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Diffstat (limited to 'absl/random/internal/fast_uniform_bits_test.cc')
| -rw-r--r-- | absl/random/internal/fast_uniform_bits_test.cc | 290 |
1 files changed, 290 insertions, 0 deletions
diff --git a/absl/random/internal/fast_uniform_bits_test.cc b/absl/random/internal/fast_uniform_bits_test.cc new file mode 100644 index 00000000..f4b9cd5f --- /dev/null +++ b/absl/random/internal/fast_uniform_bits_test.cc @@ -0,0 +1,290 @@ +// Copyright 2017 The Abseil Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// https://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +#include "absl/random/internal/fast_uniform_bits.h" + +#include <random> + +#include "gtest/gtest.h" + +namespace { + +template <typename IntType> +class FastUniformBitsTypedTest : public ::testing::Test {}; + +using IntTypes = ::testing::Types<uint8_t, uint16_t, uint32_t, uint64_t>; + +TYPED_TEST_SUITE(FastUniformBitsTypedTest, IntTypes); + +TYPED_TEST(FastUniformBitsTypedTest, BasicTest) { + using Limits = std::numeric_limits<TypeParam>; + using FastBits = absl::random_internal::FastUniformBits<TypeParam>; + + EXPECT_EQ(0, FastBits::min()); + EXPECT_EQ(Limits::max(), FastBits::max()); + + constexpr int kIters = 10000; + std::random_device rd; + std::mt19937 gen(rd()); + FastBits fast; + for (int i = 0; i < kIters; i++) { + const auto v = fast(gen); + EXPECT_LE(v, FastBits::max()); + EXPECT_GE(v, FastBits::min()); + } +} + +TEST(FastUniformBitsTest, TypeBoundaries32) { + // Tests that FastUniformBits can adapt to 32-bit boundaries. + absl::random_internal::FastUniformBits<uint32_t, 1> a; + absl::random_internal::FastUniformBits<uint32_t, 31> b; + absl::random_internal::FastUniformBits<uint32_t, 32> c; + + { + std::mt19937 gen; // 32-bit + a(gen); + b(gen); + c(gen); + } + + { + std::mt19937_64 gen; // 64-bit + a(gen); + b(gen); + c(gen); + } +} + +TEST(FastUniformBitsTest, TypeBoundaries64) { + // Tests that FastUniformBits can adapt to 64-bit boundaries. + absl::random_internal::FastUniformBits<uint64_t, 1> a; + absl::random_internal::FastUniformBits<uint64_t, 31> b; + absl::random_internal::FastUniformBits<uint64_t, 32> c; + absl::random_internal::FastUniformBits<uint64_t, 33> d; + absl::random_internal::FastUniformBits<uint64_t, 63> e; + absl::random_internal::FastUniformBits<uint64_t, 64> f; + + { + std::mt19937 gen; // 32-bit + a(gen); + b(gen); + c(gen); + d(gen); + e(gen); + f(gen); + } + + { + std::mt19937_64 gen; // 64-bit + a(gen); + b(gen); + c(gen); + d(gen); + e(gen); + f(gen); + } +} + +class UrngOddbits { + public: + using result_type = uint8_t; + static constexpr result_type min() { return 1; } + static constexpr result_type max() { return 0xfe; } + result_type operator()() { return 2; } +}; + +class Urng4bits { + public: + using result_type = uint8_t; + static constexpr result_type min() { return 1; } + static constexpr result_type max() { return 0xf + 1; } + result_type operator()() { return 2; } +}; + +class Urng32bits { + public: + using result_type = uint32_t; + static constexpr result_type min() { return 0; } + static constexpr result_type max() { return 0xffffffff; } + result_type operator()() { return 1; } +}; + +// Compile-time test to validate the helper classes used by FastUniformBits +TEST(FastUniformBitsTest, FastUniformBitsDetails) { + using absl::random_internal::FastUniformBitsLoopingConstants; + using absl::random_internal::FastUniformBitsURBGConstants; + + // 4-bit URBG + { + using constants = FastUniformBitsURBGConstants<Urng4bits>; + static_assert(constants::kPowerOfTwo == true, + "constants::kPowerOfTwo == false"); + static_assert(constants::kRange == 16, "constants::kRange == false"); + static_assert(constants::kRangeBits == 4, "constants::kRangeBits == false"); + static_assert(constants::kRangeMask == 0x0f, + "constants::kRangeMask == false"); + } + { + using looping = FastUniformBitsLoopingConstants<uint32_t, 31, Urng4bits>; + // To get 31 bits from a 4-bit generator, issue 8 calls and extract 4 bits + // per call on all except the first. + static_assert(looping::kN0 == 1, "looping::kN0"); + static_assert(looping::kW0 == 3, "looping::kW0"); + static_assert(looping::kM0 == 0x7, "looping::kM0"); + // (The second set of calls, kN1, will not do anything.) + static_assert(looping::kN1 == 8, "looping::kN1"); + static_assert(looping::kW1 == 4, "looping::kW1"); + static_assert(looping::kM1 == 