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Solver.cc
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Solver.cc
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/***************************************************************************************[Solver.cc]
Glucose -- Copyright (c) 2009-2014, Gilles Audemard, Laurent Simon
CRIL - Univ. Artois, France
LRI - Univ. Paris Sud, France (2009-2013)
Labri - Univ. Bordeaux, France
Syrup (Glucose Parallel) -- Copyright (c) 2013-2014, Gilles Audemard, Laurent Simon
CRIL - Univ. Artois, France
Labri - Univ. Bordeaux, France
Glucose sources are based on MiniSat (see below MiniSat copyrights). Permissions and copyrights of
Glucose (sources until 2013, Glucose 3.0, single core) are exactly the same as Minisat on which it
is based on. (see below).
Glucose-Syrup sources are based on another copyright. Permissions and copyrights for the parallel
version of Glucose-Syrup (the "Software") are granted, free of charge, to deal with the Software
without restriction, including the rights to use, copy, modify, merge, publish, distribute,
sublicence, 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 and below copyrights notices and this permission notice shall be included in all
copies or substantial portions of the Software;
- The parallel version of Glucose (all files modified since Glucose 3.0 releases, 2013) cannot
be used in any competitive event (sat competitions/evaluations) without the express permission of
the authors (Gilles Audemard / Laurent Simon). This is also the case for any competitive event
using Glucose Parallel as an embedded SAT engine (single core or not).
--------------- Original Minisat Copyrights
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 "utils/System.h"
#include "mtl/Sort.h"
#include "core/Solver.h"
#include "core/Constants.h"
#include"simp/SimpSolver.h"
using namespace Glucose;
//=================================================================================================
// Statistics
//=================================================================================================
//=================================================================================================
// Options:
static const char *_cat = "CORE";
static const char *_cr = "CORE -- RESTART";
static const char *_cred = "CORE -- REDUCE";
static const char *_cm = "CORE -- MINIMIZE";
static DoubleOption opt_K(_cr, "K", "The constant used to force restart", 0.8, DoubleRange(0, false, 1, false));
static DoubleOption opt_R(_cr, "R", "The constant used to block restart", 1.4, DoubleRange(1, false, 5, false));
static IntOption opt_size_lbd_queue(_cr, "szLBDQueue", "The size of moving average for LBD (restarts)", 50, IntRange(10, INT32_MAX));
static IntOption opt_size_trail_queue(_cr, "szTrailQueue", "The size of moving average for trail (block restarts)", 5000, IntRange(10, INT32_MAX));
static IntOption opt_first_reduce_db(_cred, "firstReduceDB", "The number of conflicts before the first reduce DB (or the size of leernts if chanseok is used)",
2000, IntRange(0, INT32_MAX));
static IntOption opt_inc_reduce_db(_cred, "incReduceDB", "Increment for reduce DB", 300, IntRange(0, INT32_MAX));
static IntOption opt_spec_inc_reduce_db(_cred, "specialIncReduceDB", "Special increment for reduce DB", 1000, IntRange(0, INT32_MAX));
static IntOption opt_lb_lbd_frozen_clause(_cred, "minLBDFrozenClause", "Protect clauses if their LBD decrease and is lower than (for one turn)", 30,
IntRange(0, INT32_MAX));
static BoolOption opt_chanseok_hack(_cred, "chanseok",
"Use Chanseok Oh strategy for LBD (keep all LBD<=co and remove half of firstreduceDB other learnt clauses", false);
static IntOption opt_chanseok_limit(_cred, "co", "Chanseok Oh: all learnt clauses with LBD<=co are permanent", 5, IntRange(2, INT32_MAX));
