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SATSolver.cpp
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/////////////////
// OS Includes
#include <memory.h>
#include <stdlib.h>
//////////////
// Includes
#include "Clause.h"
#include "Random.h"
#include "SATInstance.h"
#include "SATSolver.h"
#include "VariableList.h"
/////////////////////////////
// Static Data Initialization
/////////////
// Defines
//////////////////////////////////////////////////////////////////////////////////////////////////
// Public Methods
SATSolver::SATSolver(SATInstance* pSATInstance_, ostream& xOutputStream_)
: xOutputStream(xOutputStream_),
_pPrimaryVariables(0)
{
_pInstance = pSATInstance_;
_aAssignment = 0;
// Set intelligent defaults for runtime parameters:
_bFindAll = 1; // default to finding one solution
_iMaxSolutions = 1;
_fFudgeFactor = .9;
_iLearnOrder = 3;
_bNoTimeLimit = 0;
_iMaxTime = 43200; // 12 hours
_bFavorSmallClauses = 1;
_bRelevanceBounding = 1;
_bPrintStack = 1;
_iPrintStackPeriod = 10;
_bRestarts = 0;
_iRestartIncrement = 0;
}
SATSolver::~SATSolver()
{
_xLearnedClauses.vDestroy();
delete _pPrimaryVariables;
}
relsat_enum SATSolver::eSolve()
{
time(&_iElapsedTime);
_iLastCheckTime = _iElapsedTime;
relsat_enum eReturn;
_iBranchSelections = _iVariablesLabeled = _iContradictions = 0;
if (!_bInitialize()) {
eReturn = UNSAT;
}
else {
// Here we do an initial unit propagation to handle base unit clauses.
if (_bUnitPropagate()) {
eReturn = UNSAT;
}
else {
boolean bFailed_;
boolean bReturn;
if (_bRestarts) {
bReturn = _bRestartLoop(bFailed_);
}
else {
bReturn = _bLoop(bFailed_);
}
if (bFailed_) {
eReturn = TIMEOUT;
xOutputStream << "c Timeout." << endl;
}
else if (bReturn == 1) {
eReturn = SAT;
}
else {
eReturn = UNSAT;
}
}
}
_vCleanup();
time_t iEnd;
time(&iEnd);
_iElapsedTime = iEnd - _iElapsedTime;
return eReturn;
}
void SATSolver::vSetPrintStackPeriod(long int iSeconds_)
{
_iPrintStackPeriod = iSeconds_;
_bPrintStack = 1;
}
void SATSolver::vSetRestartInterval(int iSeconds_)
{
_iRestartInterval = iSeconds_;
_bRestarts = 1;
}
void SATSolver::vSetRestartIncrement(int iSeconds_)
{
_iRestartIncrement = iSeconds_;
}
void SATSolver::vOutputStatusUpdateInterval()
{
if (_bPrintStack) {
xOutputStream << "c Status update interval: " << _iPrintStackPeriod << " seconds." << endl;
}
}
void SATSolver::vOutputWarnings()
{
xOutputStream << "c Learn order: " << _iLearnOrder << endl;
xOutputStream << "c Fudge factor: " << _fFudgeFactor << endl;
if (!_bNoTimeLimit) {
xOutputStream << "c Solution phase timeout after: " << _iMaxTime << " seconds." << endl;
}
if (_bRestarts) {
xOutputStream << "c Restart interval: " << _iRestartInterval << " seconds." << endl;
if (_iRestartIncrement) {
xOutputStream << "c Restart interval increment: " << _iRestartIncrement << " seconds." << endl;
}
if (!_bFindAll) {
xOutputStream << "c WARNING: Restarts override model counting. Searching for first solution only."
