ccnr_cms.cpp

/******************************************
Copyright (C) 2009-2020 Authors of CryptoMiniSat, see AUTHORS file <soos.mate@gmail.com>

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#include "time_mem.h"
#include <limits>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include "constants.h"
#include "ccnr_cms.h"
#include "solver.h"
#include "ccnr.h"
#include "sqlstats.h"
//#define SLOW_DEBUG

using namespace CMSat;

CMS_ccnr::CMS_ccnr(Solver* _solver) :
    solver(_solver),
    seen(_solver->seen),
    toClear(_solver->toClear)
{
    ls_s = new CCNR::ls_solver(solver->conf.sls_ccnr_asipire);
    ls_s->set_verbosity(solver->conf.verbosity);
}

CMS_ccnr::~CMS_ccnr()
{
    delete ls_s;
}

lbool CMS_ccnr::main(const uint32_t num_sls_called)
{
    //It might not work well with few number of variables
    //rnovelty could also die/exit(-1), etc.
    if (solver->nVars() < 50 ||
        solver->binTri.irredBins + solver->longIrredCls.size() < 10
    ) {
        verb_print(1, "[ccnr] too few variables & clauses");
        return l_Undef;
    }
    double startTime = cpuTime();

    if (!init_problem()) {
        //it's actually l_False under assumptions
        //but we'll set the real SAT solver deal with that
        if (solver->conf.verbosity) {
            cout << "c [ccnr] problem UNSAT under assumptions, returning to main solver"
            << endl;
        }
        return l_Undef;
    }

    vector<bool> phases(solver->nVars()+1);
    for(uint32_t i = 0; i < solver->nVars(); i++) {
        phases[i+1] = solver->varData[i].best_polarity;
    }

    int res = ls_s->local_search(&phases, solver->conf.yalsat_max_mems*2*1000*1000);
    lbool ret = deal_with_solution(res, num_sls_called);

    double time_used = cpuTime()-startTime;
    if (solver->conf.verbosity) {
        cout << "c [ccnr] time: " << time_used << endl;
    }
    if (solver->sqlStats) {
        solver->sqlStats->time_passed_min(
            solver
            , "sls-ccnr"
            , time_used
        );
    }

    return ret;
}

template<class T>
CMS_ccnr::add_cl_ret CMS_ccnr::add_this_clause(const T& cl)
{
    uint32_t sz = 0;
    bool sat = false;
    yals_lits.clear();
    for(size_t i3 = 0; i3 < cl.size(); i3++) {
        Lit lit = cl[i3];
        assert(solver->varData[lit.var()].removed == Removed::none);
        lbool val = l_Undef;
        if (solver->value(lit) != l_Undef) {
            val = solver->value(lit);
        } else {
            val = solver->lit_inside_assumptions(lit);
        }

        if (val == l_True) {
            //clause is SAT, skip!
            sat = true;
            continue;
        } else if (val == l_False) {
            continue;
        }
        int l = lit.var()+1;
        l *= lit.sign() ? -1 : 1;
        yals_lits.push_back(l);
        sz++;
    }
    if (sat) {
        return add_cl_ret::skipped_cl;
    }
    if (sz == 0) {
        //it's unsat because of assumptions
        if (solver->conf.verbosity) {
            cout << "c [walksat] UNSAT because of assumptions in clause: " << cl << endl;
        }
        return add_cl_ret::unsat;
    }

    for(auto& lit: yals_lits) {
        ls_s->_clauses[cl_num].literals.push_back(CCNR::lit(lit, cl_num));
    }
    cl_num++;

    return add_cl_ret::added_cl;
}

bool CMS_ccnr::init_problem()
{
    if (solver->check_assumptions_contradict_foced_assignment())
    {
        return false;
    }
    #ifdef SLOWDEBUG
    solver->check_stats();
    #endif

    ls_s->_num_vars = solver->nVars();
    ls_s->_num_clauses = solver->longIrredCls.size() + solver->binTri.irredBins;
    ls_s->make_space();

    vector<Lit> this_clause;
    for(size_t i2 = 0; i2 < solver->nVars()*2; i2++) {
        Lit lit = Lit::toLit(i2);
        for(const Watched& w: solver->watches[lit]) {
            if (w.isBin() && !w.red() && lit < w.lit2()) {
                this_clause.clear();
                this_clause.push_back(lit);
                this_clause.push_back(w.lit2());

                if (add_this_clause(this_clause) == add_cl_ret::unsat) {
                    return false;
                }
            }
        }
    }
    for(ClOffset offs: solver->longIrredCls) {
        const Clause* cl = solver->cl_alloc.ptr(offs);
        assert(!cl->freed());
        assert(!cl->getRemoved());

        if (add_this_clause(*cl) == add_cl_ret::unsat) {
            return false;
        }
    }

    //Shrink the space if we have to
    assert(ls_s->_num_clauses >= (int)cl_num);
    ls_s->_num_clauses = (int)cl_num;
    ls_s->make_space();

    for (int c=0; c < ls_s->_num_clauses; c++) {
        for(CCNR::lit item: ls_s->_clauses[c].literals) {
            int v = item.var_num;
            ls_s->_vars[v].literals.push_back(item);
        }
    }
    ls_s->build_neighborhood();

    return true;
}

struct ClWeightSorter
{
    bool operator()(const CCNR::clause& a, const CCNR::clause& b)
    {
        return a.weight > b.weight;
    }
};

struct VarAndVal {
    VarAndVal(uint32_t _var, long long _score) :
        var(_var),
        val(_score)
    {
    }
    uint32_t var;
    long long val;
};

struct VarValSorter
{
    bool operator()(const VarAndVal& a, const VarAndVal& b) {
        return a.val > b.val;
    }
};

vector<pair<uint32_t, double>> CMS_ccnr::get_bump_based_on_cls()
{
    verb_print(1,"[ccnr] bumping based on clause weights");

