[BUG] Fix Autoencoderkl train script (#11113)

* add disc_optimizer step (not fix)

* support syncbatchnorm in discriminator

examples/research_projects/autoencoderkl/train_autoencoderkl.py

@@ -627,6 +627,7 @@ def main(args):
         ema_vae = EMAModel(vae.parameters(), model_cls=AutoencoderKL, model_config=vae.config)
     perceptual_loss = lpips.LPIPS(net="vgg").eval()
     discriminator = NLayerDiscriminator(input_nc=3, n_layers=3, use_actnorm=False).apply(weights_init)
+    discriminator = torch.nn.SyncBatchNorm.convert_sync_batchnorm(discriminator)
 
     # Taken from [Sayak Paul's Diffusers PR #6511](https://github.com/huggingface/diffusers/pull/6511/files)
     def unwrap_model(model):
@@ -951,13 +952,20 @@ def main(args):
                     logits_fake = discriminator(reconstructions)
                     disc_loss = hinge_d_loss if args.disc_loss == "hinge" else vanilla_d_loss
                     disc_factor = args.disc_factor if global_step >= args.disc_start else 0.0
-                    disc_loss = disc_factor * disc_loss(logits_real, logits_fake)
+                    d_loss = disc_factor * disc_loss(logits_real, logits_fake)
                     logs = {
-                        "disc_loss": disc_loss.detach().mean().item(),
+                        "disc_loss": d_loss.detach().mean().item(),
                         "logits_real": logits_real.detach().mean().item(),
                         "logits_fake": logits_fake.detach().mean().item(),
                         "disc_lr": disc_lr_scheduler.get_last_lr()[0],
                     }
+                    accelerator.backward(d_loss)
+                    if accelerator.sync_gradients:
+                        params_to_clip = discriminator.parameters()
+                        accelerator.clip_grad_norm_(params_to_clip, args.max_grad_norm)
+                    disc_optimizer.step()
+                    disc_lr_scheduler.step()
+                    disc_optimizer.zero_grad(set_to_none=args.set_grads_to_none)
             # Checks if the accelerator has performed an optimization step behind the scenes
             if accelerator.sync_gradients:
                 progress_bar.update(1)