FeenoX vs ngspice

FeenoX is free, open-source computational engineering software for solving mathematical and engineering problems, including work across computers in parallel. It handles ODEs and DAEs, along with finite-element problems such as heat conduction, thermo-mechanical analysis, modal analysis, neutron diffusion, and neutron transport. Users describe problems in self-descriptive, English-like plain-text input files, so changes do not require recompiling. FeenoX reads Gmsh meshes and writes results in Gmsh MSH or ParaView VTK/VTU formats. It uses GNU GSL, SUNDIALS, PETSc, and SLEPc for computational tasks, and supports MPI parallelization. Installation options include Debian or Ubuntu packages, source tarballs, the GitHub repository, and generic statically linked GNU/Linux binaries. Ubuntu packages are available from version 25.04 onward. The generic binaries omit MUMPS and MPI and use basic optimization flags. FeenoX has no graphical interface, targets GNU/Linux, and is not expected to run in Windows. Browser access is available through interfaces such as SunCAE and CAEplex.

ngspice is a free, open-source simulator for electric and electronic circuits described as netlists. It handles analog, digital, and mixed-signal designs, with models for active, passive, analog, and digital elements; model parameters can come from collections, manufacturers, or foundries. Its SPICE compatibility supports PSPICE or LTSPICE device model parameters and netlists for discrete circuits. For mixed-signal co-simulation, it supports Verilog blocks compiled with Verilator and, since ngspice-44, VHDL blocks using GHDL. The OSDI/OpenVAF interface connects Verilog-A compact device models without requiring programming on the ngspice side. It can also be built as a shared library or DLL for another application to control. Listed integrations include KiCad, Autodesk Fusion, and Python interfaces such as PySpice. ngspice does not include schematic entry: input is through the command line or files. The stable download page offers source archives and Windows binaries; Linux users are directed to their distributor or source compilation, and the project's own macOS release is unavailable there.