/// <summary>
/// Reduction rules for a BDD.
/// </summary>
/// <param name="node">The node to reduce.</param>
/// <param name="result">The modified node.</param>
/// <returns>If there was a reduction.</returns>
public virtual bool Reduce(CBDDNode node, out DDIndex result)
{
result = DDIndex.False;
if (node.Low.Equals(node.High))
{
result = node.Low;
return(true);
}
if (node.Low.IsConstant())
{
return(false);
}
var lo = this.Manager.LookupNodeByIndex(node.Low);
if (lo.Variable == node.NextVariable && lo.High.Equals(node.High))
{
var reduced = new CBDDNode(node.Variable, lo.NextVariable, lo.Low, node.High);
result = this.Manager.Allocate(reduced);
return(true);
}
return(false);
}
/// <summary>
/// Remove all elements matching a predicate.
/// </summary>
/// <param name="forwardingAddresses">The forwarding addresses.</param>
/// <returns>A new handle table after garbage collection.</returns>
public HandleTable <T> Rebuild(int[] forwardingAddresses)
{
var table = new HandleTable <T>(this.manager, this.Count);
for (int bucket = 0; bucket < this.buckets.Length; bucket++)
{
int i = this.buckets[bucket];
while (i >= 0)
{
var entry = this.entries[i];
var index = entry.Key;
var wref = entry.Value;
var position = index.GetPosition();
var newPosition = forwardingAddresses[position];
if (newPosition != 0 || index.IsConstant())
{
var newIndex = new DDIndex(newPosition, index.IsComplemented());
if (wref.TryGetTarget(out DD target))
{
target.Index = newIndex;
}
table.AddUnique(newIndex, wref);
}
i = entry.Next;
}
}
return(table);
}
/// <summary>
/// Rebuild the unique table.
/// </summary>
/// <param name="newSize">The new number of nodes in use after a GC.</param>
/// <param name="forwardingAddresses">The index forwarding addresses.</param>
/// <returns>A new table with valid indicies.</returns>
public UniqueTable <T> Rebuild(int newSize, int[] forwardingAddresses)
{
var values = new DDIndex[newSize];
var table = new UniqueTable <T>(this.manager, this.Count);
for (int bucket = 0; bucket < this.buckets.Length; bucket++)
{
int i = this.buckets[bucket];
while (i >= 0)
{
var entry = this.entries[i];
var ddindex = entry.Value;
var newPosition = forwardingAddresses[ddindex.GetPosition()];
if (newPosition != 0 || ddindex.IsConstant())
{
values[newPosition] = new DDIndex(newPosition, ddindex.IsComplemented());
}
i = entry.Next;
}
}
for (int i = 0; i < values.Length; i++)
{
table.AddUnchecked(this.manager.MemoryPool[i], values[i]);
}
return(table);
}
/// <summary>
/// Returns a new formula that repairs the order after a substitution.
/// </summary>
/// <param name="level">Variable level of the new node.</param>
/// <param name="lo">The node's lo branch.</param>
/// <param name="hi">The node's hi branch.</param>
/// <returns></returns>
private DDIndex RepairOrder(int level, DDIndex lo, DDIndex hi)
{
var loNode = this.Manager.MemoryPool[lo.GetPosition()];
var hiNode = this.Manager.MemoryPool[hi.GetPosition()];
loNode = lo.IsComplemented() ? Flip(loNode) : loNode;
hiNode = hi.IsComplemented() ? Flip(hiNode) : hiNode;
var loLevel = Level(lo, loNode);
var hiLevel = Level(hi, hiNode);
if (level < loLevel && level < hiLevel)
{
return(this.Manager.Allocate(new BDDNode(level, lo, hi)));
}
else if (loLevel < hiLevel)
{
var l = RepairOrder(level, loNode.Low, hi);
var h = RepairOrder(level, loNode.High, hi);
return(this.Manager.Allocate(new BDDNode(loNode.Variable, l, h)));
}
else if (loLevel > hiLevel)
{
var l = RepairOrder(level, lo, hiNode.Low);
var h = RepairOrder(level, lo, hiNode.High);
return(this.Manager.Allocate(new BDDNode(hiNode.Variable, l, h)));
}
else
{
var l = RepairOrder(level, loNode.Low, hiNode.Low);
var h = RepairOrder(level, loNode.High, hiNode.High);
return(this.Manager.Allocate(new BDDNode(loNode.Variable, l, h)));
}
}
/// <summary>
/// The logical conjunction of two BDDs as the
/// standard BDD "apply" operation.
