Liger GRPO meets TRL
Report on debugging Liger GRPO loss with DeepSpeed ZeRO-3 using Qwen/Qwen2.5-0.5B-Instruct in bf16, highlighting a shape mismatch during training. The traceback traces through grpo_loss and fused_linear_ppo, pointing to a forward pass issue in the Liger kernel. No fix is shown, but it identifies the code paths to inspect (grpo_loss, fused_linear_ppo).