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Diffstat (limited to 'absl/random/internal/pool_urbg_test.cc')
| -rw-r--r-- | absl/random/internal/pool_urbg_test.cc | 182 |
1 files changed, 182 insertions, 0 deletions
diff --git a/absl/random/internal/pool_urbg_test.cc b/absl/random/internal/pool_urbg_test.cc new file mode 100644 index 000000000000..53f4eacf16fe --- /dev/null +++ b/absl/random/internal/pool_urbg_test.cc @@ -0,0 +1,182 @@ +// 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/pool_urbg.h" + +#include <algorithm> +#include <bitset> +#include <cmath> +#include <cstdint> +#include <iterator> + +#include "gtest/gtest.h" +#include "absl/meta/type_traits.h" +#include "absl/types/span.h" + +using absl::random_internal::PoolURBG; +using absl::random_internal::RandenPool; + +namespace { + +// is_randen_pool trait is true when parameterized by an RandenPool +template <typename T> +using is_randen_pool = typename absl::disjunction< // + std::is_same<T, RandenPool<uint8_t>>, // + std::is_same<T, RandenPool<uint16_t>>, // + std::is_same<T, RandenPool<uint32_t>>, // + std::is_same<T, RandenPool<uint64_t>>>; // + +// MyFill either calls RandenPool::Fill() or std::generate(..., rng) +template <typename T, typename V> +typename absl::enable_if_t<absl::negation<is_randen_pool<T>>::value, void> // +MyFill(T& rng, absl::Span<V> data) { // NOLINT(runtime/references) + std::generate(std::begin(data), std::end(data), rng); +} + +template <typename T, typename V> +typename absl::enable_if_t<is_randen_pool<T>::value, void> // +MyFill(T& rng, absl::Span<V> data) { // NOLINT(runtime/references) + rng.Fill(data); +} + +template <typename EngineType> +class PoolURBGTypedTest : public ::testing::Test {}; + +using EngineTypes = ::testing::Types< // + RandenPool<uint8_t>, // + RandenPool<uint16_t>, // + RandenPool<uint32_t>, // + RandenPool<uint64_t>, // + PoolURBG<uint8_t, 2>, // + PoolURBG<uint16_t, 2>, // + PoolURBG<uint32_t, 2>, // + PoolURBG<uint64_t, 2>, // + PoolURBG<unsigned int, 8>, // NOLINT(runtime/int) + PoolURBG<unsigned long, 8>, // NOLINT(runtime/int) + PoolURBG<unsigned long int, 4>, // NOLINT(runtime/int) + PoolURBG<unsigned long long, 4>>; // NOLINT(runtime/int) + +TYPED_TEST_SUITE(PoolURBGTypedTest, EngineTypes); + +// This test is checks that the engines meet the URBG interface requirements +// defined in [rand.req.urbg]. +TYPED_TEST(PoolURBGTypedTest, URBGInterface) { + using E = TypeParam; + using T = typename E::result_type; + + static_assert(std::is_copy_constructible<E>::value, + "engine must be copy constructible"); + + static_assert(absl::is_copy_assignable<E>::value, + "engine must be copy assignable"); + + E e; + const E x; + + e(); + + static_assert(std::is_same<decltype(e()), T>::value, + "return type of operator() must be result_type"); + + E u0(x); + u0(); + + E u1 = e; + u1(); +} + +// This validates that sequences are independent. +TYPED_TEST(PoolURBGTypedTest, VerifySequences) { + using E = TypeParam; + using result_type = typename E::result_type; + + E rng; + (void)rng(); // Discard