pqc/external/flint-2.4.3/fmpz_poly/pow_multinomial.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) 2010 Sebastian Pancratz
******************************************************************************/
#include <stdlib.h>
#include <gmp.h>
#include "flint.h"
#include "fmpz.h"
#include "fmpz_vec.h"
#include "fmpz_poly.h"
void
_fmpz_poly_pow_multinomial(fmpz * res, const fmpz * poly, slong len, ulong e)
{
slong k, low, rlen;
fmpz_t d, t;
fmpz * P;
rlen = (slong) e * (len - WORD(1)) + WORD(1);
_fmpz_vec_zero(res, rlen);
for (low = WORD(0); poly[low] == WORD(0); low++) ;
if (low == WORD(0))
{
P = (fmpz *) poly;
}
else
{
P = (fmpz *) poly + low;
len -= low;
res += (slong) e * low;
rlen -= (slong) e * low;
}
fmpz_init(d);
fmpz_init(t);
fmpz_pow_ui(res, P, e);
for (k = 1; k < rlen; k++)
{
slong i, u = -k;
for (i = 1; i <= FLINT_MIN(k, len - 1); i++)
{
fmpz_mul(t, P + i, res + (k - i));
u += (slong) e + 1;
if (u >= 0)
fmpz_addmul_ui(res + k, t, (ulong) u);
else
fmpz_submul_ui(res + k, t, - ((ulong) u));
}
fmpz_add(d, d, P);
fmpz_divexact(res + k, res + k, d);
}
fmpz_clear(d);
fmpz_clear(t);
}
void
fmpz_poly_pow_multinomial(fmpz_poly_t res, const fmpz_poly_t poly, ulong e)
{
const slong len = poly->length;
slong rlen;
if ((len < 2) | (e < UWORD(3)))
{
if (e == UWORD(0))
fmpz_poly_set_ui(res, 1);
else if (len == 0)
fmpz_poly_zero(res);
else if (len == 1)
{
fmpz_poly_fit_length(res, 1);
fmpz_pow_ui(res->coeffs, poly->coeffs, e);
_fmpz_poly_set_length(res, 1);
}
else if (e == UWORD(1))
fmpz_poly_set(res, poly);
else /* e == UWORD(2) */
fmpz_poly_sqr(res, poly);
return;
}
rlen = (slong) e * (len - 1) + 1;
if (res != poly)
{
fmpz_poly_fit_length(res, rlen);
_fmpz_poly_pow_multinomial(res->coeffs, poly->coeffs, len, e);
_fmpz_poly_set_length(res, rlen);
}
else
{
fmpz_poly_t t;
fmpz_poly_init2(t, rlen);
_fmpz_poly_pow_multinomial(t->coeffs, poly->coeffs, len, e);
_fmpz_poly_set_length(t, rlen);
fmpz_poly_swap(res, t);
fmpz_poly_clear(t);
}
}