[gcc r14-12880] libstdc++: Update underlying gamma_distribution in param() [PR123409]
Tomasz Kaminski
tkaminsk@gcc.gnu.org
Mon Sep 21 09:49:59 GMT 2026
https://gcc.gnu.org/g:ffbb2d70429e8848bad8bd4dd640fd7d6d556d4a
commit r14-12880-gffbb2d70429e8848bad8bd4dd640fd7d6d556d4a
Author: Tomasz Kamiński <tkaminsk@redhat.com>
Date: Wed Sep 16 10:10:00 2026 +0200
libstdc++: Update underlying gamma_distribution in param() [PR123409]
This updates the underlying gamma distribution in the param function by
invoking the param function on the corresponding member:
* _M_gd for negative_binomial_distribution, student_t_distribution;
* _M_gd_x, _M_gd_y for fisher_f_distribution.
The distribution_param.cc test, validates that for all distributions,
constructing from or setting params results in equal distribution that
produces same values. The test uses -ffloat-store for -m32, following
chi_squared_distribution test for PR83833 - that is removed, as all
cases are covered in new test.
libstdc++-v3/ChangeLog:
PR libstdc++/123409
* include/bits/random.h (negative_binomial_distribution::param)
(fisher_f_distribution::param, student_t_distribution::param):
Updated underlying gamma distributions, by calling param.
(chi_squared_distribution::param): Use type alias and parenthesis
for consistency.
* testsuite/26_numerics/random/distribution_param.cc: New test.
* testsuite/26_numerics/random/chi_squared_distribution/83833.cc:
Removed, covered by above.
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
(cherry picked from commit c638dae26f3134951e11aafe696787f83121571c)
Diff:
---
libstdc++-v3/include/bits/random.h | 32 +++++++++---
.../random/chi_squared_distribution/83833.cc | 41 ---------------
.../26_numerics/random/distribution_param.cc | 60 ++++++++++++++++++++++
3 files changed, 86 insertions(+), 47 deletions(-)
diff --git a/libstdc++-v3/include/bits/random.h b/libstdc++-v3/include/bits/random.h
index 5fda21af882c..fba82515b94e 100644
--- a/libstdc++-v3/include/bits/random.h
+++ b/libstdc++-v3/include/bits/random.h
@@ -2889,9 +2889,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
param(const param_type& __param)
{
_M_param = __param;
- typedef typename std::gamma_distribution<result_type>::param_type
- param_type;
- _M_gd.param(param_type{__param.n() / 2});
+
+ using param_type
+ = typename std::gamma_distribution<result_type>::param_type;
+ _M_gd.param(param_type(__param.n() / 2));
}
/**
@@ -3345,7 +3346,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
*/
void
param(const param_type& __param)
- { _M_param = __param; }
+ {
+ _M_param = __param;
+
+ using param_type
+ = typename std::gamma_distribution<result_type>::param_type;
+ _M_gd_x.param(param_type(__param.m() / 2));
+ _M_gd_y.param(param_type(__param.n() / 2));
+ }
/**
* @brief Returns the greatest lower bound value of the distribution.
@@ -3574,7 +3582,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
*/
void
param(const param_type& __param)
- { _M_param = __param; }
+ {
+ _M_param = __param;
+
+ using param_type
+ = typename std::gamma_distribution<result_type>::param_type;
+ _M_gd.param(param_type(__param.n() / 2, 2));
+ }
/**
* @brief Returns the greatest lower bound value of the distribution.
@@ -4505,7 +4519,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
*/
void
param(const param_type& __param)
- { _M_param = __param; }
+ {
+ _M_param = __param;
+
+ using param_type
+ = typename std::gamma_distribution<double>::param_type;
+ _M_gd.param(param_type(__param.k(), (1.0 - __param.p()) / __param.p()));
+ }
/**
* @brief Returns the greatest lower bound value of the distribution.
diff --git a/libstdc++-v3/testsuite/26_numerics/random/chi_squared_distribution/83833.cc b/libstdc++-v3/testsuite/26_numerics/random/chi_squared_distribution/83833.cc
deleted file mode 100644
index 985bdbaed7d1..000000000000
--- a/libstdc++-v3/testsuite/26_numerics/random/chi_squared_distribution/83833.cc
+++ /dev/null
@@ -1,41 +0,0 @@
-// Copyright (C) 2018-2024 Free Software Foundation, Inc.
