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/*
Copyright (C) 2011 Fredrik Johansson
This file is part of FLINT.
FLINT is free software: you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License (LGPL) as published
by the Free Software Foundation; either version 3 of the License, or
(at your option) any later version. See <https://www.gnu.org/licenses/>.
*/
#include "longlong.h"
#include "fmpz_poly.h"
#include "fmpz_poly_mat.h"
void
fmpz_poly_mat_pow(fmpz_poly_mat_t B, const fmpz_poly_mat_t A, ulong exp)
{
slong d = fmpz_poly_mat_nrows(A);
if (exp == 0 || d == 0)
{
fmpz_poly_mat_one(B);
}
else if (exp == 1)
{
fmpz_poly_mat_set(B, A);
}
else if (exp == 2)
{
fmpz_poly_mat_sqr(B, A);
}
else if (d == 1)
{
fmpz_poly_pow(fmpz_poly_mat_entry(B, 0, 0),
fmpz_poly_mat_entry(A, 0, 0), exp);
}
else
{
fmpz_poly_mat_t T, U;
slong i;
fmpz_poly_mat_init_set(T, A);
fmpz_poly_mat_init(U, d, d);
for (i = ((slong) FLINT_BIT_COUNT(exp)) - 2; i >= 0; i--)
{
fmpz_poly_mat_sqr(U, T);
if (exp & (WORD(1) << i))
fmpz_poly_mat_mul(T, U, A);
else
fmpz_poly_mat_swap(T, U);
}
fmpz_poly_mat_swap(B, T);
fmpz_poly_mat_clear(T);
fmpz_poly_mat_clear(U);
}
}