1 files changed, 45 insertions, 5 deletions
diff --git a/libcxx/test/numerics/rand/rand.dis/rand.dist.uni/rand.dist.uni.int/eval_param.pass.cpp b/libcxx/test/numerics/rand/rand.dis/rand.dist.uni/rand.dist.uni.int/eval_param.pass.cpp
index 62507d73ca1..6bbd4fabb68 100644
--- a/libcxx/test/numerics/rand/rand.dis/rand.dist.uni/rand.dist.uni.int/eval_param.pass.cpp
+++ b/libcxx/test/numerics/rand/rand.dis/rand.dist.uni/rand.dist.uni.int/eval_param.pass.cpp
@@ -16,20 +16,60 @@
 
 #include <random>
 #include <cassert>
+#include <vector>
+#include <numeric>
+
+template <class T>
+inline
+T
+sqr(T x)
+{
+    return x * x;
+}
 
 int main()
 {
     {
         typedef std::uniform_int_distribution<> D;
+        typedef std::minstd_rand G;
         typedef D::param_type P;
-        typedef std::minstd_rand0 G;
         G g;
-        D d(-6, 106);
+        D d(5, 100);
         P p(-10, 20);
-        for (int i = 0; i < 10000; ++i)
+        const int N = 100000;
+        std::vector<D::result_type> u;
+        for (int i = 0; i < N; ++i)
+        {
+            D::result_type v = d(g, p);
+            assert(p.a() <= v && v <= p.b());
+            u.push_back(v);
+        }
+        double mean = std::accumulate(u.begin(), u.end(),
+                                              double(0)) / u.size();
+        double var = 0;
+        double skew = 0;
+        double kurtosis = 0;
+        for (int i = 0; i < u.size(); ++i)
         {
-            int u = d(g, p);
-            assert(-10 <= u && u <= 20);
+            double d = (u[i] - mean);
+            double d2 = sqr(d);
+            var += d2;
+            skew += d * d2;
+            kurtosis += d2 * d2;
         }
+        var /= u.size();
+        double dev = std::sqrt(var);
+        skew /= u.size() * dev * var;
+        kurtosis /= u.size() * var * var;
+        kurtosis -= 3;
+        double x_mean = ((double)p.a() + p.b()) / 2;
+        double x_var = (sqr((double)p.b() - p.a() + 1) - 1) / 12;
+        double x_skew = 0;
+        double x_kurtosis = -6. * (sqr((double)p.b() - p.a() + 1) + 1) /
+                            (5. * (sqr((double)p.b() - p.a() + 1) - 1));
+        assert(std::abs(mean - x_mean) / x_mean < 0.01);
+        assert(std::abs(var - x_var) / x_var < 0.01);
+        assert(std::abs(skew - x_skew) < 0.01);
+        assert(std::abs(kurtosis - x_kurtosis) / x_kurtosis < 0.01);
     }
 }