public static int GenerateAssignment(SatProblem origProblem, IWellAnalyzed algorithm, out VariableAssignment assignment)
{
assignment = new VariableAssignment();
var curProblem = origProblem;
foreach (var problemVariable in origProblem.Variables)
{
var subsProblem0 = SubstituteVaraible(curProblem, problemVariable, false);
var subsProblem1 = SubstituteVaraible(curProblem, problemVariable, true);
double W0 = algorithm.GetExpectedValue(subsProblem0);
double W1 = algorithm.GetExpectedValue(subsProblem1);
if (W0 <= W1)
{
assignment[problemVariable] = true;
curProblem = subsProblem1;
}
else
{
assignment[problemVariable] = false;
curProblem = subsProblem0;
}
}
return(origProblem.GetNumberOfSatisfiedClauses(assignment));
}
private static SatProblem SubstituteVaraible(SatProblem problem, Variable variable, bool value)
{
SatProblem result = new SatProblem();
foreach (var clause in problem)
{
if (clause.TryGetValue(variable, out bool negated))
{
if (negated != value)
{
result.Add(new Clause());
}
else if (clause.Count > 1)
{
Clause newClause = new Clause(clause);
newClause.Remove(variable);
result.Add(newClause);
}
}
else
{
result.Add(new Clause(clause));
}
}
return(result);
}
public double GetExpectedValue(SatProblem problem)
{
var algoObjectToUse = this;
if (problem != _problem)
{
algoObjectToUse = new AlgorithmB(problem);
}
if (algoObjectToUse._probailities == null)
{
algoObjectToUse.GenerateProbabilities();
}
double result = 0;
foreach (var problemClause in problem.Clauses)
{
if (problemClause.Count == 0)
{
result++;
continue;
}
double falsePropability = 1;
foreach (var literal in problemClause)
{
falsePropability *= literal.Value ? 1 - algoObjectToUse._probailities[literal.Key] : algoObjectToUse._probailities[literal.Key];
}
result += 1 - falsePropability;
}
return(result);
}
public int GenerateAssingment(SatProblem problem, out VariableAssignment assignment)
{
assignment = new VariableAssignment();
foreach (var problemVariable in problem.Variables)
{
assignment[problemVariable] = _rand.NextDouble() < _probailities[problemVariable];
}
return(problem.GetNumberOfSatisfiedClauses(assignment));
}
public int GenerateAssingment(SatProblem problem, int trys, out VariableAssignment assignment)
{
int bestSatisfaction = 0;
assignment = null;
for (int i = 0; i < trys; i++)
{
int newSatisfaction;
if ((newSatisfaction = GenerateAssingment(problem, out VariableAssignment newAssignment)) > bestSatisfaction)
{
assignment = newAssignment;
bestSatisfaction = newSatisfaction;
}
}
return(bestSatisfaction);
}
public AlgorithmB(SatProblem problem)
{
_problem = problem;
}
static void Main(string[] args)
{
Variable x1 = new Variable(1);
Variable x2 = new Variable(2);
Variable x3 = new Variable(3);
SatProblem parsedProblem = CnfFileParser.Parse(args[0]);
SatProblem problem = new SatProblem
{
new Clause {
{ x1, true }, x2
},
new Clause {
{ x2, true }, x3
}
};
problem = parsedProblem;
Console.WriteLine($"Problem: n={problem.Variables.Count}, m={problem.Clauses.Count}");
int benchmarkRuns = 1000;
int trys = 100;
Console.WriteLine();
Console.WriteLine("Algorithmus A:");
AlgorithmA algoA = new AlgorithmA();
int satisfiedClausesA = algoA.GenerateAssingment(problem, trys, out VariableAssignment assignmentA);
