1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
|
// 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.
// Unit tests for the variant template. The 'is' and 'IsEmpty' methods
// of variant are not explicitly tested because they are used repeatedly
// in building other tests. All other public variant methods should have
// explicit tests.
#include "absl/types/variant.h"
#include <cstddef>
#include <cstdlib>
#include <string>
#include <tuple>
#include "benchmark/benchmark.h"
#include "absl/utility/utility.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace {
template <std::size_t I>
struct VariantAlternative {
char member;
};
template <class Indices>
struct VariantOfAlternativesImpl;
template <std::size_t... Indices>
struct VariantOfAlternativesImpl<absl::index_sequence<Indices...>> {
using type = absl::variant<VariantAlternative<Indices>...>;
};
template <std::size_t NumAlternatives>
using VariantOfAlternatives = typename VariantOfAlternativesImpl<
absl::make_index_sequence<NumAlternatives>>::type;
struct Empty {};
template <class... T>
void Ignore(T...) noexcept {}
template <class T>
Empty DoNotOptimizeAndReturnEmpty(T&& arg) noexcept {
benchmark::DoNotOptimize(arg);
return {};
}
struct VisitorApplier {
struct Visitor {
template <class... T>
void operator()(T&&... args) const noexcept {
Ignore(DoNotOptimizeAndReturnEmpty(args)...);
}
};
template <class... Vars>
void operator()(const Vars&... vars) const noexcept {
absl::visit(Visitor(), vars...);
}
};
template <std::size_t NumIndices, std::size_t CurrIndex = NumIndices - 1>
struct MakeWithIndex {
using Variant = VariantOfAlternatives<NumIndices>;
static Variant Run(std::size_t index) {
return index == CurrIndex
? Variant(absl::in_place_index_t<CurrIndex>())
: MakeWithIndex<NumIndices, CurrIndex - 1>::Run(index);
}
};
template <std::size_t NumIndices>
struct MakeWithIndex<NumIndices, 0> {
using Variant = VariantOfAlternatives<NumIndices>;
static Variant Run(std::size_t /*index*/) { return Variant(); }
};
template <std::size_t NumIndices, class Dimensions>
struct MakeVariantTuple;
template <class T, std::size_t /*I*/>
using always_t = T;
template <std::size_t NumIndices>
VariantOfAlternatives<NumIndices> MakeVariant(std::size_t dimension,
std::size_t index) {
return dimension == 0
? MakeWithIndex<NumIndices>::Run(index % NumIndices)
: MakeVariant<NumIndices>(dimension - 1, index / NumIndices);
}
template <std::size_t NumIndices, std::size_t... Dimensions>
struct MakeVariantTuple<NumIndices, absl::index_sequence<Dimensions...>> {
using VariantTuple =
std::tuple<always_t<VariantOfAlternatives<NumIndices>, Dimensions>...>;
static VariantTuple Run(int index) {
return std::make_tuple(MakeVariant<NumIndices>(Dimensions, index)...);
}
};
constexpr std::size_t integral_pow(std::size_t base, std::size_t power) {
return power == 0 ? 1 : base * integral_pow(base, power - 1);
}
template <std::size_t End, std::size_t I = 0>
struct VisitTestBody {
template <class Vars, class State>
static bool Run(Vars& vars, State& state) {
if (state.KeepRunning()) {
absl::apply(VisitorApplier(), vars[I]);
return VisitTestBody<End, I + 1>::Run(vars, state);
}
return false;
}
};
template <std::size_t End>
struct VisitTestBody<End, End> {
template <class Vars, class State>
static bool Run(Vars& /*vars*/, State& /*state*/) {
return true;
}
};
// Visit operations where branch prediction is likely to give a boost.
template <std::size_t NumIndices, std::size_t NumDimensions = 1>
void BM_RedundantVisit(benchmark::State& state) {
auto vars =
MakeVariantTuple<NumIndices, absl::make_index_sequence<NumDimensions>>::
Run(static_cast<std::size_t>(state.range(0)));
for (auto _ : state) { // NOLINT
benchmark::DoNotOptimize(vars);
absl::apply(VisitorApplier(), vars);
}
}
// Visit operations where branch prediction is unlikely to give a boost.
template <std::size_t NumIndices, std::size_t NumDimensions = 1>
void BM_Visit(benchmark::State& state) {
constexpr std::size_t num_possibilities =
integral_pow(NumIndices, NumDimensions);
using VariantTupleMaker =
MakeVariantTuple<NumIndices, absl::make_index_sequence<NumDimensions>>;
using Tuple = typename VariantTupleMaker::VariantTuple;
Tuple vars[num_possibilities];
for (std::size_t i = 0; i < num_possibilities; ++i)
vars[i] = VariantTupleMaker::Run(i);
while (VisitTestBody<num_possibilities>::Run(vars, state)) {
}
}
// Visitation
// Each visit is on a different variant with a different active alternative)
// Unary visit
BENCHMARK_TEMPLATE(BM_Visit, 1);
BENCHMARK_TEMPLATE(BM_Visit, 2);
BENCHMARK_TEMPLATE(BM_Visit, 3);
BENCHMARK_TEMPLATE(BM_Visit, 4);
BENCHMARK_TEMPLATE(BM_Visit, 5);
BENCHMARK_TEMPLATE(BM_Visit, 6);
BENCHMARK_TEMPLATE(BM_Visit, 7);
BENCHMARK_TEMPLATE(BM_Visit, 8);
BENCHMARK_TEMPLATE(BM_Visit, 16);
BENCHMARK_TEMPLATE(BM_Visit, 32);
BENCHMARK_TEMPLATE(BM_Visit, 64);
// Binary visit
BENCHMARK_TEMPLATE(BM_Visit, 1, 2);
BENCHMARK_TEMPLATE(BM_Visit, 2, 2);
BENCHMARK_TEMPLATE(BM_Visit, 3, 2);
BENCHMARK_TEMPLATE(BM_Visit, 4, 2);
BENCHMARK_TEMPLATE(BM_Visit, 5, 2);
// Ternary visit
BENCHMARK_TEMPLATE(BM_Visit, 1, 3);
BENCHMARK_TEMPLATE(BM_Visit, 2, 3);
BENCHMARK_TEMPLATE(BM_Visit, 3, 3);
// Quaternary visit
BENCHMARK_TEMPLATE(BM_Visit, 1, 4);
BENCHMARK_TEMPLATE(BM_Visit, 2, 4);
// Redundant Visitation
// Each visit consistently has the same alternative active
// Unary visit
BENCHMARK_TEMPLATE(BM_RedundantVisit, 1)->Arg(0);
BENCHMARK_TEMPLATE(BM_RedundantVisit, 2)->DenseRange(0, 1);
BENCHMARK_TEMPLATE(BM_RedundantVisit, 8)->DenseRange(0, 7);
// Binary visit
BENCHMARK_TEMPLATE(BM_RedundantVisit, 1, 2)->Arg(0);
BENCHMARK_TEMPLATE(BM_RedundantVisit, 2, 2)
->DenseRange(0, integral_pow(2, 2) - 1);
BENCHMARK_TEMPLATE(BM_RedundantVisit, 4, 2)
->DenseRange(0, integral_pow(4, 2) - 1);
} // namespace
ABSL_NAMESPACE_END
} // namespace absl
|
