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Diffstat (limited to 'libs/minisat/Solver.cc')
| -rw-r--r-- | libs/minisat/Solver.cc | 1068 |
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diff --git a/libs/minisat/Solver.cc b/libs/minisat/Solver.cc new file mode 100644 index 000000000..ab476853a --- /dev/null +++ b/libs/minisat/Solver.cc @@ -0,0 +1,1068 @@ +#define __STDC_FORMAT_MACROS +#define __STDC_LIMIT_MACROS +/***************************************************************************************[Solver.cc] +Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson +Copyright (c) 2007-2010, Niklas Sorensson + +Permission is hereby granted, free of charge, to any person obtaining a copy of this software and +associated documentation files (the "Software"), to deal in the Software without restriction, +including without limitation the rights to use, copy, modify, merge, publish, distribute, +sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is +furnished to do so, subject to the following conditions: + +The above copyright notice and this permission notice shall be included in all copies or +substantial portions of the Software. + +THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT +NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND +NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, +DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT +OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. +**************************************************************************************************/ + +#include <math.h> + +#include "Alg.h" +#include "Sort.h" +#include "System.h" +#include "Solver.h" + +using namespace Minisat; + +//================================================================================================= +// Options: + + +static const char* _cat = "CORE"; + +static DoubleOption opt_var_decay (_cat, "var-decay", "The variable activity decay factor", 0.95, DoubleRange(0, false, 1, false)); +static DoubleOption opt_clause_decay (_cat, "cla-decay", "The clause activity decay factor", 0.999, DoubleRange(0, false, 1, false)); +static DoubleOption opt_random_var_freq (_cat, "rnd-freq", "The frequency with which the decision heuristic tries to choose a random variable", 0, DoubleRange(0, true, 1, true)); +static DoubleOption opt_random_seed (_cat, "rnd-seed", "Used by the random variable selection", 91648253, DoubleRange(0, false, HUGE_VAL, false)); +static IntOption opt_ccmin_mode (_cat, "ccmin-mode", "Controls conflict clause minimization (0=none, 1=basic, 2=deep)", 2, IntRange(0, 2)); +static IntOption opt_phase_saving (_cat, "phase-saving", "Controls the level of phase saving (0=none, 1=limited, 2=full)", 2, IntRange(0, 2)); +static BoolOption opt_rnd_init_act (_cat, "rnd-init", "Randomize the initial activity", false); +static BoolOption opt_luby_restart (_cat, "luby", "Use the Luby restart sequence", true); +static IntOption opt_restart_first (_cat, "rfirst", "The base restart interval", 100, IntRange(1, INT32_MAX)); +static DoubleOption opt_restart_inc (_cat, "rinc", "Restart interval increase factor", 2, DoubleRange(1, false, HUGE_VAL, false)); +static DoubleOption opt_garbage_frac (_cat, "gc-frac", "The fraction of wasted memory allowed before a garbage collection is triggered", 0.20, DoubleRange(0, false, HUGE_VAL, false)); +static IntOption opt_min_learnts_lim (_cat, "min-learnts", "Minimum learnt clause limit", 0, IntRange(0, INT32_MAX)); + + +//================================================================================================= +// Constructor/Destructor: + + +Solver::Solver() : + + // Parameters (user settable): + // + verbosity (0) + , var_decay (opt_var_decay) + , clause_decay (opt_clause_decay) + , random_var_freq (opt_random_var_freq) + , random_seed (opt_random_seed) + , luby_restart (opt_luby_restart) + , ccmin_mode (opt_ccmin_mode) + , phase_saving (opt_phase_saving) + , rnd_pol (false) + , rnd_init_act (opt_rnd_init_act) + , garbage_frac (opt_garbage_frac) + , min_learnts_lim (opt_min_learnts_lim) + , restart_first (opt_restart_first) + , restart_inc (opt_restart_inc) + + // Parameters (the rest): + // + , learntsize_factor((double)1/(double)3), learntsize_inc(1.1) + + // Parameters (experimental): + // + , learntsize_adjust_start_confl (100) + , learntsize_adjust_inc (1.5) + + // Statistics: (formerly in 'SolverStats') + // + , solves(0), starts(0), decisions(0), rnd_decisions(0), propagations(0), conflicts(0) + , dec_vars(0), num_clauses(0), num_learnts(0), clauses_literals(0), learnts_literals(0), max_literals(0), tot_literals(0) + + , watches (WatcherDeleted(ca)) + , order_heap (VarOrderLt(activity)) + , ok (true) + , cla_inc (1) + , var_inc (1) + , qhead (0) + , simpDB_assigns (-1) + , simpDB_props (0) + , progress_estimate (0) + , remove_satisfied (true) + , next_var (0) + + // Resource constraints: + // + , conflict_budget (-1) + , propagation_budget (-1) + , asynch_interrupt (false) +{} + + +Solver::~Solver() +{ +} + + +//================================================================================================= +// Minor methods: + + +// Creates a new SAT variable in the solver. If 'decision' is cleared, variable will not be +// used as a decision variable (NOTE! This has effects on the meaning of a SATISFIABLE result). +// +Var Solver::newVar(lbool upol, bool dvar) +{ + Var v; + if (free_vars.size() > 0){ + v = free_vars.last(); + free_vars.pop(); + }else + v = next_var++; + + watches .init(mkLit(v, false)); + watches .init(mkLit(v, true )); + assigns .insert(v, l_Undef); + vardata .insert(v, mkVarData(CRef_Undef, 0)); + activity .insert(v, rnd_init_act ? drand(random_seed) * 0.00001 : 0); + seen .insert(v, 0); + polarity .insert(v, true); + user_pol .insert(v, upol); + decision .reserve(v); + trail .capacity(v+1); + setDecisionVar(v, dvar); + return v; +} + + +// Note: at the moment, only unassigned variable will be released (this is to avoid duplicate +// releases of the same variable). +void Solver::releaseVar(Lit l) +{ + if (value(l) == l_Undef){ + addClause(l); + released_vars.push(var(l)); + } +} + + +bool Solver::addClause_(vec<Lit>& ps) +{ + assert(decisionLevel() == 0); + if (!ok) return false; + + // Check if clause is satisfied and remove false/duplicate literals: + sort(ps); + Lit p; int i, j; + for (i = j = 0, p = lit_Undef; i < ps.size(); i++) + if (value(ps[i]) == l_True || ps[i] == ~p) + return true; + else if (value(ps[i]) != l_False && ps[i] != p) + ps[j++] = p = ps[i]; + ps.shrink(i - j); + + if (ps.size() == 0) + return ok = false; + else if (ps.size() == 1){ + uncheckedEnqueue(ps[0]); + return ok = (propagate() == CRef_Undef); + }else{ + CRef cr = ca.alloc(ps, false); + clauses.push(cr); + attachClause(cr); + } + + return true; +} + + +void Solver::attachClause(CRef cr){ + const Clause& c = ca[cr]; + assert(c.size() > 1); + watches[~c[0]].push(Watcher(cr, c[1])); + watches[~c[1]].push(Watcher(cr, c[0])); + if (c.learnt()) num_learnts++, learnts_literals += c.size(); + else num_clauses++, clauses_literals += c.size(); +} + + +void Solver::detachClause(CRef cr, bool strict){ + const Clause& c = ca[cr]; + assert(c.size() > 1); + + // Strict or lazy detaching: + if (strict){ + remove(watches[~c[0]], Watcher(cr, c[1])); + remove(watches[~c[1]], Watcher(cr, c[0])); + }else{ + watches.smudge(~c[0]); + watches.smudge(~c[1]); + } + + if (c.learnt()) num_learnts--, learnts_literals -= c.size(); + else num_clauses--, clauses_literals -= c.size(); +} + + +void Solver::removeClause(CRef cr) { + Clause& c = ca[cr]; + detachClause(cr); + // Don't leave pointers to free'd memory! + if (locked(c)) vardata[var(c[0])].reason = CRef_Undef; + c.mark(1); + ca.free(cr); +} + + +bool Solver::satisfied(const Clause& c) const { + for (int i = 0; i < c.size(); i++) + if (value(c[i]) == l_True) + return true; + return false; } + + +// Revert to the state at given level (keeping all assignment at 'level' but not beyond). +// +void Solver::cancelUntil(int level) { + if (decisionLevel() > level){ + for (int c = trail.size()-1; c >= trail_lim[level]; c--){ + Var x = var(trail[c]); + assigns [x] = l_Undef; + if (phase_saving > 1 || (phase_saving == 1 && c > trail_lim.last())) + polarity[x] = sign(trail[c]); + insertVarOrder(x); } + qhead = trail_lim[level]; + trail.shrink(trail.size() - trail_lim[level]); + trail_lim.shrink(trail_lim.size() - level); + } } + + +//================================================================================================= +// Major methods: + + +Lit Solver::pickBranchLit() +{ + Var next = var_Undef; + + // Random decision: + if (drand(random_seed) < random_var_freq && !order_heap.empty()){ + next = order_heap[irand(random_seed,order_heap.size())]; + if (value(next) == l_Undef && decision[next]) + rnd_decisions++; } + + // Activity based decision: + while (next == var_Undef || value(next) != l_Undef || !decision[next]) + if (order_heap.empty()){ + next = var_Undef; + break; + }else + next = order_heap.removeMin(); + + // Choose polarity based on different polarity modes (global or per-variable): + if (next == var_Undef) + return lit_Undef; + else if (user_pol[next] != l_Undef) + return mkLit(next, user_pol[next] == l_True); + else if (rnd_pol) + return mkLit(next, drand(random_seed) < 0.5); + else + return mkLit(next, polarity[next]); +} + + +/*_________________________________________________________________________________________________ +| +| analyze : (confl : Clause*) (out_learnt : vec<Lit>&) (out_btlevel : int&) -> [void] +| +| Description: +| Analyze conflict and produce a reason clause. +| +| Pre-conditions: +| * 'out_learnt' is assumed to be cleared. +| * Current decision level must be greater than root level. +| +| Post-conditions: +| * 'out_learnt[0]' is the asserting literal at level 'out_btlevel'. +| * If out_learnt.size() > 1 then 'out_learnt[1]' has the greatest decision level of the +| rest of literals. There may be others from the same level though. +| +|________________________________________________________________________________________________@*/ +void Solver::analyze(CRef confl, vec<Lit>& out_learnt, int& out_btlevel) +{ + int pathC = 0; + Lit p = lit_Undef; + + // Generate conflict clause: + // + out_learnt.push(); // (leave room for the asserting literal) + int index = trail.size() - 1; + + do{ + assert(confl != CRef_Undef); // (otherwise should be UIP) + Clause& c = ca[confl]; + + if (c.learnt()) + claBumpActivity(c); + + for (int j = (p == lit_Undef) ? 0 : 1; j < c.size(); j++){ + Lit q = c[j]; + + if (!seen[var(q)] && level(var(q)) > 0){ + varBumpActivity(var(q)); + seen[var(q)] = 1; + if (level(var(q)) >= decisionLevel()) + pathC++; + else + out_learnt.push(q); + } + } + + // Select next clause to look at: + while (!seen[var(trail[index--])]); + p = trail[index+1]; + confl = reason(var(p)); + seen[var(p)] = 0; + pathC--; + + }while (pathC > 0); + out_learnt[0] = ~p; + + // Simplify conflict clause: + // + int i, j; + out_learnt.copyTo(analyze_toclear); + if (ccmin_mode == 2){ + for (i = j = 1; i < out_learnt.size(); i++) + if (reason(var(out_learnt[i])) == CRef_Undef || !litRedundant(out_learnt[i])) + out_learnt[j++] = out_learnt[i]; + + }else if (ccmin_mode == 1){ + for (i = j = 1; i < out_learnt.size(); i++){ + Var x = var(out_learnt[i]); + + if (reason(x) == CRef_Undef) + out_learnt[j++] = out_learnt[i]; + else{ + Clause& c = ca[reason(var(out_learnt[i]))]; + for (int k = 