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// Copyright 2014 Michael E. Stillman
#include "aring-gf-flint.hpp"
#include "relem.hpp"
#include "poly.hpp"
#include "ringmap.hpp"
namespace M2 {
ARingGFFlint::ARingGFFlint(const PolynomialRing& R, const ring_elem a)
: mOriginalRing(R),
mCharacteristic(R.characteristic()),
mGeneratorComputed(false)
{
ring_elem b = R.copy(a);
mPrimitiveElement = RingElement::make_raw(&R, b);
ring_elem minpoly = mOriginalRing.quotient_element(0);
std::vector<long> poly;
RingElement F(&R, minpoly);
F.getSmallIntegerCoefficients(poly);
// warning: flint expects unsigned longs, so we must make
// all of these coeffs non-negative.
for (long i = poly.size() - 1; i >= 0; i--)
{
long a = poly[i];
if (a == 0) continue;
if (a < 0) poly[i] += characteristic();
}
mDimension = poly.size() - 1;
#if 0
printf("minpoly: ");
for (long i=0; i<poly.size(); i++)
printf(" %ld", poly[i]);
printf("\n");
#endif
nmod_poly_t mMinPoly;
nmod_poly_init(mMinPoly, R.characteristic());
for (long i = poly.size() - 1; i >= 0; i--)
if (poly[i] != 0) nmod_poly_set_coeff_ui(mMinPoly, i, poly[i]);
fq_zech_ctx_init_modulus(mContext, mMinPoly, "a");
fq_nmod_ctx_init_modulus(mBigContext, mMinPoly, "a");
#if 0
fq_zech_ctx_print(mContext);
#endif
nmod_poly_clear(mMinPoly);
// powers of p, as ulongs's
mPPowers = newarray_atomic(mp_limb_t, mDimension + 1);
mPPowers[0] = 1;
for (long i = 1; i <= mDimension; i++)
mPPowers[i] = mPPowers[i - 1] * static_cast<ulong>(mCharacteristic);
flint_randinit(mRandomState);
}
ARingGFFlint::~ARingGFFlint()
{
fq_zech_ctx_clear(mContext);
fq_nmod_ctx_clear(mBigContext);
mPrimitiveElement = 0;
freemem(mPPowers);
flint_randclear(mRandomState);
if (mGeneratorComputed) fq_zech_clear(&mCachedGenerator, mContext);
}
void ARingGFFlint::getSmallIntegerCoefficients(const ElementType& a,
std::vector<long>& poly) const
{
fq_nmod_t f;
fq_nmod_init(f, mBigContext);
fq_zech_get_fq_nmod(f, &a, mContext);
long deg = nmod_poly_degree(f);
poly.resize(deg + 1);
for (long i = deg; i >= 0; i--) poly[i] = nmod_poly_get_coeff_ui(f, i);
fq_nmod_clear(f, mBigContext);
}
void ARingGFFlint::fromSmallIntegerCoefficients(
ElementType& result,
const std::vector<long>& poly) const
{
fq_nmod_t f;
fq_nmod_init(f, mBigContext);
#if 0
printf("input = ");
for (long i=0; i<poly.size(); i++)
printf("%ld ", poly[i]);
printf("\n");
#endif
for (long i = poly.size() - 1; i >= 0; i--)
{
long a = poly[i];
if (a == 0) continue;
if (a < 0) a += characteristic();
nmod_poly_set_coeff_ui(f, i, a);
}
#if 0
printf(" result before reduction = ");
fq_nmod_print_pretty(f, mBigContext);
printf("\n");
#endif
fq_nmod_reduce(f, mBigContext);
#if 0
printf(" result = ");
fq_nmod_print_pretty(f, mBigContext);
printf("\n");
#endif
fq_zech_set_fq_nmod(&result, f, mContext);
#if 0
printf(" zech result = %lu", result.value);
printf("\n");
#endif
fq_nmod_clear(f, mBigContext);
}
void ARingGFFlint::getGenerator(ElementType& result_gen) const
{
if (not mGeneratorComputed)
{
fq_zech_init(&mCachedGenerator, mContext);
if (mCharacteristic == 2 and mDimension == 1)
// This is currently a bug in flint...
set_from_long(mCachedGenerator, 1);
else
fq_zech_gen(&mCachedGenerator, mContext);
mGeneratorComputed = true;
}
copy(result_gen, mCachedGenerator);
}
bool ARingGFFlint::promote(const Ring* Rf,
const ring_elem f,
ElementType& result) const
{
if (&originalRing() != Rf) return false;
std::vector<long> poly;
RingElement F(Rf, f);
F.getSmallIntegerCoefficients(poly);
fromSmallIntegerCoefficients(result, poly);
return true;
}
void ARingGFFlint::lift_to_original_ring(ring_elem& result,
const ElementType& f) const
{
std::vector<long> poly;
getSmallIntegerCoefficients(f, poly);
result =
originalRing().getNumeratorRing()->fromSmallIntegerCoefficients(poly, 0);
}
bool ARingGFFlint::lift(const Ring* Rg,
const ElementType& f,
ring_elem& result) const
{
// Rg = ZZ/p[x]/F(x) ---> GF(p,n)
if (&originalRing() != Rg) return false;
lift_to_original_ring(result, f);
return true;
}
void ARingGFFlint::eval(const RingMap* map,
const ElementType& f,
int first_var,
ring_elem& result) const
{
// f is represented by: f.value, the power of the generator
if (is_zero(f))
result = map->get_ring()->zero();
else
result =
map->get_ring()->power(map->elem(first_var), static_cast<int>(f.value));
}
void ARingGFFlint::text_out(buffer& o) const
{
o << "GF(" << characteristic() << "^" << dimension() << ",Flint)";
}
void ARingGFFlint::elem_text_out(buffer& o,
const ElementType& a,
bool p_one,
bool p_plus,
bool p_parens) const
{
if (is_zero(a))
{
o << "0";
return;
}
ring_elem b;
lift(&originalRing(), a, b);
originalRing().elem_text_out(o, b, p_one, p_plus, p_parens);
}
int ARingGFFlint::compare_elems(const ElementType& f,
const ElementType& g) const
{
if (f.value > g.value) return GT;
if (f.value < g.value) return LT;
return EQ;
}
};
// Local Variables:
// compile-command: "make -C $M2BUILDDIR/Macaulay2/e "
// indent-tabs-mode: nil
// End:
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