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