@Override
public double similarity(SparseVector vec1, SparseVector vec2) {
final double distance;
// One of the vector is empty
if (Scalars.isZero(vec1.norm()) || Scalars.isZero(vec2.norm())) {
return Double.NaN;
}
LongSet ts = LongUtils.setUnion(vec1.keySet(), vec2.keySet());
MutableSparseVector v1 = MutableSparseVector.create(ts);
v1.fill(0);
v1.set(vec1);
v1.multiply(1.0 / v1.norm());
v1.addScaled(vec2, -1.0 / vec2.norm());
distance = v1.norm();
return 1 - distance;
}
