Crossbeam is a Rust library workspace providing a comprehensive set of concurrent programming primitives. It includes multi-producer multi-consumer (MPMC) channels with a select! macro for multiplexing, work-stealing deques (Chase-Lev), lock-free queues (bounded ArrayQueue and unbounded SegQueue), epoch-based memory reclamation for safe lock-free memory management, lock-free skip lists (SkipMap/SkipSet), and utilities like cache-padded values, exponential backoff, thread parking, sharded locks, and scoped threads. The library is designed for building high-performance concurrent systems and supports no_std environments. The architecture is modular: each major component lives in its own crate (crossbeam-channel, crossbeam-deque, crossbeam-epoch, crossbeam-queue, crossbeam-skiplist, crossbeam-utils) with a root umbrella crate that re-exports them. The implementations are based on academic literature (Chase-Lev, Michael-Scott, Vyukov queues) and include extensive testing with Miri, Loom model checking, and sanitizers. The codebase demonstrates advanced Rust patterns: unsafe but carefully encapsulated atomic operations, macro_rules-based DSLs, and trait-based abstraction for selectable channels. While primarily a library, the repository also contains benchmarks and examples that serve as both documentation and performance validation. The project is actively maintained with a clear MSRV policy and regular releases. Some components, like the epoch GC and work-stealing deque, are self-contained patterns that could be extracted for use in other concurrent Rust projects.
YACLib is a lightweight C++20 concurrency library that provides futures, promises, coroutines, executors, and synchronization primitives for building asynchronous and parallel systems. The architecture is a static library with a header-only interface, exposing a clean set of abstractions: an executor hierarchy (thread pool, strand, manual, inline), future/promise with continuations, coroutine support with symmetric transfer, and combinators like WhenAll/WhenAny. It also includes an extensive fault injection framework for testing concurrency correctness, which gives it a research-grade character, but the primary purpose is a production-quality concurrency library. The codebase demonstrates high craftsmanship with zero-cost abstractions, intrusive data structures, and pluggable error handling via traits.
Spice is a Zig library for low-overhead parallelism using heartbeat scheduling. It provides a fork/join model where workers maintain local work queues and a heartbeat thread periodically signals workers to offload work to others. The design avoids common work-stealing pitfalls: dynamic dispatch is minimized by using static calls for local work, queues are truly local (no atomics for push/pop in common case), and spinning is eliminated by using blocking waits. The library is demonstrated with a binary tree sum benchmark showing sub-nanosecond overhead. While primarily a research project with noted limitations (lack of tests, no array support), the implementation exhibits high craftsmanship in its concurrency primitives and performance optimizations.
Fetch is a Scala library for simple and efficient data access, built on cats-effect. It provides a monadic abstraction (`Fetch[F, A]`) that automatically optimizes data fetching through batching, caching, deduplication, and parallel execution. Users define data sources by implementing the `DataSource` trait, specifying how to fetch individual identities or batches. The library then composes fetches using standard monadic and applicative combinators, transparently batching requests to the same source and running independent fetches concurrently. It supports custom caches, optional fetches, error handling, and debugging via a separate `fetch-debug` module. The architecture is a pure library with no runtime dependencies beyond cats-effect, making it suitable for both JVM and Scala.js. Key entry points include `Fetch.apply`, `Fetch.run`, `Fetch.runLog`, and `Fetch.runCache`. External dependencies are minimal: cats-effect, cats-core, and scalatest for testing.
This repository implements Composite, a component-based research operating system where kernel policies (scheduling, memory management, synchronization) are implemented as user-level components. It runs on x86-32, x86-64, and ARMv7a architectures, primarily under QEMU. The system provides a minimal kernel with capability-based security, synchronous invocation (sinv) for inter-component communication, and shared-memory channels. It includes a full musl libc port for POSIX compatibility, a DPDK-based network stack, an lwIP adapter for TCP/IP, and a simple VMM with virtio-net and device emulation. The architecture is closer to a microkernel than a traditional monolithic kernel, with components loaded and composed via a Rust-based composer tool that reads TOML specifications. A large suite of microbenchmarks measures IPC, scheduling, and synchronization latency. The codebase is pre-alpha quality, with many FIXMEs and incomplete features, but demonstrates strong craftsmanship in its abstraction layers (assembly stubs, channel library, scheduler framework, perfdata utility).