void SingleCRT::toPoly(ZZX& poly, const IndexSet& s) const
{
IndexSet s1 = map.getIndexSet() & s;
if (card(s1) == 0) {
clear(poly);
return;
}
ZZ p = to_ZZ(context.ithPrime(s1.first())); // the first modulus
poly = map[s1.first()]; // Get poly modulo the first prime
vec_ZZ& vp = poly.rep;
// ensure that coeficient vector is of size phi(m) with entries in [-p/2,p/2]
long phim = context.zMstar.phiM();
long vpLength = vp.length();
if (vpLength<phim) { // just in case of leading zeros in poly
vp.SetLength(phim);
for (long j=vpLength; j<phim; j++) vp[j]=0;
}
ZZ p_over_2 = p/2;
for (long j=0; j<phim; j++) if (vp[j] > p_over_2) vp[j] -= p;
// do incremental integer CRT for other levels
for (long i = s1.next(s1.first()); i <= s1.last(); i = s1.next(i)) {
long q = context.ithPrime(i); // the next modulus
// CRT the coefficient vectors of poly and current
intVecCRT(vp, p, map[i].rep, q); // defined in the module NumbTh
p *= q; // update the modulus
}
poly.normalize(); // need to call this after we work on the coeffs
}
// If the IndexSet is omitted, default to all the primes in the chain
void PowerfulDCRT::ZZXtoPowerful(Vec<ZZ>& out, const ZZX& poly,
IndexSet set) const
{
if (empty(set))
set = IndexSet(0, pConvVec.length()-1);
zz_pBak bak; bak.save(); // backup NTL's current modulus
ZZ product = conv<ZZ>(1L);
for (long i = set.first(); i <= set.last(); i = set.next(i)) {
pConvVec[i].restoreModulus();
long newPrime = zz_p::modulus();
zz_pX oneRowPoly;
conv(oneRowPoly, poly); // reduce mod p and convert to zz_pX
HyperCube<zz_p> oneRowPwrfl(indexes.shortSig);
pConvVec[i].polyToPowerful(oneRowPwrfl, oneRowPoly);
if (i == set.first()) // just copy
conv(out, oneRowPwrfl.getData());
else // CRT
intVecCRT(out, product, oneRowPwrfl.getData(), newPrime); // in NumbTh
product *= newPrime;
}
}
void PowerfulDCRT::dcrtToPowerful(Vec<ZZ>& out, const DoubleCRT& dcrt) const
{
const IndexSet& set = dcrt.getIndexSet();
if (empty(set)) { // sanity check
clear(out);
return;
}
zz_pBak bak; bak.save(); // backup NTL's current modulus
ZZ product = conv<ZZ>(1L);
for (long i = set.first(); i <= set.last(); i = set.next(i)) {
pConvVec[i].restoreModulus();
zz_pX oneRowPoly;
long newPrime = dcrt.getOneRow(oneRowPoly,i);
HyperCube<zz_p> oneRowPwrfl(indexes.shortSig);
pConvVec[i].polyToPowerful(oneRowPwrfl, oneRowPoly);
if (i == set.first()) // just copy
conv(out, oneRowPwrfl.getData());
else // CRT
intVecCRT(out, product, oneRowPwrfl.getData(), newPrime); // in NumbTh
product *= newPrime;
}
}
