pqc/external/flint-2.4.3/fq_poly_templates/inv_series_newton.c
2014-05-24 23:16:06 +02:00

138 lines
4.2 KiB
C

/*=============================================================================
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, 2011 Sebastian Pancratz
Copyright (C) 2013 Mike Hansen
******************************************************************************/
#ifdef T
#include "templates.h"
#define FQ_POLY_INV_NEWTON_CUTOFF 64
void
_TEMPLATE(T, poly_inv_series_newton) (TEMPLATE(T, struct) * Qinv,
const TEMPLATE(T, struct) * Q, slong n,
const TEMPLATE(T, t) cinv,
const TEMPLATE(T, ctx_t) ctx)
{
if (n == 1) /* {Q,1} x* cinv == 1 mod (x) */
{
TEMPLATE(T, set) (Qinv, cinv, ctx);
}
else
{
const slong alloc = FLINT_MAX(n, 3 * FQ_POLY_INV_NEWTON_CUTOFF);
slong *a, i, m;
TEMPLATE(T, struct) * W;
W = _TEMPLATE(T, vec_init) (alloc, ctx);
for (i = 1; (WORD(1) << i) < n; i++) ;
a = (slong *) flint_malloc(i * sizeof(slong));
a[i = 0] = n;
while (n >= FQ_POLY_INV_NEWTON_CUTOFF)
a[++i] = (n = (n + 1) / 2);
/* Base case */
{
TEMPLATE(T, struct) * Qrev = W + 2 * FQ_POLY_INV_NEWTON_CUTOFF;
_TEMPLATE(T, poly_reverse) (Qrev, Q, n, n, ctx);
_TEMPLATE(T, vec_zero) (W, 2 * n - 2, ctx);
TEMPLATE(T, one) (W + (2 * n - 2), ctx);
_TEMPLATE(T, poly_div_basecase) (Qinv, W, W, 2 * n - 1, Qrev, n,
cinv, ctx);
_TEMPLATE(T, poly_reverse) (Qinv, Qinv, n, n, ctx);
}
for (i--; i >= 0; i--)
{
m = n;
n = a[i];
_TEMPLATE(T, poly_mullow) (W, Q, n, Qinv, m, n, ctx);
_TEMPLATE(T, poly_mullow) (Qinv + m, Qinv, m, W + m, n - m, n - m,
ctx);
_TEMPLATE(T, poly_neg) (Qinv + m, Qinv + m, n - m, ctx);
}
_TEMPLATE(T, vec_clear) (W, alloc, ctx);
flint_free(a);
}
}
void
TEMPLATE(T, poly_inv_series_newton) (TEMPLATE(T, poly_t) Qinv,
const TEMPLATE(T, poly_t) Q, slong n,
const TEMPLATE(T, ctx_t) ctx)
{
TEMPLATE(T, t) cinv;
TEMPLATE(T, struct) * Qcopy;
int Qalloc;
if (Q->length >= n)
{
Qcopy = Q->coeffs;
Qalloc = 0;
}
else
{
Qcopy = _TEMPLATE(T, vec_init) (n, ctx);
_TEMPLATE(T, vec_set) (Qcopy, Q->coeffs, Q->length, ctx);
Qalloc = 1;
}
TEMPLATE(T, init) (cinv, ctx);
TEMPLATE(T, inv) (cinv, Q->coeffs, ctx);
if (Qinv != Q)
{
TEMPLATE(T, poly_fit_length) (Qinv, n, ctx);
_TEMPLATE(T, poly_inv_series_newton) (Qinv->coeffs, Qcopy, n, cinv,
ctx);
}
else
{
TEMPLATE(T, struct) * t = _TEMPLATE(T, vec_init) (n, ctx);
_TEMPLATE(T, poly_inv_series_newton) (t, Qcopy, n, cinv, ctx);
_TEMPLATE(T, vec_clear) (Qinv->coeffs, Qinv->alloc, ctx);
Qinv->coeffs = t;
Qinv->alloc = n;
Qinv->length = n;
}
_TEMPLATE(T, poly_set_length) (Qinv, n, ctx);
_TEMPLATE(T, poly_normalise) (Qinv, ctx);
if (Qalloc)
_TEMPLATE(T, vec_clear) (Qcopy, n, ctx);
TEMPLATE(T, clear) (cinv, ctx);
}
#endif