// knn search.
  arma::Mat<size_t> neighbors;
  arma::mat distances;

  KNN knn(dataset);
  knn.Search(N - 1, neighbors, distances);

  // Initialize impostors & targetNeighbors.
  arma::mat impostors(N, N);
  impostors.fill(arma::datum::inf);
  arma::mat targetNeighors(k, N, arma::fill::zeros);

  size_t impCount = 0;

  // Generate k Target Neighbors and variable number of impostors that invade last element boundary
  // for each data points.
  for (size_t i = 0; i < N; i++)
  {
    for( size_t j=0, gen=0, imp = 0; j < N && gen < k; j++ )
    {
      if( labels.at( neighbors.col(i)[j] ) == labels[i] )
      {
        targetNeighors.col(i)[gen++] = neighbors.col(i)[j];
      }
      else
      {
        impostors.col(i)[imp++] = neighbors.col(i)[j];
        impCount++;
      }
    }
  }

  // Generate Triplets.
  triplets = arma::mat(3, k * impCount , arma::fill::zeros);

  for( size_t i=0, r=0; i < N; i++ )
  {
    for( size_t j=0;j < k; j++)
    {
      for( size_t l=0; arma::is_finite(impostors.col(i)[l]); l++, r++ )
      {
          triplets(0, r) = i;
          triplets(1, r) = targetNeighors.col(i)[j];
          triplets(2, r) = impostors.col(i)[l];
      }
    }
  }