private void SortFinalResults()
{
// if the best list didn't fill up
if (NumberValidSolutions_ < MaxResults_)
{
SolutionHeap_ = new HeapWithComparer <Solution>(MaxResults_, UnorderedSolutions_, Comparer_);
}
// run heapsort on the top solutions, copy into solution list
Solutions_.AddRange(SolutionHeap_.GetSorted());
}
public SolverResult Compute(BackgroundWorker worker, DoWorkEventArgs e)
{
if (Timetable_ == null || !Timetable_.HasData())
{
return(SolverResult.NoTimetable);
}
Solutions_.Clear();
StreamSets_.Clear();
long totalSolutions = 1;
SolutionHeap_ = null;
UnorderedSolutions_ = new Solution[MaxResults_];
#region Build lists of stream options
foreach (Type type in Timetable_.TypeList)
{
// if the stream type is ignored, skip
if (!type.Required)
{
continue;
}
// create a list of streams for each type
List <Stream> streams = new List <Stream>();
// stream already enabled? only one option
if (type.SelectedStream != null)
{
streams.Add(type.SelectedStream);
}
else
{
// for each stream in the current type
foreach (Stream stream in type.UniqueStreams)
{
// if stream can't be selected, skip it
if (!Timetable_.Fits(stream))
{
continue;
}
streams.Add(stream);
}
// no streams made it - skip
if (streams.Count == 0)
{
return(SolverResult.Clash);
}
}
// add streams to list
StreamSets_.Add(streams);
// update the complexity of the solution
totalSolutions *= streams.Count;
}
#endregion
#region Optimise unique stream list order
// order determined greedily on basis of maximum clashes
float[,] clashChance = new float[StreamSets_.Count, StreamSets_.Count];
// build 2D clash probability table
for (int i = 0; i < StreamSets_.Count; i++)
{
List <Stream> set = StreamSets_[i];
for (int j = i + 1; j < StreamSets_.Count; j++)
{
List <Stream> otherSet = StreamSets_[j];
int total = set.Count * otherSet.Count;
int clash = 0;
foreach (Stream stream in set)
{
foreach (Stream otherStream in otherSet)
{
if (stream.ClashesWith(otherStream))
{
clash++;
}
}
}
float chance = (float)clash / (float)total;
clashChance[i, j] = chance;
clashChance[j, i] = chance;
}
}
// build index lists, extract sets of only one stream
List <int> ordered = new List <int>();
List <int> remaining = new List <int>();
for (int i = 0; i < StreamSets_.Count; i++)
{
if (StreamSets_[i].Count == 1)
{
ordered.Add(i);
}
else
{
remaining.Add(i);
}
}
// get probability for single-option sets
foreach (int i in ordered)
{
float chance = 1f;
foreach (int j in ordered)
{
// reached same index - compared to all preceding
if (j == i)
{
break;
}
chance *= 1f - clashChance[i, j];
}
chance = 1f - chance;
}
// order by probability of clash with previously selected items
while (remaining.Count > 0)
{
float maxChance = 0;
float maxFuture = 0;
int maxIndex = -1;
foreach (int i in remaining)
{
float chance = 1f;
float future = 1f;
foreach (int j in ordered)
{
// find chance of not successively not clashing
chance *= 1f - clashChance[i, j];
}
foreach (int j in remaining)
{
if (i == j)
{
continue;
}
// chance of clashing with remaining options
future *= 1f - clashChance[i, j];
}
// chance of clashing
chance = 1f - chance;
future = 1f - future;
// check if there's a pair which is more likely to clash
float pairMax = 0f;
foreach (int j in remaining)
{
if (i == j)
{
continue;
}
if (clashChance[i, j] > pairMax)
{
pairMax = clashChance[i, j];
}
}
if (pairMax > chance)
{
chance = pairMax;
// give preference to any instant solution
future = -1;
}
if (maxIndex < 0 || chance > maxChance || (chance == maxChance && future > maxFuture))
{
maxIndex = i;
maxChance = chance;
maxFuture = future;
}
}
remaining.Remove(maxIndex);
ordered.Add(maxIndex);
}
/*
* // do specialised selection sort to bring most incompatible streams to the front
*
* // first find single worst instance of incompatibility
* float maxValue = -1;
* int maxIndex = -1;
* // look for worst incompatibility between a set of streams
* foreach (int i in remaining)
* {
* if (StreamSets_[i].Count == 1)
* {
* maxIndex = i;
* break;
* }
* // and all sets of streams which follow
* foreach (int j in remaining)
* {
* if (i == j)
* continue;
* if (clashChance[i, j] > maxValue)
* {
* maxValue = clashChance[i, j];
* maxIndex = i;
* }
* }
* }
*
* remaining.Remove(maxIndex);
* ordered.Add(maxIndex);
*
* // selection sort the rest of the list
* while (remaining.Count > 0)
* {
* // TODO: initialisation required?
