arb/fmpcb_mat/pow_ui.c

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/*=============================================================================
This file is part of ARB.
ARB 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.
ARB 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 ARB; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
=============================================================================*/
/******************************************************************************
Copyright (C) 2012 Fredrik Johansson
******************************************************************************/
#include "fmpcb_mat.h"
void
fmpcb_mat_pow_ui(fmpcb_mat_t B, const fmpcb_mat_t A, ulong exp, long prec)
{
long d = fmpcb_mat_nrows(A);
if (exp <= 2 || d <= 1)
{
if (exp == 0 || d == 0)
{
fmpcb_mat_one(B);
}
else if (d == 1)
{
fmpcb_pow_ui(fmpcb_mat_entry(B, 0, 0),
fmpcb_mat_entry(A, 0, 0), exp, prec);
}
else if (exp == 1)
{
fmpcb_mat_set(B, A);
}
else if (exp == 2)
{
fmpcb_mat_mul(B, A, A, prec); /* todo: sqr */
}
}
else
{
fmpcb_mat_t T, U;
long i;
fmpcb_mat_init(T, d, d);
fmpcb_mat_set(T, A);
fmpcb_mat_init(U, d, d);
for (i = ((long) FLINT_BIT_COUNT(exp)) - 2; i >= 0; i--)
{
fmpcb_mat_mul(U, T, T, prec); /* todo: sqr */
if (exp & (1L << i))
fmpcb_mat_mul(T, U, A, prec);
else
fmpcb_mat_swap(T, U);
}
fmpcb_mat_swap(B, T);
fmpcb_mat_clear(T);
fmpcb_mat_clear(U);
}
}