Merge pull request #148 from boostorg/seedseq

Fix xoshiro constructors using seed seq incorrectly

include/boost/random/detail/xoshiro_base.hpp

@@ -53,12 +53,12 @@ private:
     template <typename Sseq>
     inline void sseq_seed_64(Sseq& seq)
     {
-        for (auto& i : state_)
-        {
-            std::array<std::uint32_t, 2> seeds;
-            seq.generate(seeds.begin(), seeds.end());
+        std::array<std::uint32_t, N * 2> seeds;
+        seq.generate(seeds.begin(), seeds.end());
 
-            i = concatenate(seeds[0], seeds[1]);
+        for (std::size_t i = 0; i < state_.size(); ++i)
+        {
+            state_[i] = concatenate(seeds[2*i], seeds[2*i + 1]);
         }
     }
 

test/Jamfile.v2

@@ -87,6 +87,7 @@ run test_xoshiro128f.cpp /boost/test//boost_unit_test_framework ;
 run test_comp_xoshiro128f.cpp ;
 
 run github_issue_133.cpp ;
+run github_issue_147.cpp ;
 
 run niederreiter_base2_validate.cpp /boost/test//boost_unit_test_framework ;
 run sobol_validate.cpp /boost/test//boost_unit_test_framework ;

test/github_issue_147.cpp

@@ -0,0 +1,57 @@
+/*
+* Copyright Matt Borland 2025.
+ * Distributed under the Boost Software License, Version 1.0. (See
+        * accompanying file LICENSE_1_0.txt or copy at
+ * http://www.boost.org/LICENSE_1_0.txt)
+ *
+ * See http://www.boost.org for most recent version including documentation.
+ *
+ * $Id$
+ */
+
+#include <boost/random.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <array>
+#include <vector>
+#include <random>
+#include <cstdint>
+
+template <class Arr>
+bool all_words_equal(const Arr& a)
+{
+    for (std::size_t i = 1; i < a.size(); ++i)
+    {
+        if (a[i] != a[0]) return false;
+    }
+
+    return true;
+}
+
+template <class Engine, class SSeq>
+void test_engine_with_sseq(SSeq& sseq)
+{
+    Engine eng(sseq);
+    auto st = eng.state();
+    BOOST_TEST(!all_words_equal(st));
+}
+
+int main()
+{
+    const std::vector<std::uint32_t> seed_words = {
+        0x12345678u, 0x9abcdef0u, 0xc0ffee12u, 0xdeadbeefu
+    };
+
+    // xoshiro128mm (4 x 32-bit state)
+    std::seed_seq stdseq(seed_words.begin(), seed_words.end());
+    boost::random::seed_seq bseq(seed_words.begin(), seed_words.end());
+    test_engine_with_sseq<boost::random::xoshiro128mm>(stdseq);
+    test_engine_with_sseq<boost::random::xoshiro128mm>(bseq);
+
+    // xoshiro256mm (4 x 64-bit state)
+    std::seed_seq stdseq2(seed_words.begin(), seed_words.end());
+    boost::random::seed_seq bseq2(seed_words.begin(), seed_words.end());
+    test_engine_with_sseq<boost::random::xoshiro256mm>(stdseq2);
+    test_engine_with_sseq<boost::random::xoshiro256mm>(bseq2);
+
+    return boost::report_errors();
+}

test/test_xoshiro256d.cpp

@@ -19,7 +19,7 @@
 
 // principal operation validated with CLHEP, values by experiment
 #define BOOST_RANDOM_VALIDATION_VALUE 0.91719108108351499
-#define BOOST_RANDOM_SEED_SEQ_VALIDATION_VALUE 0.34930769688746899
+#define BOOST_RANDOM_SEED_SEQ_VALIDATION_VALUE 0.68650209712672527
 
 // Since we are using splitmix64 we need to allow 64 bit seeds
 // The test harness only allows for 32 bit seeds

test/test_xoshiro256mm.cpp

@@ -19,6 +19,6 @@
 
 // principal operation validated with CLHEP, values by experiment
 #define BOOST_RANDOM_VALIDATION_VALUE UINT64_C(2196391076106727935)
-#define BOOST_RANDOM_SEED_SEQ_VALIDATION_VALUE UINT64_C(3823370830110671407)
+#define BOOST_RANDOM_SEED_SEQ_VALIDATION_VALUE UINT64_C(8340052881247508375)
 
 #include "test_generator.ipp"

test/test_xoshiro256pp.cpp

@@ -19,6 +19,6 @@
 
 // principal operation validated with CLHEP, values by experiment
 #define BOOST_RANDOM_VALIDATION_VALUE UINT64_C(8911602566162972150)
-#define BOOST_RANDOM_SEED_SEQ_VALIDATION_VALUE UINT64_C(11693002297289060464)
+#define BOOST_RANDOM_SEED_SEQ_VALIDATION_VALUE UINT64_C(9091783836875527177)
 
 #include "test_generator.ipp"

test/test_xoshiro512d.cpp

@@ -19,7 +19,7 @@
 
 // principal operation validated with CLHEP, values by experiment
 #define BOOST_RANDOM_VALIDATION_VALUE 0.85594919700533156
-#define BOOST_RANDOM_SEED_SEQ_VALIDATION_VALUE 0.25120475433393952
+#define BOOST_RANDOM_SEED_SEQ_VALIDATION_VALUE 0.77731098639989704
 
 // Since we are using splitmix64 we need to allow 64 bit seeds
 // The test harness only allows for 32 bit seeds

test/test_xoshiro512mm.cpp

@@ -19,6 +19,6 @@
 
 // principal operation validated with CLHEP, values by experiment
 #define BOOST_RANDOM_VALIDATION_VALUE UINT64_C(9446215307655316885)
-#define BOOST_RANDOM_SEED_SEQ_VALIDATION_VALUE UINT64_C(13183137209047681026)
+#define BOOST_RANDOM_SEED_SEQ_VALIDATION_VALUE UINT64_C(7700017102361224222)
 
 #include "test_generator.ipp"

test/test_xoshiro512pp.cpp

@@ -19,6 +19,6 @@
 
 // principal operation validated with CLHEP, values by experiment
 #define BOOST_RANDOM_VALIDATION_VALUE UINT64_C(11685388408145467864)
-#define BOOST_RANDOM_SEED_SEQ_VALIDATION_VALUE UINT64_C(15400500895396352743)
+#define BOOST_RANDOM_SEED_SEQ_VALIDATION_VALUE UINT64_C(6773570493308843014)
 
 #include "test_generator.ipp"