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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) 2012 Fredrik Johansson
******************************************************************************/
#include <gmp.h>
#include "flint.h"
#include "ulong_extras.h"
#include "nmod_poly.h"
/* This gives some speedup for small lengths. */
static __inline__ void _nmod_poly_rem_2(mp_ptr r, mp_srcptr a, slong al,
mp_srcptr b, slong bl, nmod_t mod)
{
if (al == 2)
r[0] = nmod_sub(a[0], nmod_mul(a[1], b[0], mod), mod);
else
_nmod_poly_rem(r, a, al, b, bl, mod);
}
void
_nmod_poly_evaluate_nmod_vec_fast_precomp(mp_ptr vs, mp_srcptr poly,
slong plen, const mp_ptr * tree, slong len, nmod_t mod)
{
slong height, i, j, pow, left;
slong tree_height;
slong tlen;
mp_ptr t, u, swap, pa, pb, pc;
/* avoid worrying about some degenerate cases */
if (len < 2 || plen < 2)
{
if (len == 1)
vs[0] = _nmod_poly_evaluate_nmod(poly, plen,
nmod_neg(tree[0][0], mod), mod);
else if (len != 0 && plen == 0)
_nmod_vec_zero(vs, len);
else if (len != 0 && plen == 1)
for (i = 0; i < len; i++)
vs[i] = poly[0];
return;
}
t = _nmod_vec_init(len);
u = _nmod_vec_init(len);
left = len;
/* Initial reduction. We allow the polynomial to be larger
or smaller than the number of points. */
height = FLINT_BIT_COUNT(plen - 1) - 1;
tree_height = FLINT_CLOG2(len);
while (height >= tree_height)
height--;
pow = WORD(1) << height;
for (i = j = 0; i < len; i += pow, j += (pow + 1))
{
tlen = ((i + pow) <= len) ? pow : len % pow;
_nmod_poly_rem(t + i, poly, plen, tree[height] + j, tlen + 1, mod);
}
for (i = height - 1; i >= 0; i--)
{
pow = WORD(1) << i;
left = len;
pa = tree[i];
pb = t;
pc = u;
while (left >= 2 * pow)
{
_nmod_poly_rem_2(pc, pb, 2 * pow, pa, pow + 1, mod);
_nmod_poly_rem_2(pc + pow, pb, 2 * pow, pa + pow + 1, pow + 1, mod);
pa += 2 * pow + 2;
pb += 2 * pow;
pc += 2 * pow;
left -= 2 * pow;
}
if (left > pow)
{
_nmod_poly_rem(pc, pb, left, pa, pow + 1, mod);
_nmod_poly_rem(pc + pow, pb, left, pa + pow + 1, left - pow + 1, mod);
}
else if (left > 0)
_nmod_vec_set(pc, pb, left);
swap = t;
t = u;
u = swap;
}
_nmod_vec_set(vs, t, len);
_nmod_vec_clear(t);
_nmod_vec_clear(u);
}
void _nmod_poly_evaluate_nmod_vec_fast(mp_ptr ys, mp_srcptr poly, slong plen,
mp_srcptr xs, slong n, nmod_t mod)
{
mp_ptr * tree;
tree = _nmod_poly_tree_alloc(n);
_nmod_poly_tree_build(tree, xs, n, mod);
_nmod_poly_evaluate_nmod_vec_fast_precomp(ys, poly, plen, tree, n, mod);
_nmod_poly_tree_free(tree, n);
}
void
nmod_poly_evaluate_nmod_vec_fast(mp_ptr ys,
const nmod_poly_t poly, mp_srcptr xs, slong n)
{
_nmod_poly_evaluate_nmod_vec_fast(ys, poly->coeffs,
poly->length, xs, n, poly->mod);
}
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