C++ (Cpp) MulByXMod Examples

Example #1

File: lzz_pX1.c Project: av-elier/fast-exponentiation-algs

void PlainUpdateMap(vec_zz_p& xx, const vec_zz_p& a, 
                    const zz_pX& b, const zz_pX& f)
{
   long n = deg(f);
   long i, m;

   if (IsZero(b)) {
      xx.SetLength(0);
      return;
   }

   m = n-1 - deg(b);

   vec_zz_p x(INIT_SIZE, n);

   for (i = 0; i <= m; i++)
      InnerProduct(x[i], a, b.rep, i);

   if (deg(b) != 0) {
      zz_pX c(INIT_SIZE, n);
      LeftShift(c, b, m);

      for (i = m+1; i < n; i++) {
         MulByXMod(c, c, f);
         InnerProduct(x[i], a, c.rep);
      }
   }

   xx = x;
}

Example #2

File: lzz_pXCharPoly.cpp Project: shayne-fletcher/cppf

NTL_START_IMPL

static
void HessCharPoly(zz_pX& g, const zz_pX& a, const zz_pX& f)
{
   long n = deg(f);
   if (n <= 0 || deg(a) >= n)
      Error("HessCharPoly: bad args");

   mat_zz_p M;
   M.SetDims(n, n);

   long i, j;

   zz_pX t;
   t = a;

   for (i = 0; i < n; i++) {
      for (j = 0; j < n; j++) 
         M[i][j] = coeff(t, j);

      if (i < n-1) 
         MulByXMod(t, t, f);
   }

   CharPoly(g, M);
}

Example #3

File: ZZ_pEXFactoring.cpp Project: Brainloop-Security/secret-sharing

static
void MulByXPlusY(vec_ZZ_pEX& h, const ZZ_pEX& f, const ZZ_pEX& g)
// h represents the bivariate polynomial h[0] + h[1]*Y + ... + h[n-1]*Y^k,
// where the h[i]'s are polynomials in X, each of degree < deg(f),
// and k < deg(g).
// h is replaced by the bivariate polynomial h*(X+Y) (mod f(X), g(Y)).

{
   long n = deg(g);
   long k = h.length()-1;

   if (k < 0) return;

   if (k < n-1) {
      h.SetLength(k+2);
      h[k+1] = h[k];
      for (long i = k; i >= 1; i--) {
         MulByXMod(h[i], h[i], f);
         add(h[i], h[i], h[i-1]);
      }
      MulByXMod(h[0], h[0], f);
   }
   else {
      ZZ_pEX b, t;

      b = h[n-1];
      for (long i = n-1; i >= 1; i--) {
         mul(t, b, g.rep[i]);
         MulByXMod(h[i], h[i], f);
         add(h[i], h[i], h[i-1]);
         sub(h[i], h[i], t);
      }
      mul(t, b, g.rep[0]);
      MulByXMod(h[0], h[0], f);
      sub(h[0], h[0], t);
   }

   // normalize

   k = h.length()-1;
   while (k >= 0 && IsZero(h[k])) k--;
   h.SetLength(k+1);
}