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/*
Copyright (C) 2015, Elias Tsigaridas
Copyright (C) 2016, Vincent Delecroix
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 "fmpz.h"
#include "fmpz_poly.h"
void _fmpz_poly_scale_2exp(fmpz * pol, slong len, slong k)
{
slong i;
ulong p, z;
if (k == 0 || len <= 1)
return;
else if (k > 0)
{
if (fmpz_is_zero(pol))
z = UWORD_MAX;
else
z = fmpz_val2(pol);
p = k;
for (i = 1; i < len; i++, p += k)
{
if (!fmpz_is_zero(pol + i))
{
z = FLINT_MIN(z, fmpz_val2(pol + i) + p);
fmpz_mul_2exp(pol + i, pol + i, p);
}
}
}
else
{
if (fmpz_is_zero(pol + len - 1))
z = UWORD_MAX;
else
z = fmpz_val2(pol + len - 1);
p = -k;
for (i = len - 2; i >= 0; i--, p -= k)
{
if (!fmpz_is_zero(pol + i))
{
z = FLINT_MIN(z, fmpz_val2(pol + i) + p);
fmpz_mul_2exp(pol + i, pol + i, p);
}
}
}
if (z)
{
for (i = 0; i < len; i++)
fmpz_fdiv_q_2exp(pol + i, pol + i, z);
}
}