Add uniform_integer_distribution

1 files changed, 385 insertions, 0 deletions

diff --git a/tests/SelfTest/IntrospectiveTests/RandomNumberGeneration.tests.cpp b/tests/SelfTest/IntrospectiveTests/RandomNumberGeneration.tests.cpp
index d432b445..5c17fb2b 100644
--- a/tests/SelfTest/IntrospectiveTests/RandomNumberGeneration.tests.cpp
+++ b/tests/SelfTest/IntrospectiveTests/RandomNumberGeneration.tests.cpp
@@ -12,7 +12,9 @@
 #include <catch2/internal/catch_random_number_generator.hpp>
 #include <catch2/internal/catch_random_seed_generation.hpp>
 #include <catch2/internal/catch_uniform_floating_point_distribution.hpp>
+#include <catch2/internal/catch_uniform_integer_distribution.hpp>
 #include <catch2/generators/catch_generators.hpp>
+#include <catch2/matchers/catch_matchers_range_equals.hpp>
 
 TEST_CASE("Our PCG implementation provides expected results for known seeds", "[rng]") {
     Catch::SimplePcg32 rng;
@@ -104,3 +106,386 @@ TEST_CASE( "fillBitsFrom - shortening and stretching", "[rng][approvals]" ) {
         REQUIRE( stretched == 0xccbe'5f04'a424'a486 );
     }
 }
+
+TEST_CASE("uniform_integer_distribution can return the bounds", "[rng][distribution]") {
+    Catch::uniform_integer_distribution<int32_t> dist( -10, 10 );
+    REQUIRE( dist.a() == -10 );
+    REQUIRE( dist.b() == 10 );
+}
+
+namespace {
+    template <typename T>
+    static void CheckReturnValue(Catch::uniform_integer_distribution<T>& dist,
+                                 Catch::SimplePcg32& rng,
+                                 T target) {
+        REQUIRE( dist.a() == dist.b() );
+        for (int i = 0; i < 1'000; ++i) {
+            REQUIRE( dist( rng ) == target );
+        }
+    }
+}
+
+TEMPLATE_TEST_CASE( "uniform_integer_distribution can handle unit ranges",
+                    "[rng][distribution][approvals]",
+                    unsigned char,
+                    signed char,
+                    char,
+                    uint8_t,
+                    int8_t,
+                    uint16_t,
+                    int16_t,
+                    uint32_t,
+                    int32_t,
+                    uint64_t,
+                    int64_t ) {
+    // We want random seed to sample different parts of the rng state,
+    // the output is predetermined anyway
+    std::random_device rd;
+    auto seed = rd();
+    CAPTURE( seed );
+    Catch::SimplePcg32 pcg( seed );
+
+    // We check unitary ranges of 3 different values, min for type, max for type,
+    // some value inbetween just to make sure
+    SECTION("lowest value") {
+        constexpr auto lowest = std::numeric_limits<TestType>::min();
+        Catch::uniform_integer_distribution<TestType> dist( lowest, lowest );
+        CheckReturnValue( dist, pcg, lowest );
+    }
+    SECTION( "highest value" ) {
+        constexpr auto highest = std::numeric_limits<TestType>::max();
+        Catch::uniform_integer_distribution<TestType> dist( highest, highest );
+        CheckReturnValue( dist, pcg, highest );
+    }
+    SECTION( "some value" ) {
+        constexpr auto some = TestType( 42 );
+        Catch::uniform_integer_distribution<TestType> dist( some, some );
+        CheckReturnValue( dist, pcg, some );
+    }
+}
+
+// Bool needs its own test because it doesn't have a valid "third" value
+TEST_CASE( "uniform_integer_distribution can handle boolean unit ranges",
+           "[rng][distribution][approvals]" ) {
+    // We want random seed to sample different parts of the rng state,
+    // the output is predetermined anyway
+    std::random_device rd;
+    auto seed = rd();
+    CAPTURE( seed );
+    Catch::SimplePcg32 pcg( seed );
+
+    // We check unitary ranges of 3 different values, min for type, max for
+    // type, some value inbetween just to make sure
+    SECTION( "lowest value" ) {
+        Catch::uniform_integer_distribution<bool> dist( false, false );
+        CheckReturnValue( dist, pcg, false );
+    }
+    SECTION( "highest value" ) {
+        Catch::uniform_integer_distribution<bool> dist( true, true );
+        CheckReturnValue( dist, pcg, true );
+    }
+}
+
+TEMPLATE_TEST_CASE( "uniform_integer_distribution can handle full width ranges",
+                    "[rng][distribution][approvals]",
+                    unsigned char,
+                    signed char,
+                    char,
+                    uint8_t,
+                    int8_t,
+                    uint16_t,
+                    int16_t,
+                    uint32_t,
+                    int32_t,
+                    uint64_t,
+                    int64_t ) {
+    // We want random seed to sample different parts of the rng state,
+    // the output is predetermined anyway
+    std::random_device rd;
+    auto seed = rd();
+    CAPTURE( seed );
+    Catch::SimplePcg32 pcg( seed );
+
+    constexpr auto lowest = std::numeric_limits<TestType>::min();
+    constexpr auto highest = std::numeric_limits<TestType>::max();
+    Catch::uniform_integer_distribution<TestType> dist( lowest, highest );
+    STATIC_REQUIRE( std::is_same<TestType, decltype( dist( pcg ) )>::value );
+
+    // We need to do bit operations on the results, so we will have to
+    // cast them to unsigned type.
