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polynomial fixes

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This commit is contained in:
Mirek Kratochvil 2012-04-07 16:46:56 +02:00
parent e4c75fe0e0
commit b4381c473e
1 changed files with 33 additions and 14 deletions

47
lib/polynomial.cpp
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@ -39,6 +39,10 @@ void polynomial::add_mult (const polynomial&f, uint mult, gf2m&fld)
void polynomial::mod (const polynomial&f, gf2m&fld)
{
int df = f.degree();
if (df < 0) { //mod 0 -> 0
clear();
return;
}
int d;
uint hi = fld.inv (f[df]);
// while there's place to substract, reduce by x^(d-df)-multiply of f
@ -271,20 +275,36 @@ void polynomial::sqrt (vector<polynomial>& sqInv, gf2m&fld)
void polynomial::div (polynomial&p, polynomial&m, gf2m&fld)
{
int degp = p.degree();
if (degp < 0) return;
polynomial r0, r1, s0, s1, s2, q1, q2;
uint headInv = fld.inv (p[degp]);
polynomial A = *this;
A.mod (m, fld);
clear();
int da;
while ( (da = A.degree() ) >= degp) {
int rp = da - degp;
if (size() < rp + 1) resize (rp + 1, 0);
item (rp) = fld.mult (headInv, A[da]);
for (uint i = 0; i <= degp; ++i)
A[i+rp] = fld.add (A[i+rp], fld.mult (item (rp), p[i]) );
r0 = m;
r1 = p;
r1.mod (m, fld);
s0.clear();
s1 = *this;
s1.mod (m, fld);
while (r1.degree() >= 0) {
r0.divmod (r1, q1, q2, fld);
r0.swap (r1);
r1.swap (q2);
s2 = s0;
q1.mult (s1, fld);
q1.mod (m, fld);
s2.add (q1, fld);
s0.swap (s1);
s1.swap (s2);
}
*this = s0;
if (r0.degree() >= 0) {
uint m = fld.inv (r0[r0.degree() ]);
for (uint i = 0; i < size(); ++i) item (i) = fld.mult (item (i), m);
}
}
@ -320,7 +340,6 @@ void polynomial::mod_to_fracton (polynomial&a, polynomial&b, polynomial&m, gf2m&
int deg = m.degree() / 2;
polynomial a0, a1, b0, b1, t1, t2;
a0 = m;
a0.make_monic (fld);
a1 = *this;
a1.mod (m, fld);
b0.resize (1, 0);