public void all_set( long val ) {
      long[] t = _t;
      for( int i=0; i<t.length; i++ ) 
        t[i] = val;
      if( _next != null ) _next.all_set(val);
      if( _sum_cache != Long.MIN_VALUE )
        _sum_cache = Long.MIN_VALUE; // Blow out cache
    }