long RecComputeDegree(long u, const ZZ_pEX& h, const ZZ_pEXModulus& F,
FacVec& fvec)
{
if (IsX(h)) return 1;
if (fvec[u].link == -1) return BaseCase(h, fvec[u].q, fvec[u].a, F);
ZZ_pEX h1, h2;
long q1, q2, r1, r2;
q1 = fvec[fvec[u].link].val;
q2 = fvec[fvec[u].link+1].val;
TandemPowerCompose(h1, h2, h, q1, q2, F);
r1 = RecComputeDegree(fvec[u].link, h2, F, fvec);
r2 = RecComputeDegree(fvec[u].link+1, h1, F, fvec);
return r1*r2;
}
long ComputeDegree(const ZZ_pX& h, const ZZ_pXModulus& F)
// f = F.f is assumed to be an "equal degree" polynomial
// h = X^p mod f
// the common degree of the irreducible factors of f is computed
{
if (F.n == 1 || IsX(h)) return 1;
FacVec fvec;
FactorInt(fvec, F.n);
return RecComputeDegree(fvec.length()-1, h, F, fvec);
}
