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- a4e14440b870dbf7b36975eaebf783a70a7fcee4 Release string_view microbenchmarks. by Alex Strelnikov <strel@google.com>

Browse Source 
- 7cec68e37e16fb4e266368236ae1de6419f6946a Increase Abseil's minimum supported cmake version to 3.1.... by Jon Cohen <cohenjon@google.com>
  - b977456175c8db380676bd56c44b32efbfc6f606 Fix a typo in the mutex.h comments. by Abseil Team <absl-team@google.com>
  - 3d30cec131d08b066bc1cf877e4f661e8ee0584c Release StrSplit microbenchmarks. by Alex Strelnikov <strel@google.com>
  - dddece6031feac1cca4689e623462f895f28d019 Release StrReplace microbenchmarks. by Alex Strelnikov <strel@google.com>
  - ac3b40e1694f74bdcf31b8d1152481e92edfd441 Internal Change by Abseil Team <absl-team@google.com>
  - d0e69ad6ddf0e59596a02ccab0253967f2909cdb Release StrCat microbenchmarks. by Alex Strelnikov <strel@google.com>
  - db4d471030fa320d2b9d2ce241610333f0eb7a50 Release StrJoin microbenchmarks. by Alex Strelnikov <strel@google.com>

GitOrigin-RevId: a4e14440b870dbf7b36975eaebf783a70a7fcee4
Change-Id: I3f12700aafce677049f4d1a6e09ea821963a8c9e
pull/130/head
Abseil Team 7 years ago committed by jueminyang
parent 30de20488b
commit 59ae4d5a0e
8 changed files with 923 additions and 2 deletions
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  1. 5
      CMakeLists.txt
  2. 65
      absl/strings/BUILD.bazel
  3. 142
      absl/strings/str_cat_benchmark.cc
  4. 98
      absl/strings/str_join_benchmark.cc
  5. 124
      absl/strings/str_replace_benchmark.cc
  6. 158
      absl/strings/str_split_benchmark.cc
  7. 331
      absl/strings/string_view_benchmark.cc
  8. 2
      absl/synchronization/mutex.h

5
CMakeLists.txt
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@ -13,7 +13,10 @@
# See the License for the specific language governing permissions and
# limitations under the License.
#
cmake_minimum_required(VERSION 2.8.12)
# We require 3.0 for modern, target-based CMake. We require 3.1 for the use of
# CXX_STANDARD in our targets.
cmake_minimum_required(VERSION 3.1)
project(absl)
list(APPEND CMAKE_MODULE_PATH ${PROJECT_SOURCE_DIR}/CMake)

65
absl/strings/BUILD.bazel
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@ -172,6 +172,20 @@ cc_test(
],
)
cc_test(
name = "string_view_benchmark",
srcs = ["string_view_benchmark.cc"],
copts = ABSL_TEST_COPTS,
tags = ["benchmark"],
visibility = ["//visibility:private"],
deps = [
":strings",
"//absl/base",
"//absl/base:core_headers",
"@com_github_google_benchmark//:benchmark",
],
)
cc_test(
name = "string_view_test",
size = "small",
@ -200,6 +214,19 @@ cc_test(
],
)
cc_test(
name = "str_replace_benchmark",
srcs = ["str_replace_benchmark.cc"],
copts = ABSL_TEST_COPTS,
tags = ["benchmark"],
visibility = ["//visibility:private"],
deps = [
":strings",
"//absl/base",
"@com_github_google_benchmark//:benchmark",
],
)
cc_test(
name = "str_replace_test",
size = "small",
@ -225,6 +252,19 @@ cc_test(
],
)
cc_test(
name = "str_split_benchmark",
srcs = ["str_split_benchmark.cc"],
copts = ABSL_TEST_COPTS,
tags = ["benchmark"],
visibility = ["//visibility:private"],
deps = [
":strings",
"//absl/base",
"@com_github_google_benchmark//:benchmark",
],
)
cc_test(
name = "ostringstream_test",
size = "small",
@ -267,6 +307,19 @@ cc_test(
],
)
cc_test(
name = "str_join_benchmark",
srcs = ["str_join_benchmark.cc"],
copts = ABSL_TEST_COPTS,
tags = ["benchmark"],
visibility = ["//visibility:private"],
deps = [
":strings",
"//absl/memory",
"@com_github_google_benchmark//:benchmark",
],
)
cc_test(
name = "str_cat_test",
size = "small",
@ -280,6 +333,18 @@ cc_test(
],
)
cc_test(
name = "str_cat_benchmark",
srcs = ["str_cat_benchmark.cc"],
copts = ABSL_TEST_COPTS,
tags = ["benchmark"],
visibility = ["//visibility:private"],
deps = [
":strings",
"@com_github_google_benchmark//:benchmark",
],
)
cc_test(
name = "numbers_test",
size = "small",

142
absl/strings/str_cat_benchmark.cc
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@ -0,0 +1,142 @@
// Copyright 2018 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
//
// http://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/strings/str_cat.h"
#include <cstdint>
#include <string>
#include "benchmark/benchmark.h"
#include "absl/strings/substitute.h"
namespace {
const char kStringOne[] = "Once Upon A Time, ";
const char kStringTwo[] = "There was a std::string benchmark";
// We want to include negative numbers in the benchmark, so this function
// is used to count 0, 1, -1, 2, -2, 3, -3, ...
