arb/double_interval/fast_sqr.c
2021-12-08 11:12:52 +01:00

41 lines
824 B
C

/*
Copyright (C) 2021 Fredrik Johansson
This file is part of Arb.
Arb 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 2.1 of the License, or
(at your option) any later version. See <http://www.gnu.org/licenses/>.
*/
#include "double_interval.h"
di_t di_fast_sqr(di_t x)
{
di_t res;
if (x.a >= 0)
{
res.a = x.a * x.a;
res.b = x.b * x.b;
}
else if (x.b <= 0)
{
res.a = x.b * x.b;
res.b = x.a * x.a;
}
else
{
res.a = 0.0;
res.b = FLINT_MAX(x.a * x.a, x.b * x.b);
}
if (res.a != 0.0)
res.a = _di_below(res.a);
res.b = _di_above(res.b);
return res;
}