using eigen triangular view to add col * col'
using eigen triangular view to add col * col'

jaak-s/macau,ExaScience/smurff,ExaScience/smurff,ExaScience/smurff,ExaScience/smurff,ExaScience/smurff,jaak-s/macau,ExaScience/smurff,jaak-s/macau