public void backTrack(DecisionLevel db)
{
//TODO make this more efficient (linked list?)
recentBacktrack = true;
int ndbidx = decisionLevel.IndexOf(db) + 1;
if (ndbidx >= decisionLevel.Count)
{
return;
}
db = decisionLevel[ndbidx];
for (int j = db.Level; j < decisions.Count; j++)
{
decisions[j].Assignment = Assignment.Unassigned;
decisions[j].Reason = null;
//this is expensive
foreach (Watcher wa in decisions[j].WatchList)
{
wa.Clause.Satisfied = wa.Clause.watcher[0].Lit.Satisfied() || wa.Clause.watcher[1].Lit.Satisfied();
//wa.Clause.Satisfied = false; //this should take other watcher into account
}
}
decisions.RemoveRange(db.Level, decisions.Count - db.Level);
//int i = decisionLevel.IndexOf(db);
int i = ndbidx;
i = Math.Max(1, i);
decisionLevel.RemoveRange(i, decisionLevel.Count - i);
}
public CNSat()
{
UseIntervalProp = true;
this.CNSMTGSolver = null;
decisionLevelNull = new DecisionLevel(0);
UnitDecissions = 0;
r = new Random();
}
protected bool AssignmentInsideRange(DecisionLevel dl, double[,] range)
{
for (int i = dl.Level; i < decisions.Count; i++)
{
if (!VarAssignmentInsideRange(decisions[i], range))
{
return(false);
}
}
return(true);
}
public static Var DecideVariableCountBased(List <Var> variables, CNSat solver)
{
int vars = variables.Count;
Lit l = null;
int maxCount = Int32.MaxValue;
int minCount = -1;
for (int i = 0; i < vars; i++)
{
if (variables[i].Assignment != Assignment.Unassigned)
{
continue;
}
for (int j = 0; j < variables[i].WatchList.Count; j++)
{
if (!variables[i].WatchList[j].Clause.Satisfied)
{
/*if(maxCount>variables[i].WatchList[j].Lit.VariableCount) {
* l = variables[i].WatchList[j].Lit;
* maxCount = l.VariableCount;
* }*/
if (minCount < variables[i].WatchList[j].Lit.VariableCount)
{
l = variables[i].WatchList[j].Lit;
minCount = l.VariableCount;
}
}
}
}
if (l == null)
{
return(null);
}
Assignment ass;
Var v = l.Var;
ass = l.Sign;
DecisionLevel d = new DecisionLevel(solver.Decisions.Count);
solver.DecisionLevel.Add(d);
v.Assignment = ass;
solver.Decisions.Add(v);
v.Reason = null;
v.DecisionLevel = d;
return(v);
}
public static Var DecideActivityBased(List <Var> variables, CNSat solver)
{
int vars = variables.Count;
Random r = solver.r;
int init = r.Next(vars);
Var v = null, next = null;
int maxActivity = 0;
//Search Lit with highest Activity
if (solver.CNSMTGSolver == null)
{
for (int i = 0; i < vars; i++)
{
int p = (init + i) % vars;
if (p < 0 || p >= vars)
{
Console.WriteLine("p = " + p);
}
v = variables[p];
if (v.Assignment == Assignment.Unassigned)
{
if (maxActivity <= v.Activity)
{
maxActivity = v.Activity;
next = v;
}
}
}
//Decide it
if (next != null)
{
DecisionLevel d = new DecisionLevel(solver.Decisions.Count);
solver.DecisionLevel.Add(d);
double rel = next.PositiveAppearance + next.NegativeAppearance;
if (rel != 0)
{
rel = ((double)next.PositiveAppearance) / rel;
}
else
{
rel = 0.5;
}
next.Assignment = (r.NextDouble() < rel) ? Assignment.True : Assignment.False;
solver.Decisions.Add(next);
next.Reason = null;
next.DecisionLevel = d;
return(next);
}
}
else
{
init = r.Next(solver.Clauses.Count);
for (int i = 0; i < solver.Clauses.Count; i++)
{
Clause c = solver.Clauses[(i + init) % solver.Clauses.Count];
if (!c.Satisfied && c.Literals.Count > 1)
{
if (!c.watcher[0].Lit.Satisfied())
{
next = c.watcher[0].Lit.Var;
DecisionLevel d = new DecisionLevel(solver.Decisions.Count);
solver.DecisionLevel.Add(d);
next.Assignment = c.watcher[0].Lit.Sign;
solver.Decisions.Add(next);
next.Reason = null;
next.DecisionLevel = d;
return(next);
}
else if (!c.watcher[1].Lit.Satisfied())
{
DecisionLevel d = new DecisionLevel(solver.Decisions.Count);
solver.DecisionLevel.Add(d);
next = c.watcher[1].Lit.Var;
next.Assignment = c.watcher[1].Lit.Sign;
solver.Decisions.Add(next);
next.Reason = null;
next.DecisionLevel = d;
return(next);
}
else
{
Console.WriteLine("This shoud Never Happen!!");
}
}
}
}
return(null);
}
public static Var DecideRangeBased(List <Var> variables, CNSat solver)
{
List <Lit> choices = new List <Lit>();
int vars = variables.Count;
for (int i = 0; i < vars; i++)
{
if (variables[i].Assignment != Assignment.Unassigned)
{
continue;
}
bool hT = false;
bool hF = false;
for (int j = 0; j < variables[i].WatchList.Count; j++)
{
if (!variables[i].WatchList[j].Clause.Satisfied)
{
if (variables[i].WatchList[j].Lit.Sign == Assignment.True)
{
if (!hT)
{
choices.Add(variables[i].WatchList[j].Lit);
}
hT = true;
}
else
{
if (!hF)
{
choices.Add(variables[i].WatchList[j].Lit);
}
hF = true;
}
}
if (hT && hF)
{
break;
}
}
}
if (choices.Count == 0)
{
return(null);
}
choices.Sort(LitRangeCompare);
/*Console.WriteLine("======");
* foreach(Lit l in choices) {
* Console.WriteLine("{0}",(l.Sign == Assignment.True ? l.Var.PositiveRangeSize:l.Var.NegativeRangeSize));
* }
* Console.WriteLine("======");*/
//Choices are now in ascending order!