/// </summary>
/// <param name="xid">The left operand index.</param>
/// <param name="x">The left operand node.</param>
/// <param name="yid">The right operand index.</param>
/// <param name="y">The right operand node.</param>
/// <returns>A new node representing the "And".</returns>
public DDIndex And(DDIndex xid, CBDDNode x, DDIndex yid, CBDDNode y)
{
if (x.Variable < y.Variable)
{
if (x.NextVariable <= y.Variable)
{
var xlow = this.Manager.And(x.Low, yid);
var xhigh = this.Manager.And(x.High, yid);
return(this.Manager.Allocate(new CBDDNode(x.Variable, x.NextVariable, xlow, xhigh)));
}
else
{
var child = this.Manager.Allocate(new CBDDNode(y.Variable, x.NextVariable, x.Low, x.High));
var xlow = this.Manager.And(child, yid);
var xhigh = this.Manager.And(x.High, yid);
return(this.Manager.Allocate(new CBDDNode(x.Variable, y.Variable, xlow, xhigh)));
}
}
else if (y.Variable < x.Variable)
{
if (y.NextVariable <= x.Variable)
{
var ylow = this.Manager.And(y.Low, xid);
var yhigh = this.Manager.And(y.High, xid);
return(this.Manager.Allocate(new CBDDNode(y.Variable, y.NextVariable, ylow, yhigh)));
}
else
{
var child = this.Manager.Allocate(new CBDDNode(x.Variable, y.NextVariable, y.Low, y.High));
var ylow = this.Manager.And(child, xid);
var yhigh = this.Manager.And(y.High, xid);
return(this.Manager.Allocate(new CBDDNode(y.Variable, x.Variable, ylow, yhigh)));
}
}
else
{
if (x.NextVariable == y.NextVariable)
{
var lo = this.Manager.And(x.Low, y.Low);
var hi = this.Manager.And(x.High, y.High);
return(this.Manager.Allocate(new CBDDNode(x.Variable, x.NextVariable, lo, hi)));
}
else if (x.NextVariable < y.NextVariable)
{
var ychild = this.Manager.Allocate(new CBDDNode(x.NextVariable, y.NextVariable, y.Low, y.High));
var lo = this.Manager.And(x.Low, ychild);
var hi = this.Manager.And(x.High, y.High);
return(this.Manager.Allocate(new CBDDNode(x.Variable, x.NextVariable, lo, hi)));
}
else
{
var xchild = this.Manager.Allocate(new CBDDNode(y.NextVariable, x.NextVariable, x.Low, x.High));
var lo = this.Manager.And(y.Low, xchild);
var hi = this.Manager.And(y.High, x.High);
return(this.Manager.Allocate(new CBDDNode(y.Variable, y.NextVariable, lo, hi)));
}
}
}
/// <summary>
/// Reduction rules for a BDD.
/// </summary>
/// <param name="node">The node to reduce.</param>
/// <param name="result">The modified node.</param>
/// <returns>If there was a reduction.</returns>
public virtual bool Reduce(BDDNode node, out DDIndex result)
{
result = DDIndex.False;
if (node.Low.Equals(node.High))
{
result = node.Low;
return(true);
}
return(false);
}
/// <summary>
/// Either get the existing value or create a
/// new one in a single operation.