inline int IncrementAlternatingSign(int i) {
return i > 0 ? -i : 1 - i;
}
void BM_Sum_By_StrCat(benchmark::State& state) {
int i = 0;
char foo[100];
for (auto _ : state) {
// NOLINTNEXTLINE(runtime/printf)
strcpy(foo, absl::StrCat(kStringOne, i, kStringTwo, i * 65536ULL).c_str());
int sum = 0;
for (char* f = &foo[0]; *f != 0; ++f) {
sum += *f;
}
benchmark::DoNotOptimize(sum);
i = IncrementAlternatingSign(i);
}
}
BENCHMARK(BM_Sum_By_StrCat);
void BM_StrCat_By_snprintf(benchmark::State& state) {
int i = 0;
char on_stack[1000];
for (auto _ : state) {
snprintf(on_stack, sizeof(on_stack), "%s %s:%d", kStringOne, kStringTwo, i);
i = IncrementAlternatingSign(i);
}
}
BENCHMARK(BM_StrCat_By_snprintf);
void BM_StrCat_By_Strings(benchmark::State& state) {
int i = 0;
for (auto _ : state) {
std::string result =
std::string(kStringOne) + " " + kStringTwo + ":" + absl::StrCat(i);
benchmark::DoNotOptimize(result);
i = IncrementAlternatingSign(i);
}
}
BENCHMARK(BM_StrCat_By_Strings);
void BM_StrCat_By_StringOpPlus(benchmark::State& state) {
int i = 0;
for (auto _ : state) {
std::string result = kStringOne;
result += " ";
result += kStringTwo;
result += ":";
result += absl::StrCat(i);
benchmark::DoNotOptimize(result);
i = IncrementAlternatingSign(i);
}
}
BENCHMARK(BM_StrCat_By_StringOpPlus);
void BM_StrCat_By_StrCat(benchmark::State& state) {
int i = 0;
for (auto _ : state) {
std::string result = absl::StrCat(kStringOne, " ", kStringTwo, ":", i);
benchmark::DoNotOptimize(result);
i = IncrementAlternatingSign(i);
}
}
BENCHMARK(BM_StrCat_By_StrCat);
void BM_HexCat_By_StrCat(benchmark::State& state) {
int i = 0;
for (auto _ : state) {
std::string result =
absl::StrCat(kStringOne, " ", absl::Hex(int64_t{i} + 0x10000000));
benchmark::DoNotOptimize(result);
i = IncrementAlternatingSign(i);
}
}
BENCHMARK(BM_HexCat_By_StrCat);
void BM_HexCat_By_Substitute(benchmark::State& state) {
int i = 0;
for (auto _ : state) {
std::string result = absl::Substitute(
"$0 $1", kStringOne, reinterpret_cast<void*>(int64_t{i} + 0x10000000));
benchmark::DoNotOptimize(result);
i = IncrementAlternatingSign(i);
}
}
BENCHMARK(BM_HexCat_By_Substitute);
void BM_FloatToString_By_StrCat(benchmark::State& state) {
int i = 0;
float foo = 0.0f;
for (auto _ : state) {
std::string result = absl::StrCat(foo += 1.001f, " != ", int64_t{i});
benchmark::DoNotOptimize(result);
i = IncrementAlternatingSign(i);
}
}
BENCHMARK(BM_FloatToString_By_StrCat);
void BM_DoubleToString_By_SixDigits(benchmark::State& state) {
int i = 0;
double foo = 0.0;
for (auto _ : state) {
std::string result =
absl::StrCat(absl::SixDigits(foo += 1.001), " != ", int64_t{i});
benchmark::DoNotOptimize(result);
i = IncrementAlternatingSign(i);
}
}
BENCHMARK(BM_DoubleToString_By_SixDigits);
} // namespace
BENCHMARK_MAIN();

98
absl/strings/str_join_benchmark.cc
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//
// Copyright 2018 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
//
