Benchmark
A library to benchmark code snippets, similar to unit tests. Example:
#include <benchmark/registration.h>
#include <benchmark/state.h>
static void BM_SomeFunction(benchmark::State& state) {
// Perform setup here
for (auto _ : state) {
// This code gets timed
SomeFunction();
}
}
// Register the function as a benchmark
BENCHMARK(BM_SomeFunction);
// Run the benchmark
BENCHMARK_MAIN();
Getting Started
To get started, see Requirements and
Installation. See Usage for a full example and the
User Guide for a more comprehensive feature overview.
It may also help to read the Google Test documentation
as some of the structural aspects of the APIs are similar.
Resources
Discussion group
IRC channels:
Additional Tooling Documentation
Assembly Testing Documentation
Building and installing Python bindings
Requirements
The library can be used with C++11. However, it requires C++17 to build,
including compiler and standard library support.
See dependencies.md for more details regarding supported
compilers and standards.
If you have need for a particular compiler to be supported, patches are very welcome.
See Platform-Specific Build Instructions.
Installation
This describes the installation process using cmake. As pre-requisites, you'll
need git and cmake installed.
See dependencies.md for more details regarding supported
versions of build tools.
# Check out the library.
$ git clone https://github.com/google/benchmark.git
# Go to the library root directory
$ cd benchmark
# Make a build directory to place the build output.
$ cmake -E make_directory "build"
# Generate build system files with cmake, and download any dependencies.
$ cmake -DBENCHMARK_DOWNLOAD_DEPENDENCIES=on -DCMAKE_BUILD_TYPE=Release -S . -B "build"
# Build the library.
$ cmake --build "build" --config Release
This builds the benchmark and benchmark_main libraries and tests.
On a unix system, the build directory should now look something like this:
/benchmark
/build
/src
/libbenchmark.a
/libbenchmark_main.a
/test
...
Next, you can run the tests to check the build.
$ cmake -E chdir "build" ctest --build-config Release
If you want to install the library globally, also run:
sudo cmake --build "build" --config Release --target install
Note that Google Benchmark requires Google Test to build and run the tests. This
dependency can be provided two ways:
- Checkout the Google Test sources into
benchmark/googletest.
- Otherwise, if
-DBENCHMARK_DOWNLOAD_DEPENDENCIES=ON is specified during
configuration as above, the library will automatically download and build
any required dependencies.
If you do not wish to build and run the tests, add -DBENCHMARK_ENABLE_GTEST_TESTS=OFF
to CMAKE_ARGS.
Debug vs Release
By default, benchmark builds as a debug library. You will see a warning in the
output when this is the case. To build it as a release library instead, add
-DCMAKE_BUILD_TYPE=Release when generating the build system files, as shown
above. The use of --config Release in build commands is needed to properly
support multi-configuration tools (like Visual Studio for example) and can be
skipped for other build systems (like Makefile).
To enable link-time optimisation, also add -DBENCHMARK_ENABLE_LTO=true when
generating the build system files.
If you are using gcc, you might need to set GCC_AR and GCC_RANLIB cmake
cache variables, if autodetection fails.
If you are using clang, you may need to set LLVMAR_EXECUTABLE,
LLVMNM_EXECUTABLE and LLVMRANLIB_EXECUTABLE cmake cache variables.
To enable sanitizer checks (eg., asan and tsan), add:
-DCMAKE_C_FLAGS="-g -O2 -fno-omit-frame-pointer -fsanitize=address -fsanitize=thread -fno-sanitize-recover=all"
-DCMAKE_CXX_FLAGS="-g -O2 -fno-omit-frame-pointer -fsanitize=address -fsanitize=thread -fno-sanitize-recover=all "
Stable and Experimental Library Versions
The main branch contains the latest stable version of the benchmarking library;
the API of which can be considered largely stable, with source breaking changes
being made only upon the release of a new major version.
Newer, experimental, features are implemented and tested on the
v2 branch. Users who wish
to use, test, and provide feedback on the new features are encouraged to try
this branch. However, this branch provides no stability guarantees and reserves
the right to change and break the API at any time.
Usage
Basic usage
Define a function that executes the code to measure, register it as a benchmark
function using the BENCHMARK macro, and ensure an appropriate main function
is available:
#include <benchmark/benchmark.h>
static void BM_StringCreation(benchmark::State& state) {
for (auto _ : state)
std::string empty_string;
}
// Register the function as a benchmark
BENCHMARK(BM_StringCreation);
// Define another benchmark
static void BM_StringCopy(benchmark::State& state) {
std::string x = "hello";
for (auto _ : state)
std::string copy(x);
}
BENCHMARK(BM_StringCopy);
BENCHMARK_MAIN();
To run the benchmark, compile and link against the benchmark library
(libbenchmark.a/.so). If you followed the build steps above, this library will
be under the build directory you created.
