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Update 2026-02-07

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Doncho N. Gunchev 2026-02-07 15:41:27 +02:00
parent b6930e02c5
commit 6526f7ae04
6 changed files with 125 additions and 38 deletions
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65
CMakeLists.txt
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@ -1,13 +1,13 @@
cmake_minimum_required(VERSION 3.20.0) # RHEL 8
project(benchmarks
VERSION 0.0.0.1 # PROJECT_VERSION_MAJOR, PROJECT_VERSION_MINOR, PROJECT_VERSION_PATCH, and PROJECT_VERSION_TWEAK.
VERSION 0.0.1.0 # PROJECT_VERSION_MAJOR, PROJECT_VERSION_MINOR, PROJECT_VERSION_PATCH, and PROJECT_VERSION_TWEAK.
DESCRIPTION "Various benchmarks"
HOMEPAGE_URL "https://github.com/gunchev/bench/"
LANGUAGES C CXX)
set(CMAKE_C_STANDARD 11)
set(CMAKE_C_STANDARD_REQUIRED TRUE)
set(CMAKE_CXX_STANDARD 20)
set(CMAKE_CXX_STANDARD 23)
set(CMAKE_CXX_STANDARD_REQUIRED TRUE)
# set(CMAKE_VERBOSE_MAKEFILE TRUE) # or "cd build; make VERBOSE=1"
@ -18,6 +18,9 @@ if(NOT CMAKE_BUILD_TYPE)
"Choose the type of build, options are: Debug DebugCov RelWithDebInfo Release MinSizeRel." FORCE)
endif()
include(FetchContent)
# SOVERSION is ignored if NO_SONAME property is set.
# "${PROJECT_VERSION_MAJOR}.${PROJECT_VERSION_MINOR}.${PROJECT_VERSION_PATCH}.${PROJECT_VERSION_TWEAK}"
set(${PROJECT_NAME}_SOVERSION "${PROJECT_VERSION_MAJOR}.${PROJECT_VERSION_MINOR}")
@ -47,19 +50,14 @@ set(CMAKE_POSITION_INDEPENDENT_CODE ON)
# Compiler/linker flags
if(EXISTS "/etc/fedora-release")
set(CMAKE_C_FLAGS "-Wall -Wextra")
set(CMAKE_CXX_FLAGS "-Wall -Wextra")
else()
set(CMAKE_C_FLAGS "-Wall -Wextra -Werror")
set(CMAKE_CXX_FLAGS "-Wall -Wextra -Werror")
endif()
# https://gcc.gnu.org/onlinedocs/gcc/Template-Instantiation.html#Template-Instantiation
include(CheckCCompilerFlag)
include(CheckCXXCompilerFlag)
# https://gcc.gnu.org/onlinedocs/gcc/Template-Instantiation.html#Template-Instantiation
set(CMAKE_REQUIRED_QUIET_OLD ${CMAKE_REQUIRED_QUIET})
set(CMAKE_REQUIRED_QUIET ON)
macro(CheckAndAddFlag flag)
@ -120,20 +118,24 @@ set(CMAKE_C_FLAGS_MINSIZEREL "-Os -ggdb3 -D_FORTIFY_SOURCE=2 -DN
set(CMAKE_CXX_FLAGS_MINSIZEREL "-Os -ggdb3 -D_FORTIFY_SOURCE=2 -DNDEBUG")
# Google benchmark
find_package(benchmark 1.9.4)
if (NOT benchmark_FOUND)
message(STATUS "Google Benchmark not found, fetching it...")
# Enable testing?
include(FindPkgConfig)
pkg_check_modules(CPPUNIT cppunit>=1.14.0) # REQUIRED
if(CPPUNIT_FOUND)
enable_testing()
include(CTest)
find_program(CTEST_COVERAGE_COMMAND NAMES gcov)
find_program(CTEST_MEMORYCHECK_COMMAND NAMES valgrind)
add_custom_target(check COMMAND ${CMAKE_CTEST_COMMAND})
FetchContent_Declare(
benchmark
GIT_REPOSITORY https://github.com/google/benchmark.git
GIT_TAG v1.9.4
)
# Disable benchmark's own tests
set(BENCHMARK_ENABLE_TESTING OFF CACHE BOOL "" FORCE)
set(BENCHMARK_ENABLE_GTEST_TESTS OFF CACHE BOOL "" FORCE)
FetchContent_MakeAvailable(benchmark)
endif()
find_package(benchmark REQUIRED)
message(STATUS "Found Google benchmark version: ${benchmark_VERSION}")
# Threads library
# set(THREADS_PREFER_PTHREAD_FLAG TRUE)
@ -145,8 +147,29 @@ find_package(benchmark REQUIRED)
# pkg_check_modules(HIREDIS REQUIRED hiredis>=1.0.2)
# Enable testing?
#include(FindPkgConfig)
#pkg_check_modules(CPPUNIT cppunit>=1.14.0) # REQUIRED
# set(GTEST_MIN_VERSION 1.13.0)
# find_package(GTest ${GTEST_MIN_VERSION} QUIET)
# if (NOT GTest_FOUND)
# message(STATUS "GoogleTest not found, fetching it...")
# FetchContent_Declare(
# googletest
# GIT_REPOSITORY https://github.com/google/googletest.git
# GIT_TAG v1.14.0
# )
# # Don't install or build gtest's own tests
# set(INSTALL_GTEST OFF CACHE BOOL "" FORCE)
# set(BUILD_GMOCK OFF CACHE BOOL "" FORCE)
# FetchContent_MakeAvailable(googletest)
# endif()
# include_directories(src)
add_executable(transform src/transform.cpp)
target_link_libraries(transform PRIVATE benchmark::benchmark) # fmt::fmt Threads::Threads)
target_compile_features(transform PRIVATE cxx_std_17)
install(TARGETS transform DESTINATION bin)