    //Check prerequisites
    assert(toClear.empty());
    SLOW_DEBUG_DO(for(const auto x: seen) assert(x == 0));

    vector<pair<uint32_t, double>> tobump_cl_var;
    std::sort(ls_s->_clauses.begin(), ls_s->_clauses.end(), ClWeightSorter());
    uint32_t vars_bumped = 0;
    uint32_t individual_vars_bumped = 0;
    for(const auto& c: ls_s->_clauses) {
        if (vars_bumped > solver->conf.sls_how_many_to_bump)
            break;

        for(uint32_t i = 0; i < c.literals.size(); i++) {
            uint32_t v = c.literals[i].var_num-1;
            if (v < solver->nVars() &&
                solver->varData[v].removed == Removed::none &&
                solver->value(v) == l_Undef &&
                seen[v] < solver->conf.sls_bump_var_max_n_times)
            {
                if (seen[v] == 0) individual_vars_bumped++;
                seen[v]++;
                toClear.push_back(Lit(v, false));
                tobump_cl_var.push_back(std::make_pair(v, 3.0));
                vars_bumped++;
            }
        }
    }

    for(const auto x: toClear) seen[x.var()] = 0;
    toClear.clear();

    return tobump_cl_var;
}

vector<pair<uint32_t, double>> CMS_ccnr::get_bump_based_on_var_scores()
{
    vector<VarAndVal> vs;
    for(uint32_t i = 1; i < ls_s->_vars.size(); i++) {
        vs.push_back(VarAndVal(i-1, ls_s->_vars[i].score));
    }
    std::sort(vs.begin(), vs.end(), VarValSorter());

    vector<pair<uint32_t, double>> tobump;
    for(uint32_t i = 0; i < solver->conf.sls_how_many_to_bump; i++) {
//         cout << "var: " << vs[i].var + 1 << " score: " <<  vs[i].val << endl;
        tobump.push_back(std::make_pair(vs[i].var, 3.0));
    }
    return tobump;
}

vector<pair<uint32_t, double>> CMS_ccnr::get_bump_based_on_conflict_ct()
{
    if (solver->conf.verbosity) {
        cout << "c [ccnr] bumping based on var unsat frequency: conflict_ct" << endl;
    }

    vector<pair<uint32_t, double>> tobump;
    int mymax = 0;
    for(uint32_t i = 1; i < ls_s->_conflict_ct.size(); i++) {
        mymax = std::max(mymax, ls_s->_conflict_ct[i]);
    }

    for(uint32_t i = 1; i < ls_s->_conflict_ct.size(); i++) {
        double val = ls_s->_conflict_ct[i];
        if (mymax > 0) {
            tobump.push_back(std::make_pair(i-1, (double)val/(double)mymax * 3.0));
        } else {
            tobump.push_back(std::make_pair(i-1, 0));
        }
//         if (tobump.back().second > 0) {
//             cout << "var: " << tobump.back().first << " bump by: " << tobump.back().second << endl;
//         }
    }
    return tobump;
}

lbool CMS_ccnr::deal_with_solution(int res, const uint32_t num_sls_called)
{
    if (solver->conf.sls_get_phase || res) {
        if (solver->conf.verbosity) {
            cout
            << "c [ccnr] saving best assignment phase to stable_polar";
            if (res) cout << " + best_polar";
            cout << endl;
        }

        for(size_t i = 0; i < solver->nVars(); i++) {
            solver->varData[i].stable_polarity = ls_s->_best_solution[i+1];
            if (res) {
                solver->varData[i].best_polarity = ls_s->_best_solution[i+1];
            }
        }
    }

    //Clause score sorting
    vector<pair<uint32_t, double>> tobump;
    switch (solver->conf.sls_bump_type) {
        case 1:
            tobump = get_bump_based_on_cls();
            break;
        case 2:
            assert(false && "Does not work, removed");
            break;
        case 3:
            tobump = get_bump_based_on_var_scores();
            break;
        case 4:
            tobump = get_bump_based_on_conflict_ct();
            break;
        case 5:
            if (num_sls_called % 3 == 0) {
                tobump = get_bump_based_on_conflict_ct();
            } else {
                tobump = get_bump_based_on_cls();
            }
            break;
        case 6:
            if (num_sls_called % 3 == 0) {
                tobump = get_bump_based_on_cls();
            } else {
                tobump = get_bump_based_on_conflict_ct();
            }
            break;
        default:
            assert(false && "No such SLS bump type");
            exit(-1);
    }


    for(const auto& v: tobump) solver->bump_var_importance_all(v.first);
    if (solver->branch_strategy == branch::vsids) {
        solver->vsids_decay_var_act();
    }


    verb_print(1, "[ccnr] Bumped vars: " << tobump.size()
        << " bump type: " << solver->conf.sls_bump_type);

    if (!res) verb_print(2, "[ccnr] ASSIGNMENT NOT FOUND");
    else verb_print(1, "[ccnr] ASSIGNMENT FOUND");

    return l_Undef;
}