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Diffstat (limited to 'libs/minisat/SimpSolver.cc')
| -rw-r--r-- | libs/minisat/SimpSolver.cc | 727 |
1 files changed, 727 insertions, 0 deletions
diff --git a/libs/minisat/SimpSolver.cc b/libs/minisat/SimpSolver.cc new file mode 100644 index 00000000..23236810 --- /dev/null +++ b/libs/minisat/SimpSolver.cc @@ -0,0 +1,727 @@ +#define __STDC_FORMAT_MACROS +#define __STDC_LIMIT_MACROS +/***********************************************************************************[SimpSolver.cc] +Copyright (c) 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 "libs/minisat/Sort.h" +#include "libs/minisat/SimpSolver.h" +#include "libs/minisat/System.h" + +using namespace Minisat; + +//================================================================================================= +// Options: + + +static const char* _cat = "SIMP"; + +static BoolOption opt_use_asymm (_cat, "asymm", "Shrink clauses by asymmetric branching.", false); +static BoolOption opt_use_rcheck (_cat, "rcheck", "Check if a clause is already implied. (costly)", false); +static BoolOption opt_use_elim (_cat, "elim", "Perform variable elimination.", true); +static IntOption opt_grow (_cat, "grow", "Allow a variable elimination step to grow by a number of clauses.", 0); +static IntOption opt_clause_lim (_cat, "cl-lim", "Variables are not eliminated if it produces a resolvent with a length above this limit. -1 means no limit", 20, IntRange(-1, INT32_MAX)); +static IntOption opt_subsumption_lim (_cat, "sub-lim", "Do not check if subsumption against a clause larger than this. -1 means no limit.", 1000, IntRange(-1, INT32_MAX)); +static DoubleOption opt_simp_garbage_frac(_cat, "simp-gc-frac", "The fraction of wasted memory allowed before a garbage collection is triggered during simplification.", 0.5, DoubleRange(0, false, HUGE_VAL, false)); + + +//================================================================================================= +// Constructor/Destructor: + + +SimpSolver::SimpSolver() : + grow (opt_grow) + , clause_lim (opt_clause_lim) + , subsumption_lim (opt_subsumption_lim) + , simp_garbage_frac (opt_simp_garbage_frac) + , use_asymm (opt_use_asymm) + , use_rcheck (opt_use_rcheck) + , use_elim (opt_use_elim) + , extend_model (true) + , merges (0) + , asymm_lits (0) + , eliminated_vars (0) + , elimorder (1) + , use_simplification (true) + , occurs (ClauseDeleted(ca)) + , elim_heap (ElimLt(n_occ)) + , bwdsub_assigns (0) + , n_touched (0) +{ + vec<Lit> dummy(1,lit_Undef); + ca.extra_clause_field = true; // NOTE: must happen before allocating the dummy clause below. + bwdsub_tmpunit = ca.alloc(dummy); + remove_satisfied = false; +} + + +SimpSolver::~SimpSolver() +{ +} + + +Var SimpSolver::newVar(lbool upol, bool dvar) { + Var v = Solver::newVar(upol, dvar); + + frozen .insert(v, (char)false); + eliminated.insert(v, (char)false); + + if (use_simplification){ + n_occ .insert( mkLit(v), 0); + n_occ .insert(~mkLit(v), 0); + occurs .init (v); + touched .insert(v, 0); + elim_heap .insert(v); + } + return v; } + + +void SimpSolver::releaseVar(Lit l) +{ + assert(!isEliminated(var(l))); + if (!use_simplification && var(l) >= max_simp_var) + // Note: Guarantees that no references to this variable is + // left in model extension datastructure. Could be improved! + Solver::releaseVar(l); + else + // Otherwise, don't allow variable to be reused. + Solver::addClause(l); +} + + +lbool SimpSolver::solve_(bool do_simp, bool turn_off_simp) +{ + vec<Var> extra_frozen; + lbool result = l_True; + + do_simp &= use_simplification; + + if (do_simp){ + // Assumptions must be temporarily frozen to run variable elimination: + for (int i = 0; i < assumptions.size(); i++){ + Var v = var(assumptions[i]); + + // If an assumption has been eliminated, remember it. + assert(!isEliminated(v)); + + if (!frozen[v]){ + // Freeze and store. + setFrozen(v, true); + extra_frozen.push(v); + } } + + result = lbool(eliminate(turn_off_simp)); + } + + if (result == l_True) + result = Solver::solve_(); + else if (verbosity >= 1) + printf("===============================================================================\n"); + + if (result == l_True && extend_model) + extendModel(); + + if (do_simp) + // Unfreeze the assumptions that were frozen: + for (int i = 0; i < extra_frozen.size(); i++) + setFrozen(extra_frozen[i], false); + + return result; +} + + + +bool SimpSolver::addClause_(vec<Lit>& ps) +{ +#ifndef NDEBUG + for (int i = 0; i < ps.size(); i++) + assert(!isEliminated(var(ps[i]))); +#endif + + int nclauses = clauses.size(); + + if (use_rcheck && implied(ps)) + return true; + + if (!Solver::addClause_(ps)) + return false; + + if (use_simplification && clauses.size() == nclauses + 1){ + CRef cr = clauses.last(); + const Clause& c = ca[cr]; + + // NOTE: the clause is added to the queue immediately and then + // again during 'gatherTouchedClauses()'. If nothing happens + // in between, it will only be checked once. Otherwise, it may + // be checked twice unnecessarily. This is an unfortunate + // consequence of how backward subsumption is used to mimic + // forward subsumption. + subsumption_queue.insert(cr); + for (int i = 0; i < c.size(); i++){ + occurs[var(c[i])].push(cr); + n_occ[c[i]]++; + touched[var(c[i])] = 1; + n_touched++; + if (elim_heap.inHeap(var(c[i]))) + elim_heap.increase(var(c[i])); + } + } + + return true; +} + + +void SimpSolver::removeClause(CRef cr) +{ + const Clause& c = ca[cr]; + + if (use_simplification) + for (int i = 0; i < c.size(); i++){ + n_occ[c[i]]--; + updateElimHeap(var(c[i])); + occurs.smudge(var(c[i])); + } + + Solver::removeClause(cr); +} + + +bool SimpSolver::strengthenClause(CRef cr, Lit l) +{ + Clause& c = ca[cr]; + assert(decisionLevel() == 0); + assert(use_simplification); + + // FIX: this is too inefficient but would be nice to have (properly implemented) + // if (!find(subsumption_queue, &c)) + subsumption_queue.insert(cr); + + if (c.size() == 2){ + removeClause(cr); + c.strengthen(l); + }else{ + detachClause(cr, true); + c.strengthen(l); + attachClause(cr); + remove(occurs[var(l)], cr); + n_occ[l]--; + updateElimHeap(var(l)); + } + + return c.size() == 1 ? enqueue(c[0]) && propagate() == CRef_Undef : true; +} + + +// Returns FALSE if clause is always satisfied ('out_clause' should not be used). +bool SimpSolver::merge(const Clause& _ps, const Clause& _qs, Var v, vec<Lit>& out_clause) +{ + merges++; + out_clause.clear(); + + bool ps_smallest = _ps.size() < _qs.size(); + const Clause& ps = ps_smallest ? _qs : _ps; + const Clause& qs = ps_smallest ? _ps : _qs; + + for (int i = 0; i < qs.size(); i++){ + if (var(qs[i]) != v){ + for (int j = 0; j < ps.size(); j++) + if (var(ps[j]) == var(qs[i])){ + if (ps[j] == ~qs[i]) + return false; + else + goto next; + } + out_clause.push(qs[i]); + } + next:; + } + + for (int i = 0; i < ps.size(); i++) + if (var(ps[i]) != v) + out_clause.push(ps[i]); + + return true; +} + + +// Returns FALSE if clause is always satisfied. +bool SimpSolver::merge(const Clause& _ps, const Clause& _qs, Var v, int& size) +{ + merges++; + + bool ps_smallest = _ps.size() < _qs.size(); + const Clause& ps = ps_smallest ? _qs : _ps; + const Clause& qs = ps_smallest ? _ps : _qs; + const Lit* __ps = (const Lit*)ps; + const Lit* __qs = (const Lit*)qs; + + size = ps.size()-1; + + for (int i = 0; i < qs.size(); i++){ + if (var(__qs[i]) != v){ + for (int j = 0; j < ps.size(); j++) + if (var(__ps[j]) == var(__qs[i])){ + if (__ps[j] == ~__qs[i]) + return false; + else + goto next; + } + size++; + } + next:; + } + + return true; +} + + +void SimpSolver::gatherTouchedClauses() +{ + if (n_touched == 0) return; + + int i,j; + for (i = j = 0; i < subsumption_queue.size(); i++) + if (ca[subsumption_queue[i]].mark() == 0) + ca[subsumption_queue[i]].mark(2); + + for (i = 0; i < nVars(); i++) + if (touched[i]){ + const vec<CRef>& cs = occurs.lookup(i); + for (j = 0; j < cs.size(); j++) + if (ca[cs[j]].mark() == 0){ + subsumption_queue.insert(cs[j]); + ca[cs[j]].mark(2); + } + touched[i] = 0; + } + + for (i = 0; i < subsumption_queue.size(); i++) + if (ca[subsumption_queue[i]].mark() == 2) + ca[subsumption_queue[i]].mark(0); + + n_touched = 0; +} + + +bool SimpSolver::implied(const vec<Lit>& c) +{ + assert(decisionLevel() == 0); + + trail_lim.push(trail.size()); + for (int i = 0; i < c.size(); i++) + if (value(c[i]) == l_True){ + cancelUntil(0); + return true; + }else if (value(c[i]) != l_False){ + assert(value(c[i]) == l_Undef); + uncheckedEnqueue(~c[i]); + } + + bool result = propagate() != CRef_Undef; + cancelUntil(0); + return result; +} + + +// Backward subsumption + backward subsumption resolution +bool SimpSolver::backwardSubsumptionCheck(bool verbose) +{ + int cnt = 0; + int subsumed = 0; + int deleted_literals = 0; + assert(decisionLevel() == 0); + + while (subsumption_queue.size() > 0 || bwdsub_assigns < trail.size()){ + + // Empty subsumption queue and return immediately on user-interrupt: + if (asynch_interrupt){ + subsumption_queue.clear(); + bwdsub_assigns = trail.size(); + break; } + + // Check top-level assignments by creating a dummy clause and placing it in the queue: + if (subsumption_queue.size() == 0 && bwdsub_assigns < trail.size()){ + Lit l = trail[bwdsub_assigns++]; + ca[bwdsub_tmpunit][0] = l; + ca[bwdsub_tmpunit].calcAbstraction(); + subsumption_queue.insert(bwdsub_tmpunit); } + + CRef cr = subsumption_queue.peek(); subsumption_queue.pop(); + Clause& c = ca[cr]; + + if (c.mark()) continue; + + if (verbose && verbosity >= 2 && cnt++ % 1000 == 0) + printf("subsumption left: %10d (%10d subsumed, %10d deleted literals)\r", subsumption_queue.size(), subsumed, deleted_literals); + + assert(c.size() > 1 || value(c[0]) == l_True); // Unit-clauses should have been propagated before this point. + + // Find best variable to scan: + Var best = var(c[0]); + for (int i = 1; i < c.size(); i++) + if (occurs[var(c[i])].size() < occurs[best].size()) + best = var(c[i]); + + // Search all candidates: + vec<CRef>& _cs = occurs.lookup(best); + CRef* cs = (CRef*)_cs; + + for (int j = 0; j < _cs.size(); j++) + if (c.mark()) + break; + else if (!ca[cs[j]].mark() && cs[j] != cr && (subsumption_lim == -1 || ca[cs[j]].size() < subsumption_lim)){ + Lit l = c.subsumes(ca[cs[j]]); + + if (l == lit_Undef) + subsumed++, removeClause(cs[j]); + else if (l != lit_Error){ + deleted_literals++; + + if (!strengthenClause(cs[j], ~l)) + return false; + + // Did current candidate get deleted from cs? Then check candidate at index j again: + if (var(l) == best) + j--; + } + } + } + + return true; +} + + +bool SimpSolver::asymm(Var v, CRef cr) +{ + Clause& c = ca[cr]; + assert(decisionLevel() == 0); + + if (c.mark() || satisfied(c)) return true; + + trail_lim.push(trail.size()); + Lit l = lit_Undef; + for (int i = 0; i < c.size(); i++) + if (var(c[i]) != v && value(c[i]) != l_False) + uncheckedEnqueue(~c[i]); + else + l = c[i]; + + if (propagate() != CRef_Undef){ + cancelUntil(0); + asymm_lits++; + if (!strengthenClause(cr, l)) + return