// http://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/strings/str_join.h"
#include <string>
#include <vector>
#include <utility>
#include "benchmark/benchmark.h"
namespace {
void BM_Join2_Strings(benchmark::State& state) {
const int string_len = state.range(0);
const int num_strings = state.range(1);
const std::string s(string_len, 'x');
const std::vector<std::string> v(num_strings, s);
for (auto _ : state) {
std::string s = absl::StrJoin(v, "-");
benchmark::DoNotOptimize(s);
}
}
BENCHMARK(BM_Join2_Strings)
->ArgPair(1 << 0, 1 << 3)
->ArgPair(1 << 10, 1 << 3)
->ArgPair(1 << 13, 1 << 3)
->ArgPair(1 << 0, 1 << 10)
->ArgPair(1 << 10, 1 << 10)
->ArgPair(1 << 13, 1 << 10)
->ArgPair(1 << 0, 1 << 13)
->ArgPair(1 << 10, 1 << 13)
->ArgPair(1 << 13, 1 << 13);
void BM_Join2_Ints(benchmark::State& state) {
const int num_ints = state.range(0);
const std::vector<int> v(num_ints, 42);
for (auto _ : state) {
std::string s = absl::StrJoin(v, "-");
benchmark::DoNotOptimize(s);
}
}
BENCHMARK(BM_Join2_Ints)->Range(0, 1 << 13);
void BM_Join2_KeysAndValues(benchmark::State& state) {
const int string_len = state.range(0);
const int num_pairs = state.range(1);
const std::string s(string_len, 'x');
const std::vector<std::pair<std::string, int>> v(num_pairs, std::make_pair(s, 42));
for (auto _ : state) {
std::string s = absl::StrJoin(v, ",", absl::PairFormatter("="));
benchmark::DoNotOptimize(s);
}
}
BENCHMARK(BM_Join2_KeysAndValues)
->ArgPair(1 << 0, 1 << 3)
->ArgPair(1 << 10, 1 << 3)
->ArgPair(1 << 13, 1 << 3)
->ArgPair(1 << 0, 1 << 10)
->ArgPair(1 << 10, 1 << 10)
->ArgPair(1 << 13, 1 << 10)
->ArgPair(1 << 0, 1 << 13)
->ArgPair(1 << 10, 1 << 13)
->ArgPair(1 << 13, 1 << 13);
void BM_JoinStreamable(benchmark::State& state) {
const int string_len = state.range(0);
const int num_strings = state.range(1);
const std::vector<std::string> v(num_strings, std::string(string_len, 'x'));
for (auto _ : state) {
std::string s = absl::StrJoin(v, "", absl::StreamFormatter());
benchmark::DoNotOptimize(s);
}
}
BENCHMARK(BM_JoinStreamable)
->ArgPair(0, 0)
->ArgPair(16, 1)
->ArgPair(256, 1)
->ArgPair(16, 16)
->ArgPair(256, 16)
->ArgPair(16, 256)
->ArgPair(256, 256);
} // namespace
BENCHMARK_MAIN();

124
absl/strings/str_replace_benchmark.cc
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// Copyright 2018 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
//
// http://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/strings/str_replace.h"
#include <cstring>
#include <string>
#include "benchmark/benchmark.h"
#include "absl/base/internal/raw_logging.h"
namespace {
std::string* big_string;
std::string* after_replacing_the;
std::string* after_replacing_many;
struct Replacement {
const char* needle;
const char* replacement;
} replacements[] = {
{"the", "box"}, //
{"brown", "quick"}, //
{"jumped", "liquored"}, //
{"dozen", "brown"}, //
{"lazy", "pack"}, //
{"liquor", "shakes"}, //
};
// Here, we set up a std::string for use in global-replace benchmarks.
