To speed up the training, we train the vectors in parallel with shared parameters, and they are updated asynchronously.
top 1 accuracy or error rate for each category is frequently used metric for this task, however, in this case these rank-based measures may not be an appropriate measure since the total number of unique n-grams (e.g., SISG) or unique words (e.g., SG) over the same corpus largely differ from each other.