forked from 0ad/0ad
Ykkrosh
7c2e9027c2
Giant merge from http://svn.wildfiregames.com/hg-source/file/5fb522019d5e Infrastructure is largely complete, gameplay is largely missing Disabled by default; use command-line flag "-sim2" (Second attempt at commit...) This was SVN commit r7259.
49 lines
1.4 KiB
C++
49 lines
1.4 KiB
C++
/* Copyright (C) 2010 Wildfire Games.
|
|
* This file is part of 0 A.D.
|
|
*
|
|
* 0 A.D. 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.
|
|
*
|
|
* 0 A.D. 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 0 A.D. If not, see <http://www.gnu.org/licenses/>.
|
|
*/
|
|
|
|
#include "precompiled.h"
|
|
|
|
#include "Sqrt.h"
|
|
|
|
// Based on http://freaknet.org/martin/tape/gos/misc/personal/msc/sqrt/sqrt.html
|
|
u32 isqrt64(u64 n)
|
|
{
|
|
u64 op = n;
|
|
u64 res = 0;
|
|
u64 one = (u64)1 << 62; // highest power of four <= than the argument
|
|
|
|
while (one > op)
|
|
one >>= 2;
|
|
|
|
while (one != 0)
|
|
{
|
|
if (op >= res + one)
|
|
{
|
|
op -= (res + one);
|
|
res += (one << 1);
|
|
}
|
|
res >>= 1;
|
|
one >>= 2;
|
|
}
|
|
return (u32)res;
|
|
}
|
|
|
|
// TODO: This should be equivalent to (u32)sqrt((double)n), and in practice
|
|
// that seems to be true for all input, so do we actually need this integer-only
|
|
// implementation? i.e. are there any platforms / compiler settings where
|
|
// sqrt(double) won't give the correct answer? and is sqrt(double) faster?
|