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Fix hang in 1F1 #1446

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Merged
jzmaddock merged 4 commits into from
Sep 3, 2026
+12 −2
Merged

Fix hang in 1F1 #1446

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729986d
Fix hang in 1F1
NAThompson Sep 1, 2026
a35457a
1F1: move fix higher up the evaluation chain.
jzmaddock Sep 2, 2026
d09a871
1F1: Correct macro usage.
jzmaddock Sep 2, 2026
c2da3c6
1F1 tests: Fix min/max usage.
jzmaddock Sep 2, 2026
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4 changes: 3 additions & 1 deletion include/boost/math/special_functions/detail/hypergeometric_asym.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -44,8 +44,10 @@
}
else
{
e = z > static_cast<T>((std::numeric_limits<long long>::max)()) ? (std::numeric_limits<long long>::max)() : lltrunc(z, pol);
e = z >= static_cast<T>((std::numeric_limits<long long>::max)()) ? (std::numeric_limits<long long>::max)() : lltrunc(z, pol);
log_scaling += e;
if (z - e > tools::log_max_value<T>())
return policies::raise_overflow_error<T, Policy>(function, nullptr, pol);
prefix = exp(z - e);
}
if ((fabs(a) < 10) && (fabs(b) < 10))
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3 changes: 2 additions & 1 deletion include/boost/math/special_functions/hypergeometric_1F1.hpp
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Expand Up @@ -13,6 +13,7 @@
#include <boost/math/tools/config.hpp>
#include <boost/math/policies/policy.hpp>
#include <boost/math/policies/error_handling.hpp>
#include <boost/math/special_functions/fpclassify.hpp>
#include <boost/math/special_functions/detail/hypergeometric_series.hpp>
#include <boost/math/special_functions/detail/hypergeometric_asym.hpp>
#include <boost/math/special_functions/detail/hypergeometric_rational.hpp>
Expand Down Expand Up @@ -637,7 +638,7 @@ namespace boost { namespace math { namespace detail {
static const thread_local long long max_scaling = lltrunc(boost::math::tools::log_max_value<T>()) - 2;
static const thread_local T max_scale_factor = exp(T(max_scaling));

while (log_scaling > max_scaling)
while (!(boost::math::isinf)(result) && (log_scaling > max_scaling))
{
result *= max_scale_factor;
log_scaling -= max_scaling;
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7 changes: 7 additions & 0 deletions test/test_1F1.hpp
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Expand Up @@ -420,6 +420,13 @@ void test_spots6(T, const char* type_name)
T val = boost::math::hypergeometric_1F1(hypergeometric_1F1_big_bugs[i][0], hypergeometric_1F1_big_bugs[i][1], hypergeometric_1F1_big_bugs[i][2]);
BOOST_CHECK((boost::math::isinf)(val));
}
// https://github.com/boostorg/math/issues/1288
BOOST_CHECK_EQUAL(boost::math::hypergeometric_1F1(SC_(2.0), SC_(3.0), SC_(1e30)),
(std::numeric_limits<double>::infinity)());
// This is the largest log_hypergeometric_1F1 we can currently compute, beyond this the fix for the above
// bug causes premature overflow. However, there is no easy fix and Wolfram also fails in this case. It's **hard** :(
BOOST_CHECK_CLOSE_FRACTION(boost::math::log_hypergeometric_1F1(SC_(2.0), SC_(3.0), static_cast<T>((std::numeric_limits<std::int64_t>::max)())),
SC_(9223372036854775765.02487480528339082), boost::math::tools::epsilon<T>() * 10);
}
}

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