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.
VASPy is a pure Python library for manipulating and analyzing VASP (Vienna Ab initio Simulation Package) input and output files. It provides object-oriented parsers for common VASP formats including POSCAR, CONTCAR, XDATCAR, OUTCAR, OSZICAR, INCAR, DOS, ELFCAR, CHGCAR, and also supports Materials Studio formats (XSD, ARC, XTD). The library exposes high-level classes like PosCar, OutCar, DosX, and InCar that encapsulate file parsing, coordinate transformations, and data extraction, enabling users to programmatically read, modify, and visualize simulation results. It also includes a set of command-line scripts for common tasks such as creating VASP inputs, extracting forces, computing zero-point energies, and converting between file formats. The architecture is modular, with separate modules for atomic coordinates, electronic structure, iterative outputs, and Material Studio interoperability, all built on a shared base class and utility functions. Visualization is a key feature, with matplotlib and PyVista backends for plotting DOS, charge densities, and trajectories. The library is designed for computational materials science researchers and DFT practitioners who need to automate post-processing and workflow tasks around VASP calculations.