<< endl;
_bFindAll = 1;
_iMaxSolutions = 1;
}
else {
if (_iMaxSolutions == 0) {
xOutputStream << "c WARNING: Find all solutions not a valid option when using restarts.\n"
<< "c Searching for first solution only." << endl;
_iMaxSolutions = 1;
}
}
xOutputStream << "c Finding up to " << _iMaxSolutions << " solutions with restarts." << endl;
if (_iMaxSolutions > 1) {
xOutputStream <<"c WARNING: With restarts, some solutions may be duplicates." << endl;
}
}
else {
if (!_bFindAll) {
xOutputStream << "c Counting solutions (will output first solution if one exists)..." << endl;
#ifdef NO_GMP
xOutputStream << "c WARNING: Not using a bignum package. Solution counts may overflow." << endl;
#endif
}
else {
if (_iMaxSolutions == 0) {
xOutputStream << "c Finding all solutions..." << endl;
}
else {
xOutputStream << "c Finding up to " << _iMaxSolutions << " solutions..." << endl;
}
}
}
}
//////////////////////////////////////////////////////////////////////////////////////////////////
// Protected Methods
//////////////////////////////////////////////////////////////////////////////////////////////////
// Private Methods
boolean SATSolver::_bLoop(boolean& bFailed_)
{
bFailed_ = 0;
boolean bReturnValue = 0;
while (1) {
if (_bTimeLimitExpired()) {
bFailed_ = 1;
return bReturnValue;
}
if (_bPrintStackCheck()) {
_vPrintStack();
}
VariableID eBestID;
boolean bZeroFirst;
if (_pPrimaryVariables) {
eBestID = _eGiveMeTheBest(bZeroFirst, true);
}
else {
eBestID = _eGiveMeTheBest(bZeroFirst, false);
}
if (eBestID == -1) {
bReturnValue = 1;
if (_iCurrentVariable == _iVariableCount) {
if (_bOutputSolution()) {
xOutputStream << "c Solution limit reached. " << endl;
return bReturnValue;
}
}
if (_bSpecialBackup()) {
xOutputStream << "c All solutions found." << endl;
return bReturnValue;
}
}
else {
_aVariableStruct[eBestID].bBranch = 1;
if (bZeroFirst) {
_pUnitVariables0->vAddVariableNoCheck(eBestID);
}
else {
_pUnitVariables1->vAddVariableNoCheck(eBestID);
}
if (_bUnitPropagate()) {
if (_bBackup()) {
return bReturnValue;
}
}
}
}
}
boolean SATSolver::_bOutputSolution()
{
_iSolutionCount++;
if (_bFindAll || _iSolutionCount == 1) { // output only first solution found if counting
xOutputStream << "Solution " << _iSolutionCount << ": ";
for (int i=0; i<_iVariableCount; i++) {
assert(_aAssignment[i] != NON_VALUE);
if (_aAssignment[i]) {
xOutputStream << i+1 << " ";
}
}
xOutputStream << endl;
}
#ifndef NDEBUG
if (_bVerifySolution()) {
// xOutputStream << "c Solution verified" << endl;
}
else {
Debug::vErrorReport("Found an invalid solution.");
}
#endif
if (_bFindAll && _iSolutionCount >= _iMaxSolutions && _iMaxSolutions) {
return 1;
}
return 0;
}
boolean SATSolver::_bVerifySolution()
{
// returns 1 if solution checks out OK
for (int i=0; i<_pInstance->iClauseCount(); i++) {
Clause* pTestMe = _pInstance->pClause(i);
boolean bSatisfied = 0;
for (int j=0; j<pTestMe->iVariableCount(); j++) {
VariableID eCheckMe = pTestMe->eConstrainedVariable(j);
if (_aAssignment[eCheckMe] && !pTestMe->iIsNegated(j) ||
!_aAssignment[eCheckMe] && pTestMe->iIsNegated(j)) {
bSatisfied = 1;
break;
}
}
if (!bSatisfied) {
return 0;
}
}
return 1;
}
VariableStruct* SATSolver::_pBackupToFirstBranch()
{
//returns 1 if the search is complete.
