[DDIMScheduler] fix noise device in ddim step (#1189)

* fix noise device in ddim sched

* fix typo

* self.device -> device

* remove duplicated if

* use str device

* don't use str for device

Author: patil-suraj

src/diffusers/schedulers/scheduling_ddim.py

@@ -288,17 +288,22 @@ def step(
 
         if eta > 0:
             # randn_like does not support generator https://github.com/pytorch/pytorch/issues/27072
-            device = model_output.device if torch.is_tensor(model_output) else "cpu"
+            device = model_output.device if torch.is_tensor(model_output) else torch.device("cpu")
             if variance_noise is not None and generator is not None:
                 raise ValueError(
                     "Cannot pass both generator and variance_noise. Please make sure that either `generator` or"
                     " `variance_noise` stays `None`."
                 )
 
             if variance_noise is None:
-                variance_noise = torch.randn(model_output.shape, dtype=model_output.dtype, generator=generator).to(
-                    device
-                )
+                if device.type == "mps":
+                    # randn does not work reproducibly on mps
+                    variance_noise = torch.randn(model_output.shape, dtype=model_output.dtype, generator=generator)
+                    variance_noise = variance_noise.to(device)
+                else:
+                    variance_noise = torch.randn(
+                        model_output.shape, generator=generator, device=device, dtype=model_output.dtype
+                    )
             variance = self._get_variance(timestep, prev_timestep) ** (0.5) * eta * variance_noise
 
             prev_sample = prev_sample + variance