Add targeted flow guidance training for flow based models

toolkit/guidance.py

@@ -603,6 +603,94 @@ def get_guided_tnt(
 
     return loss
 
+def targeted_flow_guidance(
+    noisy_latents: torch.Tensor,
+    conditional_embeds: 'PromptEmbeds',
+    match_adapter_assist: bool,
+    network_weight_list: list,
+    timesteps: torch.Tensor,
+    pred_kwargs: dict,
+    batch: 'DataLoaderBatchDTO',
+    noise: torch.Tensor,
+    sd: 'StableDiffusion',
+    unconditional_embeds: Optional[PromptEmbeds] = None,
+    mask_multiplier=None,
+    prior_pred=None,
+    scaler=None,
+    train_config=None,
+    **kwargs
+):
+    if not sd.is_flow_matching:
+        raise ValueError("targeted_flow only works on flow matching models")
+    dtype = get_torch_dtype(sd.torch_dtype)
+    device = sd.device_torch
+    with torch.no_grad():
+        dtype = get_torch_dtype(dtype)
+        noise = noise.to(device, dtype=dtype).detach()
+
+        conditional_latents = batch.latents.to(device, dtype=dtype).detach()
+        unconditional_latents = batch.unconditional_latents.to(device, dtype=dtype).detach()
+        
+        # get noisy latents for both conditional and unconditional predictions
+        unconditional_noisy_latents = sd.add_noise(
+            unconditional_latents,
+            noise,
+            timesteps
+        ).detach()
+        conditional_noisy_latents = sd.add_noise(
+            conditional_latents,
+            noise,
+            timesteps
+        ).detach()
+        
+        # disable the lora to get a baseline prediction
+        sd.network.is_active = False
+        sd.unet.eval()
+        
+        # get a baseline prediction of the model knowledge without the lora network
+        # we do this with the unconditional noisy latents
+        baseline_prediction = sd.predict_noise(
+            latents=unconditional_noisy_latents.to(device, dtype=dtype).detach(),
+            conditional_embeddings=conditional_embeds.to(device, dtype=dtype).detach(),
+            timestep=timesteps,
+            guidance_scale=1.0,
+            **pred_kwargs
+        ).detach()
+        
+        # This is our normal flowmatching target
+        # target = noise - latents
+        # we need to target the baseline noise but with our conditional latents
+        # to do this we first have to determine the baseline_prediction noise by reversing the flowmatching target
+        baseline_predicted_noise = baseline_prediction + unconditional_latents
+        
+        # baseline_predicted_noise is now the noise prediction our model would make with a the unconditional image.
+        # we use this as our new noise target to preserve the existing knowledge of the image
+        target_noise = baseline_predicted_noise
+        
+        # compute our new target prediction using our current knowledge noise with our conditional latents
+        # this makes it so the only new information is the differential of our conditional and unconditional latents
+        # forcing the network to preserve existing knowledge, but learn only our changes
+        target_pred = (target_noise - conditional_latents).detach()
+        
+    # make a prediction with the lora network active
+    sd.unet.train()
+    sd.network.is_active = True
+    sd.network.multiplier = network_weight_list
+    prediction = sd.predict_noise(
+        latents=conditional_noisy_latents.to(device, dtype=dtype).detach(),
+        conditional_embeddings=conditional_embeds.to(device, dtype=dtype).detach(),
+        timestep=timesteps,
+        guidance_scale=1.0,
+        **pred_kwargs
+    )
+    
+    # target our baseline + diffirential noise target
+    pred_loss = torch.nn.functional.mse_loss(
+        prediction.float(),
+        target_pred.float()
+    )
+    
+    return pred_loss
 
 
 # this processes all guidance losses based on the batch information
@@ -702,5 +790,23 @@ def get_guidance_loss(
             prior_pred=prior_pred,
             **kwargs
         )
+    elif guidance_type == "targeted_flow":
+        return targeted_flow_guidance(
+            noisy_latents,
+            conditional_embeds,
+            match_adapter_assist,
+            network_weight_list,
+            timesteps,
+            pred_kwargs,
+            batch,
+            noise,
+            sd,
+            unconditional_embeds=unconditional_embeds,
+            mask_multiplier=mask_multiplier,
+            prior_pred=prior_pred,
+            scaler=scaler,
+            train_config=train_config,
+            **kwargs
+        )
     else:
         raise NotImplementedError(f"Guidance type {guidance_type} is not implemented")