Below is an algorithm for union of two quasi reduced BDDs p and q resulting in r.
bdd Union(bdd p, bdd q)
local bdd r;
1 if p=0 or q=1 then return q;
2 if q=0 or p=1 then return p;
3 if p=q then return p;
4 if Cachecontainsentry⟨UnionCODE,{p,q}:r⟩ then return r;
//p.lvl = q.lvl in case of quasi reduced BDDs
5 r ← UniqueTableInsert(p.lvl, Union(p[0], q[0]), Union(p[1], q[1]));
6 enter⟨UnionCODE,{p,q}:r⟩ in Cache;
7 return r;
Since there is no variable skipping, p.lvl is always equal to q.lvl. I have a question about this algorithm.
If I want to implement Xor or Xnor for quasi-reduced BDDs, can it be done the same way as union or should I implement the expression pq' + p'q where q' = !q.
