/** Computes the inner product of two instances */
private double innerProduct(Instance i1, Instance i2) throws Exception {
// we can do a fast dot product
double result = 0;
int n1 = i1.numValues();
int n2 = i2.numValues();
int classIndex = m_Train.classIndex();
for (int p1 = 0, p2 = 0; p1 < n1 && p2 < n2; ) {
int ind1 = i1.index(p1);
int ind2 = i2.index(p2);
if (ind1 == ind2) {
if (ind1 != classIndex) {
result += i1.valueSparse(p1) * i2.valueSparse(p2);
}
p1++;
p2++;
} else if (ind1 > ind2) {
p2++;
} else {
p1++;
}
}
result += 1.0;
if (m_Exponent != 1) {
return Math.pow(result, m_Exponent);
} else {
return result;
}
}