pqc/external/flint-2.4.3/qadic/log.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) 2012 Sebastian Pancratz
******************************************************************************/
#include "qadic.h"
void _qadic_log(fmpz *z, const fmpz *y, slong v, slong len,
const fmpz *a, const slong *j, slong lena,
const fmpz_t p, slong N, const fmpz_t pN)
{
if (N < (WORD(1) < 10) / (slong) fmpz_bits(p))
{
_qadic_log_rectangular(z, y, v, len, a, j, lena, p, N, pN);
}
else
{
_qadic_log_balanced(z, y, len, a, j, lena, p, N, pN);
}
}
int qadic_log(qadic_t rop, const qadic_t op, const qadic_ctx_t ctx)
{
const fmpz *p = (&ctx->pctx)->p;
const slong d = qadic_ctx_degree(ctx);
const slong N = qadic_prec(rop);
const slong len = op->length;
if (op->val < 0)
{
return 0;
}
else
{
fmpz *x;
fmpz_t pN;
int alloc, ans;
x = _fmpz_vec_init(len + 1);
alloc = _padic_ctx_pow_ui(pN, N, &ctx->pctx);
/* Set x := (1 - op) mod p^N */
fmpz_pow_ui(x + len, p, op->val);
_fmpz_vec_scalar_mul_fmpz(x, op->coeffs, len, x + len);
fmpz_sub_ui(x, x, 1);
_fmpz_vec_neg(x, x, len);
_fmpz_vec_scalar_mod_fmpz(x, x, len, pN);
if (_fmpz_vec_is_zero(x, len))
{
padic_poly_zero(rop);
ans = 1;
}
else
{
const slong v = _fmpz_vec_ord_p(x, len, p);
if (v >= 2 || (*p != WORD(2) && v >= 1))
{
if (v >= N)
{
padic_poly_zero(rop);
}
else
{
padic_poly_fit_length(rop, d);
_qadic_log(rop->coeffs, x, v, len,
ctx->a, ctx->j, ctx->len, p, N, pN);
rop->val = 0;
_padic_poly_set_length(rop, d);
_padic_poly_normalise(rop);
padic_poly_canonicalise(rop, p);
}
ans = 1;
}
else
{
ans = 0;
}
}
_fmpz_vec_clear(x, len + 1);
if (alloc)
fmpz_clear(pN);
return ans;
}
}