GEM is a Gym-like framework for training and evaluating agentic LLMs via reinforcement learning. It provides a diverse set of environments (games, math, code, QA, etc.) that can be used to train LLMs to interact with tools, solve problems, and make sequential decisions. The framework features a modular design with composable wrappers for observation modification, tool integration, and episode tracking, along with vectorized environments for parallel execution. It supports integration with multiple RL training frameworks (Oat, Verl, Tinker, OpenRLHF, RL2) through example scripts, making it a versatile tool for LLM agent research.
OpenAI Gym is a foundational Python library providing a standard API for Reinforcement Learning (RL) environments. It defines the core `Env` interface (`reset`, `step`, `render`) and includes a registry of environments spanning classic control (CartPole), physics simulations (MuJoCo, Box2D), and grid worlds. The architecture relies heavily on a composition-based wrapper pattern (`gym.wrappers`) to modify environment behavior without altering core logic, and includes a vectorization module (`gym.vector`) for parallel execution using shared memory. While the codebase demonstrates strong architectural craftsmanship in its abstraction layers and space definitions, it is in a maintenance phase with development migrated to Gymnasium. It relies on external compiled libraries (MuJoCo, Box2D, Pygame) which introduce platform-specific complexity and dependency drift.