// We started with a million blanks, and then deterministically insert
// 10,000 copies each of two pangrams. The result is a std::string that is
// 40% blank space and 60% these words. 'the' occurs 18,247 times and
// all the substitutions together occur 49,004 times.
//
// We then create "after_replacing_the" to be a std::string that is a result of
// replacing "the" with "box" in big_string.
//
// And then we create "after_replacing_many" to be a std::string that is result
// of preferring several substitutions.
void SetUpStrings() {
if (big_string == nullptr) {
size_t r = 0;
big_string = new std::string(1000 * 1000, ' ');
for (std::string phrase : {"the quick brown fox jumped over the lazy dogs",
"pack my box with the five dozen liquor jugs"}) {
for (int i = 0; i < 10 * 1000; ++i) {
r = r * 237 + 41; // not very random.
memcpy(&(*big_string)[r % (big_string->size() - phrase.size())],
phrase.data(), phrase.size());
}
}
// big_string->resize(50);
// OK, we've set up the std::string, now let's set up expectations - first by
// just replacing "the" with "box"
after_replacing_the = new std::string(*big_string);
for (size_t pos = 0;
(pos = after_replacing_the->find("the", pos)) != std::string::npos;) {
memcpy(&(*after_replacing_the)[pos], "box", 3);
}
// And then with all the replacements.
after_replacing_many = new std::string(*big_string);
for (size_t pos = 0;;) {
size_t next_pos = static_cast<size_t>(-1);
const char* needle_string = nullptr;
const char* replacement_string = nullptr;
for (const auto& r : replacements) {
auto needlepos = after_replacing_many->find(r.needle, pos);
if (needlepos != std::string::npos && needlepos < next_pos) {
next_pos = needlepos;
needle_string = r.needle;
replacement_string = r.replacement;
}
}
if (next_pos > after_replacing_many->size()) break;
after_replacing_many->replace(next_pos, strlen(needle_string),
replacement_string);
next_pos += strlen(replacement_string);
pos = next_pos;
}
}
}
void BM_StrReplaceAllOneReplacement(benchmark::State& state) {
SetUpStrings();
std::string src = *big_string;
for (auto _ : state) {
std::string dest = absl::StrReplaceAll(src, {{"the", "box"}});
ABSL_RAW_CHECK(dest == *after_replacing_the,
"not benchmarking intended behavior");
}
}
BENCHMARK(BM_StrReplaceAllOneReplacement);
void BM_StrReplaceAll(benchmark::State& state) {
SetUpStrings();
std::string src = *big_string;
for (auto _ : state) {
std::string dest = absl::StrReplaceAll(src, {{"the", "box"},
{"brown", "quick"},
{"jumped", "liquored"},
{"dozen", "brown"},
{"lazy", "pack"},
{"liquor", "shakes"}});
ABSL_RAW_CHECK(dest == *after_replacing_many,
"not benchmarking intended behavior");
}
}
BENCHMARK(BM_StrReplaceAll);
} // namespace
BENCHMARK_MAIN();

158
absl/strings/str_split_benchmark.cc
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// Copyright 2018 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
//
// http://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/strings/str_split.h"
#include <iterator>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>
#include "benchmark/benchmark.h"
#include "absl/base/internal/raw_logging.h"
#include "absl/strings/string_view.h"
namespace {
std::string MakeTestString(int desired_length) {
static const int kAverageValueLen = 25;
std::string test(desired_length * kAverageValueLen, 'x');
for (int i = 1; i < test.size(); i += kAverageValueLen) {
test[i] = ';';
}
return test;
}
void BM_Split2StringPiece(benchmark::State& state) {
std::string test = MakeTestString(state.range(0));
for (auto _ : state) {
std::vector<absl::string_view> result = absl::StrSplit(test, ';');
benchmark::DoNotOptimize(result);
}
}
BENCHMARK_RANGE(BM_Split2StringPiece, 0, 1 << 20);
void BM_Split2StringPieceLifted(benchmark::State& state) {
std::string test = MakeTestString(state.range(0));
std::vector<absl::string_view> result;
for (auto _ : state) {
result = absl::StrSplit(test, ';');
}
benchmark::DoNotOptimize(result);
}
BENCHMARK_RANGE(BM_Split2StringPieceLifted, 0, 1 << 20);
void BM_Split2String(benchmark::State& state) {
std::string test = MakeTestString(state.range(0));
for (auto _ : state) {
std::vector<std::string> result = absl::StrSplit(test, ';');
benchmark::DoNotOptimize(result);
}
}
BENCHMARK_RANGE(BM_Split2String, 0, 1 << 20);
// This benchmark is for comparing Split2 to Split1 (SplitStringUsing). In
// particular, this benchmark uses SkipEmpty() to match SplitStringUsing's
// behavior.
