docs: public void setK(final int K)
      {
          if(K < 2)
              throw new IllegalArgumentException("At least 2 topics must be learned");
          this.K = K;
          gammaLocal = new ThreadLocal<Vec>()
          {
              @Override
              protected Vec initialValue()
              {
                  return new DenseVector(K);
              }
          };
          logThetaLocal  = new ThreadLocal<Vec>()
          {
              @Override
              protected Vec initialValue()
              {
                  return new DenseVector(K);
              }
          };
          expLogThetaLocal = new ThreadLocal<Vec>()
          {
              @Override
              protected Vec initialValue()
              {
                  return new DenseVector(K);
              }
          };
          
          lambda = null;
      }