0xf, "looping::kM1"); + } + + // ~7-bit URBG + { + using constants = FastUniformBitsURBGConstants<UrngOddbits>; + static_assert(constants::kPowerOfTwo == false, + "constants::kPowerOfTwo == false"); + static_assert(constants::kRange == 0xfe, "constants::kRange == 0xfe"); + static_assert(constants::kRangeBits == 7, "constants::kRangeBits == 7"); + static_assert(constants::kRangeMask == 0x7f, + "constants::kRangeMask == 0x7f"); + } + { + using looping = FastUniformBitsLoopingConstants<uint64_t, 60, UrngOddbits>; + // To get 60 bits from a 7-bit generator, issue 10 calls and extract 6 bits + // per call, discarding the excess entropy. + static_assert(looping::kN0 == 10, "looping::kN0"); + static_assert(looping::kW0 == 6, "looping::kW0"); + static_assert(looping::kM0 == 0x3f, "looping::kM0"); + // (The second set of calls, kN1, will not do anything.) + static_assert(looping::kN1 == 10, "looping::kN1"); + static_assert(looping::kW1 == 7, "looping::kW1"); + static_assert(looping::kM1 == 0x7f, "looping::kM1"); + } + { + using looping = FastUniformBitsLoopingConstants<uint64_t, 63, UrngOddbits>; + // To get 63 bits from a 7-bit generator, issue 10 calls--the same as we + // would issue for 60 bits--however this time we use two groups. The first + // group (kN0) will issue 7 calls, extracting 6 bits per call. + static_assert(looping::kN0 == 7, "looping::kN0"); + static_assert(looping::kW0 == 6, "looping::kW0"); + static_assert(looping::kM0 == 0x3f, "looping::kM0"); + // The second group (kN1) will issue 3 calls, extracting 7 bits per call. + static_assert(looping::kN1 == 10, "looping::kN1"); + static_assert(looping::kW1 == 7, "looping::kW1"); + static_assert(looping::kM1 == 0x7f, "looping::kM1"); + } +} + +TEST(FastUniformBitsTest, Urng4_VariousOutputs) { + // Tests that how values are composed; the single-bit deltas should be spread + // across each invocation. + Urng4bits urng4; + Urng32bits urng32; + + // 8-bit types + { + absl::random_internal::FastUniformBits<uint8_t, 1> fast1; + EXPECT_EQ(0x1, fast1(urng4)); + EXPECT_EQ(0x1, fast1(urng32)); + } + { + absl::random_internal::FastUniformBits<uint8_t, 2> fast2; + EXPECT_EQ(0x1, fast2(urng4)); + EXPECT_EQ(0x1, fast2(urng32)); + } + + { + absl::random_internal::FastUniformBits<uint8_t, 4> fast4; + EXPECT_EQ(0x1, fast4(urng4)); + EXPECT_EQ(0x1, fast4(urng32)); + } + { + absl::random_internal::FastUniformBits<uint8_t, 6> fast6; + EXPECT_EQ(0x9, fast6(urng4)); // b001001 (2x3) + EXPECT_EQ(0x1, fast6(urng32)); + } + { + absl::random_internal::FastUniformBits<uint8_t, 6> fast7; + EXPECT_EQ(0x9, fast7(urng4)); // b00001001 (1x4 + 1x3) + EXPECT_EQ(0x1, fast7(urng32)); + } + + { + absl::random_internal::FastUniformBits<uint8_t> fast8; + EXPECT_EQ(0x11, fast8(urng4)); + EXPECT_EQ(0x1, fast8(urng32)); + } + + // 16-bit types + { + absl::random_internal::FastUniformBits<uint16_t, 10> fast10; + EXPECT_EQ(0x91, fast10(urng4)); // b 0010010001 (2x3 + 1x4) + EXPECT_EQ(0x1, fast10(urng32)); + } + { + absl::random_internal::FastUniformBits<uint16_t, 11> fast11; + EXPECT_EQ(0x111, fast11(urng4)); + EXPECT_EQ(0x1, fast11(urng32)); + } + { + absl::random_internal::FastUniformBits<uint16_t, 12> fast12; + EXPECT_EQ(0x111, fast12(urng4)); + EXPECT_EQ(0x1, fast12(urng32)); + } + + { + absl::random_internal::FastUniformBits<uint16_t> fast16; + EXPECT_EQ(0x1111, fast16(urng4)); + EXPECT_EQ(0x1, fast16(urng32)); + } + + // 32-bit types + { + absl::random_internal::FastUniformBits<uint32_t, 21> fast21; + EXPECT_EQ(0x49111, fast21(urng4)); // b 001001001 000100010001 (3x3 + 3x4) + EXPECT_EQ(0x1, fast21(urng32)); + } + { + absl::random_internal::FastUniformBits<uint32_t, 24> fast24; + EXPECT_EQ(0x111111, fast24(urng4)); + EXPECT_EQ(0x1, fast24(urng32)); + } + + { + absl::random_internal::FastUniformBits<uint32_t> fast32; + EXPECT_EQ(0x11111111, fast32(urng4)); + EXPECT_EQ(0x1, fast32(urng32)); + } + + // 64-bit types + { + absl::random_internal::FastUniformBits<uint64_t, 5> fast5; + EXPECT_EQ(0x9, fast5(urng4)); + EXPECT_EQ(0x1, fast5(urng32)); + } + + { + absl::random_internal::FastUniformBits<uint64_t, 48> fast48; + EXPECT_EQ(0x111111111111, fast48(urng4)); + // computes in 2 steps, should be 24 << 24 + EXPECT_EQ(0x000001000001, fast48(urng32)); + } + + { + absl::random_internal::FastUniformBits<uint64_t> fast64; + EXPECT_EQ(0x1111111111111111, fast64(urng4)); + EXPECT_EQ(0x0000000100000001, fast64(urng32)); + } +} + +} // namespace |