docs: public static boolean isEquivalent(DMatrix a , DMatrix b , double tol )
      {
          if( a.getNumRows() != b.getNumRows() || a.getNumCols() != b.getNumCols() )
              return false;
  
          for( int i = 0; i < a.getNumRows(); i++ ) {
              for( int j = 0; j < a.getNumCols(); j++ ) {
                  double diff = Math.abs(a.get(i,j) - b.get(i,j));
  
                  if( diff > tol )
                      return false;
              }
          }
  
          return true;
      }