Using the proper c++ way to get the min double value

[simgrid.git] / src / xbt / random.cpp

diff --git a/src/xbt/random.cpp b/src/xbt/random.cpp
index 95aed12..03c544a 100644 (file)
--- a/src/xbt/random.cpp
+++ b/src/xbt/random.cpp
@@ -5,6 +5,7 @@
 
 #include "xbt/random.hpp"
 #include "xbt/asserts.h"
+#include <limits>
 #include <random>
 
 namespace simgrid {
@@ -46,6 +47,20 @@ double exponential(double lambda)
   return -1 / lambda * log(numerator / divisor);
 }
 
+double normal(double mean, double sd)
+{
+  unsigned long numeratorA = mt19937_gen() - mt19937_gen.min();
+  unsigned long numeratorB = mt19937_gen() - mt19937_gen.min();
+  unsigned long divisor    = mt19937_gen.max() - mt19937_gen.min();
+  double u1                = numeratorA / divisor;
+  while (u1 < std::numeric_limits<double>::min()) {
+    numeratorA = mt19937_gen() - mt19937_gen.min();
+    u1         = numeratorA / divisor;
+  }
+  double z0 = sqrt(-2.0 * log(numeratorA / divisor)) * cos(2 * M_PI * numeratorB / divisor);
+  return z0 * sd + mean;
+}
+
 } // namespace random
 } // namespace xbt
 } // namespace simgrid