public string InterpretDPLLResult(DPLLResultHolder result)
{
if (result != null)
{
if (!result.SAT)
{
return("No hamiltonian path exist.");
}
var variableNames = result.Model.VariablesDict.Keys.ToList();
variableNames.Sort((x, y) => x.CompareTo(y));
StringBuilder stringBuilder = new StringBuilder();
foreach (var variableName in variableNames)
{
if (result.Model.VariablesDict[variableName][0].Value)
{
string[] tokens = variableName.Split('-');
if (tokens.Length != 3) // The "result" is not a result of hamiltonian path problem converted to SAT problem
{
throw new ArgumentException();
}
stringBuilder.Append(String.Format("{0}. position is vertex {1}\n", tokens[1], tokens[2]));
}
}
return(stringBuilder.ToString());
}
return(null);
}
// Each thread's "main" function
private DPLLResultHolder Solve(DPLL parallelDPLL, Queue <CNF> sharedModelQueue, IdleThreadsCounter idleThreadsCounter, CancellationToken token)
{
CNF model;
while (true)
{
lock (sharedModelQueue)
{
while (sharedModelQueue.Count == 0)
{
Monitor.Wait(sharedModelQueue); // Wait if there's nothing to solve
token.ThrowIfCancellationRequested();
}
Interlocked.Decrement(ref idleThreadsCounter.Counter); // This task started working - is no longer idle
model = sharedModelQueue.Dequeue(); // Get a CNF model from the shared queue
}
token.ThrowIfCancellationRequested();
DPLLResultHolder solverThreadResult = parallelDPLL.Satisfiable(model);
if (solverThreadResult.SAT)
{
return(solverThreadResult); // The task has found SAT model
}
else
{
Interlocked.Increment(ref idleThreadsCounter.Counter); // The task is idle for now
}
lock (sharedModelQueue)
{
// If all threads are idle and the queue is empty -> we're done and result remains unsat
if (Interlocked.Read(ref idleThreadsCounter.Counter) == Environment.ProcessorCount && sharedModelQueue.Count == 0)
{
return(solverThreadResult);
}
}
}
}
// Returns a string explaining the result of the DPLL algorithm
public string InterpretDPLLResult(DPLLResultHolder result)
{
if (result != null)
{
if (!result.SAT)
{
return("Such independent set does not exist.");
}
StringBuilder stringBuilder = new StringBuilder();
stringBuilder.Append(String.Format("The following vertices can be chosen for the independent set of size atleast {0}:\n", K));
var variableNames = result.Model.VariablesDict.Keys.ToList();
variableNames.Sort((x, y) =>
{
if (x[0] != 'X' && y[0] != 'X')
{
return(Convert.ToInt32(x).CompareTo(Convert.ToInt32(y)));
}
else
{
return(x.CompareTo(y));
}
});
foreach (var variableName in variableNames)
{
if (!variableName.Contains('X') && result.Model.VariablesDict[variableName][0].Value) // Helper variables start with 'X', we do not want to output them
{
stringBuilder.Append(String.Format("{0}\n", variableName));
}
}
return(stringBuilder.ToString());
}
return(null);
}
