private Pair<Double,Long> compareLang(LearnerGraph from, LearnerGraph to,
Collection<List<Label>> sequences)
{
final long startTime = System.nanoTime();
ConfusionMatrix matrix = classify(sequences, from,to);
final long duration = System.nanoTime() - startTime;
double result = matrix.fMeasure();
assert !Double.isNaN(result);
return new Pair<Double,Long>(result,duration);
}