-//
-// This file is part of the GNU ISO C++ Library. This library is free
-// software; you can redistribute it and/or modify it under the
-// terms of the GNU General Public License as published by the
-// Free Software Foundation; either version 3, or (at your option)
-// any later version.
-
-// This library is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-// GNU General Public License for more details.
-
-// You should have received a copy of the GNU General Public License along
-// with this library; see the file COPYING3. If not see
-// <http://www.gnu.org/licenses/>.
-
-// { dg-do run { target c++11 } }
-// { dg-additional-options "-ffloat-store" { target { m68*-*-* || ia32 } } }
-// { dg-require-cstdint "" }
-
-#include <random>
-#include <testsuite_hooks.h>
-
-void
-test01()
-{
- std::default_random_engine r1, r2;
- using chi = std::chi_squared_distribution<double>;
- chi::param_type p(5);
- chi d1(p);
- chi d2;
- d2.param(p);
- VERIFY( d1(r1) == d2(r2) ); // PR libstdc++/83833
-}
-
-int
-main()
-{
- test01();
-}
diff --git a/libstdc++-v3/testsuite/26_numerics/random/distribution_param.cc b/libstdc++-v3/testsuite/26_numerics/random/distribution_param.cc
new file mode 100644
index 000000000000..d6c067662336
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/random/distribution_param.cc
@@ -0,0 +1,60 @@
+// { dg-do run { target c++11 } }
+// { dg-additional-options "-ffloat-store" { target { m68*-*-* || ia32 } } }
+// { dg-require-cstdint "" }
+
+#include <random>
+#include <testsuite_hooks.h>
+
+template<typename Distribution>
+void
+validate(Distribution&& source)
+{
+ const auto& params = source.param();
+
+ Distribution constr(params);
+ VERIFY( constr == source );
+
+ Distribution setter;
+ setter.param(params);
+ VERIFY( setter == source );
+
+ std::mt19937_64 e1(0x19650809ull), e2 = e1, e3 = e1;
+ for (int i = 0; i < 10; ++i)
+ {
+ const auto expected = source(e1);
+ VERIFY( constr(e2) == expected );
+ VERIFY( setter(e3) == expected );
+ }
+}
+
+int main()
+{
+ // PR83833, PR123409
+ validate(std::uniform_int_distribution<>(13, 22));
+ validate(std::uniform_real_distribution<>(1.0, 9.0));
+
+ validate(std::bernoulli_distribution(0.478));
+ validate(std::binomial_distribution<>(7, 0.334));
+ validate(std::negative_binomial_distribution<>(726, 0.65));
+ validate(std::geometric_distribution<>(0.545));
+
+ validate(std::poisson_distribution<>(6));
+ validate(std::exponential_distribution<>(3));
+ validate(std::gamma_distribution<>(1.1, 2.2));
+ validate(std::weibull_distribution<>(1.7, 3.0));
+ validate(std::extreme_value_distribution<>(-1.628, 1.628));
+
+ validate(std::normal_distribution<>(5.0, 2.0));
+ validate(std::lognormal_distribution<>(1.67, 0.25));
+ validate(std::chi_squared_distribution<>(5));
+ validate(std::cauchy_distribution<>(-3, 0.25));
+ validate(std::fisher_f_distribution<>(26.0, 7.0));
+ validate(std::student_t_distribution<>(65.0));
+
+ const auto wf = [](double x) { return 1 + x; };
+ validate(std::discrete_distribution<>(4, 1.2, 4.5, wf));
+ validate(std::piecewise_constant_distribution<>(5, 0.5, 9, wf));
+ validate(std::piecewise_linear_distribution<>(3, 1.2, 3.4, wf));
+
+ return 0;
+}
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