pqc/external/flint-2.4.3/fmpz_poly_factor/factor_squarefree.c

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2014-05-18 22:03:37 +00:00
/*=============================================================================
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 Andy Novocin
Copyright (C) 2011 Sebastian Pancratz
******************************************************************************/
#include <stdlib.h>
#include <gmp.h>
#include "flint.h"
#include "fmpz.h"
#include "fmpz_poly.h"
void fmpz_poly_factor_squarefree(fmpz_poly_factor_t fac, const fmpz_poly_t F)
{
fmpz_poly_content(&(fac->c), F);
if (fmpz_sgn(fmpz_poly_lead(F)) < 0)
fmpz_neg(&(fac->c), &(fac->c));
if (F->length > 1)
{
fmpz_poly_t f, d, t1;
fmpz_poly_init(f);
fmpz_poly_init(d);
fmpz_poly_init(t1);
fmpz_poly_scalar_divexact_fmpz(f, F, &(fac->c));
fmpz_poly_derivative(t1, f);
fmpz_poly_gcd(d, f, t1);
if (d->length == 1)
{
fmpz_poly_factor_insert(fac, f, 1);
}
else
{
fmpz_poly_t v, w, s;
slong i;
fmpz_poly_init(v);
fmpz_poly_init(w);
fmpz_poly_init(s);
fmpz_poly_div(v, f, d);
fmpz_poly_div(w, t1, d);
for (i = 1; ; i++)
{
fmpz_poly_derivative(t1, v);
fmpz_poly_sub(s, w, t1);
if (s->length == 0)
{
if (v->length > 1)
fmpz_poly_factor_insert(fac, v, i);
break;
}
fmpz_poly_gcd(d, v, s);
fmpz_poly_div(v, v, d);
fmpz_poly_div(w, s, d);
if (d->length > 1)
fmpz_poly_factor_insert(fac, d, i);
}
fmpz_poly_clear(v);
fmpz_poly_clear(w);
fmpz_poly_clear(s);
}
fmpz_poly_clear(f);
fmpz_poly_clear(d);
fmpz_poly_clear(t1);
}
}