[rollout] partial rollout

[HelloWorldBeginner]

What does this PR do?

We conducted tests on the partial rollout feature using the DAPO algorithm with the qwen3-0.6B and qwen2.5-7B models. The blue curve represents the scenario where the partial rollout feature is enabled, while the red curve represents it being disabled. As shown in the results, there is a significant improvement in throughput and a reduction in inference latency. Meanwhile, the trend of the rewards curve remains consistent with that of the scenario where partial rollout is disabled.

qwen2.5-7B

qwen3-0.6B

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