false; + }else + cancelUntil(0); + + return true; +} + + +bool SimpSolver::asymmVar(Var v) +{ + assert(use_simplification); + + const vec<CRef>& cls = occurs.lookup(v); + + if (value(v) != l_Undef || cls.size() == 0) + return true; + + for (int i = 0; i < cls.size(); i++) + if (!asymm(v, cls[i])) + return false; + + return backwardSubsumptionCheck(); +} + + +static void mkElimClause(vec<uint32_t>& elimclauses, Lit x) +{ + elimclauses.push(toInt(x)); + elimclauses.push(1); +} + + +static void mkElimClause(vec<uint32_t>& elimclauses, Var v, Clause& c) +{ + int first = elimclauses.size(); + int v_pos = -1; + + // Copy clause to elimclauses-vector. Remember position where the + // variable 'v' occurs: + for (int i = 0; i < c.size(); i++){ + elimclauses.push(toInt(c[i])); + if (var(c[i]) == v) + v_pos = i + first; + } + assert(v_pos != -1); + + // Swap the first literal with the 'v' literal, so that the literal + // containing 'v' will occur first in the clause: + uint32_t tmp = elimclauses[v_pos]; + elimclauses[v_pos] = elimclauses[first]; + elimclauses[first] = tmp; + + // Store the length of the clause last: + elimclauses.push(c.size()); +} + + + +bool SimpSolver::eliminateVar(Var v) +{ + assert(!frozen[v]); + assert(!isEliminated(v)); + assert(value(v) == l_Undef); + + // Split the occurrences into positive and negative: + // + const vec<CRef>& cls = occurs.lookup(v); + vec<CRef> pos, neg; + for (int i = 0; i < cls.size(); i++) + (find(ca[cls[i]], mkLit(v)) ? pos : neg).push(cls[i]); + + // Check wether the increase in number of clauses stays within the allowed ('grow'). Moreover, no + // clause must exceed the limit on the maximal clause size (if it is set): + // + int cnt = 0; + int clause_size = 0; + + for (int i = 0; i < pos.size(); i++) + for (int j = 0; j < neg.size(); j++) + if (merge(ca[pos[i]], ca[neg[j]], v, clause_size) && + (++cnt > cls.size() + grow || (clause_lim != -1 && clause_size > clause_lim))) + return true; + + // Delete and store old clauses: + eliminated[v] = true; + setDecisionVar(v, false); + eliminated_vars++; + + if (pos.size() > neg.size()){ + for (int i = 0; i < neg.size(); i++) + mkElimClause(elimclauses, v, ca[neg[i]]); + mkElimClause(elimclauses, mkLit(v)); + }else{ + for (int i = 0; i < pos.size(); i++) + mkElimClause(elimclauses, v, ca[pos[i]]); + mkElimClause(elimclauses, ~mkLit(v)); + } + + for (int i = 0; i < cls.size(); i++) + removeClause(cls[i]); + + // Produce clauses in cross product: + vec<Lit>& resolvent = add_tmp; + for (int i = 0; i < pos.size(); i++) + for (int j = 0; j < neg.size(); j++) + if (merge(ca[pos[i]], ca[neg[j]], v, resolvent) && !addClause_(resolvent)) + return false; + + // Free occurs list for this variable: + occurs[v].clear(true); + + // Free watchers lists for this variable, if possible: + if (watches[ mkLit(v)].size() == 0) watches[ mkLit(v)].clear(true); + if (watches[~mkLit(v)].size() == 0) watches[~mkLit(v)].clear(true); + + return backwardSubsumptionCheck(); +} + + +bool SimpSolver::substitute(Var v, Lit x) +{ + assert(!frozen[v]); + assert(!isEliminated(v)); + assert(value(v) == l_Undef); + + if (!ok) return false; + + eliminated[v] = true; + setDecisionVar(v, false); + const vec<CRef>& cls = occurs.lookup(v); + + vec<Lit>& subst_clause = add_tmp; + for (int i = 0; i < cls.size(); i++){ + Clause& c = ca[cls[i]]; + + subst_clause.clear(); + for (int j = 0; j < c.size(); j++){ + Lit p = c[j]; + subst_clause.push(var(p) == v ? x ^ sign(p) : p); + } + + removeClause(cls[i]); + + if (!addClause_(subst_clause)) + return ok = false; + } + + return true; +} + + +void SimpSolver::extendModel() +{ + int i, j; + Lit x; + + for (i = elimclauses.size()-1; i > 0; i -= j){ + for (j = elimclauses[i--]; j > 1; j--, i--) + if (modelValue(toLit(elimclauses[i])) != l_False) + goto next; + + x = toLit(elimclauses[i]); + model[var(x)] = lbool(!sign(x)); + next:; + } +} + + +bool SimpSolver::eliminate(bool turn_off_elim) +{ + if (!simplify()) + return false; + else if (!use_simplification) + return true; + + // Main simplification loop: + // + while (n_touched > 0 || bwdsub_assigns < trail.size() || elim_heap.size() > 0){ + + gatherTouchedClauses(); + // printf(" ## (time = %6.2f s) BWD-SUB: queue = %d, trail = %d\n", cpuTime(), subsumption_queue.size(), trail.size() - bwdsub_assigns); + if ((subsumption_queue.size() > 0 || bwdsub_assigns < trail.size()) && + !backwardSubsumptionCheck(true)){ + ok = false; goto cleanup; } + + // Empty elim_heap and return immediately on user-interrupt: + if (asynch_interrupt){ + assert(bwdsub_assigns == trail.size()); + assert(subsumption_queue.size() == 0); + assert(n_touched == 0); + elim_heap.clear(); + goto cleanup; } + + // printf(" ## (time = %6.2f s) ELIM: vars = %d\n", cpuTime(), elim_heap.size()); + for (int cnt = 0; !elim_heap.empty(); cnt++){ + Var elim = elim_heap.removeMin(); + + if (asynch_interrupt) break; + + if (isEliminated(elim) || value(elim) != l_Undef) continue; + + if (verbosity >= 2 && cnt % 100 == 0) + printf("elimination left: %10d\r", elim_heap.size()); + + if (use_asymm){ + // Temporarily freeze variable. Otherwise, it would immediately end up on the queue again: + bool was_frozen = frozen[elim]; + frozen[elim] = true; + if (!asymmVar(elim)){ + ok = false; goto cleanup; } + frozen[elim] = was_frozen; } + + // At this point, the variable may have been set by assymetric branching, so check it + // again. Also, don't eliminate frozen variables: + if (use_elim && value(elim) == l_Undef && !frozen[elim] && !eliminateVar(elim)){ + ok = false; goto cleanup; } + + checkGarbage(simp_garbage_frac); + } + + assert(subsumption_queue.size() == 0); + } + cleanup: + + // If no more simplification is needed, free all simplification-related data structures: + if (turn_off_elim){ + touched .clear(true); + occurs .clear(true); + n_occ .clear(true); + elim_heap.clear(true); + subsumption_queue.clear(true); + + use_simplification = false; + remove_satisfied = true; + ca.extra_clause_field = false; + max_simp_var = nVars(); + + // Force full cleanup (this is safe and desirable since it only happens once): + rebuildOrderHeap(); + garbageCollect(); + }else{ + // Cheaper cleanup: + checkGarbage(); + } + + if (verbosity >= 1 && elimclauses.size() > 0) + printf("| Eliminated clauses: %10.2f Mb |\n", + double(elimclauses.size() * sizeof(uint32_t)) / (1024*1024)); + + return ok; +} + + +//================================================================================================= +// Garbage Collection methods: + + +void SimpSolver::relocAll(ClauseAllocator& to) +{ + if (!use_simplification) return; + + // All occurs lists: + // + for (int i = 0; i < nVars(); i++){ + occurs.clean(i); + vec<CRef>& cs = occurs[i]; + for (int j = 0; j < cs.size(); j++) + ca.reloc(cs[j], to); + } + + // Subsumption queue: + // + for (int i = subsumption_queue.size(); i > 0; i--){ + CRef cr = subsumption_queue.peek(); subsumption_queue.pop(); + if (ca[cr].mark()) continue; + ca.reloc(cr, to); + subsumption_queue.insert(cr); + } + + // Temporary clause: + // + ca.reloc(bwdsub_tmpunit, to); +} + + +void SimpSolver::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()); + + to.extra_clause_field = ca.extra_clause_field; // NOTE: this is important to keep (or lose) the extra fields. + relocAll(to); + Solver::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); +} |