183 lines
6.3 KiB
C++
183 lines
6.3 KiB
C++
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// 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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