docs: public double dissimilarity(int ni, int nj, int nk, double d_ij, double d_ik, double d_jk)
      {
          return  aConst(true, ni, nj, nk)  * d_ik  +
                  aConst(false, ni, nj, nk) * d_jk  + 
                  bConst(ni, nj, nk)        * d_ij  + 
                  cConst(ni, nj, nk)        * abs(d_ik-d_jk);
      }