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llvm-project/libcxx/benchmarks/string.bench.cpp

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#include <cstdint>
#include <new>
#include <vector>
#include "CartesianBenchmarks.hpp"
#include "GenerateInput.hpp"
#include "benchmark/benchmark.h"
#include "test_macros.h"
constexpr std::size_t MAX_STRING_LEN = 8 << 14;
// Benchmark when there is no match.
static void BM_StringFindNoMatch(benchmark::State &state) {
std::string s1(state.range(0), '-');
std::string s2(8, '*');
for (auto _ : state)
benchmark::DoNotOptimize(s1.find(s2));
}
BENCHMARK(BM_StringFindNoMatch)->Range(10, MAX_STRING_LEN);
// Benchmark when the string matches first time.
static void BM_StringFindAllMatch(benchmark::State &state) {
std::string s1(MAX_STRING_LEN, '-');
std::string s2(state.range(0), '-');
for (auto _ : state)
benchmark::DoNotOptimize(s1.find(s2));
}
BENCHMARK(BM_StringFindAllMatch)->Range(1, MAX_STRING_LEN);
// Benchmark when the string matches somewhere in the end.
static void BM_StringFindMatch1(benchmark::State &state) {
std::string s1(MAX_STRING_LEN / 2, '*');
s1 += std::string(state.range(0), '-');
std::string s2(state.range(0), '-');
for (auto _ : state)
benchmark::DoNotOptimize(s1.find(s2));
}
BENCHMARK(BM_StringFindMatch1)->Range(1, MAX_STRING_LEN / 4);
// Benchmark when the string matches somewhere from middle to the end.
static void BM_StringFindMatch2(benchmark::State &state) {
std::string s1(MAX_STRING_LEN / 2, '*');
s1 += std::string(state.range(0), '-');
s1 += std::string(state.range(0), '*');
std::string s2(state.range(0), '-');
for (auto _ : state)
benchmark::DoNotOptimize(s1.find(s2));
}
BENCHMARK(BM_StringFindMatch2)->Range(1, MAX_STRING_LEN / 4);
static void BM_StringCtorDefault(benchmark::State &state) {
for (auto _ : state) {
std::string Default;
benchmark::DoNotOptimize(Default);
}
}
BENCHMARK(BM_StringCtorDefault);
enum class Length { Empty, Small, Large, Huge };
struct AllLengths : EnumValuesAsTuple<AllLengths, Length, 4> {
static constexpr const char* Names[] = {"Empty", "Small", "Large", "Huge"};
};
enum class Opacity { Opaque, Transparent };
struct AllOpacity : EnumValuesAsTuple<AllOpacity, Opacity, 2> {
static constexpr const char* Names[] = {"Opaque", "Transparent"};
};
enum class DiffType { Control, ChangeFirst, ChangeMiddle, ChangeLast };
struct AllDiffTypes : EnumValuesAsTuple<AllDiffTypes, DiffType, 4> {
static constexpr const char* Names[] = {"Control", "ChangeFirst",
"ChangeMiddle", "ChangeLast"};
};
TEST_ALWAYS_INLINE const char* getSmallString(DiffType D) {
switch (D) {
case DiffType::Control:
return "0123456";
case DiffType::ChangeFirst:
return "-123456";
case DiffType::ChangeMiddle:
return "012-456";
case DiffType::ChangeLast:
return "012345-";
}
}
TEST_ALWAYS_INLINE const char* getLargeString(DiffType D) {
#define LARGE_STRING_FIRST "123456789012345678901234567890"
#define LARGE_STRING_SECOND "234567890123456789012345678901"
switch (D) {
case DiffType::Control:
return "0" LARGE_STRING_FIRST "1" LARGE_STRING_SECOND "2";
case DiffType::ChangeFirst:
return "-" LARGE_STRING_FIRST "1" LARGE_STRING_SECOND "2";
case DiffType::ChangeMiddle:
return "0" LARGE_STRING_FIRST "-" LARGE_STRING_SECOND "2";
case DiffType::ChangeLast:
return "0" LARGE_STRING_FIRST "1" LARGE_STRING_SECOND "-";
}
}
TEST_ALWAYS_INLINE const char* getHugeString(DiffType D) {
#define HUGE_STRING0 "0123456789"
#define HUGE_STRING1 HUGE_STRING0 HUGE_STRING0 HUGE_STRING0 HUGE_STRING0
#define HUGE_STRING2 HUGE_STRING1 HUGE_STRING1 HUGE_STRING1 HUGE_STRING1
#define HUGE_STRING3 HUGE_STRING2 HUGE_STRING2 HUGE_STRING2 HUGE_STRING2
#define HUGE_STRING4 HUGE_STRING3 HUGE_STRING3 HUGE_STRING3 HUGE_STRING3
switch (D) {
case DiffType::Control:
