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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) 2011 Fredrik Johansson
******************************************************************************/
#include <stdlib.h>
#include "flint.h"
#include "fmpz_poly.h"
#include "fmpz_poly_mat.h"
void
fmpz_poly_mat_pow_trunc(fmpz_poly_mat_t B, const fmpz_poly_mat_t A, ulong exp,
slong len)
{
slong d = fmpz_poly_mat_nrows(A);
if (len < 1)
{
fmpz_poly_mat_zero(B);
}
else if (exp == 0 || d == 0)
{
fmpz_poly_mat_one(B);
}
else if (exp == 1)
{
fmpz_poly_mat_set(B, A);
fmpz_poly_mat_truncate(B, len);
}
else if (exp == 2)
{
fmpz_poly_mat_sqrlow(B, A, len);
}
else if (d == 1)
{
fmpz_poly_pow_trunc(fmpz_poly_mat_entry(B, 0, 0),
fmpz_poly_mat_entry(A, 0, 0), exp, len);
}
else
{
fmpz_poly_mat_t T, U;
slong i;
fmpz_poly_mat_init_set(T, A);
fmpz_poly_mat_truncate(T, len);
fmpz_poly_mat_init(U, d, d);
for (i = ((slong) FLINT_BIT_COUNT(exp)) - 2; i >= 0; i--)
{
fmpz_poly_mat_sqrlow(U, T, len);
if (exp & (WORD(1) << i))
fmpz_poly_mat_mullow(T, U, A, len);
else
fmpz_poly_mat_swap(T, U);
}
fmpz_poly_mat_swap(B, T);
fmpz_poly_mat_clear(T);
fmpz_poly_mat_clear(U);
}
}
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