Chaste  Release::2018.1
RandomNumberGenerator.cpp
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34 */
35 
36 #include "RandomNumberGenerator.hpp"
37 #include "Exception.hpp"
38 
39 #if BOOST_VERSION < 106400 // #2893
40 // Forward compatibility with Boost 1.64 onwards
43 #endif
44 
46 
48  : mMersenneTwisterGenerator(0u),
49  mGenerateUnitReal(mMersenneTwisterGenerator, boost::uniform_real<>()),
50 #if BOOST_VERSION < 106400 // #2585 and #2893
51  mGenerateStandardNormal(mMersenneTwisterGenerator, boost::random::normal_distribution_v165<>(0.0, 1.0))
52 #else
53  mGenerateStandardNormal(mMersenneTwisterGenerator, boost::normal_distribution<>(0.0, 1.0))
54 #endif
55 {
56  assert(mpInstance == nullptr); // Ensure correct serialization
57 }
58 
60 {
61  if (mpInstance == nullptr)
62  {
64  }
65  return mpInstance;
66 }
67 
69 {
70  if (mpInstance)
71  {
72  delete mpInstance;
73  mpInstance = nullptr;
74  }
75 }
76 
77 unsigned RandomNumberGenerator::randMod(unsigned base)
78 {
79  assert(base > 0u);
80  /*
81  * The contents of this method are copied out of
82  * boost/include/boost/random/uniform_smallint.hpp lines 235 - 255
83  * as of v 1.48 (preserved at least as far as 1.51).
84  * to make sure we get the same
85  * result on earlier versions of boost.
86  *
87  * It was then simplified as we know '_min' is zero, '_max' is 'base-1u'
88  * and all the types are unsigneds.
89  */
90 
91  // equivalent to (eng() - eng.min()) % (_max - _min + 1) + _min,
92  // but guarantees no overflow.
93  unsigned base_range = boost::random::detail::subtract<unsigned>()((mMersenneTwisterGenerator.max)(), (mMersenneTwisterGenerator.min)());
94  unsigned val = boost::random::detail::subtract<unsigned>()(mMersenneTwisterGenerator(), (mMersenneTwisterGenerator.min)());
95 
96  if (base - 1u >= base_range)
97  {
98  // This was in the original boost file for when '_min' is large, but here it is zero so
99  // we shouldn't ever reach this.
101  //return val;
102  }
103  else
104  {
105  return (val % base);
106  }
107 }
108 
110 {
111  return mGenerateUnitReal();
112 }
113 
115 {
116  return mGenerateStandardNormal();
117 }
118 
119 double RandomNumberGenerator::NormalRandomDeviate(double mean, double stdDev)
120 {
121  return stdDev * StandardNormalRandomDeviate() + mean;
122 }
123 
124 double RandomNumberGenerator::GammaRandomDeviate(double shape, double scale)
125 {
126 // make a gamma distribution and `merge' this distribution with our random number generator
127 
128 #if BOOST_VERSION < 106400
130  boost::variate_generator<boost::mt19937&, boost::random::gamma_distribution_v165<> > var_gamma(mMersenneTwisterGenerator, gd);
131 #else
132  boost::gamma_distribution<> gd(shape);
133  boost::variate_generator<boost::mt19937&, boost::gamma_distribution<> > var_gamma(mMersenneTwisterGenerator, gd);
134 #endif
135  return scale * var_gamma();
136 }
137 
139 {
140 // make an exponential distribution and `merge' this distribution with our random number generator
141 
142 #if BOOST_VERSION < 106400
144  boost::variate_generator<boost::mt19937&, boost::random::exponential_distribution_v165<> > var_exponential(mMersenneTwisterGenerator, ed);
145 #else
146  boost::exponential_distribution<> ed(scale);
147  boost::variate_generator<boost::mt19937&, boost::exponential_distribution<> > var_exponential(mMersenneTwisterGenerator, ed);
148 #endif
149  // return the random number
150  return var_exponential();
151 }
152 
153 void RandomNumberGenerator::Reseed(unsigned seed)
154 {
155  mMersenneTwisterGenerator.seed(seed);
156 
157  // Because this does some Box-Muller type thing it remembers if you don't reset it - see #2633
158  mGenerateStandardNormal.distribution().reset();
159 
160  // Probably don't need to do this, but it probably is good practice!
161  mGenerateUnitReal.distribution().reset();
162 }
163 
164 void RandomNumberGenerator::Shuffle(unsigned num, std::vector<unsigned>& rValues)
165 {
166  rValues.resize(num);
167  for (unsigned i = 0; i < num; i++)
168  {
169  rValues[i] = i;
170  }
171 
172  for (unsigned end = num - 1; end > 0; end--)
173  {
174  // Pick a random integer from {0,..,end}
175  unsigned k = RandomNumberGenerator::Instance()->randMod(end + 1);
176  unsigned temp = rValues[end];
177  rValues[end] = rValues[k];
178  rValues[k] = temp;
179  }
180 }
unsigned randMod(unsigned base)
boost::variate_generator< boost::mt19937 &, boost::random::normal_distribution_v165<> > mGenerateStandardNormal
static RandomNumberGenerator * mpInstance
double NormalRandomDeviate(double mean, double stdDev)
#define NEVER_REACHED
Definition: Exception.hpp:206
boost::variate_generator< boost::mt19937 &, boost::uniform_real<> > mGenerateUnitReal
void Shuffle(std::vector< boost::shared_ptr< T > > &rValues)
boost::mt19937 mMersenneTwisterGenerator
static RandomNumberGenerator * Instance()
double GammaRandomDeviate(double shape, double scale)
double ExponentialRandomDeviate(double scale)