A2C vs A3C — the difference.

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Answer

$A3C (Asynchronous Advantage Actor-Critic, Mnih 2016): multiple async workers each with own env, updating shared params — lock-free async gradient updates.$
$A2C (synchronous): workers step in parallel, batch gradients synchronously, single update per batch — better GPU utilization, more reproducible.$
$A2C is simpler and empirically as good; A3C was pre-GPU thinking.$
$Modern default: A2C or PPO on batched vectorized envs.$

Check yourself — multiple choice

Same thing
A3C: async workers + lock-free updates; A2C: sync workers + batched update (better GPU); modern default = A2C / PPO on vectorized envs
Random
Not real

A3C async / A2C sync; A2C simpler + GPU-friendly; PPO usually preferred.

#policy-methods#actor-critic

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