one value. + + constexpr int kNumOutputs = 64; + result_type a[kNumOutputs]; + result_type b[kNumOutputs]; + std::fill(std::begin(b), std::end(b), 0); + + // Fill a using Fill or generate, depending on the engine type. + { + E x = rng; + MyFill(x, absl::MakeSpan(a)); + } + + // Fill b using std::generate(). + { + E x = rng; + std::generate(std::begin(b), std::end(b), x); + } + + // Test that generated sequence changed as sequence of bits, i.e. if about + // half of the bites were flipped between two non-correlated values. + size_t changed_bits = 0; + size_t unchanged_bits = 0; + size_t total_set = 0; + size_t total_bits = 0; + size_t equal_count = 0; + for (size_t i = 0; i < kNumOutputs; ++i) { + equal_count += (a[i] == b[i]) ? 1 : 0; + std::bitset<sizeof(result_type) * 8> bitset(a[i] ^ b[i]); + changed_bits += bitset.count(); + unchanged_bits += bitset.size() - bitset.count(); + + std::bitset<sizeof(result_type) * 8> a_set(a[i]); + std::bitset<sizeof(result_type) * 8> b_set(b[i]); + total_set += a_set.count() + b_set.count(); + total_bits += 2 * 8 * sizeof(result_type); + } + // On average, half the bits are changed between two calls. + EXPECT_LE(changed_bits, 0.60 * (changed_bits + unchanged_bits)); + EXPECT_GE(changed_bits, 0.40 * (changed_bits + unchanged_bits)); + + // verify using a quick normal-approximation to the binomial. + EXPECT_NEAR(total_set, total_bits * 0.5, 4 * std::sqrt(total_bits)) + << "@" << total_set / static_cast<double>(total_bits); + + // Also, A[i] == B[i] with probability (1/range) * N. + // Give this a pretty wide latitude, though. + const double kExpected = kNumOutputs / (1.0 * sizeof(result_type) * 8); + EXPECT_LE(equal_count, 1.0 + kExpected); +} + +} // namespace + +/* +$ nanobenchmarks 1 RandenPool construct +$ nanobenchmarks 1 PoolURBG construct + +RandenPool<uint32_t> | 1 | 1000 | 48482.00 ticks | 48.48 ticks | 13.9 ns +RandenPool<uint32_t> | 10 | 2000 | 1028795.00 ticks | 51.44 ticks | 14.7 ns +RandenPool<uint32_t> | 100 | 1000 | 5119968.00 ticks | 51.20 ticks | 14.6 ns +RandenPool<uint32_t> | 1000 | 500 | 25867936.00 ticks | 51.74 ticks | 14.8 ns + +RandenPool<uint64_t> | 1 | 1000 | 49921.00 ticks | 49.92 ticks | 14.3 ns +RandenPool<uint64_t> | 10 | 2000 | 1208269.00 ticks | 60.41 ticks | 17.3 ns +RandenPool<uint64_t> | 100 | 1000 | 5844955.00 ticks | 58.45 ticks | 16.7 ns +RandenPool<uint64_t> | 1000 | 500 | 28767404.00 ticks | 57.53 ticks | 16.4 ns + +PoolURBG<uint32_t,8> | 1 | 1000 | 86431.00 ticks | 86.43 ticks | 24.7 ns +PoolURBG<uint32_t,8> | 10 | 1000 | 206191.00 ticks | 20.62 ticks | 5.9 ns +PoolURBG<uint32_t,8> | 100 | 1000 | 1516049.00 ticks | 15.16 ticks | 4.3 ns +PoolURBG<uint32_t,8> | 1000 | 500 | 7613936.00 ticks | 15.23 ticks | 4.4 ns + +PoolURBG<uint64_t,4> | 1 | 1000 | 96668.00 ticks | 96.67 ticks | 27.6 ns +PoolURBG<uint64_t,4> | 10 | 1000 | 282423.00 ticks | 28.24 ticks | 8.1 ns +PoolURBG<uint64_t,4> | 100 | 1000 | 2609587.00 ticks | 26.10 ticks | 7.5 ns +PoolURBG<uint64_t,4> | 1000 | 500 | 12408757.00 ticks | 24.82 ticks | 7.1 ns + +*/ |