Next generation FEniCS problem solving environment for solving finite element problems
an extensive Qt5 & Qt6 Plotter framework (including a feature-richt plotter widget, a speed-optimized, but limited variant and a LaTeX equation renderer!), written fully in C/C++ and without external dependencies
Céline (Circuit Emulation Layer for Integrated Nonlinear Equation Solving) is an audio plugin for building and emulating circuits in real time. This tool is aimed at musicians who want to emulate analog hardware, and keeps the experimentation safe and portable.
The Stan Math Library is a C++ template library for automatic differentiation of any order using forward, reverse, and mixed modes. It includes a range of built-in functions for probabilistic modeling, linear algebra, and equation solving.
Fast C++ and Python library for state-vector simulation of quantum circuits.
FreeFEM source code
Netgen/NGSolve is a high performance multiphysics finite element software. It is widely used to analyze models from solid mechanics, fluid dynamics and electromagnetics. Due to its flexible Python interface new physical equations and solution algorithms can be implemented easily.