simpo-loss-implementation

name	simpo_loss_implementation
description	Implements the SimPO loss function using stable log-probability operations in the specified trainer file.

1. Open /root/SimPO/scripts/simpo_trainer.py.
2. Locate the simpo_loss method within the SimPOTrainer class.
3. Implement the formula: $L_{SimPO} = -\log(\sigma(\beta(\log \pi_\theta(y_w|x) - \log \pi_\theta(y_l|x)) - \gamma))$.
4. Ensure all tensor operations explicitly cast inputs to torch.float32 to maintain precision parity with the unit test's fixed tensors.
5. Use torch.nn.functional.logsigmoid or stable subtraction to prevent overflow during exponentiation.