static IntOption opt_lb_size_minimzing_clause(_cm, "minSizeMinimizingClause", "The min size required to minimize clause", 30, IntRange(3, INT32_MAX));
static IntOption opt_lb_lbd_minimzing_clause(_cm, "minLBDMinimizingClause", "The min LBD required to minimize clause", 6, IntRange(3, INT32_MAX));
static DoubleOption opt_var_decay(_cat, "var-decay", "The variable activity decay factor (starting point)", 0.8, DoubleRange(0, false, 1, false));
static DoubleOption opt_max_var_decay(_cat, "max-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 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 BoolOption opt_glu_reduction(_cat, "gr", "glucose strategy to fire clause database reduction (must be false to fire Chanseok strategy)", true);
static BoolOption opt_luby_restart(_cat, "luby", "Use the Luby restart sequence", false);
static DoubleOption opt_restart_inc(_cat, "rinc", "Restart interval increase factor", 2, DoubleRange(1, false, HUGE_VAL, false));
static IntOption opt_luby_restart_factor(_cred, "luby-factor", "Luby restart factor", 100, IntRange(1, INT32_MAX));
static IntOption opt_randomize_phase_on_restarts(_cat, "phase-restart",
"The amount of randomization for the phase at each restart (0=none, 1=first branch, 2=first branch (no bad clauses), 3=first branch (only initial clauses)",
0, IntRange(0, 3));
static BoolOption opt_fixed_randomize_phase_on_restarts(_cat, "fix-phas-rest", "Fixes the first 7 levels at random phase", false);
static BoolOption opt_adapt(_cat, "adapt", "Adapt dynamically stategies after 100000 conflicts", true);
static BoolOption opt_forceunsat(_cat,"forceunsat","Force the phase for UNSAT",true);
//=================================================================================================
// Constructor/Destructor:
Solver::Solver() :
// Parameters (user settable):
//
verbosity(0)
, showModel(0)
, K(opt_K)
, R(opt_R)
, sizeLBDQueue(opt_size_lbd_queue)
, sizeTrailQueue(opt_size_trail_queue)
, firstReduceDB(opt_first_reduce_db)
, incReduceDB(opt_chanseok_hack ? 0 : opt_inc_reduce_db)
, specialIncReduceDB(opt_chanseok_hack ? 0 : opt_spec_inc_reduce_db)
, lbLBDFrozenClause(opt_lb_lbd_frozen_clause)
, chanseokStrategy(opt_chanseok_hack)
, coLBDBound (opt_chanseok_limit)
, lbSizeMinimizingClause(opt_lb_size_minimzing_clause)
, lbLBDMinimizingClause(opt_lb_lbd_minimzing_clause)
, var_decay(opt_var_decay)
, max_var_decay(opt_max_var_decay)
, clause_decay(opt_clause_decay)
, random_var_freq(opt_random_var_freq)
, random_seed(opt_random_seed)
, ccmin_mode(opt_ccmin_mode)
, phase_saving(opt_phase_saving)
, rnd_pol(false)
, rnd_init_act(opt_rnd_init_act)
, randomizeFirstDescent(false)
, garbage_frac(opt_garbage_frac)
, certifiedOutput(NULL)
, certifiedUNSAT(false) // Not in the first parallel version
, vbyte(false)
, panicModeLastRemoved(0), panicModeLastRemovedShared(0)
, useUnaryWatched(false)
, promoteOneWatchedClause(true)
,solves(0),starts(0),decisions(0),propagations(0),conflicts(0),conflictsRestarts(0)
, curRestart(1)
, glureduce(opt_glu_reduction)
, restart_inc(opt_restart_inc)
, luby_restart(opt_luby_restart)
, adaptStrategies(opt_adapt)
, luby_restart_factor(opt_luby_restart_factor)
, randomize_on_restarts(opt_randomize_phase_on_restarts)
, fixed_randomize_on_restarts(opt_fixed_randomize_phase_on_restarts)
, newDescent(0)
, randomDescentAssignments(0)
, forceUnsatOnNewDescent(opt_forceunsat)
, ok(true)
, cla_inc(1)
, var_inc(1)
, watches(WatcherDeleted(ca))
, watchesBin(WatcherDeleted(ca))
, unaryWatches(WatcherDeleted(ca))
, qhead(0)
, simpDB_assigns(-1)
, simpDB_props(0)
, order_heap(VarOrderLt(activity))
, progress_estimate(0)
, remove_satisfied(true)
,lastLearntClause(CRef_Undef)
// Resource constraints:
//
, conflict_budget(-1)
, propagation_budget(-1)
, asynch_interrupt(false)
, incremental(false)
, nbVarsInitialFormula(INT32_MAX)
, totalTime4Sat(0.)
, totalTime4Unsat(0.)
