Create benchmark for [[likely]] performance by konard · Pull Request #122 · linksplatform/Numbers

konard · 2025-10-30T04:07:41Z

Summary

This PR implements comprehensive benchmarks to evaluate the performance impact of [[likely]]/[[unlikely]] branch prediction attributes across C#, C++, and Rust implementations of the Factorial function.

Fixes #96

Background

Issue #96 requested benchmarks comparing performance with and without C++ [[likely]]/[[unlikely]] attributes. This PR provides equivalent benchmarks across all three language implementations in the repository.

Implementation Details

C# Benchmarks (`csharp/Platform.Numbers.Benchmarks/MathBenchmarks.cs`)

Uses BenchmarkDotNet with 15 benchmark variants testing:

AggressiveInlining, AggressiveOptimization, and combined
[DoesNotReturn] + [NoInlining] for cold path separation
Inline exception vs separated throw helper
Unlikely-first anti-pattern comparison
Generic IUnsignedNumber<T> optimized version
Various array access and recursion patterns

C++ Benchmarks (`cpp/Platform.Numbers.Benchmarks/MathBenchmarks.cpp`)

Uses Google Benchmark (fetched via CMake FetchContent) with 9 benchmark variants testing:

Baseline: No attributes (standard if/else with inline throw)
[[likely]]/[[unlikely]]: C++20 standard attributes
[[likely]] + separate throw: Cold path in [[noreturn]] __attribute__((noinline)) function
[[likely]] + force inline: __attribute__((always_inline)) on hot path
__builtin_expect: GCC/Clang intrinsic (pre-C++20 approach)
Unlikely-first: Anti-pattern with exception check before happy path
Without attributes: Separate throw but no branch hints
Direct array access: No bounds checking (baseline reference)
Generic template: Template version with [[likely]]

Rust Benchmarks (`rust/benches/math_benchmarks.rs`)

Uses Criterion with 5 benchmark variants testing:

Baseline: Standard if/else with inline panic
Cold-path optimization: Panic in #[cold] #[inline(never)] function
Unlikely-first: Anti-pattern comparison
Force inline: #[inline(always)] with cold-path separation
Direct array access: No bounds checking (baseline reference)

Also adds a new math module with Factorial implementation and unit tests.

Running the Benchmarks

# C#
cd csharp/Platform.Numbers.Benchmarks
dotnet run -c Release

# C++
cd cpp
mkdir build && cd build
cmake .. -DLINKS_PLATFORM_BENCHMARKS=ON -DCMAKE_BUILD_TYPE=Release
cmake --build .
./bin/Platform.Numbers.Benchmarks

# Rust
cd rust
cargo bench

Changes Made

C++ (cpp/): Added MathBenchmarks.cpp with 9 factorial benchmark variants; updated CMakeLists.txt with benchmark build support via FetchContent
Rust (rust/): Added math.rs with factorial implementation and tests; added benches/math_benchmarks.rs with 5 Criterion benchmarks; updated Cargo.toml with criterion dependency; added rust-toolchain.toml for nightly requirement
C# (csharp/): Existing benchmarks with 15 variants (unchanged in this update)
C++ Math.h: Restored correct version from main branch

Verification

All C# tests pass (7/7)
All Rust tests pass (4/4)
C++ benchmarks compile and run successfully
Rust benchmarks compile and run successfully
C# benchmarks compile successfully

Generated with Claude Code

Adding CLAUDE.md with task information for AI processing. This file will be removed when the task is complete. Issue: undefined

Implements comprehensive benchmarks comparing different optimization strategies in C# that simulate C++ [[likely]]/[[unlikely]] branch prediction hints: - AggressiveInlining: Forces method inlining for hot paths - AggressiveOptimization: Enables aggressive optimizations - DoesNotReturn attribute: Helps optimizer understand exception paths - Code organization: Hot path first vs exception path first - Generic version: Tests modern .NET generic math optimizations These benchmarks help evaluate performance impact of different approaches to branch prediction optimization in C#, addressing issue #96. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>

This reverts commit 46de952.

konard · 2025-10-30T04:13:11Z

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konard · 2026-04-14T13:02:48Z

We also should add similar benchmarks for C++ version and also for Rust version.

We need to ensure all changes are correct, consistent, validated, tested, logged and fully meet each and all discussed requirements (check issue description and all comments in issue and in pull request). Ensure all CI/CD checks pass.

konard · 2026-04-14T13:04:14Z

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- C++ benchmarks using Google Benchmark with variants: baseline, [[likely]]/[[unlikely]], __builtin_expect, force_inline, separate throw, unlikely-first pattern, direct array access, and generic - Rust benchmarks using Criterion with variants: baseline, cold-path optimization, unlikely-first, force-inline, and direct array access - Rust factorial implementation with tests - Updated CMakeLists.txt with FetchContent for Google Benchmark - Restored correct C++ Math.h from main branch Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

# Conflicts: # rust/Cargo.lock # rust/Cargo.toml # rust/rust-toolchain.toml

- Apply cargo fmt to math.rs and math_benchmarks.rs - Add changelog fragment for [[likely]] benchmark additions Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

konard · 2026-04-14T13:24:07Z

Work Session Update

Added C++ and Rust benchmarks as requested:

C++ (`cpp/Platform.Numbers.Benchmarks/MathBenchmarks.cpp`)

9 benchmark variants using Google Benchmark (fetched via CMake FetchContent):

Baseline (no attributes)
[[likely]]/[[unlikely]] (C++20 standard attributes)
[[likely]] + separate [[noreturn]] throw
[[likely]] + __attribute__((always_inline))
__builtin_expect (GCC/Clang intrinsic)
Unlikely-first anti-pattern
No attributes with separate throw
Direct array access (no bounds check)
Generic template with [[likely]]

Rust (`rust/benches/math_benchmarks.rs`)

5 benchmark variants using Criterion:

Baseline (inline panic)
Cold-path optimization (#[cold] #[inline(never)])
Unlikely-first anti-pattern
Force inline (#[inline(always)]) with cold-path
Direct array access (no bounds check)

Also added Rust math module with Factorial implementation and 4 unit tests.

