cryptominisat-5.8.0/src/cardfinder.cpp

/******************************************
Copyright (c) 2018, Mate Soos

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#include "cardfinder.h"
#include "time_mem.h"
#include "solver.h"
#include "watched.h"
#include "watchalgos.h"

#include <limits>
#include <sstream>

//TODO read: https://sat-smt.in/assets/slides/daniel1.pdf

using namespace CMSat;
using std::cout;
using std::endl;

CardFinder::CardFinder(Solver* _solver) :
    solver(_solver)
    , seen(solver->seen)
    , seen2(solver->seen2)
    , toClear(solver->toClear)
{
}

//TODO order encoding!
//Also, convert to order encoding.

std::string CardFinder::print_card(const vector<Lit>& lits) const {
    std::stringstream ss;
    for(size_t i = 0; i < lits.size(); i++) {
        ss << lits[i];
        if (i != lits.size()-1) {
            ss << ", ";
        }
    }

    return ss.str();
}

bool CardFinder::find_connector(Lit lit1, Lit lit2) const
{
    //cout << "Finding connector: " << lit1 << ", " << lit2 << endl;

    //look through the shorter one
    if (solver->watches[lit1].size() > solver->watches[lit2].size()) {
        std::swap(lit1, lit2);
    }

    for(const Watched& x : solver->watches[lit1]) {
        if (!x.isBin()) {
            continue;
        }

        if (x.lit2() == lit2)
            return true;
    }
    return false;
}

void CardFinder::get_vars_with_clash(const vector<Lit>& lits, vector<uint32_t>& clash) const {
    Lit last_lit = lit_Undef;
    for(const Lit x: lits) {
        if (x == ~last_lit) {
            clash.push_back(x.var());
        }
        last_lit = x;
    }
}

//See "Detecting cardinality constraints in CNF"
//By Armin Biere, Daniel Le Berre, Emmanuel Lonca, and Norbert Manthey
//Sect. 3.3 -- two-product encoding
//
void CardFinder::find_two_product_atmost1() {
    vector<vector<Lit>> new_cards;
    for(size_t at_row = 0; at_row < cards.size(); at_row++) {
        vector<Lit>& card_row = cards[at_row];
        seen2[at_row] = 1;
        if (card_row.empty()) {
            continue;
        }
        Lit r = card_row[0];

        //find min(NAG(r))
        Lit l = lit_Undef;
        for(const auto& ws: solver->watches[r]) {
            if (!ws.isBin()) continue;
            if (l == lit_Undef) {
                l = ws.lit2();
            } else {
                if (ws.lit2() < l) {
                    l = ws.lit2();
                }
            }
        }
        if (l == lit_Undef) {
            continue;
        }

        //find the column
        for(const auto& ws: solver->watches[l]) {
            if (ws.isBin()) {
                Lit c = ws.lit2();
                if (c == r) continue;
                for(const auto& ws2: solver->watches[c]) {
                    if (ws2.isIdx()) {
                        size_t at_col = ws2.get_idx();
                        if (seen2[at_col]) {
                            //only do row1->row2, it's good enough
                            //don't do reverse too
                            continue;
                        }
                        vector<Lit>& card_col = cards[at_col];
                        if (card_col.empty()) continue;

                        /*cout << "c [cardfind] Potential card for"
                        << " row: " << print_card(card_row)
                        << " -- col: " << print_card(card_col)
                        << endl;*/

                        vector<Lit> card;

                        //mark all lits in row's bin-connected graph
                        for(const Lit row: card_row) {
                            for(const auto& ws3: solver->watches[row]) {
                                if (ws3.isBin()) {
                                    seen[ws3.lit2().toInt()] = 1;
                                }
                            }
                        }

                        //find matching column
                        for(const Lit col: card_col) {
                            for(const auto& ws3: solver->watches[col]) {
                                if (ws3.isBin()) {
                                    Lit conn_lit = ws3.lit2();
                                    if (seen[conn_lit.toInt()]) {
                                        //cout << "part of card: " << ~conn_lit << endl;
                                        card.push_back(~conn_lit);
                                    }
                                }
                            }
                        }

                        if (card.size() > 2) {
                            /*cout << "Reassembled two product: "
                            << print_card(card) << endl;*/
                            new_cards.push_back(card);
                        }

                        //unmark
                        for(const Lit row: card_row) {
                            for(const auto& ws3: solver->watches[row]) {
                                if (ws3.isBin()) {
                                    seen[ws3.lit2().toInt()] = 0;
                                }
                            }
                        }
                    }
                }
            }
        }
    }

    size_t old_size = cards.size();
    cards.resize(cards.size()+new_cards.size());
    for(auto& card: new_cards) {
        std::sort(card.begin(), card.end());
        std::swap(cards[old_size], card);
        old_size++;
    }

    //clear seen2
    for(size_t at_row = 0; at_row < cards.size(); at_row++) {
        seen2[at_row] = 0;
    }
}

void CardFinder::print_cards(const vector<vector<Lit>>& card_constraints) const {
    for(const auto& card: card_constraints) {
        cout << "c [cardfind] final: " << print_card(card) << endl;
    }
}


void CardFinder::deal_with_clash(vector<uint32_t>& clash) {

    vector<uint32_t> idx_pos;
    vector<uint32_t> idx_neg;

    for(uint32_t var: clash) {
        Lit lit = Lit(var, false);
        if (seen[lit.toInt()] == 0 || seen[(~lit).toInt()] == 0) {
            continue;
        }

        //cout << "c [cardfind] Clash on var " << lit << endl;
        for(auto ws: solver->watches[lit]) {
            if (ws.isIdx()) {
                idx_pos.push_back(ws.get_idx());