return "0123456789" HUGE_STRING4 "0123456789" HUGE_STRING4 "0123456789";
case DiffType::ChangeFirst:
return "-123456789" HUGE_STRING4 "0123456789" HUGE_STRING4 "0123456789";
case DiffType::ChangeMiddle:
return "0123456789" HUGE_STRING4 "01234-6789" HUGE_STRING4 "0123456789";
case DiffType::ChangeLast:
return "0123456789" HUGE_STRING4 "0123456789" HUGE_STRING4 "012345678-";
}
}
TEST_ALWAYS_INLINE std::string makeString(Length L,
DiffType D = DiffType::Control,
Opacity O = Opacity::Transparent) {
switch (L) {
case Length::Empty:
return maybeOpaque("", O == Opacity::Opaque);
case Length::Small:
return maybeOpaque(getSmallString(D), O == Opacity::Opaque);
case Length::Large:
return maybeOpaque(getLargeString(D), O == Opacity::Opaque);
case Length::Huge:
return maybeOpaque(getHugeString(D), O == Opacity::Opaque);
}
}
template <class Length, class Opaque>
struct StringConstructDestroyCStr {
static void run(benchmark::State& state) {
for (auto _ : state) {
benchmark::DoNotOptimize(
makeString(Length(), DiffType::Control, Opaque()));
}
}
static std::string name() {
return "BM_StringConstructDestroyCStr" + Length::name() + Opaque::name();
}
};
template <class Length, bool MeasureCopy, bool MeasureDestroy>
static void StringCopyAndDestroy(benchmark::State& state) {
static constexpr size_t NumStrings = 1024;
auto Orig = makeString(Length());
std::aligned_storage<sizeof(std::string)>::type Storage[NumStrings];
while (state.KeepRunningBatch(NumStrings)) {
if (!MeasureCopy)
state.PauseTiming();
for (size_t I = 0; I < NumStrings; ++I) {
::new (static_cast<void*>(Storage + I)) std::string(Orig);
}
if (!MeasureCopy)
state.ResumeTiming();
if (!MeasureDestroy)
state.PauseTiming();
for (size_t I = 0; I < NumStrings; ++I) {
using S = std::string;
reinterpret_cast<S*>(Storage + I)->~S();
}
if (!MeasureDestroy)
state.ResumeTiming();
}
}
template <class Length>
struct StringCopy {
static void run(benchmark::State& state) {
StringCopyAndDestroy<Length, true, false>(state);
}
static std::string name() { return "BM_StringCopy" + Length::name(); }
};
template <class Length>
struct StringDestroy {
static void run(benchmark::State& state) {
StringCopyAndDestroy<Length, false, true>(state);
}
static std::string name() { return "BM_StringDestroy" + Length::name(); }
};
template <class Length>
struct StringMove {
static void run(benchmark::State& state) {
// Keep two object locations and move construct back and forth.
std::aligned_storage<sizeof(std::string), alignof(std::string)>::type Storage[2];
using S = std::string;
size_t I = 0;
S *newS = new (static_cast<void*>(Storage)) std::string(makeString(Length()));
for (auto _ : state) {
// Switch locations.
I ^= 1;
benchmark::DoNotOptimize(Storage);
// Move construct into the new location,
S *tmpS = new (static_cast<void*>(Storage + I)) S(std::move(*newS));
// then destroy the old one.
newS->~S();
newS = tmpS;
}
newS->~S();
}
static std::string name() { return "BM_StringMove" + Length::name(); }
};
enum class Relation { Eq, Less, Compare };
struct AllRelations : EnumValuesAsTuple<AllRelations, Relation, 3> {
static constexpr const char* Names[] = {"Eq", "Less", "Compare"};
};
template <class Rel, class LHLength, class RHLength, class DiffType>
struct StringRelational {
static void run(benchmark::State& state) {
auto Lhs = makeString(RHLength());
auto Rhs = makeString(LHLength(), DiffType());
for (auto _ : state) {
benchmark::DoNotOptimize(Lhs);
benchmark::DoNotOptimize(Rhs);
switch (Rel()) {
case Relation::Eq:
benchmark::DoNotOptimize(Lhs == Rhs);
break;
case Relation::Less:
benchmark::DoNotOptimize(Lhs < Rhs);
break;
case Relation::Compare:
benchmark::DoNotOptimize(Lhs.compare(Rhs));
break;
}
}
}
static bool skip() {
// Eq is commutative, so skip half the matrix.
