pqc/external/flint-2.4.3/fq_poly_templates/gcd_euclidean.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 William Hart
Copyright (C) 2012 Andres Goens
Copyright (C) 2013 Mike Hansen
******************************************************************************/
#ifdef T
#include "templates.h"
#include <stdlib.h>
slong
_TEMPLATE(T, poly_gcd_euclidean) (TEMPLATE(T, struct) * G,
const TEMPLATE(T, struct) * A, slong lenA,
const TEMPLATE(T, struct) * B, slong lenB,
const TEMPLATE(T, t) invB,
const TEMPLATE(T, ctx_t) ctx)
{
if (lenB == 1)
{
TEMPLATE(T, one) (G, ctx);
return 1;
}
else /* lenA >= lenB > 1 */
{
const slong lenW = FLINT_MAX(lenA - lenB + 1, lenB) + lenA + 2 * lenB;
TEMPLATE(T, t) invR3;
TEMPLATE(T, struct) * Q, *R1, *R2, *R3, *T, *W;
slong lenR2, lenR3;
W = _TEMPLATE(T, vec_init) (lenW, ctx);
Q = W;
R1 = W + FLINT_MAX(lenA - lenB + 1, lenB);
R2 = R1 + lenA;
R3 = R2 + lenB;
_TEMPLATE(T, poly_divrem) (Q, R1, A, lenA, B, lenB, invB, ctx);
lenR3 = lenB - 1;
TEMPLATE(CAP_T, VEC_NORM) (R1, lenR3, ctx);
if (lenR3 == 0)
{
_TEMPLATE(T, vec_set) (G, B, lenB, ctx);
_TEMPLATE(T, vec_clear) (W, lenW, ctx);
return lenB;
}
TEMPLATE(T, init) (invR3, ctx);
T = R3;
R3 = R1;
R1 = T;
_TEMPLATE(T, vec_set) (R2, B, lenB, ctx);
lenR2 = lenB;
do
{
TEMPLATE(T, inv) (invR3, R3 + (lenR3 - 1), ctx);
_TEMPLATE(T, poly_divrem) (Q, R1, R2, lenR2, R3, lenR3, invR3,
ctx);
lenR2 = lenR3--;
TEMPLATE(CAP_T, VEC_NORM) (R1, lenR3, ctx);
T = R2;
R2 = R3;
R3 = R1;
R1 = T;
}
while (lenR3 > 0);
_TEMPLATE(T, vec_set) (G, R2, lenR2, ctx);
_TEMPLATE(T, vec_clear) (W, lenW, ctx);
TEMPLATE(T, clear) (invR3, ctx);
return lenR2;
}
}
void
TEMPLATE(T, poly_gcd_euclidean) (TEMPLATE(T, poly_t) G,
const TEMPLATE(T, poly_t) A,
const TEMPLATE(T, poly_t) B,
const TEMPLATE(T, ctx_t) ctx)
{
if (A->length < B->length)
{
TEMPLATE(T, poly_gcd_euclidean) (G, B, A, ctx);
}
else /* lenA >= lenB >= 0 */
{
slong lenA = A->length, lenB = B->length, lenG;
TEMPLATE(T, t) invB;
TEMPLATE(T, struct) * g;
if (lenA == 0) /* lenA = lenB = 0 */
{
TEMPLATE(T, poly_zero) (G, ctx);
}
else if (lenB == 0) /* lenA > lenB = 0 */
{
TEMPLATE(T, poly_make_monic) (G, A, ctx);
}
else /* lenA >= lenB >= 1 */
{
if (G == A || G == B)
{
g = _TEMPLATE(T, vec_init) (FLINT_MIN(lenA, lenB), ctx);
}
else
{
TEMPLATE(T, poly_fit_length) (G, FLINT_MIN(lenA, lenB), ctx);
g = G->coeffs;
}
TEMPLATE(T, init) (invB, ctx);
TEMPLATE(T, inv) (invB, TEMPLATE(T, poly_lead) (B, ctx), ctx);
lenG = _TEMPLATE(T, poly_gcd_euclidean) (g, A->coeffs, lenA,
B->coeffs, lenB, invB,
ctx);
TEMPLATE(T, clear) (invB, ctx);
if (G == A || G == B)
{
_TEMPLATE(T, vec_clear) (G->coeffs, G->alloc, ctx);
G->coeffs = g;
G->alloc = FLINT_MIN(lenA, lenB);
G->length = FLINT_MIN(lenA, lenB);
}
_TEMPLATE(T, poly_set_length) (G, lenG, ctx);
if (G->length == 1)
TEMPLATE(T, one) (G->coeffs, ctx);
else
TEMPLATE(T, poly_make_monic) (G, G, ctx);
}
}
}
#endif