diff options
Diffstat (limited to '')
| -rw-r--r-- | source/FastRandom.cpp | 174 | ||||
| -rw-r--r-- | source/FastRandom.h | 57 |
2 files changed, 231 insertions, 0 deletions
diff --git a/source/FastRandom.cpp b/source/FastRandom.cpp new file mode 100644 index 000000000..b778fb4bb --- /dev/null +++ b/source/FastRandom.cpp @@ -0,0 +1,174 @@ +
+// 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++)
+{
+}
+
+
+
+
+
+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 + m_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 + m_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 + m_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 + m_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);
+}
+
+
+
+
diff --git a/source/FastRandom.h b/source/FastRandom.h new file mode 100644 index 000000000..011c0c8da --- /dev/null +++ b/source/FastRandom.h @@ -0,0 +1,57 @@ +
+// FastRandom.h
+
+// Declares the cFastRandom class representing a fast random number generator
+
+/*
+The cFastRandom aims to provide a very fast, although not very cryptographically secure, random generator.
+It is fast to instantiate, fast to query next, and partially multi-thread-safe.
+It is multi-thread-safe in the sense that it can be accessed from multiple threads without crashing, but it may
+yield duplicate numbers in that case.
+
+Internally, this works similar to cNoise's integral noise generation, with some predefined inputs: the seed is
+taken from a global counter and the random is calculated using a counter that is incremented on each use (hence
+the multi-thread duplication). Two alternatives exists for each function, one that takes a range parameter,
+and another that takes an additional "salt" parameter; this salt is used as an additional input to the random,
+in order to avoid multi-thread duplication. If two threads both use the class at the same time with different
+salts, the values they get will be different.
+*/
+
+
+
+
+
+#pragma once
+
+
+
+
+
+class cFastRandom
+{
+public:
+ cFastRandom(void);
+
+ /// Returns a random int in the range [0 .. a_Range - 1]; a_Range must be less than 1M
+ int NextInt(int a_Range);
+
+ /// Returns a random int in the range [0 .. a_Range - 1]; a_Range must be less than 1M; a_Salt is additional source of randomness
+ int NextInt(int a_Range, int a_Salt);
+
+ /// Returns a random float in the range [0 .. a_Range]; a_Range must be less than 1M
+ float NextFloat(float a_Range);
+
+ /// Returns a random float in the range [0 .. a_Range]; a_Range must be less than 1M; a_Salt is additional source of randomness
+ float NextFloat(float a_Range, int a_Salt);
+
+protected:
+ int m_Seed;
+ int m_Counter;
+
+ /// Counter that is used to initialize the seed, incremented for each object created
+ static int m_SeedCounter;
+} ;
+
+
+
+
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