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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
******************************************************************************/
#include <gmp.h>
#include "flint.h"
#include "nmod_vec.h"
#include "nmod_poly.h"
#include "ulong_extras.h"
void
_nmod_poly_compose_mod_horner(mp_ptr res,
mp_srcptr f, slong lenf, mp_srcptr g, mp_srcptr h, slong lenh, nmod_t mod)
{
slong i, len;
mp_ptr t;
if (lenh == 1)
return;
if (lenf == 1)
{
res[0] = f[0];
return;
}
if (lenh == 2)
{
res[0] = _nmod_poly_evaluate_nmod(f, lenf, g[0], mod);
return;
}
len = lenh - 1;
i = lenf - 1;
t = _nmod_vec_init(len);
_nmod_vec_scalar_mul_nmod(res, g, len, f[i], mod);
i--;
if (i >= 0)
res[0] = nmod_add(res[0], f[i], mod);
while (i > 0)
{
i--;
_nmod_poly_mulmod(t, res, len, g, len, h, lenh, mod);
_nmod_poly_add(res, t, len, f + i, 1, mod);
}
_nmod_vec_clear(t);
}
void
nmod_poly_compose_mod_horner(nmod_poly_t res,
const nmod_poly_t poly1, const nmod_poly_t poly2,
const nmod_poly_t poly3)
{
slong len1 = poly1->length;
slong len2 = poly2->length;
slong len3 = poly3->length;
slong len = len3 - 1;
mp_ptr ptr2;
if (len3 == 0)
{
flint_printf("Exception (nmod_poly_compose_mod_horner). Division by zero.\n");
abort();
}
if (len1 == 0 || len3 == 1)
{
nmod_poly_zero(res);
return;
}
if (len1 == 1)
{
nmod_poly_set(res, poly1);
return;
}
if (res == poly3 || res == poly1)
{
nmod_poly_t tmp;
nmod_poly_init_preinv(tmp, res->mod.n, res->mod.ninv);
nmod_poly_compose_mod_horner(tmp, poly1, poly2, poly3);
nmod_poly_swap(tmp, res);
nmod_poly_clear(tmp);
return;
}
ptr2 = _nmod_vec_init(len);
if (len2 <= len)
{
flint_mpn_copyi(ptr2, poly2->coeffs, len2);
flint_mpn_zero(ptr2 + len2, len - len2);
}
else
{
_nmod_poly_rem(ptr2, poly2->coeffs, len2,
poly3->coeffs, len3, res->mod);
}
nmod_poly_fit_length(res, len);
_nmod_poly_compose_mod_horner(res->coeffs,
poly1->coeffs, len1, ptr2, poly3->coeffs, len3, res->mod);
res->length = len;
_nmod_poly_normalise(res);
_nmod_vec_clear(ptr2);
}
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