/// <summary>
/// Merges the sets represented by this node and the other node into a single set.
/// Returns whether or not the nodes were disjoint before the union operation (i.e. if the operation had an effect).
/// </summary>
/// <returns>True when the union had an effect, false when the nodes were already in the same set.</returns>
public bool Union(UnionFindNode other)
{
if (other == null)
{
throw new ArgumentNullException("other");
}
var root1 = this.Find();
var root2 = other.Find();
if (ReferenceEquals(root1, root2))
{
return(false);
}
if (root1.NodeId < root2.NodeId)
{
root2._parent = root1;
}
else
{
root1._parent = root2;
}
/*
* if (root1._rank < root2._rank) {
* root1._parent = root2;
* } else if (root1._rank > root2._rank) {
* root2._parent = root1;
* } else {
* root2._parent = root1;
* root1._rank++;
* }
*/
return(true);
}
private List <List <Transaction> > GroupParallelizables(List <TransactionWithResourceInfo> txsWithResources)
{
var resourceUnionSet = new Dictionary <int, UnionFindNode>();
var transactionResourceHandle = new Dictionary <Transaction, int>();
var groups = new List <List <Transaction> >();
foreach (var txWithResource in txsWithResources)
{
UnionFindNode first = null;
var transaction = txWithResource.Transaction;
var transactionResourceInfo = txWithResource.TransactionResourceInfo;
// Add resources to disjoint-set, later each resource will be connected to a node id, which will be our group id
foreach (var resource in transactionResourceInfo.Paths.Select(p => p.GetHashCode()))
{
if (!resourceUnionSet.TryGetValue(resource, out var node))
{
node = new UnionFindNode();
resourceUnionSet.Add(resource, node);
}
if (first == null)
{
first = node;
transactionResourceHandle.Add(transaction, resource);
}
else
{
node.Union(first);
}
}
}
var grouped = new Dictionary <int, List <Transaction> >();
foreach (var txWithResource in txsWithResources)
{
var transaction = txWithResource.Transaction;
if (!transactionResourceHandle.TryGetValue(transaction, out var firstResource))
{
continue;
}
// Node Id will be our group id
var gId = resourceUnionSet[firstResource].Find().NodeId;
if (!grouped.TryGetValue(gId, out var gTransactions))
{
gTransactions = new List <Transaction>();
grouped.Add(gId, gTransactions);
}
// Add transaction to its group
gTransactions.Add(transaction);
}
groups.AddRange(grouped.Values);
return(groups);
}
/// <summary>
/// Determines whether or not this node and the other node are in the same set.
/// </summary>
public bool IsUnionedWith(UnionFindNode other)
{
if (other == null)
{
throw new ArgumentNullException("other");
}
return(ReferenceEquals(Find(), other.Find()));
}
/// <summary>
/// Returns the current representative of the set this node is in.
/// Note that the representative is only accurate untl the next Union operation.
/// </summary>
public UnionFindNode Find()
{
if (!ReferenceEquals(_parent, this))
{
_parent = _parent.Find();
}
return(_parent);
}
/// <summary>
/// Creates a new disjoint node, representative of a set containing only the new node.
/// </summary>
public UnionFindNode()
{
_parent = this;
NodeId = Interlocked.Increment(ref _nextId);
}