/// </summary>
/// <param name="key">The key.</param>
/// <param name="value">The value.</param>
private void AddUnique(DDIndex key, WeakReference <DD> value)
{
int hashCode = key.GetHashCode() & 0x7FFFFFFF;
int targetBucket = hashCode & this.mask;
int index = this.Count;
this.Count++;
this.entries[index] = new Entry {
Next = this.buckets[targetBucket], Key = key, Value = value
};
this.buckets[targetBucket] = index;
}
/// <summary>
/// Either get the existing value or create a
/// new one in a single operation.
/// </summary>
/// <param name="key">The key.</param>
/// <param name="value">The value.</param>
public void AddUnchecked(T key, DDIndex value)
{
int hashCode = key.GetHashCode() & 0x7FFFFFFF;
int targetBucket = hashCode & this.mask;
int index = this.count;
this.count++;
this.entries[index] = new Entry {
Next = this.buckets[targetBucket], Value = value
};
this.buckets[targetBucket] = index;
}
/// <summary>
/// Implement the logical "exists" operation,
/// recursively calling the manager if necessary.
/// </summary>
/// <param name="xid">The left index.</param>
/// <param name="x">The left node.</param>
/// <param name="variables">The variable set.</param>
/// <returns>The resulting function.</returns>
public DDIndex Exists(DDIndex xid, BDDNode x, VariableSet <BDDNode> variables)
{
var lo = this.Manager.Exists(x.Low, variables);
var hi = this.Manager.Exists(x.High, variables);
if (variables.Contains(x.Variable))
{
return(this.Manager.Or(lo, hi));
}
return(this.Manager.Allocate(new BDDNode(x.Variable, lo, hi)));
}
/// <summary>
/// Implement a replacement operation that substitutes
/// variables for other variables.
/// </summary>
/// <param name="xid">The left index.</param>
/// <param name="x">The left node.</param>
/// <param name="variableMap">The variable set.</param>
/// <returns>A new formula with the susbtitution.</returns>
public DDIndex Replace(DDIndex xid, BDDNode x, VariableMap <BDDNode> variableMap)
{
if (x.Variable > variableMap.MaxIndex)
{
return(xid);
}
var lo = this.Manager.Replace(x.Low, variableMap);
var hi = this.Manager.Replace(x.High, variableMap);
var level = variableMap.Get(x.Variable);
level = level < 0 ? x.Variable : level;
return(RepairOrder(level, lo, hi));
}
/// <summary>
/// The logical conjunction of two BDDs as the
/// standard BDD "apply" operation.
/// </summary>
/// <param name="xid">The left operand index.</param>
/// <param name="x">The left operand node.</param>
/// <param name="yid">The right operand index.</param>
/// <param name="y">The right operand node.</param>
/// <returns>A new node representing the "And".</returns>
public DDIndex And(DDIndex xid, BDDNode x, DDIndex yid, BDDNode y)
{
if (x.Variable < y.Variable)
{
var xlow = this.Manager.And(x.Low, yid);
var xhigh = this.Manager.And(x.High, yid);
return(this.Manager.Allocate(new BDDNode(x.Variable, xlow, xhigh)));
}
else if (y.Variable < x.Variable)
{
var ylow = this.Manager.And(y.Low, xid);
var yhigh = this.Manager.And(y.High, xid);
return(this.Manager.Allocate(new BDDNode(y.Variable, ylow, yhigh)));
}
else
{
var low = this.Manager.And(x.Low, y.Low);
var high = this.Manager.And(x.High, y.High);
return(this.Manager.Allocate(new BDDNode(x.Variable, low, high)));
}
}
/// <summary>
/// Either get the existing value or create a
/// new one in a single operation.