Console.WriteLine($"Anzahl der Versuche: {trys}");
Console.WriteLine($"Erfüllte Klauseln: {satisfiedClausesA}");
TimeSpan algoAExecutionTime = Benchmark(benchmarkRuns, () => algoA.GenerateAssingment(problem, trys, out assignmentA));
Console.WriteLine($"Average Runtime for {benchmarkRuns} runs: {algoAExecutionTime.TotalMilliseconds:##0.#####} ms");
Console.WriteLine();
Console.WriteLine("Algorithmus B:");
var algoB = new AlgorithmB(parsedProblem);
algoB.GenerateProbabilities();
int satisfiedClausesB = algoB.GenerateAssingment(problem, trys, out VariableAssignment assignmentB);
Console.WriteLine($"Anzahl der Versuche: {trys}");
Console.WriteLine($"Erfüllte Klauseln: {satisfiedClausesB}");
TimeSpan algoBExecutionTime = Benchmark(benchmarkRuns, () =>
{
algoB.GenerateProbabilities();
algoB.GenerateAssingment(problem, trys, out assignmentB);
});
Console.WriteLine($"Average Runtime for {benchmarkRuns} runs: {algoBExecutionTime.TotalMilliseconds:##0.#####} ms");
Console.WriteLine();
Console.WriteLine("Algorithmus DRAND_A:");
int satisfiedClausesDrandA = ArgorithmDrand.GenerateAssignment(problem, algoA, out VariableAssignment assignmentDrandA);
Console.WriteLine($"Erfüllte Klauseln: {satisfiedClausesDrandA}");
TimeSpan algoDerandAExecutionTime = Benchmark(benchmarkRuns, () => ArgorithmDrand.GenerateAssignment(problem, algoA, out assignmentDrandA));
Console.WriteLine($"Average Runtime for {benchmarkRuns} runs: {algoDerandAExecutionTime.TotalMilliseconds:##0.#####} ms");
Console.WriteLine();
Console.WriteLine("Algorithmus DRAND_B:");
int satisfiedClausesDrandB = ArgorithmDrand.GenerateAssignment(problem, algoB, out VariableAssignment assignmentDrandB);
Console.WriteLine($"Erfüllte Klauseln: {satisfiedClausesDrandB}");
TimeSpan algoDerandBExecutionTime = Benchmark(benchmarkRuns, () => ArgorithmDrand.GenerateAssignment(problem, algoB, out assignmentDrandB));
Console.WriteLine($"Average Runtime for {benchmarkRuns} runs: {algoDerandBExecutionTime.TotalMilliseconds:##0.#####} ms");
Console.Read();
}
public double GetExpectedValue(SatProblem problem)
{
return(problem.Select(clause => clause.Count == 0 ? 1 : 1 - 1.0 / (1 << clause.Count)).Sum());
}
public static SatProblem Parse(string filePath)
{
SatProblem result = new SatProblem();
using (StreamReader reader = new StreamReader(filePath))
{
Variable[] variables = null;
Clause clause = new Clause();
string line;
while ((line = reader.ReadLine()) != null)
{
if (line.StartsWith("c"))
{
continue;
}
if (line.StartsWith("p"))
{
var match = ProblemLineRegex.Match(line);
if (match.Success && int.TryParse(match.Groups["VariableCount"].Value, out int variableCount))
{
variables = new Variable[variableCount];
for (int i = 0; i < variableCount; i++)
{
variables[i] = new Variable(i);
}
}
else
{
throw new Exception($"Could not parse problem line of file {filePath}");
}
}
else if (variables != null)
{
var match = DataLineRegex.Match(line);
if (!match.Success)
{
continue;
}
foreach (Capture capture in match.Groups["Date"].Captures)
{
if (int.TryParse(capture.Value, out int value))
{
if (value == 0)
{
result.Add(clause);
clause = new Clause();
}
else
{
clause.Add(variables[Math.Abs(value) - 1], value < 0);
}
}
}
}
}
if (clause.Count > 0)
{
result.Add(clause);
}
return(result);
}
}