int i=0;
while (i< _iCurrentVariable) {
if(_aVariableStruct[_aPositionToID[i]].bBranch) {
break;
}
i++;
}
VariableStruct* pWork = &(_aVariableStruct[_eCurrentID]);
while (_iCurrentVariable != i) {
pWork = &(_aVariableStruct[_eCurrentID]);
_vUndoClauseModifications();
pWork->bBranch = 0;
_aAssignment[_eCurrentID] = NON_VALUE;
pWork->pReason = 0;
_iCurrentVariable--;
if (_iCurrentVariable != i) {
pWork->xUnitClause.vClear();
}
if (_iCurrentVariable) {
_eCurrentID = _aPositionToID[_iCurrentVariable-1];
}
else {
_eCurrentID = -1;
}
}
return pWork;
}
boolean SATSolver::_bRestartLoop(boolean& bFailed_)
{
bFailed_ = 0;
boolean bReturnValue = 0;
time(&iLastRestart);
time_t now;
while (1) {
if (_bTimeLimitExpired()) {
bFailed_ = 1;
return bReturnValue;
}
if (_bPrintStackCheck()) {
_vPrintStack();
}
time(&now);
if (now - iLastRestart > _iRestartInterval) {
_iRestartInterval += _iRestartIncrement;
xOutputStream << "c Restarting. Next restart in "
<< _iRestartInterval
<< " seconds. " <<endl;
VariableStruct* pWork = _pBackupToFirstBranch();
if (_bNonTrivialUnitPropagate(pWork->xUnitClause) || _bUnitPropagate()) {
return 0;
}
time(&iLastRestart);
}
VariableID eBestID;
boolean bZeroFirst;
if (_pPrimaryVariables) {
eBestID = _eGiveMeTheBest(bZeroFirst, true);
}
else {
eBestID = _eGiveMeTheBest(bZeroFirst, false);
}
if (eBestID == -1) {
bReturnValue = 1;
if (_iCurrentVariable == _iVariableCount) {
if (_bOutputSolution()) {
xOutputStream << "c Solution limit reached. " << endl;
return bReturnValue;
}
}
if (_bSpecialBackup()) {
xOutputStream << "c All solutions found." << endl;
return bReturnValue;
}
}
else {
_aVariableStruct[eBestID].bBranch = 1;
if (bZeroFirst) {
_pUnitVariables0->vAddVariableNoCheck(eBestID);
}
else {
_pUnitVariables1->vAddVariableNoCheck(eBestID);
}
if (_bUnitPropagate()) {
if (_bBackup()) {
return bReturnValue;
}
}
}
}
}
VariableID SATSolver::_eGiveMeTheBest(boolean& bZeroFirst, boolean bFavorPrimary)
{
// Select the best branch variable.
assert(_pUnitVariables0->iCount() == 0);
assert(_pUnitVariables1->iCount() == 0);
double fBest = -1.0;
VariableStruct* pWorkStruct;
VariableID eID, eID2;
int i, j;
int iScore0, iScore1;
boolean bNoBinary = 1;
for (i=0; i<_pGoodList->iCount(); i++) {
eID = _pGoodList->iVariable(i);
if (_aAssignment[eID] == NON_VALUE) {
if (_aBinaryCount0[eID] || _aBinaryCount1[eID]) {
bNoBinary = 0;
}
// Compute iScore0
if (_aBinaryCount0[eID] > 0
&& _aScore0[eID] != -1
&& _aBinaryCount0[eID] > _aScore0[eID]) {
if (_bFastUnitPropagate(eID, 1, iScore0)) {
for (j=0; j<i; j++) {
eID2 = _pGoodList->iVariable(j);
if (_aAssignment[eID2] == NON_VALUE) {
_aScore0[eID2] = _aBinaryCount0[eID2];
_aScore1[eID2] = _aBinaryCount1[eID2];
}
}
for (j=i; j<_pGoodList->iCount(); j++) {
eID2 = _pGoodList->iVariable(j);
if (_aAssignment[eID2] == NON_VALUE) {
if (_aScore0[eID2] == -1) {
_aScore0[eID2] = _aBinaryCount0[eID2];
}
if (_aScore1[eID2] == -1) {
_aScore1[eID2] = _aBinaryCount1[eID2];
}
}
}
bZeroFirst = 0;
return eID; // leads to contradiction
} //if (_bFastUnit...
}
else {
iScore0 = _aBinaryCount0[eID];
}
// Compute iScore1
if (_aBinaryCount1[eID] > 0
&& _aScore1[eID] != -1
&& _aBinaryCount1[eID] > _aScore1[eID]) {
if (_bFastUnitPropagate(eID, 0, iScore1)) {
for (j=0; j<i; j++) {
eID2 = _pGoodList->iVariable(j);
if (_aAssignment[eID2] == NON_VALUE) {
_aScore0[eID2] = _aBinaryCount0[eID2];
_aScore1[eID2] = _aBinaryCount1[eID2];
}
}
for (j=i; j<_pGoodList->iCount(); j++) {
eID2 = _pGoodList->iVariable(j);
if (_aAssignment[eID2] == NON_VALUE) {
if (_aScore0[eID2] == -1) {
_aScore0[eID2] = _aBinaryCount0[eID2];
}
if (_aScore1[eID2] == -1) {
_aScore1[eID2] = _aBinaryCount1[eID2];
}
}
}
bZeroFirst = 1;
return eID; // leads to contradiction
} // if (_bFastUnit...