/// </summary>
/// <param name="key">The key.</param>
/// <returns>The value, possibly freshly created.</returns>
public DD GetOrAdd(DDIndex key)
{
int hashCode = key.GetHashCode() & 0x7FFFFFFF;
int targetBucket = hashCode & this.mask;
for (int i = this.buckets[targetBucket]; i >= 0; i = this.entries[i].Next)
{
if (this.entries[i].Key.Equals(key))
{
var wref = this.entries[i].Value;
if (!wref.TryGetTarget(out DD target))
{
target = new DD(this.manager.Uid, key);
wref.SetTarget(target);
}
return(target);
}
}
int index;
if (this.Count == this.entries.Length)
{
this.Resize();
targetBucket = hashCode & this.mask;
}
index = this.Count;
this.Count++;
var dd = new DD(this.manager.Uid, key);
var value = new WeakReference <DD>(dd);
this.entries[index] = new Entry {
Next = this.buckets[targetBucket], Key = key, Value = value
};
this.buckets[targetBucket] = index;
return(dd);
}
/// <summary>
/// Return a function capturing a variable being greater
/// than or equal to a particular value. The value is
/// represented as a byte array and should be have MSBs first.
/// For example, the 32-bit value 300 would be represented as
/// the byte array [0, 0, 1, 44].
/// </summary>
/// <param name="value">The value.</param>
/// <returns>The function representing the inequality.</returns>
public DD GreaterOrEqual(byte[] value)
{
var len = this.Indices.Length;
var eq = new DDIndex[len];
var greater = new DDIndex[len];
for (int v = len - 1; v >= 0; v--)
{
var variable = this.Indices[v];
var i = this.GetBitPositionForVariableIndex(variable);
var whichByte = i / 8;
var whichIndex = i % 8;
var set = GetBit(value[whichByte], whichIndex, 8);
if (set)
{
var node = this.Manager.IdIdx(variable);
eq[i] = node;
greater[i] = DDIndex.False;
}
else
{
var node = this.Manager.IdIdx(variable);
eq[i] = this.Manager.Not(node);
greater[i] = node;
}
}
var acc = DDIndex.True;
for (int i = len - 1; i >= 0; i--)
{
acc = this.Manager.Or(greater[i], this.Manager.And(acc, eq[i]));
}
return(this.Manager.FromIndex(acc));
}
/// <summary>
/// Initializes a new instance of the <see cref="DD"/> class.
/// </summary>
/// <param name="managerId">Id of the manager that created this node.</param>
/// <param name="index">Index of the underlying IDDNode.</param>
internal DD(ushort managerId, DDIndex index)
{
this.ManagerId = managerId;
this.Index = index;
}
/// <summary>
/// Implement the logical "exists" operation,
/// recursively calling the manager if necessary.
/// </summary>
/// <param name="xid">The left index.</param>
/// <param name="x">The left node.</param>
/// <param name="variables">The variable set.</param>
/// <returns>The resulting function.</returns>
public DDIndex Exists(DDIndex xid, CBDDNode x, VariableSet <CBDDNode> variables)
{
throw new System.NotImplementedException();
}
/// <summary>
/// Initializes a new instance of the <see cref="CBDDNode"/> struct.
/// </summary>
/// <param name="variable">The variable index.</param>
/// <param name="nextVariable">The next index.</param>
/// <param name="lo">The low (false) child.</param>
/// <param name="hi">The high (true) child.</param>
public CBDDNode(int variable, int nextVariable, DDIndex lo, DDIndex hi)
{
this.data = new NodeData32Packed(variable, false, nextVariable);
this.Low = lo;
this.High = hi;
}
public DDIndex Ite(DDIndex fid, CBDDNode f, DDIndex gid, CBDDNode g, DDIndex hid, CBDDNode h)
{
throw new System.NotSupportedException();
}
/// <summary>
/// Gets the "level" for the node, where the maximum
/// value is used for constants.
/// </summary>
/// <param name="idx">The node index.</param>
/// <param name="node">The node.</param>
/// <returns></returns>
private int Level(DDIndex idx, BDDNode node)
{
return(idx.IsConstant() ? int.MaxValue : node.Variable);
}
/// <summary>
/// Initializes a new instance of the <see cref="BDDNode"/> struct.