, nbSatCalls(0)
, nbUnsatCalls(0)
{
MYFLAG = 0;
// Initialize only first time. Useful for incremental solving (not in // version), useless otherwise
// Kept here for simplicity
lbdQueue.initSize(sizeLBDQueue);
trailQueue.initSize(sizeTrailQueue);
sumLBD = 0;
nbclausesbeforereduce = firstReduceDB;
stats.growTo(coreStatsSize, 0);
}
//-------------------------------------------------------
// Special constructor used for cloning solvers
//-------------------------------------------------------
Solver::Solver(const Solver &s) :
verbosity(s.verbosity)
, showModel(s.showModel)
, K(s.K)
, R(s.R)
, sizeLBDQueue(s.sizeLBDQueue)
, sizeTrailQueue(s.sizeTrailQueue)
, firstReduceDB(s.firstReduceDB)
, incReduceDB(s.incReduceDB)
, specialIncReduceDB(s.specialIncReduceDB)
, lbLBDFrozenClause(s.lbLBDFrozenClause)
, chanseokStrategy(opt_chanseok_hack)
, coLBDBound (opt_chanseok_limit)
, lbSizeMinimizingClause(s.lbSizeMinimizingClause)
, lbLBDMinimizingClause(s.lbLBDMinimizingClause)
, var_decay(s.var_decay)
, max_var_decay(s.max_var_decay)
, clause_decay(s.clause_decay)
, random_var_freq(s.random_var_freq)
, random_seed(s.random_seed)
, ccmin_mode(s.ccmin_mode)
, phase_saving(s.phase_saving)
, rnd_pol(s.rnd_pol)
, rnd_init_act(s.rnd_init_act)
, randomizeFirstDescent(s.randomizeFirstDescent)
, garbage_frac(s.garbage_frac)
, certifiedOutput(NULL)
, certifiedUNSAT(false) // Not in the first parallel version
, panicModeLastRemoved(s.panicModeLastRemoved), panicModeLastRemovedShared(s.panicModeLastRemovedShared)
, useUnaryWatched(s.useUnaryWatched)
, promoteOneWatchedClause(s.promoteOneWatchedClause)
// Statistics: (formerly in 'SolverStats')
//
,solves(0),starts(0),decisions(0),propagations(0),conflicts(0),conflictsRestarts(0)
, curRestart(s.curRestart)
, glureduce(s.glureduce)
, restart_inc(s.restart_inc)
, luby_restart(s.luby_restart)
, adaptStrategies(s.adaptStrategies)
, luby_restart_factor(s.luby_restart_factor)
, randomize_on_restarts(s.randomize_on_restarts)
, fixed_randomize_on_restarts(s.fixed_randomize_on_restarts)
, newDescent(s.newDescent)
, randomDescentAssignments(s.randomDescentAssignments)
, forceUnsatOnNewDescent(s.forceUnsatOnNewDescent)
, ok(true)
, cla_inc(s.cla_inc)
, var_inc(s.var_inc)
, watches(WatcherDeleted(ca))
, watchesBin(WatcherDeleted(ca))
, unaryWatches(WatcherDeleted(ca))
, qhead(s.qhead)
, simpDB_assigns(s.simpDB_assigns)
, simpDB_props(s.simpDB_props)
, order_heap(VarOrderLt(activity))
, progress_estimate(s.progress_estimate)
, remove_satisfied(s.remove_satisfied)
,lastLearntClause(CRef_Undef)
// Resource constraints:
//
, conflict_budget(s.conflict_budget)
, propagation_budget(s.propagation_budget)
, asynch_interrupt(s.asynch_interrupt)
, incremental(s.incremental)
, nbVarsInitialFormula(s.nbVarsInitialFormula)
, totalTime4Sat(s.totalTime4Sat)
, totalTime4Unsat(s.totalTime4Unsat)
, nbSatCalls(s.nbSatCalls)
, nbUnsatCalls(s.nbUnsatCalls)
{
// Copy clauses.
