TRUE, the addBoolePolynomial() will
        // automatically set all variables in the monomial to ONE
        BoolePolynomial poly(!unit.sign(), cnf.getANFRing());
        poly += m;

        loop_learnt.push_back(poly);
        ++numVarLearnt;
    }

    if (config.verbosity >= 3) {
        cout << '/'
             << numVarLearnt; // "c Num ANF assignments learnt: " <<  << endl;
    }
    return numVarLearnt;
}

int SimplifyBySat::extractBinaries(vector<BoolePolynomial>& loop_learnt)
{
    auto binXors = solver->get_all_binary_xors();
    if (config.verbosity >= 3) {
        cout << '/'
             << binXors.size(); //"c Number of binary clauses:" <<  << endl;
    }

    uint64_t numVarReplaced = 0;
    for (auto& pair : binXors) {
        CMSat::Lit lit1 = pair.first;
        CMSat::Lit lit2 = pair.second;
        uint32_t v1 = lit1.var();
        uint32_t v2 = lit2.var();
        assert(v1 != v2);

        //If any of the two vars represent a partial XOR clause, skip it
        if (!cnf.varRepresentsMonomial(v1) || !cnf.varRepresentsMonomial(v2)) {
            continue;
        }

        BooleMonomial m1 = cnf.getMonomForVar(v1);
        BooleMonomial m2 = cnf.getMonomForVar(v2);

        // Not anti/equivalence
        if (m1.deg() > 1 || m2.deg() > 1) {
            continue;
        }

        BoolePolynomial poly((lit1.sign() ^ lit2.sign()), cnf.getANFRing());
        poly += m1;
        poly += m2;

        loop_learnt.push_back(poly);
        ++numVarReplaced;
    }

    if (config.verbosity >= 3) {
        cout
            << '/'
            << numVarReplaced; //"c Num ANF anti/equivalence learnt: " <<  << endl;
    }
    return numVarReplaced;
}

bool SimplifyBySat::addPolynomial(vector<BoolePolynomial>& loop_learnt,
                                  const pair<vector<uint32_t>, bool>& cnf_poly)
{
    BoolePolynomial new_poly(cnf_poly.second, cnf.getANFRing());
    for (const uint32_t& var_idx : cnf_poly.first) {
        if (!cnf.varRepresentsMonomial(var_idx)) {
            return false;
        }
        new_poly += cnf.getMonomForVar(var_idx);
    }

    if (new_poly.deg() == 1) {
        loop_learnt.push_back(new_poly);
        return true;
    }
    return false;
}

int SimplifyBySat::process(
    vector<BoolePolynomial>& loop_learnt,
    const vector<pair<vector<uint32_t>, bool> >& extracted)
{
    int num_polys = 0;
    for (const pair<vector<uint32_t>, bool>& cnf_poly : extracted) {
        num_polys += addPolynomial(loop_learnt, cnf_poly);
    }
    return num_polys;
}

int SimplifyBySat::extractLinear(vector<BoolePolynomial>& loop_learnt)
{
    int num_polys = 0;
    num_polys += process(loop_learnt, solver->get_recovered_xors(false));
    num_polys += process(loop_learnt, solver->get_recovered_xors(true));

    if (config.verbosity >= 3) {
        cout << '/' << num_polys; //"c Num ANF linear equations learnt: "
    }
    return num_polys;
}

lbool SimplifyBySat::simplify(const uint64_t numConfl_lim,
                            const uint64_t numConflinc, const double time_limit,
                            const size_t cbeg,
                            vector<BoolePolynomial>& loop_learnt, ANF& anf)
{
    if (!anf.getOK()) {
        cout << "c Nothing to simplify: UNSAT" << endl;
        return l_False;
    }

    //Add problem to solver
    solver->new_vars(cnf.getNumVars() - solver->nVars());
    addClausesToSolver(cbeg);

    double time_left = time_limit - cpuTime();
    uint64_t numConfl_left = numConfl_lim;

    // Solve system of CNF until conflict limit
    if (config.verbosity >= 3) {
        cout << "c  Converted CNF has " << cnf.getNumVars() << " variables and "
             << cnf.getNumClauses() << " clause-sets to solve in increments of "
             << numConflinc << " conflicts until " << numConfl_lim
             << " conflicts within " << std::scientific << time_left
             << " seconds" << std::fixed << endl;
    }

    //Run the solver
    Solution sol;
    solver->set_max_time(time_left);
    solver->set_timeout_all_calls(time_left);
    solver->set_max_confl(std::min(numConflinc, numConfl_left));
    sol.ret = solver->solve();
    time_left = time_limit - cpuTime();
    numConfl_left =
        (numConfl_left > numConflinc) ? (numConfl_left - numConflinc) : 0;

    if (config.verbosity >= 4)
        cout << "c ... " << solver->get_sum_conflicts() << '/'
             << solver->get_sum_propagations() << '/'
             << solver->get_sum_decisions() << ' ' << std::scientific
             << time_left << std::fixed << " seconds" << endl;

    //Extract data
    if (config.verbosity >= 3) cout << "c  Number of unit/assigns/binary/(anti-)equiv/linear ";
    extractUnitaries(loop_learnt);
    extractBinaries(loop_learnt);
    extractLinear(loop_learnt);
    if (config.verbosity >= 3) {
        cout << endl;
    }

    //Deal with result
    if (sol.ret == l_False) {
        cout << "c UNSAT returned by solver" << endl;
        anf.addBoolePolynomial(BoolePolynomial(true, anf.getRing()));
    }

    //Solution found
    if(sol.ret == l_True) {
        if (config.verbosity >= 1) {
            cout << "c [SAT] has found a solution" << endl;
        }

        /*const size_t sz = solver->get_model().size();
        vector<lbool> solutionFromSolver(sz, l_Undef);
        for (uint32_t i = 0; i < sz; ++i) {
            //solutionFromSolver[i] = solver->get_model()[i];
            CMSat::lbool m = solver->get_model()[i];
            if (m == CMSat::l_Undef) {
                solutionFromSolver[i] = l_Undef;
            } else if (m == CMSat::l_True) {
                solutionFromSolver[i] = l_True;
            } else if (m == CMSat::l_False) {
                solutionFromSolver[i] = l_False;
            }
            assert(solutionFromSolver[i] != l_Undef);
        }

        vector<lbool> solution2 = cnf.mapSolToOrig(solutionFromSolver);
        sol.sol = anf.extendSolution(solution2);
        ....-> we could use sol.sol here, but it's useless
        */
    }

    return sol.ret;
}