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/*************************************************************************
*
* HTCd - Copyright (C) 1998-2006 Henrik Rydberg
*
* This program 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.
*
* This program 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 this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <mt/random.h>
#include <mt/mlock.h>
#include <time.h>
//////////////////////////////////////////////////////
//
// This file implements some routines from NumRec
//
const int NTAB=32; // NOTE: change in header if changing this
const int IA=16807;
const int IM=2147483647;
const float AM=1/float(IM);
const int IQ=127773;
const int IR=2836;
const int NDIV=1+(IM-1)/NTAB;
const float EPS=1.2e-7;
const float RNMX=1-EPS;
static int idum,iy,iv[32],flag;
static float extra;
static int inited;
static mutex_t mutex;
unsigned long RandomInit(unsigned long seed)
{
inited=1;
idum=seed?seed:1;
for(int j=NTAB+7;j>=0;j--) {
int k=idum/IQ;
idum=IA*(idum-k*IQ)-IR*k;
if(idum<0) idum+=IM;
if(j<NTAB) iv[j]=idum;
}
iy=iv[0];
return seed;
}
float Uniform()
{
MLOCK(mutex);
if(!inited) RandomInit(time(0));
int k=idum/IQ;
idum=IA*(idum-k*IQ)-IR*k;
if(idum<0) idum+=IM;
int j=iy/NDIV;
iy=iv[j];
iv[j]=idum;
float temp=AM*iy; if(temp>RNMX) temp=RNMX;
return temp;
}
float Exponential()
{
return -log(Uniform());
}
float Gaussian()
{
MLOCK(mutex);
float v1,v2,rsq;
if(flag) {
flag=0;
return extra;
} else {
do {
v1=2*Uniform()-1;
v2=2*Uniform()-1;
rsq=v1*v1+v2*v2;
} while(rsq>=1||rsq<=0);
float fac=sqrt(-2*log(rsq)/rsq);
flag=1; extra=v1*fac;
return v2*fac;
}
}
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