IEnumerable <BitVector> enumerateCmp(JoinGraph graph, BitVector S1)
{
int ntables = graph.vertices_.Count;
Debug.Assert(S1 != SetOp.EmptySet);
// min(S1) := min({i|v_i \in S1})
int minS1 = SetOp.MinTableIndex(S1);
// B_i(W) := {vj |v_j \in W, j <= i}
// X = union (B_min(S1), S)
BitVector BminS1 = SetOp.OrderBeforeSet(minS1);
BitVector X = SetOp.Union(BminS1, S1);
// N = neighbour(S1) \ X
BitVector N = SetOp.Substract(graph.NeighboursExcluding(S1), X);
// for all(vi 2 N by descending i)
foreach (int vi in SetOp.TablesDescending(N))
{
// emit {v_i}
BitVector VI = SetOp.SingletonSet(vi);
yield return(VI);
// recursively invoke enumerateCmp(graph, {v_i}, X union (B_i intersect N))
BitVector Bi = SetOp.OrderBeforeSet(vi);
BitVector BiN = SetOp.Intersect(Bi, N);
foreach (var csg in enumerateCsgRecursive(graph,
VI, SetOp.Union(X, BiN)))
{
yield return(csg);
}
}
}
IEnumerable <BitVector> enumerateCsgRecursive(JoinGraph graph, BitVector S, BitVector X)
{
// N = neighbour(S) \ X
BitVector N = SetOp.Substract(graph.NeighboursExcluding(S), X);
// Console.WriteLine("N: " + BitHelper.ToString(N));
// for all non-empty S' subsetof(N), emit (S union S')
if (N != SetOp.EmptySet)
{
VancePartition partitioner = new VancePartition(N);
foreach (var S_prime in partitioner.Next(true))
{
yield return(SetOp.Union(S, S_prime));
}
// for all non-empty S' subsetof(N), recursively invoke (graph, (S union S'), (X union N))
partitioner = new VancePartition(N);
foreach (var S_prime in partitioner.Next(true))
{
foreach (var v in enumerateCsgRecursive(graph,
SetOp.Union(S, S_prime), SetOp.Union(X, N)))
{
yield return(v);
}
}
}
}