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/*=============================================================================
This file is part of FLINT.
FLINT is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
FLINT is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with FLINT; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
=============================================================================*/
/******************************************************************************
Copyright (C) 2011 Fredrik Johansson
Copyright (C) 2012 Lina Kulakova
******************************************************************************/
#include <gmp.h>
#include "flint.h"
#include "fmpz_vec.h"
#include "fmpz_mod_poly.h"
#include "ulong_extras.h"
void
_fmpz_mod_poly_compose_mod(fmpz * res, const fmpz * f, slong lenf, const fmpz * g,
const fmpz * h, slong lenh, const fmpz_t p)
{
if (lenh < 12 || lenf >= lenh)
_fmpz_mod_poly_compose_mod_horner(res, f, lenf, g, h, lenh, p);
else
_fmpz_mod_poly_compose_mod_brent_kung(res, f, lenf, g, h, lenh, p);
}
void
fmpz_mod_poly_compose_mod(fmpz_mod_poly_t res, const fmpz_mod_poly_t poly1,
const fmpz_mod_poly_t poly2, const fmpz_mod_poly_t poly3)
{
fmpz_t inv3;
slong len1 = poly1->length;
slong len2 = poly2->length;
slong len3 = poly3->length;
slong len = len3 - 1;
slong vec_len = FLINT_MAX(len3 - 1, len2);
fmpz * ptr2;
if (len3 == 0)
{
flint_printf("Exception (fmpz_mod_poly_compose_mod)."
"Division by zero.\n");
abort();
}
if (len1 == 0 || len3 == 1)
{
fmpz_mod_poly_zero(res);
return;
}
if (len1 == 1)
{
fmpz_mod_poly_set(res, poly1);
return;
}
if (res == poly3 || res == poly1)
{
fmpz_mod_poly_t tmp;
fmpz_mod_poly_init(tmp, &res->p);
fmpz_mod_poly_compose_mod(tmp, poly1, poly2, poly3);
fmpz_mod_poly_swap(tmp, res);
fmpz_mod_poly_clear(tmp);
return;
}
ptr2 = _fmpz_vec_init(vec_len);
if (len2 <= len)
{
_fmpz_vec_set(ptr2, poly2->coeffs, len2);
_fmpz_vec_zero(ptr2 + len2, len - len2);
}
else
{
fmpz_init(inv3);
fmpz_invmod(inv3, poly3->coeffs + len, &res->p);
_fmpz_mod_poly_rem(ptr2, poly2->coeffs, len2,
poly3->coeffs, len3, inv3, &res->p);
fmpz_clear(inv3);
}
fmpz_mod_poly_fit_length(res, len);
_fmpz_mod_poly_compose_mod(res->coeffs,
poly1->coeffs, len1, ptr2, poly3->coeffs, len3, &res->p);
_fmpz_mod_poly_set_length(res, len);
_fmpz_mod_poly_normalise(res);
_fmpz_vec_clear(ptr2, vec_len);
}
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