}
else {
iScore1 = _aBinaryCount1[eID];
}
_aScore[eID] = _iCombineScores(iScore1, iScore0);
if (!bFavorPrimary || _pPrimaryVariables->bHasVariable(eID)) {
if (_aScore[eID] > fBest) {
fBest = _aScore[eID];
}
}
} // if (...NON_VALUE...
} // for (int i=0;...
if (bNoBinary) {
_vComputeNoBinaryScores(fBest, bFavorPrimary);
if (fBest == -2.0 && !bFavorPrimary) {
return -1;
}
else if (fBest == -2.0) {
//cout << "Setting primary to false: " << fBest << endl;
bFavorPrimary = false;
_vComputeNoBinaryScores(fBest, bFavorPrimary);
}
if (fBest == -2.0) {
return -1;
}
}
_iBranchSelections++;
try_with_non_primary:
// Danger: reusing _pUnitList
for (i=0; i<_pGoodList->iCount(); i++) {
eID = _pGoodList->iVariable(i);
if (_aAssignment[eID] == NON_VALUE) {
if (bFavorPrimary) {
if (!_pPrimaryVariables->bHasVariable(eID)) {
continue;
}
}
if (_aScore[eID] >= fBest * _fFudgeFactor) {
//cout << "Adding: " << eID << endl;
_pUnitList->vAdd(eID);
}
}
}
if (bFavorPrimary && _pUnitList->iCount() == 0) {
//cout << "No more primary vars: " << _iVariableCount << endl;
// No more primary variables left to label.
bFavorPrimary = false;
fBest = -2.0;
for (i=0; i<_pGoodList->iCount(); i++) {
eID = _pGoodList->iVariable(i);
if (_aAssignment[eID] == NON_VALUE) {
if (_aScore[eID] >= fBest) {
fBest = _aScore[eID];
}
}
}
goto try_with_non_primary;
}
VariableID eReturn = _pUnitList->iVariable(xRandom.iRandom(_pUnitList->iCount()));
_pUnitList->vClear();
bZeroFirst = xRandom.iRandom(2);
/*bZeroFirst =
_aBinaryCount1[eReturn] >
_aBinaryCount0[eReturn] ?
0 : 1;*/
memcpy(_aScore0, _aBinaryCount0, _iVariableCount * sizeof(*_aScore1));
memcpy(_aScore1, _aBinaryCount1, _iVariableCount * sizeof(*_aScore0));
//cout << "Returning branch: " << (eReturn+1) << " for loc. " << _iCurrentVariable << endl;
return eReturn;
}
void SATSolver::_vComputeNoBinaryScores(double& fBest, boolean bFavorPrimary)
{
// Scoring function for when there are no binary clauses.
