CISPO

CISPO (Clipped IS-weight Policy Optimization) is a policy-loss variant that decouples the lower/upper clip ratios to stabilize IS-ratio-weighted updates, used in MiniMax-M1.

Reference: MiniMax-M1: Scaling Test-Time Compute Efficiently with Lightning Attention.

Canonical Scripts

Script	Infer	Train	Platform
run_qwen3_8b_fsdp.sh	vLLM	FSDP	NVIDIA

Key Flags

• actor_rollout_ref.actor.policy_loss.loss_mode=cispo
• actor_rollout_ref.actor.clip_ratio_low=10 (effectively unclamped on lower side)
• actor_rollout_ref.actor.clip_ratio_high=0.2