emax
To facilitate the following derivation, we rewrite the objective J E+I(E+I) JE(E): 438 J E+I(E+I) JE(E) = E E+ I h 1X
A.1 Full derivation425 We present the complete derivation of the objective function in each subproblem defined in Section426 3.2. For brevity, let rt =(1+)rEt +rIt and V EE (st)= Vt. Under this assumption, E serves as 0 (see above). This451 enables updating E+I using the local approximation. We leave relaxing this assumption as future452 work.453
Asymptotic and Finite-Time Guarantees for Langevin-Based Temperature Annealing in InfoNCE
The InfoNCE loss in contrastive learning depends critically on a temperature parameter, yet its dynamics under fixed versus annealed schedules remain poorly understood. We provide a theoretical analysis by modeling embedding evolution under Langevin dynamics on a compact Riemannian manifold. Under mild smoothness and energy-barrier assumptions, we show that classical simulated annealing guarantees extend to this setting: slow logarithmic inverse-temperature schedules ensure convergence in probability to a set of globally optimal representations, while faster schedules risk becoming trapped in suboptimal minima. Our results establish a link between contrastive learning and simulated annealing, providing a principled basis for understanding and tuning temperature schedules.
Ensemble Value Functions for Efficient Exploration in Multi-Agent Reinforcement Learning
Schäfer, Lukas, Slumbers, Oliver, McAleer, Stephen, Du, Yali, Albrecht, Stefano V., Mguni, David
Cooperative multi-agent reinforcement learning (MARL) requires agents to explore to learn to cooperate. Existing value-based MARL algorithms commonly rely on random exploration, such as $\epsilon$-greedy, which is inefficient in discovering multi-agent cooperation. Additionally, the environment in MARL appears non-stationary to any individual agent due to the simultaneous training of other agents, leading to highly variant and thus unstable optimisation signals. In this work, we propose ensemble value functions for multi-agent exploration (EMAX), a general framework to extend any value-based MARL algorithm. EMAX trains ensembles of value functions for each agent to address the key challenges of exploration and non-stationarity: (1) The uncertainty of value estimates across the ensemble is used in a UCB policy to guide the exploration of agents to parts of the environment which require cooperation. (2) Average value estimates across the ensemble serve as target values. These targets exhibit lower variance compared to commonly applied target networks and we show that they lead to more stable gradients during the optimisation. We instantiate three value-based MARL algorithms with EMAX, independent DQN, VDN and QMIX, and evaluate them in 21 tasks across four environments. Using ensembles of five value functions, EMAX improves sample efficiency and final evaluation returns of these algorithms by 53%, 36%, and 498%, respectively, averaged all 21 tasks.