rank_k_ref_d8x6.h

  if ( aux->pc ) {
   for ( j = 0; j < 6; j ++ ) {
     for ( i = 0; i < 8; i ++ ) {
      K[ j * 8 + i ] += c[ j * 8 + i ];
     }
   }
  }
  for ( p = 0; p < k; p ++ ) {
   for ( j = 0; j < 6; j ++ ) {
     for ( i = 0; i < 8; i ++ ) {
      K[ j * 8 + i ] += a[ i ] * b [ j ];
     }
   }
   a += 8;
   b += 8;
  }