s.ca.copyTo(ca);
ca.extra_clause_field = s.ca.extra_clause_field;
// Initialize other variables
MYFLAG = 0;
// Initialize only first time. Useful for incremental solving (not in // version), useless otherwise
// Kept here for simplicity
sumLBD = s.sumLBD;
nbclausesbeforereduce = s.nbclausesbeforereduce;
// Copy all search vectors
s.watches.copyTo(watches);
s.watchesBin.copyTo(watchesBin);
s.unaryWatches.copyTo(unaryWatches);
s.assigns.memCopyTo(assigns);
s.vardata.memCopyTo(vardata);
s.activity.memCopyTo(activity);
s.seen.memCopyTo(seen);
s.permDiff.memCopyTo(permDiff);
s.polarity.memCopyTo(polarity);
s.decision.memCopyTo(decision);
s.trail.memCopyTo(trail);
s.order_heap.copyTo(order_heap);
s.clauses.memCopyTo(clauses);
s.learnts.memCopyTo(learnts);
s.permanentLearnts.memCopyTo(permanentLearnts);
s.lbdQueue.copyTo(lbdQueue);
s.trailQueue.copyTo(trailQueue);
s.forceUNSAT.copyTo(forceUNSAT);
s.stats.copyTo(stats);
}
Solver::~Solver() {
}
/****************************************************************
Certified UNSAT proof in binary format
****************************************************************/
void Solver::write_char(unsigned char ch) {
if(putc((int) ch, certifiedOutput) == EOF)
exit(1);
}
void Solver::write_lit(int n) {
for(; n > 127; n >>= 7)
write_char(128 | (n & 127));
write_char(n);
}
/****************************************************************
Set the incremental mode
****************************************************************/
// This function set the incremental mode to true.
// You can add special code for this mode here.
void Solver::setIncrementalMode() {
#ifdef INCREMENTAL
incremental = true;
#else
fprintf(stderr, "c Trying to set incremental mode, but not compiled properly for this.\n");
exit(1);
#endif
}
// Number of variables without selectors
void Solver::initNbInitialVars(int nb) {
nbVarsInitialFormula = nb;
}
bool Solver::isIncremental() {
return incremental;
}
//=================================================================================================
// 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(bool sign, bool dvar) {
int v = nVars();
watches.init(mkLit(v, false));
watches.init(mkLit(v, true));
watchesBin.init(mkLit(v, false));
watchesBin.init(mkLit(v, true));
unaryWatches.init(mkLit(v, false));
unaryWatches.init(mkLit(v, true));
assigns.push(l_Undef);
vardata.push(mkVarData(CRef_Undef, 0));
activity.push(rnd_init_act ? drand(random_seed) * 0.00001 : 0);
seen.push(0);
permDiff.push(0);
polarity.push(sign);
forceUNSAT.push(0);
decision.push();
trail.capacity(v + 1);
setDecisionVar(v, dvar);
return v;
}
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);
vec <Lit> oc;
oc.clear();
Lit p;
int i, j, flag = 0;
if(certifiedUNSAT) {
for(i = j = 0, p = lit_Undef; i < ps.size(); i++) {
oc.push(ps[i]);
if(value(ps[i]) == l_True || ps[i] == ~p || value(ps[i]) == l_False)
flag = 1;
}
}
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(flag && (certifiedUNSAT)) {
if(vbyte) {
write_char('a');
for(i = j = 0, p = lit_Undef; i < ps.size(); i++)
write_lit(2 * (var(ps[i]) + 1) + sign(ps[i]));
write_lit(0);
write_char('d');
for(i = j = 0, p = lit_Undef; i < oc.size(); i++)
write_lit(2 * (var(oc[i]) + 1) + sign(oc[i]));
write_lit(0);
}
else {
for(i = j = 0, p = lit_Undef; i < ps.size(); i++)
fprintf(certifiedOutput, "%i ", (var(ps[i]) + 1) * (-2 * sign(ps[i]) + 1));
fprintf(certifiedOutput, "0\n");
fprintf(certifiedOutput, "d ");
for(i = j = 0, p = lit_Undef; i < oc.size(); i++)
fprintf(certifiedOutput, "%i ", (var(oc[i]) + 1) * (-2 * sign(oc[i]) + 1));
fprintf(certifiedOutput, "0\n");
}
}
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);
if(c.size() == 2) {