# Example on linux after running the build steps above. Assumes the
# `benchmark` and `build` directories are under the current directory.
$ g++ mybenchmark.cc -std=c++11 -isystem benchmark/include \
-Lbenchmark/build/src -lbenchmark -lpthread -o mybenchmark
Alternatively, link against the benchmark_main library and remove
BENCHMARK_MAIN(); above to get the same behavior.
The compiled executable will run all benchmarks by default. Pass the --help
flag for option information or see the User Guide.
Usage with CMake
If using CMake, it is recommended to link against the project-provided
benchmark::benchmark or benchmark::benchmark_main targets using
target_link_libraries. Link to benchmark::benchmark when your target
defines its own main function, or link to benchmark::benchmark_main to use
the default benchmark entry point. The benchmark::benchmark_main target links
benchmark::benchmark transitively.
It is possible to use find_package to import an installed version of the
library.
find_package(benchmark REQUIRED)
Alternatively, add_subdirectory will incorporate the library directly in
to one's CMake project.
add_subdirectory(benchmark)
Either way, link to the library as follows.
target_link_libraries(MyTarget benchmark::benchmark)
# Or, when you do not define your own main:
target_link_libraries(MyTarget benchmark::benchmark_main)
When benchmark sources are shared through an intermediate CMake target, choose
an object library instead of a static library:
add_library(shared_benchmarks OBJECT bench.cc)
target_link_libraries(shared_benchmarks benchmark::benchmark_main)
add_executable(runnable_benchmarks)
target_link_libraries(runnable_benchmarks shared_benchmarks)
This links the object file that contains BENCHMARK registrations into the
final executable. If those registrations are placed only in an intermediate
STATIC library, the linker may not copy static registration symbols, and thus
benchmarks will not be part of the final executable.
Embedding Google Benchmark in another CMake project
There are two common ways to consume Google Benchmark from a CMake project:
- Use an installed or package-managed copy, for example from a system package
manager or vcpkg, and import it with
find_package(benchmark REQUIRED).
- Add this repository to the source tree, for example as a submodule or
FetchContent dependency, and call add_subdirectory.
The installed form keeps Google Benchmark's build separate from the parent
project and is usually the simplest choice for system packages and vcpkg. The
source-tree form is useful when the parent project wants to pin a specific
commit or build Google Benchmark as part of its normal CMake configure step.
When embedding from source, most projects should turn off Google Benchmark's
tests and install rules:
set(BENCHMARK_ENABLE_GTEST_TESTS OFF CACHE BOOL "" FORCE)
set(BENCHMARK_ENABLE_TESTING OFF CACHE BOOL "" FORCE)
set(BENCHMARK_ENABLE_INSTALL OFF CACHE BOOL "" FORCE)
add_subdirectory(third_party/benchmark)
target_link_libraries(MyTarget benchmark::benchmark)
If Google Test is not already provided by the parent build, either check out the
Google Test sources under benchmark/googletest or configure with
BENCHMARK_DOWNLOAD_DEPENDENCIES=ON. For projects that only link the benchmark
library and do not build Google Benchmark's tests, disabling
BENCHMARK_ENABLE_GTEST_TESTS avoids the Google Test dependency.
Google Benchmark follows CMake's BUILD_SHARED_LIBS setting when selecting
static or shared library output. On Windows, keep this setting consistent with
the rest of the project and make sure the same runtime library configuration is
used across the benchmark library and the targets that link it.
Usage with Bazel
If using Bazel with Bzlmod, add Google Benchmark to your MODULE.bazel file:
bazel_dep(name = "google_benchmark", version = "<VERSION>")
Replace <VERSION> with the Google Benchmark release version you want to use.
Then link a cc_binary or cc_test against one of the provided targets:
load("@rules_cc//cc:defs.bzl", "cc_binary")
cc_binary(
name = "my_benchmark",
srcs = ["my_benchmark.cc"],
deps = ["@google_benchmark//:benchmark_main"],
)
Use @google_benchmark//:benchmark when your target defines its own main
function, including through BENCHMARK_MAIN(). Use
@google_benchmark//:benchmark_main to use the default Google Benchmark entry
point.
For WORKSPACE setup and more examples, see Bazel.
Google Benchmark 是一个 C++ 库，用来为代码片段编写微基准测试，写法类似于编写单元测试。