  The Mean-Field approximation is a tractable approach for studying large
population dynamics. However, its assumption on homogeneity and universal
connections among all agents limits its applicability in many real-world
scenarios. Multi-Population Mean-Field Game (MP-MFG) models have been
introduced in the literature to address these limitations. When the underlying
Stochastic Block Model is known, we show that a Policy Mirror Ascent algorithm
finds the MP-MFG Nash Equilibrium. In more realistic scenarios where the block
model is unknown, we propose a re-sampling scheme from a graphon integrated
with the finite N-player MP-MFG model. We develop a novel learning framework
based on a Graphon Game with Re-Sampling (GGR-S) model, which captures the
complex network structures of agents' connections. We analyze GGR-S dynamics
and establish the convergence to dynamics of MP-MFG. Leveraging this result, we
propose an efficient sample-based N-player Reinforcement Learning algorithm for
GGR-S without population manipulation, and provide a rigorous convergence
analysis with finite sample guarantee.