+    using BitType = std::make_unsigned_t<TestType>;
+    BitType ORs = 0;
+    BitType ANDs = BitType(-1);
+    for (int i = 0; i < 100; ++i) {
+        auto bits = static_cast<BitType>( dist( pcg ) );
+        ORs |= bits;
+        ANDs &= bits;
+    }
+    // Assuming both our RNG and distribution are unbiased, asking for
+    // the full range should essentially give us random bit generator.
+    // Over long run, OR of all the generated values should have all
+    // bits set to 1, while AND should have all bits set to 0.
+    // The chance of this test failing for unbiased pipeline is
+    // 1 / 2**iters, which for 100 iterations is astronomical.
+    REQUIRE( ORs == BitType( -1 ) );
+    REQUIRE( ANDs == 0 );
+}
+
+namespace {
+    template <typename T>
+    struct uniform_integer_test_params;
+
+    template <>
+    struct uniform_integer_test_params<bool> {
+        static constexpr bool lowest = false;
+        static constexpr bool highest = true;
+        //  This seems weird, but it is an artifact of the specific seed
+        static constexpr bool expected[] = { true,
+                                             true,
+                                             true,
+                                             true,
+                                             true,
+                                             true,
+                                             false,
+                                             true,
+                                             true,
+                                             true,
+                                             true,
+                                             true,
+                                             false,
+                                             true,
+                                             true };
+    };
+
+    template <>
+    struct uniform_integer_test_params<char> {
+        static constexpr char lowest = 32;
+        static constexpr char highest = 126;
+        static constexpr char expected[] = { 'k',
+                                             '\\',
+                                             'Z',
+                                             'X',
+                                             '`',
+                                             'Q',
+                                             ';',
+                                             'o',
+                                             ']',
+                                             'T',
+                                             'v',
+                                             'p',
+                                             ':',
+                                             'S',
+                                             't' };
+    };
+
+    template <>
+    struct uniform_integer_test_params<uint8_t> {
+        static constexpr uint8_t lowest = 3;
+        static constexpr uint8_t highest = 123;
+        static constexpr uint8_t expected[] = { 'c',
+                                                'P',
+                                                'M',
+                                                'J',
+                                                'U',
+                                                'A',
+                                                '%',
+                                                'h',
+                                                'Q',
+                                                'F',
+                                                'q',
+                                                'i',
+                                                '$',
+                                                'E',
+                                                'o' };
+    };
+
+    template <>
+    struct uniform_integer_test_params<int8_t> {
+        static constexpr int8_t lowest = -27;
+        static constexpr int8_t highest = 73;
+        static constexpr int8_t expected[] = { '5',
+                                               '%',
+                                               '#',
+                                               ' ',
+                                               '*',
+                                               25,
+                                               2,
+                                               '9',
+                                               '&',
+                                               29,
+                                               'A',
+                                               ':',
+                                               1,
+                                               28,
+                                               '?' };
+    };
+
+    template <>
+    struct uniform_integer_test_params<uint16_t> {
+        static constexpr uint16_t lowest = 123;
+        static constexpr uint16_t highest = 33333;
+        static constexpr uint16_t expected[] = { 26684,
+                                                 21417,
+                                                 20658,
+                                                 19791,
+                                                 22896,
+                                                 17433,
+                                                 9806,
+                                                 27948,
+                                                 21767,
+                                                 18588,
+                                                 30556,
+                                                 28244,
+                                                 9439,
+                                                 18293,
+                                                 29949 };
+    };
+
+    template <>
+    struct uniform_integer_test_params<int16_t> {
+        static constexpr int16_t lowest = -17222;
+        static constexpr int16_t highest = 17222;
+        static constexpr int16_t expected[] = { 10326,
+                                                 4863,
+                                                 4076,
+                                                 3177,
+                                                 6397,
+                                                 731,
+                                                 -7179,
+                                                 11637,
+                                                 5226,