fBest = -2.0;
int i;
VariableID eID;
int iScore0, iScore1;
for (i=0; i<_pGoodList->iCount(); i++) {
eID = _pGoodList->iVariable(i);
if (_aAssignment[eID] == NON_VALUE) {
iScore0 = _iScoreClauseList(_aVariableStruct[eID].xPositiveClauses.pEntry(0),
_aVariableStruct[eID].xPositiveClauses.pLastEntry());
iScore1 = _iScoreClauseList(_aVariableStruct[eID].xNegativeClauses.pEntry(0),
_aVariableStruct[eID].xNegativeClauses.pLastEntry());
_aScore[eID] = _iCombineScores(iScore0, iScore1);
if (bFavorPrimary && !_pPrimaryVariables->bHasVariable(eID)) {
continue;
}
if (_aScore[eID] >= fBest) {
fBest = _aScore[eID];
}
}
}
}
boolean SATSolver::_bInitialize()
{
// temp stuff
_bReverse = 0;
// Return 0 if problem is UNSAT due to unary clauses (node-consistency)
_iRelevantClauses = 0;
_xLearnedClauses.vDestroy();
_iSolutionCount = 0;
_eCurrentID = -1;
_iCurrentVariable = 0;
_xSolutionCount.vSet(1);
_xKnownSolutions.vSet(0);
_iVariableCount = _pInstance->iVariableCount;
_aBinaryCount0 = new long int[_iVariableCount];
_aBinaryCount1 = new long int[_iVariableCount];
_aAssignment = new DomainValue[_pInstance->iVariableCount];
_aVariableStruct = new VariableStruct[_pInstance->iVariableCount];
_aPositionToID = new VariableID[_pInstance->iVariableCount];
_aIDToPosition = new long int[_pInstance->iVariableCount];
_aScore0 = new int[_pInstance->iVariableCount];
_aScore = new double[_pInstance->iVariableCount];
_aScore1 = new int[_pInstance->iVariableCount];
_pUnitVariables0 = new VariableSet(_pInstance->iVariableCount);
_pUnitVariables1 = new VariableSet(_pInstance->iVariableCount);
_pUnitList = new VariableList(_pInstance->iVariableCount);
_pPositiveBackup = new VariableSet(_pInstance->iVariableCount);
_pNegativeBackup = new VariableSet(_pInstance->iVariableCount);
_pGoodList = new VariableSet(_pInstance->iVariableCount);
_pGoodReason = new VariableList(_pInstance->iVariableCount);
int i;
for (i=0; i< _iVariableCount; i++) {
_aAssignment[i] = NON_VALUE;
_pGoodList->vAddVariableNoCheck(i);
_aBinaryCount0[i] = _aBinaryCount1[i] = _aScore0[i] = _aScore1[i] = 0;
}
for (i=0; i<_pInstance->iClauseCount(); i++) {
Clause* pClause = _pInstance->pClause(i);
pClause->vReset();
if (_bInitializeClause(pClause)) {
return 0;
}
}
for (i=0; i<_iVariableCount; i++) {
_aVariableStruct[i].xPositiveClauses.vSortClausesByLength();
_aVariableStruct[i].xNegativeClauses.vSortClausesByLength();
}
return 1;
}
boolean SATSolver::_bInitializeClause(Clause* pClause_)
{
// returns 1 if instance is UNSAT
if (pClause_->iVariableCount() == 1) {
if (_bInitializeUnaryClause(pClause_)) {
return 1;
}
}
boolean bIsBinary = (pClause_->iVariableCount() == 2);
for (int j=0; j<pClause_->iVariableCount(); j++) {
if (pClause_->iIsNegated(j)) {
_aVariableStruct[pClause_->eConstrainedVariable(j)].xNegativeClauses.vAddClause(pClause_);
if (bIsBinary) {
_aBinaryCount0[pClause_->eConstrainedVariable(j)]++;
}
}
else {
_aVariableStruct[pClause_->eConstrainedVariable(j)].xPositiveClauses.vAddClause(pClause_);
if (bIsBinary) {
_aBinaryCount1[pClause_->eConstrainedVariable(j)]++;
}
}
}
return 0;
}
boolean SATSolver::_bInitializeLearnedClause(Clause* pClause_)
{
// returns 1 if instance is UNSAT
// Call to initialize a clause learned during backtracking.
for (int j=0; j<pClause_->iPermaCount(); j++) {
if (pClause_->iIsNegated(j)) {
_aVariableStruct[pClause_->eConstrainedVariable(j)].xNegativeClauses.vAddClause(pClause_);
_aBinaryCount0[pClause_->eConstrainedVariable(j)]++;
}
else {
_aVariableStruct[pClause_->eConstrainedVariable(j)].xPositiveClauses.vAddClause(pClause_);
_aBinaryCount1[pClause_->eConstrainedVariable(j)]++;
}
}
return 0;
}
boolean SATSolver::_bInitializeUnaryClause(Clause* pClause_)
{
// returns 0 if problem is determined to be UNSAT
assert(pClause_->iVariableCount() == 1);
VariableID eConstrainedVariable = pClause_->eConstrainedVariable(0);
if (pClause_->iIsNegated(0)) {
if (_pUnitVariables1->bHasVariable(eConstrainedVariable)) {
return 1; // problem is UNSAT
}
if (_aVariableStruct[eConstrainedVariable].pReason == 0) {
_pUnitVariables0->vAddVariable(eConstrainedVariable);
_aVariableStruct[eConstrainedVariable].pReason = pClause_;
}
}
else {
if (_pUnitVariables0->bHasVariable(eConstrainedVariable)) {
return 1; // problem is UNSAT
}
if (_aVariableStruct[eConstrainedVariable].pReason == 0) {
_pUnitVariables1->vAddVariable(eConstrainedVariable);
_aVariableStruct[eConstrainedVariable].pReason = pClause_;
}
}
return 0;
}
int SATSolver::_iScoreClauseList(register Clause** pStart_, Clause** const pEnd_)
{
// Score the clause list based on clause lengths. assumes no clauses are binary.
