Check for 0 stddev when generating a random number using normal distr…

…ibution (#615)

Signed-off-by: Ian Chen <[email protected]>

src/Rand.cc

@@ -25,6 +25,8 @@
   #include <unistd.h>
 #endif
 
+#include <limits>
+
 #include "gz/math/Rand.hh"
 
 using namespace gz;
@@ -54,6 +56,10 @@ double Rand::DblUniform(double _min, double _max)
 //////////////////////////////////////////////////
 double Rand::DblNormal(double _mean, double _sigma)
 {
+  if (equal(_sigma, 0.0, std::numeric_limits<double>::epsilon()))
+
+    return _mean;
+
   NormalRealDist d(_mean, _sigma);
   return d(RandGenerator());
 }
@@ -69,6 +75,9 @@ int32_t Rand::IntUniform(int _min, int _max)
 //////////////////////////////////////////////////
 int32_t Rand::IntNormal(int _mean, int _sigma)
 {
+  if (_sigma == 0)
+    return _mean;
+
   NormalRealDist d(_mean, _sigma);
 
   return static_cast<int32_t>(d(RandGenerator()));

src/Rand_TEST.cc

@@ -51,6 +51,13 @@ TEST(RandTest, Rand)
     EXPECT_EQ(i, 9);
     EXPECT_NEAR(d, 3.00618, 1e-5);
 #endif
+
+    // Test with sigma == 0
+    d = math::Rand::DblNormal(2.0, 0.0);
+    i = math::Rand::IntNormal(10, 0);
+
+    EXPECT_NEAR(2.0, d, 1e-6);
+    EXPECT_EQ(10, i);
   }
 #endif
 }