Var v;
Assignment ass;
//Uniform:
//int idx = solver.Rand.Next(choices.Count);
//smallest range:
//int idx = 0;
//largest range:
int idx = choices.Count - 1;
//Prefer smaller:
/*int idx = choices.Count-1;
* double r = solver.Rand.NextDouble();
* double q = 0;
* for(int i=0; i<choices.Count; i++) {
* q += 1.0/(i+2);
* if (q > r) {
* idx = i;
* break;
* }
* }*/
//Prefer larger:
/*int idx = 0;
* double r = solver.Rand.NextDouble();
* double q = 0;
* for(int i=0; i<choices.Count; i++) {
* q += 1.0/(i+2);
* if (q > r) {
* idx = choices.Count-i-1;
* break;
* }
* }*/
//Pick middle:
//int idx = choices.Count/2;
v = choices[idx].Var;
ass = choices[idx].Sign;
DecisionLevel d = new DecisionLevel(solver.Decisions.Count);
solver.DecisionLevel.Add(d);
v.Assignment = ass;
solver.Decisions.Add(v);
v.Reason = null;
v.DecisionLevel = d;
return(v);
}
public bool solve()
{
int restartNum = 100;
learntNum = 700;
restartCount = 0;
double[,] curRanges = null;
double[] solution = null;
DecisionLevel evaluatedDL = null;
//check: is already undecisdable?
Clause c;
while (true)
{
c = null;
while ((c = propagate()) != null) //resolve all conflicts
{
if (decisionLevel.Count == 1)
{
return(false);
}
if (conflictCount % 50 == 0 && CNSMTGSolver != null && CNSMTGSolver.begin + CNSMTGSolver.maxSolveTime < RosCS.RosSharp.Now())
{
return(false);
}
if (!resolveConflict(c))
{
return(false);
}
}
if (CNSMTGSolver != null)
{
//check for conflict of Theoremprover
if (UseIntervalProp && !CNSMTGSolver.IntervalPropagate(decisions, out curRanges))
{
continue;
}
else
{
/*
* //TODO: Heuristic Decision whether or not to query the T-solver
* //comes in here
* //double satRatio = ((double)satClauseCount) / clauses.Count;
* //double varRatio = ((double)decisions.Count) / variables.Count;
* //if (recentBacktrack || varRatio < r.NextDouble()) { //|| satRatio > r.NextDouble()) {
* //if (recentBacktrack || satRatio > r.NextDouble()) {
* //if (decisionCount % 10 == 0) {
* // recentBacktrack = false;
* //if(solution==null || !SolutionInsideRange(solution, curRanges)) {
* //if(!VarAssignmentInsideRange(Decisions[Decisions.Count-1],curRanges)) {
* //if(evaluatedDL==null || !AssignmentInsideRange(evaluatedDL, curRanges)) {
* if (!CNSMTGSolver.ProbeForSolution(decisions, out solution)) {
* continue;
* }
* // evaluatedDL = DecisionLevel[DecisionLevel.Count-1];
* //}
* //}
*/
if (!CNSMTGSolver.ProbeForSolution(decisions, out solution))
{
continue;
}
int satClauseCount = 0;
for (int i = clauses.Count - 1; i >= 0; --i)
{
if (clauses[i].Satisfied)
{
satClauseCount++;
}
}
if (satClauseCount >= clauses.Count)
{
return(true);
}
}
}
Var next;
//Make a decission:
//Var next = Decider.DecideRangeBased(variables,this);
if (CNSMTGSolver != null)
{
next = Decider.DecideVariableCountBased(variables, this);
}
else
{
next = Decider.DecideActivityBased(variables, this);
}
//Var next = decideRangeBased();
//Var next = decide();
if (next == null) // if no unassigned vars
{
Console.WriteLine("ConflictCount: " + conflictCount + " DecisionCount " + decisionCount + " LC " + this.learnedCount);
return(true);
}
#if (CNSatDebug)
Console.Write("Decision: ");
next.Print();
Console.WriteLine();
#endif
++decisionCount;
//if(decisionCount%10000==0) PrintStatistics();
if (decisionCount % 25 == 0 && CNSMTGSolver != null && CNSMTGSolver.begin + CNSMTGSolver.maxSolveTime < RosCS.RosSharp.Now())
{
return(false);
}
//Forget unused clauses
if (decisionCount % 1000 == 0)
{
reduceDB(learntNum);
foreach (Var v in variables)
{
v.Activity /= 4;
}
}
if (false && decisionCount % restartNum == 0)
{
//perform restart
restartNum *= 2;
learntNum += learntNum / 10;
restartCount++;
for (int j = (decisionLevel[1].Level); j < decisions.Count; j++)
{
decisions[j].Assignment = Assignment.Unassigned;
decisions[j].Reason = null;
//decisions[j].Seen = false;
foreach (Watcher wa in decisions[j].WatchList)
{
wa.Clause.Satisfied = false;
}
}
decisions.RemoveRange(decisionLevel[1].Level, decisions.Count - (decisionLevel[1].Level));
decisionLevel.RemoveRange(1, decisionLevel.Count - 1);
}
}
}
