pqc/external/flint-2.4.3/padic/exp.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, 2012 Sebastian Pancratz
Copyright (C) 2012 Fredrik Johansson
******************************************************************************/
#include "padic.h"
slong _padic_exp_bound(slong v, slong N, const fmpz_t p)
{
if (fmpz_fits_si(p))
{
fmpz_t n, d, f;
slong i;
fmpz_init(n);
fmpz_init(d);
fmpz_init(f);
fmpz_sub_ui(f, p, 1);
fmpz_mul_ui(n, f, N);
fmpz_sub_ui(n, n, 1);
fmpz_mul_ui(d, f, v);
fmpz_sub_ui(d, d, 1);
fmpz_cdiv_q(f, n, d);
i = fmpz_get_si(f);
fmpz_clear(n);
fmpz_clear(d);
fmpz_clear(f);
return i;
}
else
{
return (N + (v - 1)) / v;
}
}
void _padic_exp(fmpz_t rop, const fmpz_t u, slong v, const fmpz_t p, slong N)
{
if (N < 1024)
_padic_exp_rectangular(rop, u, v, p, N);
else
_padic_exp_balanced(rop, u, v, p, N);
}
int padic_exp(padic_t rop, const padic_t op, const padic_ctx_t ctx)
{
const slong N = padic_prec(rop);
const slong v = padic_val(op);
const fmpz *p = ctx->p;
if (padic_is_zero(op))
{
padic_one(rop);
return 1;
}
if ((fmpz_equal_ui(p, 2) && v <= 1) || (v <= 0))
{
return 0;
}
else
{
if (v < N)
{
_padic_exp(padic_unit(rop), padic_unit(op), padic_val(op), p, N);
padic_val(rop) = 0;
}
else
{
padic_one(rop);
}
return 1;
}
}