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182 lines
6.3 KiB
182 lines
6.3 KiB
// Copyright 2017 The Abseil Authors. |
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// |
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// Licensed under the Apache License, Version 2.0 (the "License"); |
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// you may not use this file except in compliance with the License. |
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// You may obtain a copy of the License at |
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// |
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// https://www.apache.org/licenses/LICENSE-2.0 |
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// |
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// Unless required by applicable law or agreed to in writing, software |
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// distributed under the License is distributed on an "AS IS" BASIS, |
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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// See the License for the specific language governing permissions and |
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// limitations under the License. |
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#include "absl/random/internal/pool_urbg.h" |
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#include <algorithm> |
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#include <bitset> |
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#include <cmath> |
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#include <cstdint> |
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#include <iterator> |
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#include "gtest/gtest.h" |
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#include "absl/meta/type_traits.h" |
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#include "absl/types/span.h" |
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using absl::random_internal::PoolURBG; |
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using absl::random_internal::RandenPool; |
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namespace { |
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// is_randen_pool trait is true when parameterized by an RandenPool |
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template <typename T> |
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using is_randen_pool = typename absl::disjunction< // |
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std::is_same<T, RandenPool<uint8_t>>, // |
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std::is_same<T, RandenPool<uint16_t>>, // |
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std::is_same<T, RandenPool<uint32_t>>, // |
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std::is_same<T, RandenPool<uint64_t>>>; // |
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// MyFill either calls RandenPool::Fill() or std::generate(..., rng) |
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template <typename T, typename V> |
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typename absl::enable_if_t<absl::negation<is_randen_pool<T>>::value, void> // |
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MyFill(T& rng, absl::Span<V> data) { // NOLINT(runtime/references) |
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std::generate(std::begin(data), std::end(data), rng); |
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} |
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template <typename T, typename V> |
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typename absl::enable_if_t<is_randen_pool<T>::value, void> // |
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MyFill(T& rng, absl::Span<V> data) { // NOLINT(runtime/references) |
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rng.Fill(data); |
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} |
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template <typename EngineType> |
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class PoolURBGTypedTest : public ::testing::Test {}; |
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using EngineTypes = ::testing::Types< // |
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RandenPool<uint8_t>, // |
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RandenPool<uint16_t>, // |
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RandenPool<uint32_t>, // |
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RandenPool<uint64_t>, // |
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PoolURBG<uint8_t, 2>, // |
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PoolURBG<uint16_t, 2>, // |
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PoolURBG<uint32_t, 2>, // |
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PoolURBG<uint64_t, 2>, // |
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PoolURBG<unsigned int, 8>, // NOLINT(runtime/int) |
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PoolURBG<unsigned long, 8>, // NOLINT(runtime/int) |
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PoolURBG<unsigned long int, 4>, // NOLINT(runtime/int) |
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PoolURBG<unsigned long long, 4>>; // NOLINT(runtime/int) |
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TYPED_TEST_SUITE(PoolURBGTypedTest, EngineTypes); |
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// This test is checks that the engines meet the URBG interface requirements |
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// defined in [rand.req.urbg]. |
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TYPED_TEST(PoolURBGTypedTest, URBGInterface) { |
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using E = TypeParam; |
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using T = typename E::result_type; |
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static_assert(std::is_copy_constructible<E>::value, |
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"engine must be copy constructible"); |
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static_assert(absl::is_copy_assignable<E>::value, |
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"engine must be copy assignable"); |
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E e; |
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const E x; |
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e(); |
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static_assert(std::is_same<decltype(e()), T>::value, |
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"return type of operator() must be result_type"); |
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E u0(x); |
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u0(); |
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E u1 = e; |
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u1(); |