watchesBin[~c[0]].push(Watcher(cr, c[1]));
watchesBin[~c[1]].push(Watcher(cr, c[0]));
} else {
watches[~c[0]].push(Watcher(cr, c[1]));
watches[~c[1]].push(Watcher(cr, c[0]));
}
if(c.learnt()) stats[learnts_literals] += c.size();
else stats[clauses_literals] += c.size();
}
void Solver::attachClausePurgatory(CRef cr) {
const Clause &c = ca[cr];
assert(c.size() > 1);
unaryWatches[~c[0]].push(Watcher(cr, c[1]));
}
void Solver::detachClause(CRef cr, bool strict) {
const Clause &c = ca[cr];
assert(c.size() > 1);
if(c.size() == 2) {
if(strict) {
remove(watchesBin[~c[0]], Watcher(cr, c[1]));
remove(watchesBin[~c[1]], Watcher(cr, c[0]));
} else {
// Lazy detaching: (NOTE! Must clean all watcher lists before garbage collecting this clause)
watchesBin.smudge(~c[0]);
watchesBin.smudge(~c[1]);
}
} else {
if(strict) {
remove(watches[~c[0]], Watcher(cr, c[1]));
remove(watches[~c[1]], Watcher(cr, c[0]));
} else {
// Lazy detaching: (NOTE! Must clean all watcher lists before garbage collecting this clause)
watches.smudge(~c[0]);
watches.smudge(~c[1]);
}
}
if(c.learnt()) stats[learnts_literals] -= c.size();
else stats[clauses_literals] -= c.size();
}
// The purgatory is the 1-Watched scheme for imported clauses
void Solver::detachClausePurgatory(CRef cr, bool strict) {
const Clause &c = ca[cr];
assert(c.size() > 1);
if(strict)
remove(unaryWatches[~c[0]], Watcher(cr, c[1]));
else
unaryWatches.smudge(~c[0]);
}
void Solver::removeClause(CRef cr, bool inPurgatory) {
Clause &c = ca[cr];
if(certifiedUNSAT) {
if(vbyte) {
write_char('d');
for(int i = 0; i < c.size(); i++)
write_lit(2 * (var(c[i]) + 1) + sign(c[i]));
write_lit(0);
}
else {
fprintf(certifiedOutput, "d ");
for(int i = 0; i < c.size(); i++)
fprintf(certifiedOutput, "%i ", (var(c[i]) + 1) * (-2 * sign(c[i]) + 1));
fprintf(certifiedOutput, "0\n");
}
}
if(inPurgatory)
detachClausePurgatory(cr);
else
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 {
#ifdef INCREMENTAL
if(incremental)
return (value(c[0]) == l_True) || (value(c[1]) == l_True);
#endif
// Default mode
for(int i = 0; i < c.size(); i++)
if(value(c[i]) == l_True)
return true;
return false;
}
/************************************************************
* Compute LBD functions
*************************************************************/
template <typename T>inline unsigned int Solver::computeLBD(const T &lits, int end) {
int nblevels = 0;
MYFLAG++;
#ifdef INCREMENTAL
if(incremental) { // ----------------- INCREMENTAL MODE
if(end==-1) end = lits.size();
int nbDone = 0;
for(int i=0;i<lits.size();i++) {
if(nbDone>=end) break;
if(isSelector(var(lits[i]))) continue;
nbDone++;
int l = level(var(lits[i]));
if (permDiff[l] != MYFLAG) {
permDiff[l] = MYFLAG;
nblevels++;
}
}
} else { // -------- DEFAULT MODE. NOT A LOT OF DIFFERENCES... BUT EASIER TO READ
#endif
for(int i = 0; i < lits.size(); i++) {
int l = level(var(lits[i]));
if(permDiff[l] != MYFLAG) {
permDiff[l] = MYFLAG;
nblevels++;
}
}
#ifdef INCREMENTAL
}
#endif
return nblevels;
}
/******************************************************************
* Minimisation with binary reolution
******************************************************************/
void Solver::minimisationWithBinaryResolution(vec <Lit> &out_learnt) {
// Find the LBD measure
unsigned int lbd = computeLBD(out_learnt);
Lit p = ~out_learnt[0];
if(lbd <= lbLBDMinimizingClause) {
MYFLAG++;
for(int i = 1; i < out_learnt.size(); i++) {
permDiff[var(out_learnt[i])] = MYFLAG;
}
vec <Watcher> &wbin = watchesBin[p];
int nb = 0;
for(int k = 0; k < wbin.size(); k++) {
Lit imp = wbin[k].blocker;
if(permDiff[var(imp)] == MYFLAG && value(imp) == l_True) {
nb++;
permDiff[var(imp)] = MYFLAG - 1;
}
}
int l = out_learnt.size() - 1;
if(nb > 0) {
