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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 Andy Novocin
Copyright (C) 2011 Sebastian Pancratz
******************************************************************************/
#include <gmp.h>
#include "flint.h"
#include "fmpz.h"
#include "fmpz_poly.h"
void fmpz_poly_hensel_build_tree(slong *link, fmpz_poly_t *v, fmpz_poly_t *w,
const nmod_poly_factor_t fac)
{
const slong r = fac->num;
const nmod_t mod = (fac->p + 0)->mod;
slong i, j;
nmod_poly_t d;
nmod_poly_t *V = flint_malloc((2*r - 2)*sizeof(nmod_poly_t));
nmod_poly_t *W = flint_malloc((2*r - 2)*sizeof(nmod_poly_t));
nmod_poly_init_preinv(d, mod.n, mod.ninv);
for (i = 0; i < 2*r - 2; i++)
{
nmod_poly_init_preinv(V[i], mod.n, mod.ninv);
nmod_poly_init_preinv(W[i], mod.n, mod.ninv);
}
for (i = 0; i < r; i++)
{
nmod_poly_set(V[i], fac->p + i);
link[i] = - i - 1;
}
for (i = r, j = 0; j < 2*r - 4; i++, j += 2)
{
slong s;
slong minp, mind;
slong tmp;
minp = j;
mind = nmod_poly_degree(V[j]);
for (s = j+1; s < i; s++)
{
if (nmod_poly_degree(V[s]) < mind)
{
minp = s;
mind = nmod_poly_degree(V[s]);
}
}
nmod_poly_swap(V[j], V[minp]);
/* Swap link[j] and V[minp] */
tmp = link[j];
link[j] = link[minp];
link[minp] = tmp;
minp = j+1;
mind = nmod_poly_degree(V[j+1]);
for (s = j + 2; s < i; s++)
{
if (nmod_poly_degree(V[s]) < mind)
{
minp = s;
mind = nmod_poly_degree(V[s]);
}
}
nmod_poly_swap(V[j + 1], V[minp]);
/* Swap link[j+1] and V[minp] */
tmp = link[j + 1];
link[j+1] = link[minp];
link[minp] = tmp;
nmod_poly_mul(V[i], V[j], V[j+1]);
link[i] = j;
}
for (j = 0; j < 2*r - 2; j += 2)
{
/* N.B. d == 1 */
nmod_poly_xgcd(d, W[j], W[j+1], V[j], V[j+1]);
}
for (j = 0; j < 2*r - 2; j++)
{
fmpz_poly_set_nmod_poly(v[j], V[j]);
fmpz_poly_set_nmod_poly(w[j], W[j]);
}
for (i = 0; i < 2*r - 2; i++)
{
nmod_poly_clear(V[i]);
nmod_poly_clear(W[i]);
}
nmod_poly_clear(d);
flint_free(V);
flint_free(W);
}
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