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119 lines (108 loc) · 2.3 KB
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/*
* Copyright 2010 OpenXcom Developers.
*
* This file is part of OpenXcom.
*
* OpenXcom 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 3 of the License, or
* (at your option) any later version.
*
* OpenXcom 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 OpenXcom. If not, see <http://www.gnu.org/licenses/>.
*/
#include "RNG.h"
#define _USE_MATH_DEFINES
#include <cmath>
#include <cstdlib>
#include <ctime>
namespace OpenXcom
{
namespace RNG
{
int _seed = 0;
/**
* Seeds the random generator with a new number.
* Defaults to the current time if none is set.
* @param seed New seed.
*/
void init(int seed)
{
if (seed == -1)
{
_seed = (int)time(NULL);
}
else
{
_seed = seed;
}
srand(_seed);
}
/**
* Returns the last seed used by the generator.
* @return Generator seed.
*/
int getSeed()
{
return _seed;
}
/**
* Generates a random integer number within a certain range.
* @param min Minimum number.
* @param max Maximum number.
* @return Generated number.
*/
int generate(int min, int max)
{
_seed = rand();
return (_seed % (max - min + 1) + min);
}
/**
* Generates a random decimal number within a certain range.
* @param min Minimum number.
* @param max Maximum number.
* @return Generated number.
*/
double generate(double min, double max)
{
_seed = rand();
return (_seed * (max - min) / RAND_MAX + min);
}
/**
* Normal random variate generator
* @param m mean
* @param s standard deviation
* @return normally distributed value.
*/
double boxMuller(double m, double s)
{
double y1;
static double y2;
static int use_last = 0;
if (use_last) /* use value from previous call */
{
y1 = y2;
use_last = 0;
}
else
{
double x1, x2, w;
do {
x1 = 2.0 * generate(0.0, 1.0) - 1.0;
x2 = 2.0 * generate(0.0, 1.0) - 1.0;
w = x1 * x1 + x2 * x2;
} while ( w >= 1.0 );
w = sqrt( (-2.0 * log( w ) ) / w );
y1 = x1 * w;
y2 = x2 * w;
use_last = 1;
}
return( m + y1 * s );
}
}
}