private void do_find_best_parameters(svm_problem svmProblem) {
svm_parameter svmParam = getDefaultSvmParameters();
setWeights(svmParam);
int maxIter =
((int) Math.ceil(Math.abs((log2cEnd - log2cBegin) / log2cStep)) + 1)
* ((int) Math.ceil(Math.abs((log2gEnd - log2gBegin) / log2gStep)) + 1);
// Run the grid search in separate CV threads
ExecutorService executorService = Executors.newFixedThreadPool(numberOfThreads);
List<CvParams> cvParamsList = new ArrayList<CvParams>();
for (double log2c = log2cBegin;
(log2cBegin < log2cEnd && log2c <= log2cEnd)
|| (log2cBegin >= log2cEnd && log2c >= log2cEnd);
log2c += log2cStep) {
double c1 = Math.pow(2, log2c);
for (double log2g = log2gBegin;
(log2gBegin < log2gEnd && log2g <= log2gEnd)
|| (log2gBegin >= log2gEnd && log2g >= log2gEnd);
log2g += log2gStep) {
double gamma1 = Math.pow(2, log2g);
svm_parameter svmParam1 = (svm_parameter) svmParam.clone();
svmParam1.C = c1;
svmParam1.gamma = gamma1;
executorService.execute(
new RunnableSvmCrossValidator(svmProblem, svmParam1, nrFold, cvParamsList));
}
}
// now wait for all threads to complete by calling shutdown
// note that this will NOT terminate the currently running threads, it just signals the thread
// pool to closeWriter
// once all work is completed
executorService.shutdown();
while (!executorService.isTerminated()) {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// don't care if we get interrupted
}
// every second, report statistics
logger.debug(
String.format("%% complete: %5.2f", cvParamsList.size() / (double) maxIter * 100));
CvParams best = getBestCvParams(cvParamsList);
CvParams worst = getWorstcvParams(cvParamsList);
if (best != null) {
logger.debug("Best accuracy: " + best.accuracy);
logger.debug("Best C: " + best.c);
logger.debug("Best Gamma: " + best.gamma);
}
if (worst != null) {
logger.debug("Worst accuracy: " + worst.accuracy);
}
}
CvParams best = getBestCvParams(cvParamsList);
CvParams worst = getWorstcvParams(cvParamsList);
if (best != null) {
logger.debug("Best accuracy: " + best.accuracy);
logger.debug("Best C: " + best.c);
logger.debug("Best Gamma: " + best.gamma);
c = best.c;
gamma = best.gamma;
} else {
logger.error("Best CV parameters is null.");
}
if (worst != null) {
logger.debug("Worst accuracy: " + worst.accuracy);
}
}
