@Override
protected void buildModel() throws Exception {
for (int iter = 1; iter <= numIters; iter++) {
loss = 0;
errs = 0;
for (int s = 0, smax = numUsers * 100; s < smax; s++) {
// randomly draw (u, i, j)
int u = 0, i = 0, j = 0;
while (true) {
u = Randoms.uniform(numUsers);
SparseVector pu = userCache.get(u);
if (pu.getCount() == 0) continue;
int[] is = pu.getIndex();
i = is[Randoms.uniform(is.length)];
do {
j = Randoms.uniform(numItems);
} while (pu.contains(j));
break;
}
// update parameters
double xui = predict(u, i);
double xuj = predict(u, j);
double xuij = xui - xuj;
double vals = -Math.log(g(xuij));
loss += vals;
errs += vals;
double cmg = g(-xuij);
for (int f = 0; f < numFactors; f++) {
double puf = P.get(u, f);
double qif = Q.get(i, f);
double qjf = Q.get(j, f);
P.add(u, f, lRate * (cmg * (qif - qjf) - regU * puf));
Q.add(i, f, lRate * (cmg * puf - regI * qif));
Q.add(j, f, lRate * (cmg * (-puf) - regI * qjf));
loss += regU * puf * puf + regI * qif * qif + regI * qjf * qjf;
}
}
if (isConverged(iter)) break;
}
}
