GAMS is described as 'The General Algebraic Modeling System (GAMS) is a high-level modeling system for mathematical optimization. GAMS is designed for modeling and solving linear, nonlinear, and mixed-integer optimization problems' and is an app. There are more than 10 alternatives to GAMS for a variety of platforms, including Windows, Linux, Mac, Web-based and Chrome OS apps. The best GAMS alternative is Simulink. It's not free, so if you're looking for a free alternative, you could try Xcos or OpenModelica. Other great apps like GAMS are Minsky, BMS, Insight Maker and VisSim.