+                                                 1929,
+                                                 14342,
+                                                 11944,
+                                                 -7560,
+                                                 1623,
+                                                 13712 };
+    };
+
+    template <>
+    struct uniform_integer_test_params<uint32_t> {
+        static constexpr uint32_t lowest = 17222;
+        static constexpr uint32_t highest = 234234;
+        static constexpr uint32_t expected[] = { 190784,
+                                                 156367,
+                                                 151409,
+                                                 145743,
+                                                 166032,
+                                                 130337,
+                                                 80501,
+                                                 199046,
+                                                 158654,
+                                                 137883,
+                                                 216091,
+                                                 200981,
+                                                 78099,
+                                                 135954,
+                                                 212120 };
+    };
+
+    template <>
+    struct uniform_integer_test_params<int32_t> {
+        static constexpr int32_t lowest = -237272;
+        static constexpr int32_t highest = 234234;
+        static constexpr int32_t expected[] = { 139829,
+                                                65050,
+                                                54278,
+                                                41969,
+                                                86051,
+                                                8494,
+                                                -99785,
+                                                157781,
+                                                70021,
+                                                24890,
+                                                194815,
+                                                161985,
+                                                -105004,
+                                                20699,
+                                                186186 };
+    };
+
+    template <>
+    struct uniform_integer_test_params<uint64_t> {
+        static constexpr uint64_t lowest = 1234;
+        static constexpr uint64_t highest = 1234567890;
+        static constexpr uint64_t expected[] = { 987382749,
+                                                 763380386,
+                                                 846572137,
+                                                 359990258,
+                                                 804599765,
+                                                 1131353566,
+                                                 346324913,
+                                                 1108760730,
+                                                 1141693933,
+                                                 856999148,
+                                                 879390623,
+                                                 1149485521,
+                                                 900556586,
+                                                 952385958,
+                                                 807916408 };
+    };
+
+    template <>
+    struct uniform_integer_test_params<int64_t> {
+        static constexpr int64_t lowest = -1234567890;
+        static constexpr int64_t highest = 1234567890;
+        static constexpr int64_t expected[] = { 740197113,
+                                                292191940,
+                                                458575608,
+                                                -514589122,
+                                                374630781,
+                                                1028139036,
+                                                -541919840,
+                                                982953318,
+                                                1048819790,
+                                                479429651,
+                                                524212647,
+                                                1064402981,
+                                                566544615,
+                                                670203462,
+                                                381264073 };
+    };
+
+    // We need these definitions for C++14 and earlier, but
+    // GCC will complain about them in newer C++ standards
+#if __cplusplus <= 201402L
+    constexpr bool uniform_integer_test_params<bool>::expected[];
+    constexpr char uniform_integer_test_params<char>::expected[];
+    constexpr uint8_t uniform_integer_test_params<uint8_t>::expected[];
+    constexpr int8_t uniform_integer_test_params<int8_t>::expected[];
+    constexpr uint16_t uniform_integer_test_params<uint16_t>::expected[];
+    constexpr int16_t uniform_integer_test_params<int16_t>::expected[];
+    constexpr uint32_t uniform_integer_test_params<uint32_t>::expected[];
+    constexpr int32_t uniform_integer_test_params<int32_t>::expected[];
+    constexpr uint64_t uniform_integer_test_params<uint64_t>::expected[];
+    constexpr int64_t uniform_integer_test_params<int64_t>::expected[];
+#endif
+
+}
+
+TEMPLATE_TEST_CASE( "uniform_integer_distribution is reproducible",
+                    "[rng][distribution][approvals]",
+                   bool,
+                   char,
+                   uint8_t,
+                   int8_t,
+                   uint16_t,
+                   int16_t,
+                   uint32_t,
+                   int32_t,
+                   uint64_t,
+                   int64_t) {
+    Catch::SimplePcg32 pcg( 0xaabb'ccdd );
+
+    constexpr auto lowest = uniform_integer_test_params<TestType>::lowest;
+    constexpr auto highest = uniform_integer_test_params<TestType>::highest;
+    Catch::uniform_integer_distribution<TestType> dist(lowest, highest);
+
+    constexpr auto iters = 15;
+    std::array<TestType, iters> generated;
+    for (int i = 0; i < iters; ++i) {
+        generated[i] = dist( pcg );
+    }
+
+    REQUIRE_THAT(generated, Catch::Matchers::RangeEquals(uniform_integer_test_params<TestType>::expected));
+}