import torch def inverse_classifier_guidance( noise_pred_cond: torch.Tensor, noise_pred_uncond: torch.Tensor, guidance_scale: torch.Tensor ): """ Adjust the noise_pred_cond for the classifier free guidance algorithm to ensure that the final noise prediction equals the original noise_pred_cond. """ # To make noise_pred equal noise_pred_cond_orig, we adjust noise_pred_cond # based on the formula used in the algorithm. # We derive the formula to find the correct adjustment for noise_pred_cond: # noise_pred_cond = (noise_pred_cond_orig - noise_pred_uncond * guidance_scale) / (guidance_scale - 1) # It's important to check if guidance_scale is not 1 to avoid division by zero. if guidance_scale == 1: # If guidance_scale is 1, adjusting is not needed or possible in the same way, # since it would lead to division by zero. This also means the algorithm inherently # doesn't alter the noise_pred_cond in relation to noise_pred_uncond. # Thus, we return the original values, though this situation might need special handling. return noise_pred_cond adjusted_noise_pred_cond = (noise_pred_cond - noise_pred_uncond) / guidance_scale return adjusted_noise_pred_cond