void BM_Split2SplitStringUsing(benchmark::State& state) {
std::string test = MakeTestString(state.range(0));
for (auto _ : state) {
std::vector<std::string> result = absl::StrSplit(test, ';', absl::SkipEmpty());
benchmark::DoNotOptimize(result);
}
}
BENCHMARK_RANGE(BM_Split2SplitStringUsing, 0, 1 << 20);
void BM_SplitStringToUnorderedSet(benchmark::State& state) {
const int len = state.range(0);
std::string test(len, 'x');
for (int i = 1; i < len; i += 2) {
test[i] = ';';
}
for (auto _ : state) {
std::unordered_set<std::string> result =
absl::StrSplit(test, ':', absl::SkipEmpty());
benchmark::DoNotOptimize(result);
}
}
BENCHMARK_RANGE(BM_SplitStringToUnorderedSet, 0, 1 << 20);
void BM_SplitStringToUnorderedMap(benchmark::State& state) {
const int len = state.range(0);
std::string test(len, 'x');
for (int i = 1; i < len; i += 2) {
test[i] = ';';
}
for (auto _ : state) {
std::unordered_map<std::string, std::string> result =
absl::StrSplit(test, ':', absl::SkipEmpty());
benchmark::DoNotOptimize(result);
}
}
BENCHMARK_RANGE(BM_SplitStringToUnorderedMap, 0, 1 << 20);
void BM_SplitStringAllowEmpty(benchmark::State& state) {
const int len = state.range(0);
std::string test(len, 'x');
for (int i = 1; i < len; i += 2) {
test[i] = ';';
}
for (auto _ : state) {
std::vector<std::string> result = absl::StrSplit(test, ';');
benchmark::DoNotOptimize(result);
}
}
BENCHMARK_RANGE(BM_SplitStringAllowEmpty, 0, 1 << 20);
struct OneCharLiteral {
char operator()() const { return 'X'; }
};
struct OneCharStringLiteral {
const char* operator()() const { return "X"; }
};
template <typename DelimiterFactory>
void BM_SplitStringWithOneChar(benchmark::State& state) {
const auto delimiter = DelimiterFactory()();
std::vector<absl::string_view> pieces;
size_t v = 0;
for (auto _ : state) {
pieces = absl::StrSplit("The quick brown fox jumps over the lazy dog",
delimiter);
v += pieces.size();
}
ABSL_RAW_CHECK(v == state.iterations(), "");
}
BENCHMARK_TEMPLATE(BM_SplitStringWithOneChar, OneCharLiteral);
BENCHMARK_TEMPLATE(BM_SplitStringWithOneChar, OneCharStringLiteral);
template <typename DelimiterFactory>
void BM_SplitStringWithOneCharNoVector(benchmark::State& state) {
const auto delimiter = DelimiterFactory()();
size_t v = 0;
for (auto _ : state) {
auto splitter = absl::StrSplit(
"The quick brown fox jumps over the lazy dog", delimiter);
v += std::distance(splitter.begin(), splitter.end());
}
ABSL_RAW_CHECK(v == state.iterations(), "");
}
BENCHMARK_TEMPLATE(BM_SplitStringWithOneCharNoVector, OneCharLiteral);
BENCHMARK_TEMPLATE(BM_SplitStringWithOneCharNoVector, OneCharStringLiteral);
} // namespace
BENCHMARK_MAIN();

331
absl/strings/string_view_benchmark.cc
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// Copyright 2018 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
//
// http://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/strings/string_view.h"
#include <algorithm>
#include <cstdint>
#include <map>
#include <random>
#include <string>
#include <unordered_set>
#include <vector>
#include "benchmark/benchmark.h"
#include "absl/base/attributes.h"
#include "absl/base/internal/raw_logging.h"
#include "absl/base/macros.h"
#include "absl/strings/str_cat.h"
namespace {
// Provide a forcibly out-of-line wrapper for operator== that can be used in
// benchmarks to measure the impact of inlining.