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} |
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// This validates that sequences are independent. |
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TYPED_TEST(PoolURBGTypedTest, VerifySequences) { |
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using E = TypeParam; |
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using result_type = typename E::result_type; |
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E rng; |
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(void)rng(); // Discard one value. |
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constexpr int kNumOutputs = 64; |
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result_type a[kNumOutputs]; |
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result_type b[kNumOutputs]; |
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std::fill(std::begin(b), std::end(b), 0); |
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// Fill a using Fill or generate, depending on the engine type. |
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{ |
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E x = rng; |
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MyFill(x, absl::MakeSpan(a)); |
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} |
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// Fill b using std::generate(). |
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{ |
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E x = rng; |
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std::generate(std::begin(b), std::end(b), x); |
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} |
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// Test that generated sequence changed as sequence of bits, i.e. if about |
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// half of the bites were flipped between two non-correlated values. |
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size_t changed_bits = 0; |
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size_t unchanged_bits = 0; |
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size_t total_set = 0; |
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size_t total_bits = 0; |
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size_t equal_count = 0; |
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for (size_t i = 0; i < kNumOutputs; ++i) { |
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equal_count += (a[i] == b[i]) ? 1 : 0; |
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std::bitset<sizeof(result_type) * 8> bitset(a[i] ^ b[i]); |
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changed_bits += bitset.count(); |
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unchanged_bits += bitset.size() - bitset.count(); |
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std::bitset<sizeof(result_type) * 8> a_set(a[i]); |
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std::bitset<sizeof(result_type) * 8> b_set(b[i]); |
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total_set += a_set.count() + b_set.count(); |
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total_bits += 2 * 8 * sizeof(result_type); |
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} |
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// On average, half the bits are changed between two calls. |
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EXPECT_LE(changed_bits, 0.60 * (changed_bits + unchanged_bits)); |
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EXPECT_GE(changed_bits, 0.40 * (changed_bits + unchanged_bits)); |
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// verify using a quick normal-approximation to the binomial. |
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EXPECT_NEAR(total_set, total_bits * 0.5, 4 * std::sqrt(total_bits)) |
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<< "@" << total_set / static_cast<double>(total_bits); |
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// Also, A[i] == B[i] with probability (1/range) * N. |
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// Give this a pretty wide latitude, though. |
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const double kExpected = kNumOutputs / (1.0 * sizeof(result_type) * 8); |
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EXPECT_LE(equal_count, 1.0 + kExpected); |
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} |
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} // namespace |
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/* |
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$ nanobenchmarks 1 RandenPool construct |
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$ nanobenchmarks 1 PoolURBG construct |
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RandenPool<uint32_t> | 1 | 1000 | 48482.00 ticks | 48.48 ticks | 13.9 ns |
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RandenPool<uint32_t> | 10 | 2000 | 1028795.00 ticks | 51.44 ticks | 14.7 ns |
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RandenPool<uint32_t> | 100 | 1000 | 5119968.00 ticks | 51.20 ticks | 14.6 ns |
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RandenPool<uint32_t> | 1000 | 500 | 25867936.00 ticks | 51.74 ticks | 14.8 ns |
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RandenPool<uint64_t> | 1 | 1000 | 49921.00 ticks | 49.92 ticks | 14.3 ns |
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RandenPool<uint64_t> | 10 | 2000 | 1208269.00 ticks | 60.41 ticks | 17.3 ns |
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RandenPool<uint64_t> | 100 | 1000 | 5844955.00 ticks | 58.45 ticks | 16.7 ns |
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RandenPool<uint64_t> | 1000 | 500 | 28767404.00 ticks | 57.53 ticks | 16.4 ns |
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PoolURBG<uint32_t,8> | 1 | 1000 | 86431.00 ticks | 86.43 ticks | 24.7 ns |
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PoolURBG<uint32_t,8> | 10 | 1000 | 206191.00 ticks | 20.62 ticks | 5.9 ns |
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PoolURBG<uint32_t,8> | 100 | 1000 | 1516049.00 ticks | 15.16 ticks | 4.3 ns |
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PoolURBG<uint32_t,8> | 1000 | 500 | 7613936.00 ticks | 15.23 ticks | 4.4 ns |
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PoolURBG<uint64_t,4> | 1 | 1000 | 96668.00 ticks | 96.67 ticks | 27.6 ns |
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PoolURBG<uint64_t,4> | 10 | 1000 | 282423.00 ticks | 28.24 ticks | 8.1 ns |
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PoolURBG<uint64_t,4> | 100 | 1000 | 2609587.00 ticks | 26.10 ticks | 7.5 ns |
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PoolURBG<uint64_t,4> | 1000 | 500 | 12408757.00 ticks | 24.82 ticks | 7.1 ns |
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*/
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