67 lines
1.7 KiB
C++
67 lines
1.7 KiB
C++
|
Random.cpp - Implementation for random number class
|
||
|
|
|
||
|
|
#include "Random.h"
|
||
|
|
|
||
|
|
|
||
|
|
static const int A = 48271;
|
||
|
|
static const int M = 2147483647;
|
||
|
|
static const int Q = M / A;
|
||
|
|
static const int R = M % A;
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Construct with initialValue for the state.
|
||
|
|
*/
|
||
|
|
Random::Random( int initialValue )
|
||
|
|
{
|
||
|
|
if( initialValue < 0 )
|
||
|
|
initialValue += M;
|
||
|
|
|
||
|
|
state = initialValue;
|
||
|
|
if( state == 0 )
|
||
|
|
state = 1;
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Return a pseudorandom int, and change the
|
||
|
|
* internal state.
|
||
|
|
*/
|
||
|
|
int Random::randomInt( )
|
||
|
|
{
|
||
|
|
int tmpState = A * ( state % Q ) - R * ( state / Q );
|
||
|
|
if( tmpState >= 0 )
|
||
|
|
state = tmpState;
|
||
|
|
else
|
||
|
|
state = tmpState + M;
|
||
|
|
|
||
|
|
return state;
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Return a pseudorandom int, and change the
|
||
|
|
* internal state. DOES NOT WORK.
|
||
|
|
*/
|
||
|
|
int Random::randomIntWRONG( )
|
||
|
|
{
|
||
|
|
return state = ( A * state ) % M;
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Return a pseudorandom double in the open range 0..1
|
||
|
|
* and change the internal state.
|
||
|
|
*/
|
||
|
|
double Random::random0_1( )
|
||
|
|
{
|
||
|
|
return (double) randomInt( ) / M;
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Return an int in the closed range [low,high], and
|
||
|
|
* change the internal state.
|
||
|
|
*/
|
||
|
|
int Random::randomInt( int low, int high )
|
||
|
|
{
|
||
|
|
double partitionSize = (double) M / ( high - low + 1 );
|
||
|
|
|
||
|
|
return (int) ( randomInt( ) / partitionSize ) + low;
|
||
|
|
}
|