ABSL_ATTRIBUTE_NOINLINE
bool NonInlinedEq(absl::string_view a, absl::string_view b) { return a == b; }
// We use functions that cannot be inlined to perform the comparison loops so
// that inlining of the operator== can't optimize away *everything*.
ABSL_ATTRIBUTE_NOINLINE
void DoEqualityComparisons(benchmark::State& state, absl::string_view a,
absl::string_view b) {
for (auto _ : state) {
benchmark::DoNotOptimize(a == b);
}
}
void BM_EqualIdentical(benchmark::State& state) {
std::string x(state.range(0), 'a');
DoEqualityComparisons(state, x, x);
}
BENCHMARK(BM_EqualIdentical)->DenseRange(0, 3)->Range(4, 1 << 10);
void BM_EqualSame(benchmark::State& state) {
std::string x(state.range(0), 'a');
std::string y = x;
DoEqualityComparisons(state, x, y);
}
BENCHMARK(BM_EqualSame)
->DenseRange(0, 10)
->Arg(20)
->Arg(40)
->Arg(70)
->Arg(110)
->Range(160, 4096);
void BM_EqualDifferent(benchmark::State& state) {
const int len = state.range(0);
std::string x(len, 'a');
std::string y = x;
if (len > 0) {
y[len - 1] = 'b';
}
DoEqualityComparisons(state, x, y);
}
BENCHMARK(BM_EqualDifferent)->DenseRange(0, 3)->Range(4, 1 << 10);
// This benchmark is intended to check that important simplifications can be
// made with absl::string_view comparisons against constant strings. The idea is
// that if constant strings cause redundant components of the comparison, the
// compiler should detect and eliminate them. Here we use 8 different strings,
// each with the same size. Provided our comparison makes the implementation
// inline-able by the compiler, it should fold all of these away into a single
// size check once per loop iteration.
ABSL_ATTRIBUTE_NOINLINE
void DoConstantSizeInlinedEqualityComparisons(benchmark::State& state,
absl::string_view a) {
for (auto _ : state) {
benchmark::DoNotOptimize(a == "aaa");
benchmark::DoNotOptimize(a == "bbb");
benchmark::DoNotOptimize(a == "ccc");
benchmark::DoNotOptimize(a == "ddd");
benchmark::DoNotOptimize(a == "eee");
benchmark::DoNotOptimize(a == "fff");
benchmark::DoNotOptimize(a == "ggg");
benchmark::DoNotOptimize(a == "hhh");
}
}
void BM_EqualConstantSizeInlined(benchmark::State& state) {
std::string x(state.range(0), 'a');
DoConstantSizeInlinedEqualityComparisons(state, x);
}
// We only need to check for size of 3, and <> 3 as this benchmark only has to
// do with size differences.
BENCHMARK(BM_EqualConstantSizeInlined)->DenseRange(2, 4);
// This benchmark exists purely to give context to the above timings: this is
// what they would look like if the compiler is completely unable to simplify
// between two comparisons when they are comparing against constant strings.
ABSL_ATTRIBUTE_NOINLINE
void DoConstantSizeNonInlinedEqualityComparisons(benchmark::State& state,
absl::string_view a) {
for (auto _ : state) {
// Force these out-of-line to compare with the above function.
benchmark::DoNotOptimize(NonInlinedEq(a, "aaa"));
benchmark::DoNotOptimize(NonInlinedEq(a, "bbb"));
benchmark::DoNotOptimize(NonInlinedEq(a, "ccc"));
benchmark::DoNotOptimize(NonInlinedEq(a, "ddd"));
benchmark::DoNotOptimize(NonInlinedEq(a, "eee"));
benchmark::DoNotOptimize(NonInlinedEq(a, "fff"));
benchmark::DoNotOptimize(NonInlinedEq(a, "ggg"));
benchmark::DoNotOptimize(NonInlinedEq(a, "hhh"));
}
}
void BM_EqualConstantSizeNonInlined(benchmark::State& state) {
std::string x(state.range(0), 'a');
DoConstantSizeNonInlinedEqualityComparisons(state, x);
}
// We only need to check for size of 3, and <> 3 as this benchmark only has to
// do with size differences.