stats[nbReducedClauses]++;
for(int i = 1; i < out_learnt.size() - nb; i++) {
if(permDiff[var(out_learnt[i])] != MYFLAG) {
Lit p = out_learnt[l];
out_learnt[l] = out_learnt[i];
out_learnt[i] = p;
l--;
i--;
}
}
out_learnt.shrink(nb);
}
}
}
// 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(((randomizeFirstDescent && conflicts == 0) || 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])
stats[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();
}
if(randomize_on_restarts && !fixed_randomize_on_restarts && newDescent && (decisionLevel() % 2 == 0)) {
return mkLit(next, (randomDescentAssignments >> (decisionLevel() % 32)) & 1);
}
if(fixed_randomize_on_restarts && decisionLevel() < 7) {
return mkLit(next, (randomDescentAssignments >> (decisionLevel() % 32)) & 1);
}
if(next == var_Undef) return lit_Undef;
if(forceUnsatOnNewDescent && newDescent) {
if(forceUNSAT[next] != 0)
return mkLit(next, forceUNSAT[next] < 0);
return mkLit(next, polarity[next]);
}
return next == var_Undef ? lit_Undef : mkLit(next, rnd_pol ? drand(random_seed) < 0.5 : 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, vec <Lit> &selectors, int &out_btlevel, unsigned int &lbd, unsigned int &szWithoutSelectors) {
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];
// Special case for binary clauses
// The first one has to be SAT
if(p != lit_Undef && c.size() == 2 && value(c[0]) == l_False) {
assert(value(c[1]) == l_True);
Lit tmp = c[0];
c[0] = c[1], c[1] = tmp;
}
if(c.learnt()) {
parallelImportClauseDuringConflictAnalysis(c, confl);
claBumpActivity(c);
} else { // original clause
if(!c.getSeen()) {
stats[originalClausesSeen]++;
c.setSeen(true);
}
}
// DYNAMIC NBLEVEL trick (see competition'09 companion paper)
if(c.learnt() && c.lbd() > 2) {
unsigned int nblevels = computeLBD(c);
if(nblevels + 1 < c.lbd()) { // improve the LBD
if(c.lbd() <= lbLBDFrozenClause) {
// seems to be interesting : keep it for the next round
c.setCanBeDel(false);
}
if(chanseokStrategy && nblevels <= coLBDBound) {
c.nolearnt();
learnts.remove(confl);
permanentLearnts.push(confl);
stats[nbPermanentLearnts]++;
} else {
c.setLBD(nblevels); // Update it
}
}
}
for(int j = (p == lit_Undef) ? 0 : 1; j < c.size(); j++) {
Lit q = c[j];
if(!seen[var(q)]) {
if(level(var(q)) == 0) {
} else { // Here, the old case
if(!isSelector(var(q)))
varBumpActivity(var(q));
// This variable was responsible for a conflict,
// consider it as a UNSAT assignation for this literal
bumpForceUNSAT(~q); // Negation because q is false here
seen[var(q)] = 1;
if(level(var(q)) >= decisionLevel()) {
pathC++;
// UPDATEVARACTIVITY trick (see competition'09 companion paper)
if(!isSelector(var(q)) && (reason(var(q)) != CRef_Undef) && ca[reason(var(q))].learnt())
lastDecisionLevel.push(q);
} else {
if(isSelector(var(q))) {
assert(value(q) == l_False);
selectors.push(q);
} else
out_learnt.push(q);
}
}
} //else stats[sumResSeen]++;
}
// Select next clause to look at:
while (!seen[var(trail[index--])]);
p = trail[index + 1];
//stats[sumRes]++;
confl = reason(var(p));
seen[var(p)] = 0;
pathC--;
} while(pathC > 0);
out_learnt[0] = ~p;
// Simplify conflict clause:
//
int i, j;
for(int i = 0; i < selectors.size(); i++)
out_learnt.push(selectors[i]);
out_learnt.copyTo(analyze_toclear);
if(ccmin_mode == 2) {
uint32_t abstract_level = 0;
for(i = 1; i < out_learnt.size(); i++)
abstract_level |= abstractLevel(var(out_learnt[i])); // (maintain an abstraction of levels involved in conflict)
for(i = j = 1; i < out_learnt.size(); i++)
if(reason(var(out_learnt[i])) == CRef_Undef || !litRedundant(out_learnt[i], abstract_level))
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]))];
// Thanks to Siert Wieringa for this bug fix!
