MPTRAC vs ngspice

MPTRAC is a Lagrangian particle dispersion model for studying atmospheric transport in the free troposphere and stratosphere. It calculates forward and backward air-parcel trajectories from meteorological wind fields, with stochastic diffusion, subgrid wind variation and mixing between parcels. Optional process parameterizations cover convection, sedimentation, decay, gas-phase and aqueous-phase chemistry, and wet and dry deposition. Listed research applications include long-range pollutant transport, volcanic ash dispersion, tracer experiments and atmospheric chemistry.

The browser-based Web Runner can configure, run and visualize simulations, then download results without local installation. It is limited to 10,000 air parcels, 30 days and 10 minutes of model runtime. The model needs meteorological input, normally netCDF files on a regular pressure, longitude and latitude grid. MPTRAC supports hybrid MPI, OpenMP and OpenACC parallelization, and offers visualization interfaces for Gnuplot and ParaView. It is GPL-3.0 software for Linux, self-hosted and web use; listed pricing includes free.

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.