From: Arnaud Giersch <arnaud.giersch@univ-fcomte.fr>
Date: Thu, 6 Feb 2020 10:18:05 +0000 (+0100)
Subject: Exclude max from range for xbt::random::uniform_real.
X-Git-Tag: v3.26~1025
X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/commitdiff_plain/037217ec2176ada8eb05cd8e5f5b63e7440c63a3

Exclude max from range for xbt::random::uniform_real.

Mimic std::uniform_real_distribution.
---

diff --git a/include/xbt/random.hpp b/include/xbt/random.hpp
index b67487d623..c55ba8b713 100644
--- a/include/xbt/random.hpp
+++ b/include/xbt/random.hpp
@@ -26,7 +26,7 @@ void set_implem_std();
 void set_mersenne_seed(int);
 
 /**
- * @brief Draws an integer number uniformly between min and max included
+ * @brief Draws an integer number uniformly in range [min, max] (min and max included)
  *
  * @param min Minimum value
  * @param max Maximum value
@@ -34,7 +34,7 @@ void set_mersenne_seed(int);
 int uniform_int(int min, int max);
 
 /**
- * @brief Draws a real number uniformly between min and max included
+ * @brief Draws a real number uniformly in range [min, max) (min included, and max excluded)
  *
  * @param min Minimum value
  * @param max Maximum value
diff --git a/src/xbt/random.cpp b/src/xbt/random.cpp
index beaaf21329..22d7591650 100644
--- a/src/xbt/random.cpp
+++ b/src/xbt/random.cpp
@@ -55,7 +55,7 @@ double uniform_real(double min, double max)
   }
 
   // This reuses Boost's uniform real distribution ideas
-  constexpr unsigned long divisor = decltype(mt19937_gen)::max() - decltype(mt19937_gen)::min();
+  constexpr unsigned long divisor = decltype(mt19937_gen)::max() - decltype(mt19937_gen)::min() + 1;
   unsigned long numerator         = mt19937_gen() - decltype(mt19937_gen)::min();
   return min + (max - min) * numerator / divisor;
 }
diff --git a/src/xbt/random_test.cpp b/src/xbt/random_test.cpp
index b7c10e8a2c..f601ea9791 100644
--- a/src/xbt/random_test.cpp
+++ b/src/xbt/random_test.cpp
@@ -16,10 +16,10 @@ TEST_CASE("xbt::random: Random Number Generation")
   SECTION("Using XBT_RNG_xbt")
   {
     simgrid::xbt::random::set_mersenne_seed(12345);
-    REQUIRE_THAT(simgrid::xbt::random::exponential(25), EpsilonApprox(0.00291934351538427348));
+    REQUIRE_THAT(simgrid::xbt::random::exponential(25), EpsilonApprox(0.00291934352469749815));
     REQUIRE(simgrid::xbt::random::uniform_int(1, 6) == 4);
-    REQUIRE_THAT(simgrid::xbt::random::uniform_real(0, 1), EpsilonApprox(0.31637556043369124970));
-    REQUIRE_THAT(simgrid::xbt::random::normal(0, 2), EpsilonApprox(1.62746784745133976635));
+    REQUIRE_THAT(simgrid::xbt::random::uniform_real(0, 1), EpsilonApprox(0.31637556036002933979));
+    REQUIRE_THAT(simgrid::xbt::random::normal(0, 2), EpsilonApprox(1.62746784853777226587));
   }
 
   SECTION("Using XBT_RNG_std")