int iCount = 0;
for (; pStart_ < pEnd_; pStart_++) {
if (!(*pStart_)->bIsSatisfied()) {
switch ((*pStart_)->iWorkingLength()) {
case 3:
iCount += 256;
break;
case 4:
iCount += 16;
break;
case 5:
iCount += 4;
break;
default:
iCount += 1;
}
}
}
return iCount;
}
void SATSolver::_vFastBackupScore()
{
register Clause** pStart;
Clause** pEnd;
int i;
const int iCount = _pUnitList->iCount();
for (i=0; i<iCount; i++) {
VariableID eUndo = _pUnitList->iVariable(i);
if (_aAssignment[eUndo]) {
pStart = _aVariableStruct[eUndo].xNegativeClauses.pEntry(0);
pEnd = _aVariableStruct[eUndo].xNegativeClauses.pLastEntry();
_aScore0[eUndo] = -1; // indicate no dead end
}
else {
pStart = _aVariableStruct[eUndo].xPositiveClauses.pEntry(0);
pEnd = _aVariableStruct[eUndo].xPositiveClauses.pLastEntry();
_aScore1[eUndo] = -1; // indicate no dead end
}
for (; pStart < pEnd; pStart++) {
(*pStart)->iExpand();
}
_aAssignment[eUndo] = NON_VALUE;
}
_pUnitList->vClear();
}
void SATSolver::_vFastBackup(const int iToIndex_)
{
register Clause** pStart;
Clause** pEnd;
int i;
for (i=0; i<iToIndex_; i++) {
VariableID eUndo = _pUnitList->iVariable(i);
if (_aAssignment[eUndo]) {
pStart = _aVariableStruct[eUndo].xNegativeClauses.pEntry(0);
pEnd = _aVariableStruct[eUndo].xNegativeClauses.pLastEntry();
}
else {
pStart = _aVariableStruct[eUndo].xPositiveClauses.pEntry(0);
pEnd = _aVariableStruct[eUndo].xPositiveClauses.pLastEntry();
}
for (; pStart < pEnd; pStart++) {
(*pStart)->iExpand();
}
_aAssignment[eUndo] = NON_VALUE;
}
for (; i<_pUnitList->iCount(); i++) {
_aAssignment[_pUnitList->iVariable(i)] = NON_VALUE;
}
_pUnitList->vClear();
}
boolean SATSolver::_bFastUnitPropagate(VariableID eWhich_, DomainValue iAssignment_, int& iScore_)
{
// Return 1 if unit propagation leads to a contradiction.
int i,j;
Clause **pStart, **pEnd;
Clause *pReduceMe;
VariableID eID;
assert(_pUnitList->iCount() == 0);
_pUnitList->vAdd(eWhich_);
_aAssignment[eWhich_] = iAssignment_;
for (i=0; i<_pUnitList->iCount(); i++) {
eID = _pUnitList->iVariable(i);
if (_aAssignment[eID] == 0) {
pStart = _aVariableStruct[eID].xPositiveClauses.pEntry(0);
pEnd = _aVariableStruct[eID].xPositiveClauses.pLastEntry();
}
else {
pStart = _aVariableStruct[eID].xNegativeClauses.pEntry(0);
pEnd = _aVariableStruct[eID].xNegativeClauses.pLastEntry();
}
Clause **const pBegin = pStart;
for (;pStart < pEnd; pStart++) {
pReduceMe = *pStart;
if (!pReduceMe->bIsSatisfied()) {
switch(pReduceMe->iReduce()) {
case 0:
// Contradiction!
for (; pStart >= pBegin; pStart--) {
(*pStart)->iExpand();
}
_vFastBackup(i);
return 1;
case 1:
for (j = 0; j < pReduceMe->iPermaCount(); j++) {
eID = pReduceMe->eConstrainedVariable(j);
if (_aAssignment[eID] == NON_VALUE) {
_pUnitList->vAdd(eID);
if (pReduceMe->iIsNegated(j)) {
_aAssignment[eID] = 0;
}
else {
_aAssignment[eID] = 1;
}
break;
}
}
}
}
} // for (;pStart...
