pqc/external/flint-2.4.3/fq_poly_templates/powmod_ui_binexp.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) 2013 Mike Hansen
******************************************************************************/
#ifdef T
#include "templates.h"
#include <stdlib.h>
#include <gmp.h>
#include "flint.h"
#include "ulong_extras.h"
void
_TEMPLATE(T, poly_powmod_ui_binexp) (TEMPLATE(T, struct) * res,
const TEMPLATE(T, struct) * poly, ulong e,
const TEMPLATE(T, struct) * f, slong lenf,
const TEMPLATE(T, ctx_t) ctx)
{
TEMPLATE(T, struct) * T, *Q;
TEMPLATE(T, t) invf;
slong lenT, lenQ;
int i;
if (lenf == 2)
{
TEMPLATE(T, pow_ui) (res, poly, e, ctx);
return;
}
lenT = 2 * lenf - 3;
lenQ = FLINT_MAX(lenT - lenf + 1, 1);
T = _TEMPLATE(T, vec_init) (lenT + lenQ, ctx);
Q = T + lenT;
TEMPLATE(T, init) (invf, ctx);
TEMPLATE(T, inv) (invf, f + lenf - 1, ctx);
_TEMPLATE(T, vec_set) (res, poly, lenf - 1, ctx);
for (i = ((int)FLINT_BIT_COUNT(e) - 2); i >= 0; i--)
{
_TEMPLATE(T, poly_sqr) (T, res, lenf - 1, ctx);
_TEMPLATE(T, poly_divrem) (Q, res, T, 2 * lenf - 3, f, lenf, invf,
ctx);
if (e & (UWORD(1) << i))
{
_TEMPLATE(T, poly_mul) (T, res, lenf - 1, poly, lenf - 1, ctx);
_TEMPLATE(T, poly_divrem) (Q, res, T, 2 * lenf - 3, f, lenf, invf,
ctx);
}
}
TEMPLATE(T, clear) (invf, ctx);
_TEMPLATE(T, vec_clear) (T, lenT + lenQ, ctx);
}
void
TEMPLATE(T, poly_powmod_ui_binexp) (TEMPLATE(T, poly_t) res,
const TEMPLATE(T, poly_t) poly, ulong e,
const TEMPLATE(T, poly_t) f,
const TEMPLATE(T, ctx_t) ctx)
{
TEMPLATE(T, struct) * q;
slong len = poly->length;
slong lenf = f->length;
slong trunc = lenf - 1;
int qcopy = 0;
if (lenf == 0)
{
TEMPLATE_PRINTF
("Exception: %s_poly_powmod_ui_binexp: divide by zero\n", T);
abort();
}
if (len >= lenf)
{
TEMPLATE(T, poly_t) t, r;
TEMPLATE(T, poly_init) (t, ctx);
TEMPLATE(T, poly_init) (r, ctx);
TEMPLATE(T, poly_divrem) (t, r, poly, f, ctx);
TEMPLATE(T, poly_powmod_ui_binexp) (res, r, e, f, ctx);
TEMPLATE(T, poly_clear) (t, ctx);
TEMPLATE(T, poly_clear) (r, ctx);
return;
}
if (e <= 2)
{
if (e == UWORD(0))
{
TEMPLATE(T, poly_fit_length) (res, 1, ctx);
TEMPLATE(T, one) (res->coeffs, ctx);
_TEMPLATE(T, poly_set_length) (res, 1, ctx);
}
else if (e == UWORD(1))
{
TEMPLATE(T, poly_set) (res, poly, ctx);
}
else
TEMPLATE(T, poly_mulmod) (res, poly, poly, f, ctx);
return;
}
if (lenf == 1 || len == 0)
{
TEMPLATE(T, poly_zero) (res, ctx);
return;
}
if (len < trunc)
{
q = _TEMPLATE(T, vec_init) (trunc, ctx);
_TEMPLATE(T, vec_set) (q, poly->coeffs, len, ctx);
_TEMPLATE(T, vec_zero) (q + len, trunc - len, ctx);
qcopy = 1;
}
else
q = poly->coeffs;
if ((res == poly && !qcopy) || (res == f))
{
TEMPLATE(T, poly_t) t;
TEMPLATE(T, poly_init2) (t, 2 * lenf - 3, ctx);
_TEMPLATE(T, poly_powmod_ui_binexp) (t->coeffs, q, e, f->coeffs, lenf,
ctx);
TEMPLATE(T, poly_swap) (res, t, ctx);
TEMPLATE(T, poly_clear) (t, ctx);
}
else
{
TEMPLATE(T, poly_fit_length) (res, 2 * lenf - 3, ctx);
_TEMPLATE(T, poly_powmod_ui_binexp) (res->coeffs, q, e, f->coeffs,
lenf, ctx);
}
if (qcopy)
_TEMPLATE(T, vec_clear) (q, trunc, ctx);
_TEMPLATE(T, poly_set_length) (res, trunc, ctx);
_TEMPLATE(T, poly_normalise) (res, ctx);
}
#endif