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/*
* Copyright (C) 2011 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/* $Id: db_utilities_random.h,v 1.1 2010/08/19 18:09:20 bsouthall Exp $ */
#ifndef DB_UTILITIES_RANDOM
#define DB_UTILITIES_RANDOM
#include "db_utilities.h"
/*****************************************************************
* Lean and mean begins here *
*****************************************************************/
/*!
* \defgroup LMRandom (LM) Random numbers, random sampling
*/
/*\{*/
/*!
Random Number generator. Initialize with non-zero
integer value r. A double between zero and one is
returned.
\param r seed
\return random double
*/
inline double db_QuickRandomDouble(int &r)
{
int c;
c=r/127773;
r=16807*(r-c*127773)-2836*c;
if(r<0) r+=2147483647;
return((1.0/((double)2147483647))*r);
//return (((double)rand())/(double)RAND_MAX);
}
/*!
Random Number generator. Initialize with non-zero
integer value r. An int between and including 0 and max
\param r seed
\param max upped limit
\return random int
*/
inline int db_RandomInt(int &r,int max)
{
double dtemp;
int itemp;
dtemp=db_QuickRandomDouble(r)*(max+1);
itemp=(int) dtemp;
if(itemp<=0) return(0);
if(itemp>=max) return(max);
return(itemp);
}
/*!
Generate a random sample indexing into [0..pool_size-1].
\param s sample (out) pre-allocated array of size sample_size
\param sample_size size of sample
\param pool_size upper limit on item index
\param r_seed random number generator seed
*/
inline void db_RandomSample(int *s,int sample_size,int pool_size,int &r_seed)
{
int temp,temp2,i,j;
for(i=0;i<sample_size;i++)
{
temp=db_RandomInt(r_seed,pool_size-1-i);
for(j=0;j<i;j++)
{
if(s[j]<=temp) temp++;
else
{
/*swap*/
temp2=temp;
temp=s[j];
s[j]=temp2;
}
}
s[i]=temp;
}
}
/*\}*/
#endif /* DB_UTILITIES_RANDOM */
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