} // for (i=.n.
iScore_ = _pUnitList->iCount();
_vFastBackupScore();
return 0;
}
boolean SATSolver::_bUnitPropagate()
{
// Return 1 if unit propagation leads to a contradiction.
// Does not back up, does not learn.
// Simply leaves the list of contradicting variables intact.
VariableStruct* pWork;
while(1) {
if (_pUnitVariables1->iCount()) {
int iWhich = xRandom.iRandom(_pUnitVariables1->iCount());
_vLabelVariable(_pUnitVariables1->iVariable(iWhich), 1);
_pUnitVariables1->vRemoveVariable(_eCurrentID);
assert(_pGoodList->bHasVariable(_eCurrentID));
pWork = &_aVariableStruct[_eCurrentID];
_vSatisfyWithClauseList(pWork->xPositiveClauses.pEntry(0),
pWork->xPositiveClauses.pLastEntry());
if (_bFilterWithClauseList(pWork->xNegativeClauses.pEntry(0),
pWork->xNegativeClauses.pLastEntry())) {
return 1;
}
}
else if (_pUnitVariables0->iCount()) {
int iWhich = xRandom.iRandom(_pUnitVariables0->iCount());
_vLabelVariable(_pUnitVariables0->iVariable(iWhich), 0);
_pUnitVariables0->vRemoveVariable(_eCurrentID);
assert(_pGoodList->bHasVariable(_eCurrentID));
pWork = &_aVariableStruct[_eCurrentID];
_vSatisfyWithClauseList(pWork->xNegativeClauses.pEntry(0),
pWork->xNegativeClauses.pLastEntry());
if (_bFilterWithClauseList(pWork->xPositiveClauses.pEntry(0),
pWork->xPositiveClauses.pLastEntry())) {
return 1;
}
}
else {
return 0;
}
} // while(1);
}
boolean SATSolver::_bFilterWithClauseList(Clause** pStart_, Clause** pEnd_)
{
// return 1 if contradiction encountered.
boolean bReturn = 0;
Clause* pWorkClause;
VariableID eContradictionID;
Clause* pContradictionReason;
int j;
for (; pStart_ < pEnd_; pStart_++) {
pWorkClause = *pStart_;
if (!pWorkClause->bIsSatisfied()) {
switch (pWorkClause->iReduce()) {
case 2:
for (j=0; j<pWorkClause->iPermaCount(); j++) {
if (pWorkClause->iIsNegated(j)) {
_aBinaryCount0[pWorkClause->eConstrainedVariable(j)]++;
}
else {
_aBinaryCount1[pWorkClause->eConstrainedVariable(j)]++;
}
}
break;
case 1:
// Find the variable it filters.
for (int j = 0; ; j++) {
assert(j < pWorkClause->iPermaCount());
VariableID eID = pWorkClause->eConstrainedVariable(j);
if (_aAssignment[eID] == NON_VALUE) {
if (!_pGoodList->bHasVariable(eID)) {
// it's outside the goodlist
break;
}
// we've found the filtering variable
if (pWorkClause->iIsNegated(j)) {
if (_aVariableStruct[eID].pReason) {
if (_pUnitVariables1->bHasVariable(eID)) {
// Contradiction!
// Can't return immediately because it will confuse the state undoing code
eContradictionID = eID;
pContradictionReason = pWorkClause;
bReturn = 1;
}
else {
assert(_pUnitVariables0->bHasVariable(eID));
_vDecideFilterClause(eID, pWorkClause);
}
} // if (_...pReason)
else {
assert(!_pUnitVariables1->bHasVariable(eID));
assert(_pGoodList->bHasVariable(eID));
_pUnitVariables0->vAddVariableNoCheck(eID);
_aVariableStruct[eID].pReason = pWorkClause;
}
} // if (pWorkClause->iIsNegated(j)...
else {
if (_aVariableStruct[eID].pReason) {
if (_pUnitVariables0->bHasVariable(eID)) {
// Contradiction!
