void assignBalWeights( double[][] A )
	{
		edge e;
		e = depthFirstTraverse( null );
	  	while ( null != e ) 
	  	{
	  		if ( e.head.leaf() || e.tail.leaf() )
	  			e.WFext(A);
	  		else
	      	e.WFint(A);
	  		e = depthFirstTraverse( e );
	  	}
	}