public static VectorNode DeserializeNode(
long vecOffset,
long postingsOffset,
long componentCount,
long weight,
long terminator,
Stream vectorStream,
IStringModel tokenizer)
{
var vector = tokenizer.DeserializeVector(vecOffset, (int)componentCount, vectorStream);
var node = new VectorNode(postingsOffset, vecOffset, terminator, weight, componentCount, vector);
return(node);
}
private Hit ClosestMatchInPage(
Vector vector,
Stream indexStream,
Stream vectorStream,
IStringModel model
)
{
Span <byte> block = stackalloc byte[VectorNode.BlockSize];
var read = indexStream.Read(block);
VectorNode best = null;
float highscore = 0;
while (read > 0)
{
var vecOffset = BitConverter.ToInt64(block.Slice(0, sizeof(long)));
var componentCount = BitConverter.ToInt64(block.Slice(sizeof(long) + sizeof(long), sizeof(long)));
var cursorVector = model.DeserializeVector(vecOffset, (int)componentCount, vectorStream);
var cursorTerminator = BitConverter.ToInt64(block.Slice(sizeof(long) + sizeof(long) + sizeof(long) + sizeof(long), sizeof(long)));
var postingsOffset = BitConverter.ToInt64(block.Slice(sizeof(long), sizeof(long)));
var angle = model.CosAngle(cursorVector, vector);
if (angle >= model.IdenticalAngle)
{
if (best == null || angle > highscore)
{
highscore = angle;
best = new VectorNode(cursorVector);
best.PostingsOffsets = new List <long> {
postingsOffset
};
}
else if (angle == highscore)
{
if (best.PostingsOffsets == null)
{
best.PostingsOffsets = new List <long> {
best.PostingsOffset, postingsOffset
};
}
else
{
best.PostingsOffsets.Add(postingsOffset);
}
}
break;
}
else if (angle > model.FoldAngle)
{
if (best == null || angle > highscore)
{
highscore = angle;
best = new VectorNode(cursorVector);
best.PostingsOffsets = new List <long> {
postingsOffset
};
}
else if (angle == highscore)
{
if (best.PostingsOffsets == null)
{
best.PostingsOffsets = new List <long> {
best.PostingsOffset, postingsOffset
};
}
else
{
best.PostingsOffsets.Add(postingsOffset);
}
}
// We need to determine if we can traverse further left.
bool canGoLeft = cursorTerminator == 0 || cursorTerminator == 1;
if (canGoLeft)
{
// There exists either a left and a right child or just a left child.
// Either way, we want to go left and the next node in bitmap is the left child.
read = indexStream.Read(block);
}
else
{
// There is no left child.
break;
}
}
else
{
if (best == null || angle > highscore)
{
highscore = angle;
best = new VectorNode(cursorVector);
best.PostingsOffsets = new List <long> {
postingsOffset
};
}
else if (angle == highscore)
{
if (best.PostingsOffsets == null)
{
best.PostingsOffsets = new List <long> {
best.PostingsOffset, postingsOffset
};
}
else
{
best.PostingsOffsets.Add(postingsOffset);
}
}
// We need to determine if we can traverse further to the right.
if (cursorTerminator == 0)
{
// There exists a left and a right child.
// Next node in bitmap is the left child.
// To find cursor's right child we must skip over the left tree.
SkipTree(indexStream);
read = indexStream.Read(block);
}
else if (cursorTerminator == 2)
{
// Next node in bitmap is the right child,
// which is good because we want to go right.
read = indexStream.Read(block);
}
else
{
// There is no right child.
break;
}
}
}
return(new Hit
{
Score = highscore,
Node = best
});
}