57
README.md
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@ -4,4 +4,59 @@
Various C++ benchmarks:
- transform.cpp - benchmark std::transform vs loop and custom lowercase and tolower
![](bench_lowercase.png)
---
```shell
$ make releasec # clang++ 21.1.8
$ ./build/releasec/transform
```
2026-02-07T15:43:00+02:00
Running ./build/releasec/transform
Run on (32 X 5187.5 MHz CPU s)
CPU Caches:
L1 Data 48 KiB (x16)
L1 Instruction 32 KiB (x16)
L2 Unified 1024 KiB (x16)
L3 Unified 32768 KiB (x2)
Load Average: 0.58, 0.53, 0.60
***WARNING*** CPU scaling is enabled, the benchmark real time measurements may be noisy and will incur extra overhead.
***WARNING*** ASLR is enabled, the results may have unreproducible noise in them.
----------------------------------------------------------------------
Benchmark Time CPU Iterations
----------------------------------------------------------------------
algorithm_lowercase_my 17.8 ns 17.7 ns 39664595
loop_lowercase_my 31.9 ns 31.9 ns 22028280
algorithm_lowercase_toupper 79.3 ns 79.2 ns 8838048
loop_lowercase_toupper 69.7 ns 69.5 ns 9977740
---
```shell
$ make release # g++ 15.2.1
$ ./build/release/transform
```
2026-02-07T15:43:03+02:00
Running ./build/release/transform
Run on (32 X 5187.5 MHz CPU s)
CPU Caches:
L1 Data 48 KiB (x16)
L1 Instruction 32 KiB (x16)
L2 Unified 1024 KiB (x16)
L3 Unified 32768 KiB (x2)
Load Average: 0.61, 0.54, 0.60
***WARNING*** CPU scaling is enabled, the benchmark real time measurements may be noisy and will incur extra overhead.
***WARNING*** ASLR is enabled, the results may have unreproducible noise in them.
----------------------------------------------------------------------
Benchmark Time CPU Iterations
----------------------------------------------------------------------
algorithm_lowercase_my 17.7 ns 17.7 ns 33607332
loop_lowercase_my 28.2 ns 28.2 ns 24781013
algorithm_lowercase_toupper 77.1 ns 77.0 ns 9116098
loop_lowercase_toupper 65.5 ns 65.4 ns 10687636
---
<img src="bench_lowercase_gcc13_cpp23.png" alt="gcc13" style="width:98%;"/>
<img src="bench_lowercase_clang17_cpp23.png" alt="clang17" style="width:98%;"/>
---

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41
src/transform.cpp
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@ -3,13 +3,16 @@
#include <benchmark/benchmark.h>
#include <string>
#include <sysexits.h>
#include <cstring>
const char* data = "Hello world, to be or not to be a long string, that is the question!";
static void algorithm_lowercase_my(benchmark::State& state) {
std::string name;
name.reserve(strlen(data));
for (auto _ : state) { // Code inside this loop is measured repeatedly
std::string name = data;
name = data;
std::transform(name.cbegin(), name.cend(), name.begin(), [](char c) noexcept {
return (c >= 'a' && c <= 'z') ? c = c - 'a' + 'A' : c;
});
@ -19,8 +22,10 @@ static void algorithm_lowercase_my(benchmark::State& state) {
BENCHMARK(algorithm_lowercase_my); // Register the function as a benchmark
static void loop_lowercase_my(benchmark::State& state) {
std::string name;
name.reserve(strlen(data));
for (auto _ : state) { // Code before the loop is not measured
std::string name = data;
name = data;
for (char& c : name) {
if (c >= 'a' && c <= 'z') {
c = c - 'a' + 'A';
@ -33,8 +38,10 @@ BENCHMARK(loop_lowercase_my); // Register the function as a benchmark
static void algorithm_lowercase_toupper(benchmark::State& state) {
std::string name;
name.reserve(strlen(data));
for (auto _ : state) { // Code inside this loop is measured repeatedly
std::string name = data;
name = data;
std::transform(name.cbegin(), name.cend(), name.begin(), [](char c) noexcept {
return std::toupper(static_cast<unsigned char>(c));
});
@ -44,6 +51,21 @@ static void algorithm_lowercase_toupper(benchmark::State& state) {
BENCHMARK(algorithm_lowercase_toupper); // Register the function as a benchmark
static void loop_lowercase_toupper(benchmark::State& state) {
std::string name;
name.reserve(strlen(data));
for (auto _ : state) { // Code inside this loop is measured repeatedly
name = data;
for (char& c : name) {
if (c >= 'a' && c <= 'z') {
c = static_cast<char>(std::toupper(c));
}
}
benchmark::DoNotOptimize(name); // Make sure the variable is not optimized away by compiler
}
}
BENCHMARK(loop_lowercase_toupper); // Register the function as a benchmark
int main(int argc, char** argv) {
benchmark::Initialize(&argc, argv);
if (benchmark::ReportUnrecognizedArguments(argc, argv)) {
@ -53,16 +75,3 @@ int main(int argc, char** argv) {
benchmark::RunSpecifiedBenchmarks();
return EX_OK;
}
static void loop_lowercase_toupper(benchmark::State& state) {
for (auto _ : state) { // Code inside this loop is measured repeatedly
std::string name = data;
for (char& c : name) {
if (c >= 'a' && c <= 'z') {
c = static_cast<char>(std::toupper(c));
}
}
benchmark::DoNotOptimize(name); // Make sure the variable is not optimized away by compiler
}
}
BENCHMARK(loop_lowercase_toupper); // Register the function as a benchmark