/**
* initializes the algorithm
*
* @param data the data to work with
* @throws Exception if m_SVM is null
*/
protected void init(Instances data) throws Exception {
if (m_SVM == null) {
throw new Exception("SVM not initialized in optimizer. Use RegOptimizer.setSVMReg()");
}
m_C = m_SVM.getC();
m_data = data;
m_classIndex = data.classIndex();
m_nInstances = data.numInstances();
// Initialize kernel
m_kernel = Kernel.makeCopy(m_SVM.getKernel());
m_kernel.buildKernel(data);
// init m_target
m_target = new double[m_nInstances];
for (int i = 0; i < m_nInstances; i++) {
m_target[i] = data.instance(i).classValue();
}
m_random = new Random(m_nSeed);
// initialize alpha and alpha* array to all zero
m_alpha = new double[m_target.length];
m_alphaStar = new double[m_target.length];
m_supportVectors = new SMOset(m_nInstances);
m_b = 0.0;
m_nEvals = 0;
m_nCacheHits = -1;
}
/**
* wrap up various variables to save memeory and do some housekeeping after optimization has
* finished.
*
* @throws Exception if something goes wrong
*/
protected void wrapUp() throws Exception {
m_target = null;
m_nEvals = m_kernel.numEvals();
m_nCacheHits = m_kernel.numCacheHits();
if ((m_SVM.getKernel() instanceof PolyKernel)
&& ((PolyKernel) m_SVM.getKernel()).getExponent() == 1.0) {
// convert alpha's to weights
double[] weights = new double[m_data.numAttributes()];
for (int k = m_supportVectors.getNext(-1); k != -1; k = m_supportVectors.getNext(k)) {
for (int j = 0; j < weights.length; j++) {
if (j != m_classIndex) {
weights[j] += (m_alpha[k] - m_alphaStar[k]) * m_data.instance(k).value(j);
}
}
}
m_weights = weights;
// release memory
m_alpha = null;
m_alphaStar = null;
m_kernel = null;
}
m_bModelBuilt = true;
}
/**
* Prints out the classifier.
*
* @return a description of the classifier as a string
*/
@Override
public String toString() {
StringBuffer text = new StringBuffer();
text.append("SMOreg\n\n");
if (m_weights != null) {
text.append("weights (not support vectors):\n");
// it's a linear machine
for (int i = 0; i < m_data.numAttributes(); i++) {
if (i != m_classIndex) {
text.append(
(m_weights[i] >= 0 ? " + " : " - ")
+ Utils.doubleToString(Math.abs(m_weights[i]), 12, 4)
+ " * ");
if (m_SVM.getFilterType().getSelectedTag().getID() == SMOreg.FILTER_STANDARDIZE) {
text.append("(standardized) ");
} else if (m_SVM.getFilterType().getSelectedTag().getID() == SMOreg.FILTER_NORMALIZE) {
text.append("(normalized) ");
}
text.append(m_data.attribute(i).name() + "\n");
}
}
} else {
// non linear, print out all supportvectors
text.append("Support vectors:\n");
for (int i = 0; i < m_nInstances; i++) {
if (m_alpha[i] > 0) {
text.append("+" + m_alpha[i] + " * k[" + i + "]\n");
}
if (m_alphaStar[i] > 0) {
text.append("-" + m_alphaStar[i] + " * k[" + i + "]\n");
}
}
}
text.append((m_b <= 0 ? " + " : " - ") + Utils.doubleToString(Math.abs(m_b), 12, 4) + "\n\n");
text.append("\n\nNumber of kernel evaluations: " + m_nEvals);
if (m_nCacheHits >= 0 && m_nEvals > 0) {
double hitRatio = 1 - m_nEvals * 1.0 / (m_nCacheHits + m_nEvals);
text.append(" (" + Utils.doubleToString(hitRatio * 100, 7, 3).trim() + "% cached)");
}
return text.toString();
}
