pqc/external/flint-2.4.3/nmod_poly/sqrt_series.c
2014-05-24 23:16:06 +02:00

100 lines
2.6 KiB
C

/*=============================================================================
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 William Hart
Copyright (C) 2011 Fredrik Johansson
******************************************************************************/
#include <stdlib.h>
#include <gmp.h>
#include "flint.h"
#include "nmod_vec.h"
#include "nmod_poly.h"
#include "ulong_extras.h"
void
_nmod_poly_sqrt_series(mp_ptr g, mp_srcptr h, slong n, nmod_t mod)
{
mp_ptr t = _nmod_vec_init(n);
_nmod_poly_invsqrt_series(t, h, n, mod);
_nmod_poly_mullow(g, t, n, h, n, n, mod);
_nmod_vec_clear(t);
}
void
nmod_poly_sqrt_series(nmod_poly_t g, const nmod_poly_t h, slong n)
{
mp_ptr g_coeffs, h_coeffs;
nmod_poly_t t1;
slong hlen;
hlen = h->length;
if (n == 0)
{
flint_printf("Exception (nmod_poly_sqrt_series). Division by zero.\n");
abort();
}
if (h->length == 0 || h->coeffs[0] != UWORD(1))
{
flint_printf("Exception (nmod_poly_sqrt_series). Requires constant term 1.\n");
abort();
}
if (hlen < n)
{
h_coeffs = _nmod_vec_init(n);
flint_mpn_copyi(h_coeffs, h->coeffs, hlen);
flint_mpn_zero(h_coeffs + hlen, n - hlen);
}
else
h_coeffs = h->coeffs;
if (h == g && hlen >= n)
{
nmod_poly_init2(t1, h->mod.n, n);
g_coeffs = t1->coeffs;
}
else
{
nmod_poly_fit_length(g, n);
g_coeffs = g->coeffs;
}
_nmod_poly_sqrt_series(g_coeffs, h_coeffs, n, h->mod);
if (h == g && hlen >= n)
{
nmod_poly_swap(g, t1);
nmod_poly_clear(t1);
}
g->length = n;
if (hlen < n)
_nmod_vec_clear(h_coeffs);
_nmod_poly_normalise(g);
}