/// </summary>
/// <param name="variable">The variable index.</param>
/// <param name="lo">The low (false) child.</param>
/// <param name="hi">The high (true) child.</param>
public BDDNode(int variable, DDIndex lo, DDIndex hi)
{
this.data = new NodeData32(variable, false);
this.Low = lo;
this.High = hi;
}
/// <summary>
/// Implement the logical "ite" operation,
/// recursively calling the manager if necessary.
/// </summary>
/// <param name="fid">The f index.</param>
/// <param name="f">The f node.</param>
/// <param name="gid">The g index.</param>
/// <param name="g">The g node.</param>
/// <param name="hid">The h index.</param>
/// <param name="h">The h node.</param>
/// <returns>The ite of the three nodes.</returns>
public DDIndex Ite(DDIndex fid, BDDNode f, DDIndex gid, BDDNode g, DDIndex hid, BDDNode h)
{
var flevel = Level(fid, f);
var glevel = Level(gid, g);
var hlevel = Level(hid, h);
if (flevel == glevel)
{
if (flevel == hlevel)
{
var x = this.Manager.IteRecursive(f.Low, g.Low, h.Low);
var y = this.Manager.IteRecursive(f.High, g.High, h.High);
return(this.Manager.Allocate(new BDDNode(f.Variable, x, y)));
}
else if (flevel < hlevel)
{
var x = this.Manager.IteRecursive(f.Low, g.Low, hid);
var y = this.Manager.IteRecursive(f.High, g.High, hid);
return(this.Manager.Allocate(new BDDNode(f.Variable, x, y)));
}
else
{
var x = this.Manager.IteRecursive(fid, gid, h.Low);
var y = this.Manager.IteRecursive(fid, gid, h.High);
return(this.Manager.Allocate(new BDDNode(h.Variable, x, y)));
}
}
else if (flevel < glevel)
{
if (flevel == hlevel)
{
var x = this.Manager.IteRecursive(f.Low, gid, h.Low);
var y = this.Manager.IteRecursive(f.High, gid, h.High);
return(this.Manager.Allocate(new BDDNode(f.Variable, x, y)));
}
else if (flevel < hlevel)
{
var x = this.Manager.IteRecursive(f.Low, gid, hid);
var y = this.Manager.IteRecursive(f.High, gid, hid);
return(this.Manager.Allocate(new BDDNode(f.Variable, x, y)));
}
else
{
var x = this.Manager.IteRecursive(fid, gid, h.Low);
var y = this.Manager.IteRecursive(fid, gid, h.High);
return(this.Manager.Allocate(new BDDNode(h.Variable, x, y)));
}
}
else
{
if (glevel == hlevel)
{
var x = this.Manager.IteRecursive(fid, g.Low, h.Low);
var y = this.Manager.IteRecursive(fid, g.High, h.High);
return(this.Manager.Allocate(new BDDNode(g.Variable, x, y)));
}
else
if (glevel < hlevel)
{
var x = this.Manager.IteRecursive(fid, g.Low, hid);
var y = this.Manager.IteRecursive(fid, g.High, hid);
return(this.Manager.Allocate(new BDDNode(g.Variable, x, y)));
}
else
{
var x = this.Manager.IteRecursive(fid, gid, h.Low);
var y = this.Manager.IteRecursive(fid, gid, h.High);
return(this.Manager.Allocate(new BDDNode(h.Variable, x, y)));
}
}
}
/// <summary>
/// Implement a replacement operation that substitutes
/// variables for other variables.
/// </summary>
/// <param name="xid">The left index.</param>
/// <param name="x">The left node.</param>
/// <param name="variableMap">The variable set.</param>
/// <returns>A new formula with the susbtitution.</returns>
public DDIndex Replace(DDIndex xid, CBDDNode x, VariableMap <CBDDNode> variableMap)
{
throw new System.NotSupportedException();
}