// Can't return immediately because it will confuse the state undoing code
eContradictionID = eID;
pContradictionReason = pWorkClause;
bReturn = 1;
}
else {
assert(_pUnitVariables1->bHasVariable(eID));
_vDecideFilterClause(eID, pWorkClause);
}
} // if (...pReason...
else {
assert(!_pUnitVariables0->bHasVariable(eID));
assert(_pGoodList->bHasVariable(eID));
_pUnitVariables1->vAddVariableNoCheck(eID);
_aVariableStruct[eID].pReason = pWorkClause;
}
}
break;
}
} // for (int j=
}
}
}
if (bReturn) {
_vSetContradiction(eContradictionID, pContradictionReason);
}
return bReturn;
}
inline void SATSolver::_vSetContradiction(VariableID eContradictionID_, Clause* pReason_)
{
_eContradictionID = eContradictionID_;
_pContradictionClause1 = pReason_;
_pContradictionClause2 = _aVariableStruct[eContradictionID_].pReason;
int i;
for (i=0; i<_pUnitVariables0->iCount(); i++) {
_aVariableStruct[_pUnitVariables0->iVariable(i)].pReason = 0;
}
_pUnitVariables0->vClear();
for (i=0; i<_pUnitVariables1->iCount(); i++) {
_aVariableStruct[_pUnitVariables1->iVariable(i)].pReason = 0;
}
_pUnitVariables1->vClear();
}
void SATSolver::_vSatisfyWithClauseList(register Clause** pStart_, Clause** pEnd_)
{
Clause* pWorkClause;
for (; pStart_ < pEnd_; pStart_++) {
pWorkClause = *pStart_;
if (!pWorkClause->bIsSatisfied()) {
if (pWorkClause->iWorkingLength() == 2
) {
for (int j=0; j<pWorkClause->iPermaCount(); j++) {
if (pWorkClause->iIsNegated(j)) {
_aBinaryCount0[pWorkClause->eConstrainedVariable(j)]--;
assert(_aBinaryCount0[pWorkClause->eConstrainedVariable(j)] >= 0);
}
else {
_aBinaryCount1[pWorkClause->eConstrainedVariable(j)]--;
assert(_aBinaryCount1[pWorkClause->eConstrainedVariable(j)] >= 0);
}
}
}
}
pWorkClause->vMakeSatisfied();
}
}
boolean SATSolver::_bCreateBackupClauseFromContradiction()
{
// Create a new clause representing the nogood derived from the
// current contradiction on _eContradictionID.
_iContradictions++;
_pPositiveBackup->vClear();
_pNegativeBackup->vClear();
int i;
for (i=0; i<_pContradictionClause1->iVariableCount(); i++) {
if (_pContradictionClause1->iIsNegated(i)) {
_pNegativeBackup->vAddVariableNoCheck(_pContradictionClause1->eConstrainedVariable(i));
}
else {
_pPositiveBackup->vAddVariableNoCheck(_pContradictionClause1->eConstrainedVariable(i));
}
}
for (i=0; i<_pContradictionClause2->iVariableCount(); i++) {
if (_pContradictionClause2->iIsNegated(i)) {
_pNegativeBackup->vAddVariable(_pContradictionClause2->eConstrainedVariable(i));
}
else {
_pPositiveBackup->vAddVariable(_pContradictionClause2->eConstrainedVariable(i));
}
}
_pPositiveBackup->vRemoveVariable(_eContradictionID);
_pNegativeBackup->vRemoveVariable(_eContradictionID);
if (!_pContradictionClause1->bIsTemporary() &&
!_pContradictionClause2->bIsTemporary() &&
_pPositiveBackup->iCount() + _pNegativeBackup->iCount() >=
(_pContradictionClause1->iVariableCount() + _pContradictionClause2->iVariableCount() - 2)) {
return 0;
}
else {
return 1;
}
}
inline boolean SATSolver::_bCreateNewBackupClause(boolean bLastReasonTransient_)
{
Clause* pFailClause2;
pFailClause2 = _aVariableStruct[_eCurrentID].pReason;
int iOriginalCount =
_pNegativeBackup->iCount() +