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// FastRandom.cpp
// Implements the cFastRandom class representing a fast random number generator
#include "Globals.h"
#include <time.h>
#include "FastRandom.h"
#if 0 && defined(_DEBUG)
// Self-test
// Both ints and floats are quick-tested to see if the random is calculated correctly, checking the range in ASSERTs,
// and if it performs well in terms of distribution (checked by avg, expected to be in the range midpoint
class cFastRandomTest
{
public:
cFastRandomTest(void)
{
TestInts();
TestFloats();
}
void TestInts(void)
{
printf("Testing ints...\n");
cFastRandom rnd;
int sum = 0;
const int BUCKETS = 8;
int Counts[BUCKETS];
memset(Counts, 0, sizeof(Counts));
const int ITER = 10000;
for (int i = 0; i < ITER; i++)
{
int v = rnd.NextInt(1000);
ASSERT(v >= 0);
ASSERT(v < 1000);
Counts[v % BUCKETS]++;
sum += v;
}
double avg = (double)sum / ITER;
printf("avg: %f\n", avg);
for (int i = 0; i < BUCKETS; i++)
{
printf(" bucket %d: %d\n", i, Counts[i]);
}
}
void TestFloats(void)
{
printf("Testing floats...\n");
cFastRandom rnd;
float sum = 0;
const int BUCKETS = 8;
int Counts[BUCKETS];
memset(Counts, 0, sizeof(Counts));
const int ITER = 10000;
for (int i = 0; i < ITER; i++)
{
float v = rnd.NextFloat(1000);
ASSERT(v >= 0);
ASSERT(v <= 1000);
Counts[((int)v) % BUCKETS]++;
sum += v;
}
sum = sum / ITER;
printf("avg: %f\n", sum);
for (int i = 0; i < BUCKETS; i++)
{
printf(" bucket %d: %d\n", i, Counts[i]);
}
}
} g_Test;
#endif
int cFastRandom::m_SeedCounter = 0;
cFastRandom::cFastRandom(void) :
m_Seed(m_SeedCounter++),
m_Counter(0)
{
}
int cFastRandom::NextInt(int a_Range)
{
ASSERT(a_Range <= 1000000); // The random is not sufficiently linearly distributed with bigger ranges
ASSERT(a_Range > 0);
// Make the m_Counter operations as minimal as possible, to emulate atomicity
int Counter = m_Counter++;
// Use a_Range, m_Counter and m_Seed as inputs to the pseudorandom function:
int n = a_Range + Counter * 57 + m_Seed * 57 * 57;
n = (n << 13) ^ n;
n = ((n * (n * n * 15731 + 789221) + 1376312589) & 0x7fffffff);
return ((n / 11) % a_Range);
}
int cFastRandom::NextInt(int a_Range, int a_Salt)
{
ASSERT(a_Range <= 1000000); // The random is not sufficiently linearly distributed with bigger ranges
ASSERT(a_Range > 0);
// Make the m_Counter operations as minimal as possible, to emulate atomicity
int Counter = m_Counter++;
// Use a_Range, a_Salt, m_Counter and m_Seed as inputs to the pseudorandom function:
int n = a_Range + Counter * 57 + m_Seed * 57 * 57 + a_Salt * 57 * 57 * 57;
n = (n << 13) ^ n;
n = ((n * (n * n * 15731 + 789221) + 1376312589) & 0x7fffffff);
return ((n / 11) % a_Range);
}
float cFastRandom::NextFloat(float a_Range)
{
// Make the m_Counter operations as minimal as possible, to emulate atomicity
int Counter = m_Counter++;
// Use a_Range, a_Salt, m_Counter and m_Seed as inputs to the pseudorandom function:
int n = (int)a_Range + Counter * 57 + m_Seed * 57 * 57;
n = (n << 13) ^ n;
n = ((n * (n * n * 15731 + 789221) + 1376312589) & 0x7fffffff);
// Convert the integer into float with the specified range:
return (((float)n / (float)0x7fffffff) * a_Range);
}
float cFastRandom::NextFloat(float a_Range, int a_Salt)
{
// Make the m_Counter operations as minimal as possible, to emulate atomicity
int Counter = m_Counter++;
// Use a_Range, a_Salt, m_Counter and m_Seed as inputs to the pseudorandom function:
int n = (int)a_Range + Counter * 57 + m_Seed * 57 * 57 + a_Salt * 57 * 57 * 57;
n = (n << 13) ^ n;
n = ((n * (n * n * 15731 + 789221) + 1376312589) & 0x7fffffff);
// Convert the integer into float with the specified range:
return (((float)n / (float)0x7fffffff) * a_Range);
}
int cFastRandom::GenerateRandomInteger(int a_Begin, int a_End)
{
cFastRandom Random;
return Random.NextInt(a_End - a_Begin + 1) + a_Begin;
}
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