void ARingZZpFFPACK::power(ElementType &result, const ElementType a, STT n) const
{
if (is_zero(a))
{
if (n < 0)
ERROR("division by zero");
set(result, a);
return;
}
ElementType base;
set(base, a);
if (n < 0)
{
invert(base,base);
n = -n;
}
n = n % (mCharac-1);
set_from_int(result, 1);
if (n == 0)
return;
// Now use doubling algorithm
M2_ASSERT(n > 0);
for (;;)
{
if ((n % 2) != 0)
mFfpackField.mulin(result,base); // result *= base
n >>= 1;
if (n == 0)
return;
else
mFfpackField.mulin(base, base); // base = base^2
}
}
ARingZZpFFPACK::ElementType ARingZZpFFPACK::computeGenerator() const
{
for (UTT currIntElem=2; currIntElem < mCharac; currIntElem++)
{
ElementType currElem;
set_from_int(currElem, currIntElem);
bool found = true;
ElementType tmpElem = currElem;
for (UTT count=0;count < mCharac-2; count++)
{
mult(tmpElem, tmpElem, currElem);
if (is_equal(currElem, tmpElem))
found = false;
}
if (found)
{
std::cerr << "generator = " << currElem << std::endl;
return currElem;
}
}
M2_ASSERT(false); // we should not get here, if the program logic is OK
return ElementType(1);
}
bool ARingGF::promote(const Ring *Rf, const ring_elem f, ElementType &result) const
{
if (mOriginalRing != Rf) return false;
result = givaroField.zero;
int exp[1];
ElementType genRep;
givaroField.generator(genRep);
std::cerr << "genRep " << genRep << std::endl;
for (Nterm *t = f; t != NULL; t = t->next)
{
elem a, b;
int coeff = mOriginalRing->getCoefficientRing()->coerce_to_int(t->coeff);
set_from_int(a, coeff);
mOriginalRing->getMonoid()->to_expvector(t->monom, exp);
// exp[0] is the variable we want. Notice that since the ring is a quotient,
// this degree is < n (where Q_ = P^n).
power(b, genRep, exp[0]);
mult(a, a, b);
add(result, result, a);
}
return true;
}