1; k < c.size(); k++) + if (!seen[var(c[k])] && level(var(c[k])) > 0){ + out_learnt[j++] = out_learnt[i]; + break; } + } + } + }else + i = j = out_learnt.size(); + + max_literals += out_learnt.size(); + out_learnt.shrink(i - j); + tot_literals += out_learnt.size(); + + // Find correct backtrack level: + // + if (out_learnt.size() == 1) + out_btlevel = 0; + else{ + int max_i = 1; + // Find the first literal assigned at the next-highest level: + for (int i = 2; i < out_learnt.size(); i++) + if (level(var(out_learnt[i])) > level(var(out_learnt[max_i]))) + max_i = i; + // Swap-in this literal at index 1: + Lit p = out_learnt[max_i]; + out_learnt[max_i] = out_learnt[1]; + out_learnt[1] = p; + out_btlevel = level(var(p)); + } + + for (int j = 0; j < analyze_toclear.size(); j++) seen[var(analyze_toclear[j])] = 0; // ('seen[]' is now cleared) +} + + +// Check if 'p' can be removed from a conflict clause. +bool Solver::litRedundant(Lit p) +{ + enum { seen_undef = 0, seen_source = 1, seen_removable = 2, seen_failed = 3 }; + assert(seen[var(p)] == seen_undef || seen[var(p)] == seen_source); + assert(reason(var(p)) != CRef_Undef); + + Clause* c = &ca[reason(var(p))]; + vec<ShrinkStackElem>& stack = analyze_stack; + stack.clear(); + + for (uint32_t i = 1; ; i++){ + if (i < (uint32_t)c->size()){ + // Checking 'p'-parents 'l': + Lit l = (*c)[i]; + + // Variable at level 0 or previously removable: + if (level(var(l)) == 0 || seen[var(l)] == seen_source || seen[var(l)] == seen_removable){ + continue; } + + // Check variable can not be removed for some local reason: + if (reason(var(l)) == CRef_Undef || seen[var(l)] == seen_failed){ + stack.push(ShrinkStackElem(0, p)); + for (int i = 0; i < stack.size(); i++) + if (seen[var(stack[i].l)] == seen_undef){ + seen[var(stack[i].l)] = seen_failed; + analyze_toclear.push(stack[i].l); + } + + return false; + } + + // Recursively check 'l': + stack.push(ShrinkStackElem(i, p)); + i = 0; + p = l; + c = &ca[reason(var(p))]; + }else{ + // Finished with current element 'p' and reason 'c': + if (seen[var(p)] == seen_undef){ + seen[var(p)] = seen_removable; + analyze_toclear.push(p); + } + + // Terminate with success if stack is empty: + if (stack.size() == 0) break; + + // Continue with top element on stack: + i = stack.last().i; + p = stack.last().l; + c = &ca[reason(var(p))]; + + stack.pop(); + } + } + + return true; +} + + +/*_________________________________________________________________________________________________ +| +| analyzeFinal : (p : Lit) -> [void] +| +| Description: +| Specialized analysis procedure to express the final conflict in terms of assumptions. +| Calculates the (possibly empty) set of assumptions that led to the assignment of 'p', and +| stores the result in 'out_conflict'. +|________________________________________________________________________________________________@*/ +void Solver::analyzeFinal(Lit p, LSet& out_conflict) +{ + out_conflict.clear(); + out_conflict.insert(p); + + if (decisionLevel() == 0) + return; + + seen[var(p)] = 1; + + for (int i = trail.size()-1; i >= trail_lim[0]; i--){ + Var x = var(trail[i]); + if (seen[x]){ + if (reason(x) == CRef_Undef){ + assert(level(x) > 0); + out_conflict.insert(~trail[i]); + }else{ + Clause& c = ca[reason(x)]; + for (int j = 1; j < c.size(); j++) + if (level(var(c[j])) > 0) + seen[var(c[j])] = 1; + } + seen[x] = 0; + } + } + + seen[var(p)] = 0; +} + + +void Solver::uncheckedEnqueue(Lit p, CRef from) +{ + assert(value(p) == l_Undef); + assigns[var(p)] = lbool(!sign(p)); + vardata[var(p)] = mkVarData(from, decisionLevel()); + trail.push_(p); +} + + +/*_________________________________________________________________________________________________ +| +| propagate : [void] -> [Clause*] +| +| Description: +| Propagates all enqueued facts. If a conflict