BENCHMARK(BM_EqualConstantSizeNonInlined)->DenseRange(2, 4);
void BM_CompareSame(benchmark::State& state) {
const int len = state.range(0);
std::string x;
for (int i = 0; i < len; i++) {
x += 'a';
}
std::string y = x;
absl::string_view a = x;
absl::string_view b = y;
for (auto _ : state) {
benchmark::DoNotOptimize(a.compare(b));
}
}
BENCHMARK(BM_CompareSame)->DenseRange(0, 3)->Range(4, 1 << 10);
void BM_find_string_view_len_one(benchmark::State& state) {
std::string haystack(state.range(0), '0');
absl::string_view s(haystack);
for (auto _ : state) {
s.find("x"); // not present; length 1
}
}
BENCHMARK(BM_find_string_view_len_one)->Range(1, 1 << 20);
void BM_find_string_view_len_two(benchmark::State& state) {
std::string haystack(state.range(0), '0');
absl::string_view s(haystack);
for (auto _ : state) {
s.find("xx"); // not present; length 2
}
}
BENCHMARK(BM_find_string_view_len_two)->Range(1, 1 << 20);
void BM_find_one_char(benchmark::State& state) {
std::string haystack(state.range(0), '0');
absl::string_view s(haystack);
for (auto _ : state) {
s.find('x'); // not present
}
}
BENCHMARK(BM_find_one_char)->Range(1, 1 << 20);
void BM_rfind_one_char(benchmark::State& state) {
std::string haystack(state.range(0), '0');
absl::string_view s(haystack);
for (auto _ : state) {
s.rfind('x'); // not present
}
}
BENCHMARK(BM_rfind_one_char)->Range(1, 1 << 20);
void BM_worst_case_find_first_of(benchmark::State& state, int haystack_len) {
const int needle_len = state.range(0);
std::string needle;
for (int i = 0; i < needle_len; ++i) {
needle += 'a' + i;
}
std::string haystack(haystack_len, '0'); // 1000 zeros.
absl::string_view s(haystack);
for (auto _ : state) {
s.find_first_of(needle);
}
}
void BM_find_first_of_short(benchmark::State& state) {
BM_worst_case_find_first_of(state, 10);
}
void BM_find_first_of_medium(benchmark::State& state) {
BM_worst_case_find_first_of(state, 100);
}
void BM_find_first_of_long(benchmark::State& state) {
BM_worst_case_find_first_of(state, 1000);
}
BENCHMARK(BM_find_first_of_short)->DenseRange(0, 4)->Arg(8)->Arg(16)->Arg(32);
BENCHMARK(BM_find_first_of_medium)->DenseRange(0, 4)->Arg(8)->Arg(16)->Arg(32);
BENCHMARK(BM_find_first_of_long)->DenseRange(0, 4)->Arg(8)->Arg(16)->Arg(32);
struct EasyMap : public std::map<absl::string_view, uint64_t> {
explicit EasyMap(size_t) {}
};
// This templated benchmark helper function is intended to stress operator== or
// operator< in a realistic test. It surely isn't entirely realistic, but it's
// a start. The test creates a map of type Map, a template arg, and populates
// it with table_size key/value pairs. Each key has WordsPerKey words. After
// creating the map, a number of lookups are done in random order. Some keys
// are used much more frequently than others in this phase of the test.
template <typename Map, int WordsPerKey>
void StringViewMapBenchmark(benchmark::State& state) {
const int table_size = state.range(0);
const double kFractionOfKeysThatAreHot = 0.2;
const int kNumLookupsOfHotKeys = 20;
const int kNumLookupsOfColdKeys = 1;
const char* words[] = {"the", "quick", "brown", "fox", "jumped",
"over", "the", "lazy", "dog", "and",
"found", "a", "large", "mushroom", "and",
"a", "couple", "crickets", "eating", "pie"};
// Create some keys that consist of words in random order.
