void
computeNormalizedTfIdf()
{
cerr << "# Computing document frequencies" << endl;
int terms = dico.size();
vector<double> nt(terms+1);
double nd = trainid.size();
for(int i=0; i<terms+1; i++)
nt[i] = 0;
for(int i=0; i<(int)trainid.size(); i++)
{
int id = trainid[i];
SVector s = train[id];
for (const SVector::Pair *p = s; p->i >= 0; p++)
if (p->v > 0)
nt[p->i] += 1;
}
cerr << "# Computing TF/IDF for training set" << endl;
for(int i=0; i<(int)trainid.size(); i++)
{
int id = trainid[i];
SVector s = train[id];
SVector v;
for (const SVector::Pair *p = s; p->i >= 0; p++)
if (nt[p->i] > 0)
v.set(p->i, (1.0 + log(p->v)) * log(nd/nt[p->i]));
double norm = dot(v,v);
v.scale(1.0 / sqrt(norm));
train[id] = v;
}
cerr << "# Computing TF/IDF for testing set" << endl;
for(int i=0; i<(int)testid.size(); i++)
{
int id = testid[i];
SVector s = test[id];
SVector v;
for (const SVector::Pair *p = s; p->i >= 0; p++)
if (nt[p->i] > 0)
v.set(p->i, (1.0 + log(p->v)) * log(nd/nt[p->i]));
double norm = dot(v,v);
v.scale(1.0 / sqrt(norm));
test[id] = v;
}
cerr << "# Done." << endl;
}
void LinearLaRank::eval(Sample& sample, Result& result) {
// Evaluate the sample
if (m_sampleCount) {
// Convert the Sample to LaRank form
SVector laX;
for (int nFeat = 0; nFeat < sample.x.rows(); nFeat++) {
laX.set(nFeat, sample.x(nFeat));
}
m_svm->predict_with_scores(laX, result);
// Convert the scores to probabilities
double totalProb = 0.0;
for (int nClass = 0; nClass < *m_numClasses; nClass++) {
result.confidence[nClass] = exp(result.confidence[nClass]);
totalProb += result.confidence[nClass];
}
for (int nClass = 0; nClass < *m_numClasses; nClass++) {
result.confidence[nClass] /= (totalProb + 1e-16);
}
} else {
for (int nClass = 0; nClass < *m_numClasses; nClass++) {
result.confidence[nClass] = 1.0 / *m_numClasses;
}
result.prediction = 0;
}
}
void LinearLaRank::update(Sample& sample) {
// Convert the Sample to LaRank form
SVector laX;
for (int nFeat = 0; nFeat < sample.x.rows(); nFeat++) {
laX.set(nFeat, sample.x(nFeat));
}
// Add the sample to svm
m_sampleCount++;
m_svm->add(laX, sample.y, m_sampleCount, sample.w);
}
void
readDocs(const char *fname, docs_t &docs, bool freezedico=false)
{
cerr << "# Reading " << fname << endl;
igzstream f;
f.open(fname);
if (! f.good()) {
cerr << "ERROR: cannot open file " << fname << endl;
::exit(10);
}
string token;
f >> token;
if (token != ".I")
{
cerr << "ERROR: Cannot read initial .I in " << fname << endl;
::exit(10);
}
int id = 0;
int count = 0;
while(f.good())
{
f >> id >> token;
count += 1;
if (! f.good() || token != ".W")
{
cerr << "ERROR (" << id << "): "
<< "Cannot read \"<id> .W\"." << endl;
::exit(10);
}
int wid = -1;
string otoken;
SVector s;
for(;;)
{
f >> token;
if (!f.good() || token == ".I")
break;
if (token != otoken)
{
dico_t::iterator it = dico.find(token);
if (it != dico.end())
wid = it->second;
else if (freezedico)
continue;
else
{
wid = dico.size() + 1;
dico[token] = wid;
}
otoken = token;
}
s.set(wid, s.get(wid)+1.0);
}
if (s.npairs() <= 0)
{
cerr << "ERROR (" << id << "): "
<< "Empty vector " << id << "?" << endl;
::exit(10);
}
docs[id] = s;
}
if (!f.eof())
{
cerr << "ERROR (" << id << "): "
<< "Failed reading words" << endl;
::exit(10);
}
cerr << "# Done reading " << count << " documents." << endl;
}
