add benchmark

.github/workflows/ci-build.yml

@@ -35,6 +35,14 @@ jobs:
               working-directory: ctprintf
               run: cmake --workflow --preset release-workflow
 
+            - name: Run performance benchmarks
+              working-directory: ctprintf
+              run: |
+                  cmake --workflow --fresh --preset benchmark-workflow
+                  ./build/benchmark/benchmarks/ctprintf_benchmarks \
+                      --benchmark_min_time=1s \
+                      --benchmark_repetitions=3
+
             - name: Build Debian package
               run: ./scripts/build-package.sh
 

README.md

@@ -145,6 +145,20 @@ cmake --build build
 ctest --test-dir build --output-on-failure
 ```
 
+## Benchmarking
+
+The optional benchmarks compare `ctprintf` with `std::snprintf` using the same
+printf-style formats and fixed-size output buffers. They require Google
+Benchmark:
+
+```bash
+cmake --workflow --preset benchmark-workflow
+./ctprintf/build/benchmark/benchmarks/ctprintf_benchmarks
+```
+
+The benchmark target is separate from CTest because execution time varies
+between machines and system load.
+
 ## Creating a package
 
 CPack creates a gzip-compressed tarball containing the installable headers,

ctprintf/CMakeLists.txt

@@ -13,6 +13,7 @@ include(GNUInstallDirs)
 include(CMakePackageConfigHelpers)
 
 option(ENABLE_TESTING "Build and enable tests" OFF)
+option(ENABLE_BENCHMARKS "Build performance benchmarks" OFF)
 
 add_library(ctprintf INTERFACE)
 
@@ -62,6 +63,10 @@ if(ENABLE_TESTING)
     add_subdirectory(tests)
 endif() # ENABLE_TESTING
 
+if(ENABLE_BENCHMARKS)
+    add_subdirectory(benchmarks)
+endif() # ENABLE_BENCHMARKS
+
 set(CPACK_GENERATOR "TGZ")
 set(CPACK_PACKAGE_CONTACT "Thomas Willetal <t.willetal@googlemail.com>")
 set(CPACK_PACKAGE_DESCRIPTION_SUMMARY "Compile-time checked printf-style formatting library")

ctprintf/CMakePresets.json

@@ -35,6 +35,15 @@
       "cacheVariables": {
         "CMAKE_CXX_CLANG_TIDY": "clang-tidy;--warnings-as-errors=*"
       }
+    },
+    {
+      "name": "benchmark",
+      "displayName": "Benchmark",
+      "inherits": "release",
+      "cacheVariables": {
+        "ENABLE_BENCHMARKS": "ON",
+        "ENABLE_TESTING": "OFF"
+      }
     }
   ],
   "buildPresets": [
@@ -49,6 +58,10 @@
     {
       "name": "clang-tidy",
       "configurePreset": "clang-tidy"
+    },
+    {
+      "name": "benchmark",
+      "configurePreset": "benchmark"
     }
   ],
   "testPresets": [
@@ -135,6 +148,20 @@
           "name": "clang-tidy"
         }
       ]
+    },
+    {
+      "name": "benchmark-workflow",
+      "displayName": "Benchmark: configure and build",
+      "steps": [
+        {
+          "type": "configure",
+          "name": "benchmark"
+        },
+        {
+          "type": "build",
+          "name": "benchmark"
+        }
+      ]
     }
   ]
 }

ctprintf/benchmarks/CMakeLists.txt

@@ -0,0 +1,5 @@
+find_package(benchmark CONFIG REQUIRED)
+
+add_executable(ctprintf_benchmarks formatting.cpp)
+
+target_link_libraries(ctprintf_benchmarks PRIVATE ctprintf::ctprintf benchmark::benchmark)

ctprintf/benchmarks/formatting.cpp

@@ -0,0 +1,86 @@
+#include <benchmark/benchmark.h>
+
+#include <ctprintf/format.hpp>
+
+#include <array>
+#include <cstddef>
+#include <cstdio>
+
+namespace {
+
+class Buffer {
+  public:
+    void clear() { size_ = 0; }
+
+    void put(char character) { characters_[size_++] = character; }
+
+  private:
+    std::array<char, 128> characters_{};
+    std::size_t size_ = 0;
+};
+
+void benchmark_ctprintf_hexadecimal(benchmark::State &state)
+{
+    constexpr unsigned int value = 0xDEADBEEFU;
+    Buffer output;
+
+    for (auto _ : state) {
+        output.clear();
+        ctprintf::format(output, "value=%08x", value);
+        benchmark::DoNotOptimize(output);
+        benchmark::ClobberMemory();
+    }
+}
+
+void benchmark_snprintf_hexadecimal(benchmark::State &state)
+{
+    constexpr unsigned int value = 0xDEADBEEFU;
+    std::array<char, 128> output{};
+
+    for (auto _ : state) {
+        int result = std::snprintf(output.data(), output.size(), "value=%08x", value);
+        benchmark::DoNotOptimize(result);
+        benchmark::DoNotOptimize(output);
+        benchmark::ClobberMemory();
+    }
+}
+
+void benchmark_ctprintf_mixed(benchmark::State &state)
+{
+    constexpr unsigned int identifier = 0x42U;
+    constexpr int status = -17;
+    constexpr const char *name = "sensor";
+    Buffer output;
+
+    for (auto _ : state) {
+        output.clear();
+        ctprintf::format(output, "id=%08x status=%+d name=%s", identifier, status, name);
+        benchmark::DoNotOptimize(output);
+        benchmark::ClobberMemory();
+    }
+}
+
+void benchmark_snprintf_mixed(benchmark::State &state)
+{
+    constexpr unsigned int identifier = 0x42U;
+    constexpr int status = -17;
+    constexpr const char *name = "sensor";
+    std::array<char, 128> output{};
+
+    for (auto _ : state) {
+        int result = std::snprintf(output.data(), output.size(), "id=%08x status=%+d name=%s",
+                                   identifier, status, name);
+        benchmark::DoNotOptimize(result);
+        benchmark::DoNotOptimize(output);
+        benchmark::ClobberMemory();
+    }
+}
+
+} // namespace
+
+BENCHMARK(benchmark_ctprintf_hexadecimal);
+BENCHMARK(benchmark_snprintf_hexadecimal);
+BENCHMARK(benchmark_ctprintf_mixed);
+BENCHMARK(benchmark_snprintf_mixed);
+
+BENCHMARK_MAIN();

scripts/build-dependencies.sh

@@ -10,6 +10,7 @@ sudo DEBIAN_FRONTEND=noninteractive apt-get install --yes --no-install-recommend
     cmake \
     debhelper \
     devscripts \
+    libbenchmark-dev \
     libgtest-dev \
     ninja-build \
     pipx