// Panic if i is not in any DAG.
func (po *poset) findroot(i uint32) uint32 {
	// TODO(rasky): if needed, a way to speed up this search is
	// storing a bitset for each root using it as a mini bloom filter
	// of nodes present under that root.
	for _, r := range po.roots {
		if po.reaches(r, i, false) {
			return r
		}
	}
	panic("findroot didn't find any root")
}

		if _, ok := found[k]; !ok {
			delete(d.Cache, k)
		}
	}
}

// StringAll returns a detailed string representation of all entries in the cache.
func (d *dataUsageCache) StringAll() string {
	// Remove bloom filter from print.
	s := fmt.Sprintf("info:%+v\n", d.Info)
	for k, v := range d.Cache {
		s += fmt.Sprintf("\t%v: %+v\n", k, v)
	}
	return strings.TrimSpace(s)
}