* maxValue = -1;
* maxIndex = -1;
* // find maximum from all remaining sets of streams
* foreach (int j in remaining)
* {
* if (StreamSets_[j].Count == 1)
* {
* maxIndex = j;
* break;
* }
*
* float currentMaxValue = -1;
* // to find the maximum for a set, find its worst match from the already selected streams
* foreach (int k in ordered)
* {
* // if found new max for current stream list
* if (clashChance[j, k] > currentMaxValue)
* {
* currentMaxValue = clashChance[j, k];
* }
* }
* // if found new max for all stream lists
* if (currentMaxValue > maxValue)
* {
* maxValue = currentMaxValue;
* maxIndex = j;
* }
* }
*
* remaining.Remove(maxIndex);
* ordered.Add(maxIndex);
* }*/
List <List <Stream> > final = new List <List <Stream> >();
foreach (int index in ordered)
{
final.Add(StreamSets_[index]);
}
StreamSets_ = final;
#endregion
#region Stack-based algorithm
Stack <Solution> solutionStack = new Stack <Solution>(StreamSets_.Count);
solutionStack.Push(new Solution());
Solution solution = new Solution();
NumberValidSolutions_ = 0;
long progress = 0;
int progressPercent = 0;
long numLoops = 0;
// create an array such that the value at an index gives the number
// of complete solutions "down that alley" when processing is cut
// short at that index into the unique streams list
long[] cumulativeProduct = new long[StreamSets_.Count];
cumulativeProduct[cumulativeProduct.Length - 1] = 1;
for (int i = cumulativeProduct.Length - 2; i >= 0; i--)
{
cumulativeProduct[i] = cumulativeProduct[i + 1] * StreamSets_[i + 1].Count;
}
// setIndex represents from which set of streams the next stream is being selected
int setIndex = 0;
int[] streamIndices = new int[StreamSets_.Count];
for (int i = 0; i < streamIndices.Length; i++)
{
streamIndices[i] = 0;
}
//while (true)
while (true)
{
if (worker.CancellationPending)
{
SortFinalResults();
e.Cancel = true;
return(SolverResult.UserCancel);
}
numLoops++;
// check if the stream index is out of range
// (done all options for current set of streams)
if (streamIndices[setIndex] == StreamSets_[setIndex].Count)
{
// if we're back at the start
if (setIndex == 0)
{
// then we're spent! exit
break;
}
// tried all possibilities at the current level, backtrack a level
setIndex--;
// and go to the next possibility there
streamIndices[setIndex]++;
// pop off the saved solution from the previous level
//solution.Streams.RemoveAt(solution.Streams.Count - 1);
solutionStack.Pop();
solution = new Solution(solutionStack.Peek());
// try with the new indices!
continue;
}
// attempt to add the current stream to the solution
if (!solution.AddStream(StreamSets_[setIndex][streamIndices[setIndex]]))
{
// add to progress the number of solutions just skipped
progress += cumulativeProduct[setIndex];
int percent = (int)((float)progress / totalSolutions * 100);
if (percent > progressPercent)
{
worker.ReportProgress(percent);
progressPercent = percent;
}
// stream is incompatible, try adjacent possibility
streamIndices[setIndex]++;
// try now
continue;
}
// found stream that fits!
// if we have a complete solution
if (setIndex == StreamSets_.Count - 1)
{
// increment progress
progress++;
int percent = (int)((float)progress / totalSolutions * 100);
if (percent > progressPercent)
{
worker.ReportProgress(percent);
progressPercent = percent;
}
bool filteredOut = false;
foreach (Filter filter in Filters_)
{
// failed on a filter?
if (!filter.Pass(solution))
{
filteredOut = true;
break;
}
}
if (!filteredOut)
{
NumberValidSolutions_++;
// if the solution list is full to capacity
if (NumberValidSolutions_ > MaxResults_)
{
// if the solution is in the top so far, take the place of the worst solution
SolutionHeap_.CompareReplaceMaximum(solution);
}
else
{
// append the solution to the array
UnorderedSolutions_[NumberValidSolutions_ - 1] = solution;
// if the unordered list just filled up
if (NumberValidSolutions_ == MaxResults_)
{
// build the heap from the array
SolutionHeap_ = new HeapWithComparer <Solution>(MaxResults_, UnorderedSolutions_, Comparer_);
}
}
}
// now revert current solution
solution = new Solution(solutionStack.Peek());
//solution.Streams.RemoveAt(solution.Streams.Count - 1);
// and move to next along
streamIndices[setIndex]++;
// try next
continue;
}
// no real gain observed
// check if path is worth pursuing
/*else if (NumberValidSolutions_ > MaxResults_)
* {
* bool abort = false;
* Solution worst = SolutionHeap_.FindMaximum();
* foreach (Criteria critieria in Comparer_.Criteria)
* {
* // grows randomly
* if (critieria.Field.Progression == FieldProgression.Unknown)
* {
* break;
* }
* // grows and trying to minimise
* else if (critieria.Field.Progression == FieldProgression.Grow && critieria.Preference == Preference.Minimise)
* {
* if (solution.FieldValueToInt(critieria.Field.Index) > worst.FieldValueToInt(critieria.Field.Index))
* {
* abort = true;
* }
* break;
* }
* // shrinks and trying to maximise
* else if (critieria.Field.Progression == FieldProgression.Shrink && critieria.Preference == Preference.Maximise)
* {
* if (solution.FieldValueToInt(critieria.Field.Index) < worst.FieldValueToInt(critieria.Field.Index))
* {
* abort = true;
* }
* break;
* }
* }
* if (abort)
* {
* // stream won't work, restore and try adjacent
* solution = new Solution(solutionStack.Peek());
* streamIndices[setIndex]++;
* continue;
* }
* }*/
// move to next level
setIndex++;
// and try first option there
streamIndices[setIndex] = 0;
// push the solution with the new stream added on to the stack
solutionStack.Push(solution);
// set the working solution to a copy of the previous solution
solution = new Solution(solution);
}
//MessageBox.Show(numLoops.ToString() + " loops\n" + totalSolutions.ToString() + " combinations");
//MessageBox.Show("Number of valid solutions found: " + numValid.ToString() +
// "\nExpected number of solutions: " + totalSolutions.ToString() +
// "\nNumber of solutions \"checked\": " + progress.ToString());
SortFinalResults();
#endregion
Timetable_.RecomputeSolutions = false;
return(SolverResult.Complete);
}