The KFR library is a high-performance C++ framework for digital signal processing (DSP) and audio applications. It provides optimized implementations of FFT/DFT, filter design (FIR/IIR), sample rate conversion, audio file I/O (supporting WAV, FLAC, MP3, AIFF, CAF, etc.), SIMD-accelerated mathematical operations, and tensor/multi-dimensional array operations. The library is designed for real-time processing and scientific computing, with architecture-specific optimizations for x86 SIMD, ARM NEON, and RISC-V RVV, and runtime dispatch for multiarchitecture support. Key architectural features include a header-only design (with optional separate compilation), expression templates for lazy evaluation and operator fusion, a portable SIMD abstraction layer, and a tensor system with NumPy interoperability. The library is used in production by scientific collaborations such as LIGO, Virgo, and KAGRA for gravitational-wave signal processing, benchmarked against FFTW. It employs a dual licensing model (GPLv2+/commercial) and requires C++20 for compilation. The codebase demonstrates strong engineering practices through reusable components such as the SIMD vector abstraction (vec<T, N>), expression template system, tensor class, and audio data handling unit. These components are self-contained, exhibit non-obvious skill in C++ template metaprogramming, and can be extracted for use in other projects with minimal modification. The library is actively maintained, with recent commits and CI/CD pipelines, and shows low technical drift by keeping pace with modern C++ standards and hardware advancements.
C++ Insights is a source-to-source transformation tool built on LLVM/Clang that reveals compiler-generated code by making implicit C++ mechanisms explicit. It processes C++ source through Clang's AST, applies transformations to show template expansions, lambda desugaring, coroutine state machines, lifetime tracking, and other low-level details, outputting valid C++ that illustrates what the compiler does internally. The architecture centers on AST traversal via custom visitors and code generators, with modular components for different transformation modes (standard, Cfront-style, coroutine-specific). Key entry points include Insights.cpp (main driver) and specialized generators like CoroutinesCodeGenerator.cpp. The tool serves an educational purpose, helping developers understand C++ language semantics through visualizing compiler transformations.
Heimer is a cross-platform desktop mind map editor built with Qt (C++17). It provides a graphical interface for creating, editing, and organizing mind maps with features like adjustable grid, automatic layout optimization, undo/redo, copy/paste, image embedding, and export to PNG/SVG. The architecture follows a layered design: domain layer (Graph, MindMapData, LayoutOptimizer), application layer (services, state machine, settings proxy), view layer (Qt widgets, QGraphicsScene/View, dialogs), and infrastructure layer (file I/O, XML serialization). Key entry points include main.cpp, Application class, MainWindow, EditorView, and EditorService. Data flows from user interactions through EditorView to EditorService, which manipulates the MindMapData (graph) and triggers serialization via AlzFileIO. External dependencies are limited to Qt (5 or 6) and two bundled small libraries (SimpleLogger for logging, Argengine for CLI argument parsing). The layout optimizer uses simulated annealing to arrange nodes, and undo/redo is implemented via snapshot-based state capture. The codebase demonstrates solid engineering practices with unit tests, CI/CD pipelines, and multi-language support.