void MinPolyMod(zz_pX& hh, const zz_pX& g, const zz_pXModulus& F, long m)
{
zz_pX h, h1;
long n = F.n;
if (m < 1 || m > n) Error("MinPoly: bad args");
/* probabilistically compute min-poly */
ProbMinPolyMod(h, g, F, m);
if (deg(h) == m) { hh = h; return; }
CompMod(h1, h, g, F);
if (IsZero(h1)) { hh = h; return; }
/* not completely successful...must iterate */
long i;
zz_pX h2, h3;
zz_pXMultiplier H1;
vec_zz_p R(INIT_SIZE, n);
for (;;) {
R.SetLength(n);
for (i = 0; i < n; i++) random(R[i]);
build(H1, h1, F);
UpdateMap(R, R, H1, F);
DoMinPolyMod(h2, g, F, m-deg(h), R);
mul(h, h, h2);
if (deg(h) == m) { hh = h; return; }
CompMod(h3, h2, g, F);
MulMod(h1, h3, H1, F);
if (IsZero(h1)) { hh = h; return; }
}
}
long ProbComputeDegree(const ZZ_pX& h, const ZZ_pXModulus& F)
{
if (F.n == 1 || IsX(h))
return 1;
long n = F.n;
ZZ_pX P1, P2, P3;
random(P1, n);
TraceMap(P2, P1, n, F, h);
ProbMinPolyMod(P3, P2, F, n/2);
long r = deg(P3);
if (r <= 0 || n % r != 0)
return 0;
else
return n/r;
}