arises, the conflicting clause is returned, +| otherwise CRef_Undef. +| +| Post-conditions: +| * the propagation queue is empty, even if there was a conflict. +|________________________________________________________________________________________________@*/ +CRef Solver::propagate() +{ + CRef confl = CRef_Undef; + int num_props = 0; + + while (qhead < trail.size()){ + Lit p = trail[qhead++]; // 'p' is enqueued fact to propagate. + vec<Watcher>& ws = watches.lookup(p); + Watcher *i, *j, *end; + num_props++; + + for (i = j = (Watcher*)ws, end = i + ws.size(); i != end;){ + // Try to avoid inspecting the clause: + Lit blocker = i->blocker; + if (value(blocker) == l_True){ + *j++ = *i++; continue; } + + // Make sure the false literal is data[1]: + CRef cr = i->cref; + Clause& c = ca[cr]; + Lit false_lit = ~p; + if (c[0] == false_lit) + c[0] = c[1], c[1] = false_lit; + assert(c[1] == false_lit); + i++; + + // If 0th watch is true, then clause is already satisfied. + Lit first = c[0]; + Watcher w = Watcher(cr, first); + if (first != blocker && value(first) == l_True){ + *j++ = w; continue; } + + // Look for new watch: + for (int k = 2; k < c.size(); k++) + if (value(c[k]) != l_False){ + c[1] = c[k]; c[k] = false_lit; + watches[~c[1]].push(w); + goto NextClause; } + + // Did not find watch -- clause is unit under assignment: + *j++ = w; + if (value(first) == l_False){ + confl = cr; + qhead = trail.size(); + // Copy the remaining watches: + while (i < end) + *j++ = *i++; + }else + uncheckedEnqueue(first, cr); + + NextClause:; + } + ws.shrink(i - j); + } + propagations += num_props; + simpDB_props -= num_props; + + return confl; +} + + +/*_________________________________________________________________________________________________ +| +| reduceDB : () -> [void] +| +| Description: +| Remove half of the learnt clauses, minus the clauses locked by the current assignment. Locked +| clauses are clauses that are reason to some assignment. Binary clauses are never removed. +|________________________________________________________________________________________________@*/ +struct reduceDB_lt { + ClauseAllocator& ca; + reduceDB_lt(ClauseAllocator& ca_) : ca(ca_) {} + bool operator () (CRef x, CRef y) { + return ca[x].size() > 2 && (ca[y].size() == 2 || ca[x].activity() < ca[y].activity()); } +}; +void Solver::reduceDB() +{ + int i, j; + double extra_lim = cla_inc / learnts.size(); // Remove any clause below this activity + + sort(learnts, reduceDB_lt(ca)); + // Don't delete binary or locked clauses. From the rest, delete clauses from the first half + // and clauses with activity smaller than 'extra_lim': + for (i = j = 0; i < learnts.size(); i++){ + Clause& c = ca[learnts[i]]; + if (c.size() > 2 && !locked(c) && (i < learnts.size() / 2 || c.activity() < extra_lim)) + removeClause(learnts[i]); + else + learnts[j++] = learnts[i]; + } + learnts.shrink(i - j); + checkGarbage(); +} + + +void Solver::removeSatisfied(vec<CRef>& cs) +{ + int i, j; + for (i = j = 0; i < cs.size(); i++){ + Clause& c = ca[cs[i]]; + if (satisfied(c)) + removeClause(cs[i]); + else{ + // Trim clause: + assert(value(c[0]) == l_Undef && value(c[1]) == l_Undef); + for (int k = 2; k < c.size(); k++) + if (value(c[k]) == l_False){ + c[k--] = c[c.size()-1]; + c.pop(); + } + cs[j++] = cs[i]; + } + } + cs.shrink(i - j); +} + + +void Solver::rebuildOrderHeap() +{ + vec<Var> vs; + for (Var v = 0; v < nVars(); v++) + if (decision[v] && value(v) == l_Undef) + vs.push(v); + order_heap.build(vs); +} + + +/*_________________________________________________________________________________________________ +| +| simplify : [void] -> [bool] +| +| Description: +| Simplify the clause database according to the current top-level assigment. Currently, the only +| thing done here is the removal of satisfied