Fix PR#20843: binomial_distribution<unsigned> is broken. Add test to ensure that signed and unsigned verstions produce the same sequence.
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@217976 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/random b/include/random
index c0db1ab..e7053ce 100644
--- a/include/random
+++ b/include/random
@@ -4009,6 +4009,8 @@
}
}
+// Reference: Kemp, C.D. (1986). `A modal method for generating binomial
+// variables', Commun. Statist. - Theor. Meth. 15(3), 805-813.
template<class _IntType>
template<class _URNG>
_IntType
@@ -4035,7 +4037,8 @@
if (__u < 0)
return __rd - 1;
}
- --__rd;
+ if ( __rd != 0 )
+ --__rd;
++__ru;
if (__ru <= __pr.__t_)
{
diff --git a/test/numerics/rand/rand.dis/rand.dist.bern/rand.dist.bern.bin/eval.pass.cpp b/test/numerics/rand/rand.dis/rand.dist.bern/rand.dist.bern.bin/eval.pass.cpp
index 3bfd2af..85ff2ac 100644
--- a/test/numerics/rand/rand.dis/rand.dist.bern/rand.dist.bern.bin/eval.pass.cpp
+++ b/test/numerics/rand/rand.dis/rand.dist.bern/rand.dist.bern.bin/eval.pass.cpp
@@ -322,6 +322,17 @@
assert(std::abs((kurtosis - x_kurtosis) / x_kurtosis) < 0.01);
}
{
+ const int N = 100000;
+ std::mt19937 gen1;
+ std::mt19937 gen2;
+
+ std::binomial_distribution<> dist1(5, 0.1);
+ std::binomial_distribution<unsigned> dist2(5, 0.1);
+
+ for(int i = 0; i < N; ++i)
+ assert(dist1(gen1) == dist2(gen2));
+ }
+ {
typedef std::binomial_distribution<> D;
typedef std::mt19937 G;
G g;