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https://github.com/nlohmann/json.git
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Niels Lohmann
ec4bdc398a
* Document the benchmarks, and make them build and compare versions again The benchmark project hasn't configured since #4793: download_test_data.cmake compiles cmake/detect_libcpp_version.cpp relative to CMAKE_SOURCE_DIR, which is tests/benchmarks when that is the top-level project, so try_run fails and so does `make run_benchmarks`. The path is now relative to the module itself, which is the same file for the main build. The Dump benchmark discarded dump()'s result, which is [[nodiscard]] by now; it warned, and left the optimizer free to shorten the loop. The result is now kept with benchmark::DoNotOptimize. A new cache variable, JSON_BENCHMARK_INCLUDE_DIR, names the directory holding the nlohmann/json.hpp to benchmark (single_include by default, as before), so the same benchmarks can be built against two versions and compared. tests/benchmarks/README.md documents what is measured, how to build and run the benchmarks, how to read the output, and how to compare two versions with Google Benchmark's compare.py; it recommends doing so by hand before a release rather than in CI. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Point ci_benchmarks at tests/benchmarks The target has configured ${PROJECT_SOURCE_DIR}/benchmarks since it was added in #2561, but the benchmarks live in tests/benchmarks. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Pin Google Benchmark to release 1.9.5 The benchmarks fetched Google Benchmark's main branch, so two builds on different days could measure with different library code, and CMake 3.30 and later warn that the single-argument FetchContent_Populate() is deprecated. Fetch the 1.9.5 release archive, verified by its SHA-256, with FetchContent_MakeAvailable() instead. That needs CMake 3.14; Google Benchmark itself already needed 3.13. Its -Werror is switched off, so a newer compiler's new warnings cannot break the pinned release, and its install rules are no longer added. Signed-off-by: Niels Lohmann <mail@nlohmann.me> --------- Signed-off-by: Niels Lohmann <mail@nlohmann.me>
41 lines
1.7 KiB
CMake
41 lines
1.7 KiB
CMake
cmake_minimum_required(VERSION 3.14)
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project(JSON_Benchmarks LANGUAGES CXX)
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# set compiler flags
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if((CMAKE_CXX_COMPILER_ID MATCHES GNU) OR (CMAKE_CXX_COMPILER_ID MATCHES Clang))
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set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -flto -DNDEBUG -O3")
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endif()
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# configure Google Benchmark; a fixed release, so that results stay comparable
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set(JSON_GOOGLE_BENCHMARK_VERSION 1.9.5)
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include(FetchContent)
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# only the library is needed; -Werror would break the pinned release as soon as
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# a newer compiler adds a warning
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set(BENCHMARK_ENABLE_TESTING OFF CACHE BOOL "" FORCE)
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set(BENCHMARK_ENABLE_INSTALL OFF CACHE BOOL "" FORCE)
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set(BENCHMARK_ENABLE_WERROR OFF CACHE BOOL "" FORCE)
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FetchContent_Declare(benchmark
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URL https://github.com/google/benchmark/archive/refs/tags/v${JSON_GOOGLE_BENCHMARK_VERSION}.tar.gz
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URL_HASH SHA256=9631341c82bac4a288bef951f8b26b41f69021794184ece969f8473977eaa340
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DOWNLOAD_EXTRACT_TIMESTAMP TRUE
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)
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FetchContent_MakeAvailable(benchmark)
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# download test data
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set(CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/../../cmake ${CMAKE_MODULE_PATH})
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include(download_test_data)
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# the header to benchmark; point this at a directory holding another version's
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# nlohmann/json.hpp to compare versions (see README.md)
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set(JSON_BENCHMARK_INCLUDE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../../single_include" CACHE PATH
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"directory containing the nlohmann/json.hpp to benchmark")
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# benchmark binary
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add_executable(json_benchmarks src/benchmarks.cpp)
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target_compile_features(json_benchmarks PRIVATE cxx_std_11)
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target_link_libraries(json_benchmarks benchmark ${CMAKE_THREAD_LIBS_INIT})
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add_dependencies(json_benchmarks download_test_data)
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target_include_directories(json_benchmarks PRIVATE ${JSON_BENCHMARK_INCLUDE_DIR} ${CMAKE_BINARY_DIR}/include)
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