From aa19a3afb0b94e8b5fe055eeb38b1fb2ee1a67b0 Mon Sep 17 00:00:00 2001
From: Tiger Wang <ziwei.tiger@hotmail.co.uk>
Date: Sun, 19 Oct 2014 14:10:18 +0100
Subject: Migrated random generators to std::random

---
 src/FastRandom.cpp | 116 ++++++++++++++++++++++++++++-------------------------
 1 file changed, 62 insertions(+), 54 deletions(-)

(limited to 'src/FastRandom.cpp')

diff --git a/src/FastRandom.cpp b/src/FastRandom.cpp
index 42bf5f3f9..cfafc7486 100644
--- a/src/FastRandom.cpp
+++ b/src/FastRandom.cpp
@@ -4,13 +4,15 @@
 // Implements the cFastRandom class representing a fast random number generator
 
 #include "Globals.h"
-#include <time.h>
 #include "FastRandom.h"
 
 
 
 
 
+////////////////////////////////////////////////////////////////////////////////
+// cFastRandom:
+
 #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,
@@ -83,16 +85,8 @@ public:
 
 
 
-
-int cFastRandom::m_SeedCounter = 0;
-
-
-
-
-
 cFastRandom::cFastRandom(void) :
-	m_Seed(m_SeedCounter++),
-	m_Counter(0)
+	m_LinearRand(static_cast<unsigned>(std::chrono::system_clock::now().time_since_epoch().count()))
 {
 }
 
@@ -102,82 +96,96 @@ cFastRandom::cFastRandom(void) :
 
 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);
+	m_IntDistribution = std::uniform_int_distribution<>(0, a_Range - 1);
+	return m_IntDistribution(m_LinearRand);
 }
 
 
 
 
 
+
 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);
+	m_LinearRand.seed(a_Salt);
+	m_IntDistribution = std::uniform_int_distribution<>(0, a_Range - 1);
+	return m_IntDistribution(m_LinearRand);
 }
 
 
 
 
 
+
 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);
+	m_FloatDistribution = std::uniform_real_distribution<float>(0, a_Range - 1);
+	return m_FloatDistribution(m_LinearRand);
 }
 
 
 
 
 
+
 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);
+	m_LinearRand.seed(a_Salt);
+	m_FloatDistribution = std::uniform_real_distribution<float>(0, a_Range - 1);
+	return m_FloatDistribution(m_LinearRand);
 }
 
 
 
 
 
+
 int cFastRandom::GenerateRandomInteger(int a_Begin, int a_End)
 {
-	cFastRandom Random;
-	return Random.NextInt(a_End - a_Begin + 1) + a_Begin;
+	m_IntDistribution = std::uniform_int_distribution<>(a_Begin, a_End - 1);
+	return m_IntDistribution(m_LinearRand);
+}
+
+
+
+
+
+////////////////////////////////////////////////////////////////////////////////
+// MTRand:
+
+MTRand::MTRand() :
+	m_MersenneRand(static_cast<unsigned>(std::chrono::system_clock::now().time_since_epoch().count()))
+{
+}
+
+
+
+
+
+int MTRand::randInt(int a_Range)
+{
+	m_IntDistribution = std::uniform_int_distribution<>(0, a_Range);
+	return m_IntDistribution(m_MersenneRand);
+}
+
+
+
+
+
+int MTRand::randInt()
+{
+	m_IntDistribution = std::uniform_int_distribution<>(0, std::numeric_limits<int>::max());
+	return m_IntDistribution(m_MersenneRand);
+}
+
+
+
+
+
+double MTRand::rand(double a_Range)
+{
+	m_DoubleDistribution = std::uniform_real_distribution<>(0, a_Range);
+	return m_DoubleDistribution(m_MersenneRand);
 }
 
 
-- 
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