protected virtual void PrepareToSolve()
{
// Give some feedback because calculating deadlocks can take some time.
SetInfo("Preparing to solve level...");
// Start the clock.
startSnapshot = TimeSnapshot.Now;
// Put solver in a sane state in case there are any exceptions.
solutions.Clear();
// Validate parameter combinations.
ValidateParameters();
// Avoid recalculating as much as possible if the level hasn't changed.
if (!precalculatedLevel)
{
PrecalculateLevel();
// Check for cancellation during pre-calculation.
if (cancelInfo.Cancel)
{
return;
}
precalculatedLevel = true;
}
// Avoid reallocating these big data structures for multiple solver runs.
if (!allocated)
{
nodes = new NodeCollection(initialCapacity, validate);
transpositionTable = new TranspositionTable(nodes, initialCapacity);
current.Parents = new Node[maxParents];
allocated = true;
}
else
{
nodes.Clear();
transpositionTable.Clear();
}
// However, the positions of the occupants might have changed.
// This gives a performance boost when calculating deadlocks.
level.CopyOccupantsFrom(originalLevel);
CheckLevel();
// The push map depends on the actual starting box positions.
// This could be avoided if we didn't use the no-box map.
CalculatePushMap();
// Initialize solver variables.
current.ParentIndex = 0;
level.Validate = validate;
transpositionTable.Validate = validate;
foundSolution = false;
moveLimit = int.MaxValue;
pushLimit = int.MaxValue;
duplicates = 0;
boxStart = 0;
// Prime the "current" values.
current.Initialize(level, pathFinder);
// Create the root of the search tree.
root = new Node(nodes, current.SokobanRow, current.SokobanColumn, Direction.None, 0, 0);
// Record the clock.
donePreparingSnapshot = TimeSnapshot.Now;
}
public bool Solve()
{
PrepareToSolve();
// Check for cancel.
if (cancelInfo.Cancel)
{
SetError("Solver canceled.");
return false;
}
if (!verbose)
{
SetInfo("Verbose information not enabled.");
}
error = "";
int depth = 0;
while (true)
{
if (foundSolution && !collectSolutions)
{
break;
}
if (Finished())
{
break;
}
int lastNodeCount = nodes.Visited;
SearchTree(root, ++depth);
if (cancelInfo.Cancel)
{
SetError("Solver canceled.");
break;
}
if (nodes.Count >= maximumNodes)
{
SetError("Maximum nodes exceeded.");
break;
}
if (nodes.Visited == lastNodeCount)
{
if (solutions.Count == 0)
{
SetError("All positions examined lead to dead ends.");
}
break;
}
}
stopSnapshot = TimeSnapshot.Now;
SortSolutions();
// Populate information property.
if (verbose)
{
SetFinalInfo(depth);
}
if (validate)
{
SolverValidator validator = new SolverValidator(this, nodes, root, transpositionTable);
validator.CheckDataStructures();
}
return foundSolution;
}