Accessor Performance Benchmarks (C++26)

These benchmarks compare the performance of runtime vs compile-time JSON accessors. For the comparison to be meaningful, you must build simdjson with support for C++26 reflexion. See the p2996 repository in the main project directory.

Files

• accessor_benchmark.h - Common benchmark framework and test data
• runtime_accessors.h - Runtime at_path() benchmarks
• compile_time_accessors.h - Compile-time at_path_compiled() benchmarks (requires C++26 reflection)

Benchmarks

Each benchmark measures parsing + single field access:

1. accessor_simple - Simple field: .name
2. accessor_nested - Nested field: .address.city
3. accessor_deep - Deep nested field: .address.coordinates.lat

Building (Linux/macOS)

cmake -B build -D SIMDJSON_STATIC_REFLECTION=ON -DSIMDJSON_DEVELOPER_MODE=ON
cmake --build build --target=bench_ondemand

The SIMDJSON_STATIC_REFLECTION will be made unnecessary once mainstream compilers begin supporting C++26 sufficiently well.

Running (Linux/macOS)

# Run all accessor benchmarks
./build/bench_ondemand --benchmark_filter="accessor"

Results

We find that compile-time accessors show performance improvements that scale with path depth:

• Simple fields: ~1.2x faster
• Nested fields: ~1.5x faster
• Deep nested fields: ~1.8x faster

The speedup comes from eliminating runtime path parsing and conversion overhead.