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/*=============================================================================
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
Copyright (C) 2013 Mike Hansen
******************************************************************************/
#include "fq.h"
void
_fq_trace(fmpz_t rop, const fmpz * op, slong len, const fq_ctx_t ctx)
{
const slong d = fq_ctx_degree(ctx);
slong i, l;
fmpz *t;
t = _fmpz_vec_init(d);
fmpz_set_ui(t + 0, d);
for (i = 1; i < d; i++)
{
for (l = ctx->len - 2; l >= 0 && ctx->j[l] >= d - (i - 1); l--)
{
fmpz_addmul(t + i, t + (ctx->j[l] + i - d), ctx->a + l);
}
if (l >= 0 && ctx->j[l] == d - i)
{
fmpz_addmul_ui(t + i, ctx->a + l, i);
}
fmpz_neg(t + i, t + i);
fmpz_mod(t + i, t + i, fq_ctx_prime(ctx));
}
fmpz_zero(rop);
for (i = 0; i < d; i++)
{
fmpz_addmul(rop, op + i, t + i);
}
fmpz_mod(rop, rop, fq_ctx_prime(ctx));
_fmpz_vec_clear(t, d);
}
void
fq_trace(fmpz_t rop, const fq_t op, const fq_ctx_t ctx)
{
if (fq_is_zero(op, ctx))
{
fmpz_zero(rop);
}
else
{
_fq_trace(rop, op->coeffs, op->length, ctx);
}
}
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