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Merge pull request #134 from boostorg/133

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Avoid division by 0 in beta_distribution `operator()`
This commit is contained in:
Matt Borland
2025-06-30 13:41:39 -04:00
committed by GitHub
parent 59a5eb88ad c98dc05550
commit 3289126cd7
3 changed files with 36 additions and 2 deletions
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11
include/boost/random/beta_distribution.hpp
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@@ -101,8 +101,15 @@ public:
template<class URNG>
RealType operator()(URNG& urng) const
{
RealType a = gamma_distribution<RealType>(_alpha, RealType(1.0))(urng);
RealType b = gamma_distribution<RealType>(_beta, RealType(1.0))(urng);
RealType a = 0;
RealType b = 0;
do
{
a = gamma_distribution<RealType>(_alpha, RealType(1.0))(urng);
b = gamma_distribution<RealType>(_beta, RealType(1.0))(urng);
} while (a + b == RealType(0));
return a / (a + b);
}

2
test/Jamfile.v2
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@@ -86,6 +86,8 @@ run test_comp_xoshiro128mm.cpp ;
run test_xoshiro128f.cpp /boost/test//boost_unit_test_framework ;
run test_comp_xoshiro128f.cpp ;
run github_issue_133.cpp ;
run niederreiter_base2_validate.cpp /boost/test//boost_unit_test_framework ;
run sobol_validate.cpp /boost/test//boost_unit_test_framework ;
run faure_validate.cpp /boost/test//boost_unit_test_framework ;

25
test/github_issue_133.cpp Normal file
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@@ -0,0 +1,25 @@
// Copyright 2025 Matt Borland
// Distributed under the Boost Software License, Version 1.0.
// https://www.boost.org/LICENSE_1_0.txt
//
// See: https://github.com/boostorg/random/issues/133
#include <boost/core/lightweight_test.hpp>
#include <boost/random/beta_distribution.hpp>
#include <random>
#include <cmath>
int main()
{
constexpr double beta_param = 0.0020368700639848774;
boost::random::beta_distribution<double> dist(beta_param, beta_param);
std::mt19937_64 gen(12345);
for (int i = 0; i < 10000; ++i)
{
const double Z = dist(gen);
BOOST_TEST(!std::isnan(Z));
}
return boost::report_errors();
}