Verification

All CI checks passing (Rust CI/CD Pipeline: lint, format, tests on ubuntu/windows/macos, build package, changelog fragment)
C# tests pass (7/7)
Rust tests pass (4/4 unit + 7 doc tests)
C++ benchmarks compile and run successfully
Main branch merged into PR branch (no conflicts)

How to run benchmarks

# C++
cd cpp && mkdir build && cd build
cmake .. -DLINKS_PLATFORM_BENCHMARKS=ON -DCMAKE_BUILD_TYPE=Release
cmake --build . && ./bin/Platform.Numbers.Benchmarks

# Rust
cd rust && cargo bench

# C#
cd csharp/Platform.Numbers.Benchmarks && dotnet run -c Release

Generated with Claude Code

konard · 2026-04-14T13:24:37Z

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konard · 2026-04-14T13:26:46Z

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Add cppcheck-suppress comments for system/third-party includes that Cppcheck cannot resolve in isolation. Also exclude cpp/build/ from Codacy analysis as it contains fetched dependencies. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Cppcheck cannot resolve system/third-party includes without the full build environment. Exclude benchmark and build directories from static analysis as they are not library source code. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

konard · 2026-04-14T13:34:43Z

🔄 Auto-restart-until-mergeable Log (iteration 1)

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💰 Cost: $3.596662

📊 Context and tokens usage:

Claude Opus 4.6:

Context window: 78.2K / 1M (8%) input tokens, 13.5K / 128K (11%) output tokens

Total: (67.0K + 5.6M cached) input tokens, 13.5K output tokens, $3.555909 cost

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Total: (21.5K + 82.0K cached) input tokens, 1.2K / 64K (2%) output tokens, $0.040753 cost

🤖 Models used:

Tool: Anthropic Claude Code
Requested: opus
Main model: Claude Opus 4.6 (claude-opus-4-6)
Additional models:
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konard · 2026-04-14T13:36:49Z

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konard · 2026-04-14T13:37:45Z

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Total: (18.4K + 149.8K cached) input tokens, 1.4K output tokens, $0.225967 cost

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konard · 2026-04-14T13:40:14Z

✅ Ready to merge

This pull request is now ready to be merged:

All CI checks have passed
No merge conflicts
No pending changes

Monitored by hive-mind with --auto-restart-until-mergeable flag

Initial commit with task details for issue #96

46de952

Adding CLAUDE.md with task information for AI processing. This file will be removed when the task is complete. Issue: undefined

konard self-assigned this Oct 30, 2025

konard changed the title ~~[WIP] Create benchmark for [[likely]] performance~~ Create benchmark for [[likely]] performance Oct 30, 2025

konard marked this pull request as ready for review October 30, 2025 04:12

Revert "Initial commit with task details for issue #96"

437711e

This reverts commit 46de952.

konard marked this pull request as draft April 14, 2026 13:04

konard and others added 3 commits April 14, 2026 13:13

Merge remote-tracking branch 'origin/main' into issue-96-b6a6427e

086d35d

# Conflicts: # rust/Cargo.lock # rust/Cargo.toml # rust/rust-toolchain.toml

Fix Rust formatting and add changelog fragment

deaba77

- Apply cargo fmt to math.rs and math_benchmarks.rs - Add changelog fragment for [[likely]] benchmark additions Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

konard marked this pull request as ready for review April 14, 2026 13:24

konard and others added 2 commits April 14, 2026 13:29

konard merged commit 2c290a1 into main Apr 14, 2026
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Create benchmark for [[likely]] performance#122

Create benchmark for [[likely]] performance#122
konard merged 8 commits intomainfrom
issue-96-b6a6427e

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Summary

Background

Implementation Details

C# Benchmarks (csharp/Platform.Numbers.Benchmarks/MathBenchmarks.cs)

C++ Benchmarks (cpp/Platform.Numbers.Benchmarks/MathBenchmarks.cpp)

Rust Benchmarks (rust/benches/math_benchmarks.rs)

Running the Benchmarks

Changes Made

Verification

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konard commented Oct 30, 2025

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Work Session Update

C++ (cpp/Platform.Numbers.Benchmarks/MathBenchmarks.cpp)

Rust (rust/benches/math_benchmarks.rs)

Verification

How to run benchmarks

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konard commented Apr 14, 2026

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konard commented Apr 14, 2026

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konard commented Apr 14, 2026

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C# Benchmarks (`csharp/Platform.Numbers.Benchmarks/MathBenchmarks.cs`)

C++ Benchmarks (`cpp/Platform.Numbers.Benchmarks/MathBenchmarks.cpp`)

Rust Benchmarks (`rust/benches/math_benchmarks.rs`)

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C++ (`cpp/Platform.Numbers.Benchmarks/MathBenchmarks.cpp`)

Rust (`rust/benches/math_benchmarks.rs`)