pqc/external/flint-2.4.3/fq_poly_templates/compose_mod_brent_kung.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 Fredrik Johansson
Copyright (C) 2012 Lina Kulakova
Copyright (C) 2013 Mike Hansen
******************************************************************************/
#ifdef T
#include "templates.h"
void
_TEMPLATE(T, poly_compose_mod_brent_kung) (
TEMPLATE(T, struct) * res,
const TEMPLATE(T, struct) * poly1, slong len1,
const TEMPLATE(T, struct) * poly2,
const TEMPLATE(T, struct) * poly3, slong len3,
const TEMPLATE(T, ctx_t) ctx)
{
TEMPLATE(T, mat_t) A, B, C;
TEMPLATE(T, struct) * t, *h, *tmp;
slong i, n, m;
n = len3 - 1;
if (len3 == 1)
return;
if (len1 == 1)
{
TEMPLATE(T, set) (res, poly1, ctx);
return;
}
if (len3 == 2)
{
_TEMPLATE(T, TEMPLATE(poly_evaluate, T)) (res, poly1, len1, poly2,
ctx);
return;
}
m = n_sqrt(n) + 1;
TEMPLATE(T, mat_init) (A, m, n, ctx);
TEMPLATE(T, mat_init) (B, m, m, ctx);
TEMPLATE(T, mat_init) (C, m, n, ctx);
h = _TEMPLATE(T, vec_init) (2 * n - 1, ctx);
t = _TEMPLATE(T, vec_init) (2 * n - 1, ctx);
/* Set rows of B to the segments of poly1 */
for (i = 0; i < len1 / m; i++)
_TEMPLATE(T, vec_set) (B->rows[i], poly1 + i * m, m, ctx);
_TEMPLATE(T, vec_set) (B->rows[i], poly1 + i * m, len1 % m, ctx);
/* Set rows of A to powers of poly2 */
TEMPLATE(T, one) (A->rows[0], ctx);
_TEMPLATE(T, vec_set) (A->rows[1], poly2, n, ctx);
tmp = _TEMPLATE(T, vec_init) (2 * n - 1, ctx);
for (i = 2; i < m; i++)
{
_TEMPLATE(T, poly_mulmod) (tmp, A->rows[i - 1], n, poly2, n, poly3,
len3, ctx);
_TEMPLATE(T, vec_set) (A->rows[i], tmp, n, ctx);
}
_TEMPLATE(T, vec_clear) (tmp, 2 * n - 1, ctx);
TEMPLATE(T, mat_mul) (C, B, A, ctx);
/* Evaluate block composition using the Horner scheme */
_TEMPLATE(T, vec_set) (res, C->rows[m - 1], n, ctx);
_TEMPLATE(T, poly_mulmod) (h, A->rows[m - 1], n, poly2, n, poly3, len3,
ctx);
for (i = m - 2; i >= 0; i--)
{
_TEMPLATE(T, poly_mulmod) (t, res, n, h, n, poly3, len3, ctx);
_TEMPLATE(T, poly_add) (res, t, n, C->rows[i], n, ctx);
}
_TEMPLATE(T, vec_clear) (h, 2 * n - 1, ctx);
_TEMPLATE(T, vec_clear) (t, 2 * n - 1, ctx);
TEMPLATE(T, mat_clear) (A, ctx);
TEMPLATE(T, mat_clear) (B, ctx);
TEMPLATE(T, mat_clear) (C, ctx);
}
void
TEMPLATE(T, poly_compose_mod_brent_kung) (TEMPLATE(T, poly_t) res,
const TEMPLATE(T, poly_t) poly1,
const TEMPLATE(T, poly_t) poly2,
const TEMPLATE(T, poly_t) poly3,
const TEMPLATE(T, ctx_t) ctx)
{
slong len1 = poly1->length;
slong len2 = poly2->length;
slong len3 = poly3->length;
slong len = len3 - 1;
slong vec_len = FLINT_MAX(len3 - 1, len2);
TEMPLATE(T, struct) * ptr2;
TEMPLATE(T, t) inv3;
if (len3 == 0)
{
flint_printf("Exception: division by zero in");
TEMPLATE_PRINTF("%s_poly_compose_mod_brent_kung\n", T);
abort();
}
if (len1 >= len3)
{
TEMPLATE_PRINTF
("Exception: %s_poly_compose_brent_kung: the degree of the", T);
flint_printf
(" first polynomial must be smaller than that of the modulus\n");
abort();
}
if (len1 == 0 || len3 == 1)
{
TEMPLATE(T, poly_zero) (res, ctx);
return;
}
if (len1 == 1)
{
TEMPLATE(T, poly_set) (res, poly1, ctx);
return;
}
if (res == poly3 || res == poly1)
{
TEMPLATE(T, poly_t) tmp;
TEMPLATE(T, poly_init) (tmp, ctx);
TEMPLATE(T, poly_compose_mod_brent_kung) (tmp, poly1, poly2, poly3,
ctx);
TEMPLATE(T, poly_swap) (tmp, res, ctx);
TEMPLATE(T, poly_clear) (tmp, ctx);
return;
}
ptr2 = _TEMPLATE(T, vec_init) (vec_len, ctx);
if (len2 <= len)
{
_TEMPLATE(T, vec_set) (ptr2, poly2->coeffs, len2, ctx);
_TEMPLATE(T, vec_zero) (ptr2 + len2, vec_len - len2, ctx);
}
else
{
TEMPLATE(T, init) (inv3, ctx);
TEMPLATE(T, inv) (inv3, poly3->coeffs + len, ctx);
_TEMPLATE(T, poly_rem) (ptr2, poly2->coeffs, len2,
poly3->coeffs, len3, inv3, ctx);
TEMPLATE(T, clear) (inv3, ctx);
}
TEMPLATE(T, poly_fit_length) (res, len, ctx);
_TEMPLATE(T, poly_compose_mod_brent_kung) (res->coeffs, poly1->coeffs,
len1, ptr2, poly3->coeffs, len3,
ctx);
_TEMPLATE(T, poly_set_length) (res, len, ctx);
_TEMPLATE(T, poly_normalise) (res, ctx);
_TEMPLATE(T, vec_clear) (ptr2, vec_len, ctx);
}
#endif