public function getLogLikelihood()
     {
         $voccnt = $this->voccnt;
         $lik = 0;
         $b = $this->b;
         $a = $this->a;
         foreach ($this->count_topics_words as $topic=>$words) {
             $lik += $this->log_multi_beta(
                $words,
                $b
             );
             $lik -= $this->log_multi_beta(
                $b,
                0,
                $voccnt
             );
         }
         foreach ($this->count_docs_topics as $doc=>$topics) {
             $lik += $this->log_multi_beta(
                $topics,
                $a
             );
             $lik -= $this->log_multi_beta(
                $a,
                0,
                $this->ntopics
             );
         }

         return $lik;
     }