if (Rel() == Relation::Eq && LHLength() > RHLength())
return true;
// We only care about control when the lengths differ.
if (LHLength() != RHLength() && DiffType() != ::DiffType::Control)
return true;
// For empty, only control matters.
if (LHLength() == Length::Empty && DiffType() != ::DiffType::Control)
return true;
return false;
}
static std::string name() {
return "BM_StringRelational" + Rel::name() + LHLength::name() +
RHLength::name() + DiffType::name();
}
};
enum class Depth { Shallow, Deep };
struct AllDepths : EnumValuesAsTuple<AllDepths, Depth, 2> {
static constexpr const char* Names[] = {"Shallow", "Deep"};
};
enum class Temperature { Hot, Cold };
struct AllTemperatures : EnumValuesAsTuple<AllTemperatures, Temperature, 2> {
static constexpr const char* Names[] = {"Hot", "Cold"};
};
template <class Temperature, class Depth, class Length>
struct StringRead {
void run(benchmark::State& state) const {
static constexpr size_t NumStrings =
Temperature() == ::Temperature::Hot
? 1 << 10
: /* Enough strings to overflow the cache */ 1 << 20;
static_assert((NumStrings & (NumStrings - 1)) == 0,
"NumStrings should be a power of two to reduce overhead.");
std::vector<std::string> Values(NumStrings, makeString(Length()));
size_t I = 0;
for (auto _ : state) {
// Jump long enough to defeat cache locality, and use a value that is
// coprime with NumStrings to ensure we visit every element.
I = (I + 17) % NumStrings;
const auto& V = Values[I];
// Read everything first. Escaping data() through DoNotOptimize might
// cause the compiler to have to recalculate information about `V` due to
// aliasing.
const char* const Data = V.data();
const size_t Size = V.size();
benchmark::DoNotOptimize(Data);
benchmark::DoNotOptimize(Size);
if (Depth() == ::Depth::Deep) {
// Read into the payload. This mainly shows the benefit of SSO when the
// data is cold.
benchmark::DoNotOptimize(*Data);
}
}
}
static bool skip() {
// Huge does not give us anything that Large doesn't have. Skip it.
if (Length() == ::Length::Huge) {
return true;
}
return false;
}
std::string name() const {
return "BM_StringRead" + Temperature::name() + Depth::name() +
Length::name();
}
};
void sanityCheckGeneratedStrings() {
for (auto Lhs : {Length::Empty, Length::Small, Length::Large, Length::Huge}) {
const auto LhsString = makeString(Lhs);
for (auto Rhs :
{Length::Empty, Length::Small, Length::Large, Length::Huge}) {
if (Lhs > Rhs)
continue;
const auto RhsString = makeString(Rhs);
// The smaller one must be a prefix of the larger one.
if (RhsString.find(LhsString) != 0) {
fprintf(stderr, "Invalid autogenerated strings for sizes (%d,%d).\n",
static_cast<int>(Lhs), static_cast<int>(Rhs));
std::abort();
}
}
}
// Verify the autogenerated diffs
for (auto L : {Length::Small, Length::Large, Length::Huge}) {
const auto Control = makeString(L);
const auto Verify = [&](std::string Exp, size_t Pos) {
// Only change on the Pos char.
if (Control[Pos] != Exp[Pos]) {
Exp[Pos] = Control[Pos];
if (Control == Exp)
return;
}
fprintf(stderr, "Invalid autogenerated diff with size %d\n",
static_cast<int>(L));
std::abort();
};
Verify(makeString(L, DiffType::ChangeFirst), 0);
Verify(makeString(L, DiffType::ChangeMiddle), Control.size() / 2);
Verify(makeString(L, DiffType::ChangeLast), Control.size() - 1);
}
}
int main(int argc, char** argv) {
benchmark::Initialize(&argc, argv);
if (benchmark::ReportUnrecognizedArguments(argc, argv))
return 1;
sanityCheckGeneratedStrings();
makeCartesianProductBenchmark<StringConstructDestroyCStr, AllLengths,
AllOpacity>();
makeCartesianProductBenchmark<StringCopy, AllLengths>();
makeCartesianProductBenchmark<StringMove, AllLengths>();
makeCartesianProductBenchmark<StringDestroy, AllLengths>();
makeCartesianProductBenchmark<StringRelational, AllRelations, AllLengths,
AllLengths, AllDiffTypes>();
makeCartesianProductBenchmark<StringRead, AllTemperatures, AllDepths,
AllLengths>();
benchmark::RunSpecifiedBenchmarks();
}
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