docs: public static DMatrixRMaj triangularUpper(int dimen , int hessenberg , double min , double max , Random rand )
      {
          if( hessenberg < 0 )
              throw new RuntimeException("hessenberg must be more than or equal to 0");
  
          double range = max-min;
  
          DMatrixRMaj A = new DMatrixRMaj(dimen,dimen);
  
          for( int i = 0; i < dimen; i++ ) {
              int start = i <= hessenberg ? 0 : i-hessenberg;
  
              for( int j = start; j < dimen; j++ ) {
                  A.set(i,j, rand.nextDouble()*range+min);
              }
  
          }
  
          return A;
      }