std::random_device r;
std::seed_seq seed({r(), r(), r(), r(), r(), r(), r(), r()});
std::mt19937 rng(seed);
std::vector<std::string> keys(table_size);
std::vector<int> all_indices;
const int kBlockSize = 1 << 12;
std::unordered_set<std::string> t(kBlockSize);
std::uniform_int_distribution<int> uniform(0, ABSL_ARRAYSIZE(words) - 1);
for (int i = 0; i < table_size; i++) {
all_indices.push_back(i);
do {
keys[i].clear();
for (int j = 0; j < WordsPerKey; j++) {
absl::StrAppend(&keys[i], j > 0 ? " " : "", words[uniform(rng)]);
}
} while (!t.insert(keys[i]).second);
}
// Create a list of strings to lookup: a permutation of the array of
// keys we just created, with repeats. "Hot" keys get repeated more.
std::shuffle(all_indices.begin(), all_indices.end(), rng);
const int num_hot = table_size * kFractionOfKeysThatAreHot;
const int num_cold = table_size - num_hot;
std::vector<int> hot_indices(all_indices.begin(),
all_indices.begin() + num_hot);
std::vector<int> indices;
for (int i = 0; i < kNumLookupsOfColdKeys; i++) {
indices.insert(indices.end(), all_indices.begin(), all_indices.end());
}
for (int i = 0; i < kNumLookupsOfHotKeys - kNumLookupsOfColdKeys; i++) {
indices.insert(indices.end(), hot_indices.begin(), hot_indices.end());
}
std::shuffle(indices.begin(), indices.end(), rng);
ABSL_RAW_CHECK(
num_cold * kNumLookupsOfColdKeys + num_hot * kNumLookupsOfHotKeys ==
indices.size(),
"");
// After constructing the array we probe it with absl::string_views built from
// test_strings. This means operator== won't see equal pointers, so
// it'll have to check for equal lengths and equal characters.
std::vector<std::string> test_strings(indices.size());
for (int i = 0; i < indices.size(); i++) {
test_strings[i] = keys[indices[i]];
}
// Run the benchmark. It includes map construction but is mostly
// map lookups.
for (auto _ : state) {
Map h(table_size);
for (int i = 0; i < table_size; i++) {
h[keys[i]] = i * 2;
}
ABSL_RAW_CHECK(h.size() == table_size, "");
uint64_t sum = 0;
for (int i = 0; i < indices.size(); i++) {
sum += h[test_strings[i]];
}
benchmark::DoNotOptimize(sum);
}
}
void BM_StdMap_4(benchmark::State& state) {
StringViewMapBenchmark<EasyMap, 4>(state);
}
BENCHMARK(BM_StdMap_4)->Range(1 << 10, 1 << 16);
void BM_StdMap_8(benchmark::State& state) {
StringViewMapBenchmark<EasyMap, 8>(state);
}
BENCHMARK(BM_StdMap_8)->Range(1 << 10, 1 << 16);
void BM_CopyToStringNative(benchmark::State& state) {
std::string src(state.range(0), 'x');
absl::string_view sv(src);
std::string dst;
for (auto _ : state) {
dst.assign(sv.begin(), sv.end());
}
}
BENCHMARK(BM_CopyToStringNative)->Range(1 << 3, 1 << 12);
void BM_AppendToStringNative(benchmark::State& state) {
std::string src(state.range(0), 'x');
absl::string_view sv(src);
std::string dst;
for (auto _ : state) {
dst.clear();
dst.insert(dst.end(), sv.begin(), sv.end());
}
}
BENCHMARK(BM_AppendToStringNative)->Range(1 << 3, 1 << 12);
} // namespace
BENCHMARK_MAIN();

2
absl/synchronization/mutex.h
Unescape View File

@ -854,7 +854,7 @@ class SCOPED_LOCKABLE MutexLockMaybe {
MutexLockMaybe& operator=(MutexLockMaybe&&) = delete;
};
// ReleaseableMutexLock
// ReleasableMutexLock
//
// ReleasableMutexLock is like MutexLock, but permits `Release()` of its
// mutex before destruction. `Release()` may be called at most once.

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