                /*cout << "c [cardfind] -> IDX " << ws.get_idx() << ": "
                << print_card(cards[ws.get_idx()]) << endl;*/
            }
        }
        for(auto ws: solver->watches[~lit]) {
            if (ws.isIdx()) {
                idx_neg.push_back(ws.get_idx());

                /*cout << "c [cardfind] -> IDX " << ws.get_idx() << ": "
                << print_card(cards[ws.get_idx()]) << endl;*/
            }
        }

        //resolve each with each
        for(uint32_t pos: idx_pos) {
            for(uint32_t neg: idx_neg) {
                assert(pos != neg);
                //one has been removed already
                if (cards[pos].empty() || cards[neg].empty()) {
                    continue;
                }

                vector<Lit> new_card;
                bool found = false;
                for(Lit l: cards[pos]) {
                    if (l == lit) {
                        found = true;
                    } else {
                        new_card.push_back(l);
                    }
                }
                assert(found);

                for(Lit l: cards[neg]) {
                    if (l == ~lit) {
                        found = true;
                    } else {
                        new_card.push_back(l);
                    }
                }
                assert(found);

                std::sort(new_card.begin(), new_card.end());
                /*cout << "c [cardfind] -> Combined card: "
                << print_card(new_card) << endl;*/

                //add the new cardinality constraint
                for(Lit l: new_card) {
                    solver->watches[l].push(Watched(cards.size()));
                }
                cards.push_back(new_card);
            }
        }

        //clear old cardinality constraints
        for(uint32_t pos: idx_pos) {
            cards[pos].clear();
        }
        for(uint32_t neg: idx_neg) {
            cards[neg].clear();
        }

        idx_pos.clear();
        idx_neg.clear();
    }
}

void CardFinder::clean_empty_cards()
{
    size_t j = 0;
    for(size_t i = 0; i < cards.size(); i++) {
        if (!cards[i].empty()) {
            std::swap(cards[j], cards[i]);
            j++;
        }
    }
    cards.resize(j);
}

//See "Detecting cardinality constraints in CNF"
//By Armin Biere, Daniel Le Berre, Emmanuel Lonca, and Norbert Manthey
//Sect. 3.1 -- greeedy algorithm. "S" there is "lits_in_card" here
//
void CardFinder::find_pairwise_atmost1()
{
    assert(toClear.size() == 0);
    for (uint32_t i = 0; i < solver->nVars()*2; i++) {
        const Lit l = Lit::toLit(i);
        vector<Lit> lits_in_card;
        if (seen[l.toInt()]) {
            //cout << "Skipping " << l << " we have seen it before" << endl;
            continue;
        }

        for(const Watched& x : solver->watches[~l]) {
            if (!x.isBin()) {
                continue;
            }
            const Lit other = x.lit2();

            bool all_found = true;
            for(const Lit other2: lits_in_card) {
                if (!find_connector(other, ~other2)) {
                    all_found = false;
                    break;
                }
            }
            if (all_found) {
                lits_in_card.push_back(~other);
                // cout << "added to lits_in_card: " << ~other << endl;
            }
        }
        if (lits_in_card.size() > 1) {
            lits_in_card.push_back(l);
            for(const Lit l_c: lits_in_card) {
                if (!seen[l_c.toInt()]) {
                    toClear.push_back(l_c);
                }
                seen[l_c.toInt()]++;
                solver->watches[l_c].push(Watched(cards.size()));
                solver->watches.smudge(l_c);
            }
            total_sizes+=lits_in_card.size();
            std::sort(lits_in_card.begin(), lits_in_card.end());

            if (solver->conf.verbosity) {
                cout << "c found simple card "
                << print_card(lits_in_card)
                << " on lit " << l << endl;
            }

            //fast push-back
            cards.resize(cards.size()+1);
            std::swap(cards[cards.size()-1], lits_in_card);

        } else {
            //cout << "lits_in_card.size():" << lits_in_card.size() << endl;
            //cout << "Found none for " << l << endl;
        }
    }

    //Now deal with so-called "Nested encoding"
    //  i.e. x1+x2+x4+x5 <= 1
    //  divided into the cardinality constraints
    //  x1+x2+x3 <= 1 and \not x3+x4+x5 <= 1
    //See sect. 3.2 of same paper
    //
    std::sort(toClear.begin(), toClear.end());
    vector<uint32_t> vars_with_clash;
    get_vars_with_clash(toClear, vars_with_clash);
    deal_with_clash(vars_with_clash);
    for(const Lit x: toClear) {
        seen[x.toInt()] = 0;
    }
    toClear.clear();
}

void CardFinder::find_cards()
{
    cards.clear();
    double myTime = cpuTime();

    find_pairwise_atmost1();
    find_two_product_atmost1();

    //print result
    clean_empty_cards();
    if (solver->conf.verbosity) {
        cout << "c [cardfind] All constraints below:" << endl;
        print_cards(cards);
    }

    //clean indexes
    for(auto& lit: solver->watches.get_smudged_list()) {
        auto& ws = solver->watches[lit];
        size_t j = 0;
        for(size_t i = 0; i < ws.size(); i++) {
            if (!ws[i].isIdx()) {
                ws[j++] = ws[i];
            }
        }
        ws.resize(j);
    }
    solver->watches.clear_smudged();

    if (solver->conf.verbosity) {
        double avg = 0;
        if (cards.size() > 0) {
            avg = (double)total_sizes/(double)cards.size();
        }

        cout << "c [cardfind] "
        << "cards: " << cards.size()
        << " avg size: " << avg
        << solver->conf.print_times(cpuTime()-myTime)
        << endl;
    }
}