Support both old and new diffusers import path (#843)

* Update modeling_sd_base.py

* Update trl/models/modeling_sd_base.py

Co-authored-by: Younes Belkada <49240599+younesbelkada@users.noreply.github.com>

* make precommit

* cleaner approach

* oops

* better alternative

* rm uneeded file

---------

Co-authored-by: Younes Belkada <49240599+younesbelkada@users.noreply.github.com>
Co-authored-by: younesbelkada <younesbelkada@gmail.com>

trl/core.py

@@ -11,10 +11,11 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-
 import gc
 import random
+import warnings
 from contextlib import contextmanager
+from typing import List, Optional, Tuple, Union
 
 import numpy as np
 import torch
@@ -266,3 +267,51 @@ def empty_cuda_cache(cls):
             gc.collect()
             torch.cuda.empty_cache()
             gc.collect()
+
+
+def randn_tensor(
+    shape: Union[Tuple, List],
+    generator: Optional[Union[List["torch.Generator"], "torch.Generator"]] = None,
+    device: Optional["torch.device"] = None,
+    dtype: Optional["torch.dtype"] = None,
+    layout: Optional["torch.layout"] = None,
+):
+    """A helper function to create random tensors on the desired `device` with the desired `dtype`. When
+    passing a list of generators, you can seed each batch size individually. If CPU generators are passed, the tensor
+    is always created on the CPU.
+    """
+    # device on which tensor is created defaults to device
+    rand_device = device
+    batch_size = shape[0]
+
+    layout = layout or torch.strided
+    device = device or torch.device("cpu")
+
+    if generator is not None:
+        gen_device_type = generator.device.type if not isinstance(generator, list) else generator[0].device.type
+        if gen_device_type != device.type and gen_device_type == "cpu":
+            rand_device = "cpu"
+            if device != "mps":
+                warnings.warn(
+                    f"The passed generator was created on 'cpu' even though a tensor on {device} was expected."
+                    f" Tensors will be created on 'cpu' and then moved to {device}. Note that one can probably"
+                    f" slighly speed up this function by passing a generator that was created on the {device} device."
+                )
+        elif gen_device_type != device.type and gen_device_type == "cuda":
+            raise ValueError(f"Cannot generate a {device} tensor from a generator of type {gen_device_type}.")
+
+    # make sure generator list of length 1 is treated like a non-list
+    if isinstance(generator, list) and len(generator) == 1:
+        generator = generator[0]
+
+    if isinstance(generator, list):
+        shape = (1,) + shape[1:]
+        latents = [
+            torch.randn(shape, generator=generator[i], device=rand_device, dtype=dtype, layout=layout)
+            for i in range(batch_size)
+        ]
+        latents = torch.cat(latents, dim=0).to(device)
+    else:
+        latents = torch.randn(shape, generator=generator, device=rand_device, dtype=dtype, layout=layout).to(device)
+
+    return latents

trl/models/modeling_sd_base.py

@@ -24,7 +24,8 @@
 from diffusers.loaders import AttnProcsLayers
 from diffusers.models.attention_processor import LoRAAttnProcessor
 from diffusers.pipelines.stable_diffusion.pipeline_stable_diffusion import rescale_noise_cfg
-from diffusers.utils.torch_utils import randn_tensor
+
+from ..core import randn_tensor
 
 
 @dataclass