for(int k = ((c.size() == 2) ? 0 : 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();
// stats[max_literals]+=out_learnt.size();
out_learnt.shrink(i - j);
// stats[tot_literals]+=out_learnt.size();
/* ***************************************
Minimisation with binary clauses of the asserting clause
First of all : we look for small clauses
Then, we reduce clauses with small LBD.
Otherwise, this can be useless
*/
if(!incremental && out_learnt.size() <= lbSizeMinimizingClause) {
minimisationWithBinaryResolution(out_learnt);
}
// 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));
}
#ifdef INCREMENTAL
if(incremental) {
szWithoutSelectors = 0;
for(int i=0;i<out_learnt.size();i++) {
if(!isSelector(var((out_learnt[i])))) szWithoutSelectors++;
else if(i>0) break;
}
} else
#endif
szWithoutSelectors = out_learnt.size();
// Compute LBD
lbd = computeLBD(out_learnt, out_learnt.size() - selectors.size());
// UPDATEVARACTIVITY trick (see competition'09 companion paper)
if(lastDecisionLevel.size() > 0) {
for(int i = 0; i < lastDecisionLevel.size(); i++) {
if(ca[reason(var(lastDecisionLevel[i]))].lbd() < lbd)
varBumpActivity(var(lastDecisionLevel[i]));
}
lastDecisionLevel.clear();
}
for(int j = 0; j < analyze_toclear.size(); j++) seen[var(analyze_toclear[j])] = 0; // ('seen[]' is now cleared)
for(int j = 0; j < selectors.size(); j++) seen[var(selectors[j])] = 0;
}
// Check if 'p' can be removed. 'abstract_levels' is used to abort early if the algorithm is
// visiting literals at levels that cannot be removed later.
bool Solver::litRedundant(Lit p, uint32_t abstract_levels) {
analyze_stack.clear();
analyze_stack.push(p);
int top = analyze_toclear.size();
while(analyze_stack.size() > 0) {
assert(reason(var(analyze_stack.last())) != CRef_Undef);
Clause &c = ca[reason(var(analyze_stack.last()))];
analyze_stack.pop(); //
if(c.size() == 2 && value(c[0]) == l_False) {
assert(value(c[1]) == l_True);
Lit tmp = c[0];
c[0] = c[1], c[1] = tmp;
}
for(int i = 1; i < c.size(); i++) {
Lit p = c[i];
if(!seen[var(p)]) {
if(level(var(p)) > 0) {
if(reason(var(p)) != CRef_Undef && (abstractLevel(var(p)) & abstract_levels) != 0) {
seen[var(p)] = 1;
analyze_stack.push(p);
analyze_toclear.push(p);
} else {
for(int j = top; j < analyze_toclear.size(); j++)
seen[var(analyze_toclear[j])] = 0;
analyze_toclear.shrink(analyze_toclear.size() - top);
return false;
}
}
}
}
}
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, vec <Lit> &out_conflict) {
out_conflict.clear();
out_conflict.push(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.push(~trail[i]);
} else {
Clause &c = ca[reason(x)];
// for (int j = 1; j < c.size(); j++) Minisat (glucose 2.0) loop
// Bug in case of assumptions due to special data structures for Binary.
// Many thanks to Sam Bayless ([email protected]) for discover this bug.
for(int j = ((c.size() == 2) ? 0 : 1); j < c.size(); j++)
if(level(var(c[j])) > 0)
seen[var(c[j])] = 1;
}
seen[x] = 0;
}
}