clauses, but more things can be put here. +|________________________________________________________________________________________________@*/ +bool Solver::simplify() +{ + assert(decisionLevel() == 0); + + if (!ok || propagate() != CRef_Undef) + return ok = false; + + if (nAssigns() == simpDB_assigns || (simpDB_props > 0)) + return true; + + // Remove satisfied clauses: + removeSatisfied(learnts); + if (remove_satisfied){ // Can be turned off. + removeSatisfied(clauses); + + // TODO: what todo in if 'remove_satisfied' is false? + + // Remove all released variables from the trail: + for (int i = 0; i < released_vars.size(); i++){ + assert(seen[released_vars[i]] == 0); + seen[released_vars[i]] = 1; + } + + int i, j; + for (i = j = 0; i < trail.size(); i++) + if (seen[var(trail[i])] == 0) + trail[j++] = trail[i]; + trail.shrink(i - j); + //printf("trail.size()= %d, qhead = %d\n", trail.size(), qhead); + qhead = trail.size(); + + for (int i = 0; i < released_vars.size(); i++) + seen[released_vars[i]] = 0; + + // Released variables are now ready to be reused: + append(released_vars, free_vars); + released_vars.clear(); + } + checkGarbage(); + rebuildOrderHeap(); + + simpDB_assigns = nAssigns(); + simpDB_props = clauses_literals + learnts_literals; // (shouldn't depend on stats really, but it will do for now) + + return true; +} + + +/*_________________________________________________________________________________________________ +| +| search : (nof_conflicts : int) (params : const SearchParams&) -> [lbool] +| +| Description: +| Search for a model the specified number of conflicts. +| NOTE! Use negative value for 'nof_conflicts' indicate infinity. +| +| Output: +| 'l_True' if a partial assigment that is consistent with respect to the clauseset is found. If +| all variables are decision variables, this means that the clause set is satisfiable. 'l_False' +| if the clause set is unsatisfiable. 'l_Undef' if the bound on number of conflicts is reached. +|________________________________________________________________________________________________@*/ +lbool Solver::search(int nof_conflicts) +{ + assert(ok); + int backtrack_level; + int conflictC = 0; + vec<Lit> learnt_clause; + starts++; + + for (;;){ + CRef confl = propagate(); + if (confl != CRef_Undef){ + // CONFLICT + conflicts++; conflictC++; + if (decisionLevel() == 0) return l_False; + + learnt_clause.clear(); + analyze(confl, learnt_clause, backtrack_level); + cancelUntil(backtrack_level); + + if (learnt_clause.size() == 1){ + uncheckedEnqueue(learnt_clause[0]); + }else{ + CRef cr = ca.alloc(learnt_clause, true); + learnts.push(cr); + attachClause(cr); + claBumpActivity(ca[cr]); + uncheckedEnqueue(learnt_clause[0], cr); + } + + varDecayActivity(); + claDecayActivity(); + + if (--learntsize_adjust_cnt == 0){ + learntsize_adjust_confl *= learntsize_adjust_inc; + learntsize_adjust_cnt = (int)learntsize_adjust_confl; + max_learnts *= learntsize_inc; + + if (verbosity >= 1) + printf("| %9d | %7d %8d %8d | %8d %8d %6.0f | %6.3f %% |\n", + (int)conflicts, + (int)dec_vars - (trail_lim.size() == 0 ? trail.size() : trail_lim[0]), nClauses(), (int)clauses_literals, + (int)max_learnts, nLearnts(), (double)learnts_literals/nLearnts(), progressEstimate()*100); + } + + }else{ + // NO CONFLICT + if ((nof_conflicts >= 0 && conflictC >= nof_conflicts) || !withinBudget()){ + // Reached bound on number of conflicts: + progress_estimate = progressEstimate(); + cancelUntil(0); + return l_Undef; } + + // Simplify the set of problem clauses: + if (decisionLevel() == 0 && !simplify()) + return l_False; + + if (learnts.size()-nAssigns() >= max_learnts) + // Reduce the set of learnt clauses: + reduceDB(); + + Lit next = lit_Undef; + while (decisionLevel() < assumptions.size()){ + // Perform user provided assumption: + Lit p = assumptions[decisionLevel()]; + if (value(p) == l_True){ + // Dummy decision level: + newDecisionLevel(); + }else if (value(p) == l_False){ + analyzeFinal(~p, conflict); + return l_False; + }else{ + next = p; + break; + } + } + + if (next == lit_Undef){ + // New variable decision: + decisions++; + next = pickBranchLit(); + + if (next == lit_Undef) + // Model found: + return l_True; + } + + // Increase decision level and enqueue 'next' + newDecisionLevel(); + uncheckedEnqueue(next); + } + } +} + + +double Solver::progressEstimate() const +{ + double progress = 0; + double F = 1.0 / nVars(); + + for (int i = 0; i <= decisionLevel(); i++){ + int beg = i == 0 ? 0 : trail_lim[i - 1]; + int end = i == decisionLevel() ? trail.size() : trail_lim[i]; + progress += pow(F, i) * (end - beg); + } + + return progress / nVars(); +} + +/* + Finite subsequences of the Luby-sequence: + + 0: 1 + 1: 1 1 2 + 2: 1 1 2 1 1 2 4 + 3: 1 1 2 1 1 2 4 1 1 2 1 1 2 4 8 + ... + + + */ + +static double luby(double y, int x){ + + // Find the finite subsequence that contains index 'x', and the + // size of that subsequence: + int size, seq; + for (size = 1, seq = 0; size < x+1; seq++, size = 2*size+1); + + while (size-1 != x){ + size = (size-1)>>1; + seq--; + x = x % size; + } + + return pow(y, seq); +} + +// NOTE: assumptions passed in member-variable 'assumptions'. +lbool Solver::solve_() +{ + model.clear(); + conflict.clear(); + if (!ok) return l_False; + + solves++; + + max_learnts = nClauses() * learntsize_factor; + if (max_learnts < min_learnts_lim) + max_learnts = min_learnts_lim; + + learntsize_adjust_confl = learntsize_adjust_start_confl; + learntsize_adjust_cnt = (int)learntsize_adjust_confl; + lbool status = l_Undef; + + if (verbosity >= 1){ + printf("============================[ Search Statistics ]==============================\n"); + printf("| Conflicts | ORIGINAL | LEARNT | Progress |\n"); + printf("| | Vars Clauses Literals | Limit Clauses Lit/Cl | |\n"); + printf("===============================================================================\n"); + } + + // Search: + int curr_restarts = 0; + while (status == l_Undef){ + double rest_base = luby_restart ? luby(restart_inc, curr_restarts) : pow(restart_inc, curr_restarts); + status = search(rest_base * restart_first); + if (!withinBudget()) break; + curr_restarts++; + } + + if (verbosity >= 1) + printf("===============================================================================\n"); + + + if (status == l_True){ + // Extend & copy model: + model.growTo(nVars()); + for (int i = 0; i < nVars(); i++) model[i] = value(i); + }else if (status == l_False && conflict.size() == 0) + ok = false; + + cancelUntil(0); + return status; +} + + +bool Solver::implies(const vec<Lit>& assumps, vec<Lit>& out) +{ + trail_lim.push(trail.size()); + for (int i = 0; i < assumps.size(); i++){ + Lit a = assumps[i]; + + if (value(a) == l_False){ + cancelUntil(0); + return false; + }else if (value(a) == l_Undef) + uncheckedEnqueue(a); + } + + unsigned trail_before = trail.size(); + bool ret = true; + if (propagate() == CRef_Undef){ + out.clear(); + for (int j = trail_before; j < trail.size(); j++) + out.push(trail[j]); + }else + ret = false; + + cancelUntil(0); + return ret; +} + +//================================================================================================= +// Writing CNF to DIMACS: +// +// FIXME: this needs to be rewritten completely. + +static Var mapVar(Var x, vec<Var>& map, Var& max) +{ + if (map.size() <= x || map[x] == -1){ + map.growTo(x+1, -1); + map[x] = max++; + } + return map[x]; +} + + +void Solver::toDimacs(FILE* f, Clause& c, vec<Var>& map, Var& max) +{ + if (satisfied(c)) return; + + for (int i = 0; i < c.size(); i++) + if (value(c[i]) != l_False) + fprintf(f, "%s%d ", sign(c[i]) ? "-" : "", mapVar(var(c[i]), map, max)+1); + fprintf(f, "0\n"); +} + + +void Solver::toDimacs(const char *file, const vec<Lit>& assumps) +{ + FILE* f = fopen(file, "wr"); + if (f == NULL) + fprintf(stderr, "could not open file %s\n", file), exit(1); + toDimacs(f, assumps); + fclose(f); +} + + +void Solver::toDimacs(FILE* f, const vec<Lit>& assumps) +{ + // Handle case when solver is in contradictory state: + if (!ok){ + fprintf(f, "p cnf 1 2\n1 0\n-1 0\n"); + return; } + + vec<Var> map; Var max = 0; + + // Cannot use removeClauses here because it is not safe + // to deallocate them at this point. Could be improved. + int cnt = 0; + for (int i = 0; i < clauses.size(); i++) + if (!satisfied(ca[clauses[i]])) + cnt++; + + for (int i = 0; i < clauses.size(); i++) + if (!satisfied(ca[clauses[i]])){ + Clause& c = ca[clauses[i]]; + for (int j = 0; j < c.size(); j++) + if (value(c[j]) != l_False) + mapVar(var(c[j]), map, max); + } + + // Assumptions are added as unit clauses: + cnt += assumps.size(); + + fprintf(f, "p cnf %d %d\n", max, cnt); + + for (int i = 0; i < assumps.size(); i++){ + assert(value(assumps[i]) != l_False); + fprintf(f, "%s%d 0\n", sign(assumps[i]) ? "-" : "", mapVar(var(assumps[i]), map, max)+1); + } + + for (int i = 0; i < clauses.size(); i++) + toDimacs(f, ca[clauses[i]], map, max); + + if (verbosity > 0) + printf("Wrote DIMACS with %d variables and %d clauses.\n", max, cnt); +} + + +void Solver::printStats() const +{ + double cpu_time = cpuTime(); + double mem_used = memUsedPeak(); + printf("restarts : %" PRIu64 "\n", starts); + printf("conflicts : %-12" PRIu64 " (%.0f /sec)\n", conflicts , conflicts /cpu_time); + printf("decisions : %-12" PRIu64 " (%4.2f %% random) (%.0f /sec)\n", decisions, (float)rnd_decisions*100 / (float)decisions, decisions /cpu_time); + printf("propagations : %-12" PRIu64 " (%.0f /sec)\n", propagations, propagations/cpu_time); + printf("conflict literals : %-12" PRIu64 " (%4.2f %% deleted)\n", tot_literals, (max_literals - tot_literals)*100 / (double)max_literals); + if (mem_used != 0) printf("Memory used : %.2f MB\n", mem_used); + printf("CPU time : %g s\n", cpu_time); +} + + +//================================================================================================= +// Garbage Collection methods: + +void Solver::relocAll(ClauseAllocator& to) +{ + // All watchers: + // + watches.cleanAll(); + for (int v = 0; v < nVars(); v++) + for (int s = 0; s < 2; s++){ + Lit p = mkLit(v, s); + vec<Watcher>& ws = watches[p]; + for (int j = 0; j < ws.size(); j++) + ca.reloc(ws[j].cref, to); + } + + // All reasons: + // + for (int i = 0; i < trail.size(); i++){ + Var v = var(trail[i]); + + // Note: it is not safe to call 'locked()' on a relocated clause. This is why we keep + // 'dangling' reasons here. It is safe and does not hurt. + if (reason(v) != CRef_Undef && (ca[reason(v)].reloced() || locked(ca[reason(v)]))){ + assert(!isRemoved(reason(v))); + ca.reloc(vardata[v].reason, to); + } + } + + // All learnt: + // + int i, j; + for (i = j = 0; i < learnts.size(); i++) + if (!isRemoved(learnts[i])){ + ca.reloc(learnts[i], to); + learnts[j++] = learnts[i]; + } + learnts.shrink(i - j); + + // All original: + // + for (i = j = 0; i < clauses.size(); i++) + if (!isRemoved(clauses[i])){ + ca.reloc(clauses[i], to); + clauses[j++] = clauses[i]; + } + clauses.shrink(i - j); +} + + +void Solver::garbageCollect() +{ + // Initialize the next region to a size corresponding to the estimated utilization degree. This + // is not precise but should avoid some unnecessary reallocations for the new region: + ClauseAllocator to(ca.size() - ca.wasted()); + + relocAll(to); + if (verbosity >= 2) + printf("| Garbage collection: %12d bytes => %12d bytes |\n", + ca.size()*ClauseAllocator::Unit_Size, to.size()*ClauseAllocator::Unit_Size); + to.moveTo(ca); +} |