/**
* Count the common keys between two vectors.
*
* @param o The other vector.
* @return The number of keys appearing in both this and the other vector.
*/
public int countCommonKeys(SparseVector o) {
int count = 0;
Iterator<VectorEntry> i1 = fastIterator();
Iterator<VectorEntry> i2 = o.fastIterator();
VectorEntry e1 = i1.hasNext() ? i1.next() : null;
VectorEntry e2 = i2.hasNext() ? i2.next() : null;
while (e1 != null && e2 != null) {
final long k1 = e1.getKey();
final long k2 = e2.getKey();
if (k1 < k2) {
e1 = i1.hasNext() ? i1.next() : null;
} else if (k2 < k1) {
e2 = i2.hasNext() ? i2.next() : null;
} else {
count += 1;
e1 = i1.hasNext() ? i1.next() : null;
e2 = i2.hasNext() ? i2.next() : null;
}
}
return count;
}
/**
* Compute the dot product between two vectors.
*
* @param o The other vector.
* @return The dot (inner) product between this vector and {@var o}.
*/
public double dot(SparseVector o) {
double dot = 0;
Iterator<VectorEntry> i1 = fastIterator();
Iterator<VectorEntry> i2 = o.fastIterator();
VectorEntry e1 = i1.hasNext() ? i1.next() : null;
VectorEntry e2 = i2.hasNext() ? i2.next() : null;
while (e1 != null && e2 != null) {
final long k1 = e1.getKey();
final long k2 = e2.getKey();
if (k1 < k2) {
e1 = i1.hasNext() ? i1.next() : null;
} else if (k2 < k1) {
e2 = i2.hasNext() ? i2.next() : null;
} else {
dot += e1.getValue() * e2.getValue();
e1 = i1.hasNext() ? i1.next() : null;
e2 = i2.hasNext() ? i2.next() : null;
}
}
return dot;
}