[UNet2DConditionModel] add gradient checkpointing (#461)

* add grad ckpt to downsample blocks

* make it work

* don't pass gradient_checkpointing to upsample block

* add tests for UNet2DConditionModel

* add test_gradient_checkpointing

* add gradient_checkpointing for up and down blocks

* add functions to enable and disable grad ckpt

* remove the forward argument

* better naming

* make supports_gradient_checkpointing private

src/diffusers/modeling_utils.py

@@ -15,6 +15,7 @@
 # limitations under the License.
 
 import os
+from functools import partial
 from typing import Callable, List, Optional, Tuple, Union
 
 import torch
@@ -121,10 +122,42 @@ class ModelMixin(torch.nn.Module):
     """
     config_name = CONFIG_NAME
     _automatically_saved_args = ["_diffusers_version", "_class_name", "_name_or_path"]
+    _supports_gradient_checkpointing = False
 
     def __init__(self):
         super().__init__()
 
+    @property
+    def is_gradient_checkpointing(self) -> bool:
+        """
+        Whether gradient checkpointing is activated for this model or not.
+
+        Note that in other frameworks this feature can be referred to as "activation checkpointing" or "checkpoint
+        activations".
+        """
+        return any(hasattr(m, "gradient_checkpointing") and m.gradient_checkpointing for m in self.modules())
+
+    def enable_gradient_checkpointing(self):
+        """
+        Activates gradient checkpointing for the current model.
+
+        Note that in other frameworks this feature can be referred to as "activation checkpointing" or "checkpoint
+        activations".
+        """
+        if not self._supports_gradient_checkpointing:
+            raise ValueError(f"{self.__class__.__name__} does not support gradient checkpointing.")
+        self.apply(partial(self._set_gradient_checkpointing, value=True))
+
+    def disable_gradient_checkpointing(self):
+        """
+        Deactivates gradient checkpointing for the current model.
+
+        Note that in other frameworks this feature can be referred to as "activation checkpointing" or "checkpoint
+        activations".
+        """
+        if self._supports_gradient_checkpointing:
+            self.apply(partial(self._set_gradient_checkpointing, value=False))
+
     def save_pretrained(
         self,
         save_directory: Union[str, os.PathLike],

src/diffusers/models/unet_2d_condition.py

@@ -3,12 +3,21 @@ from typing import Optional, Tuple, Union
 
 import torch
 import torch.nn as nn
+import torch.utils.checkpoint
 
 from ..configuration_utils import ConfigMixin, register_to_config
 from ..modeling_utils import ModelMixin
 from ..utils import BaseOutput
 from .embeddings import TimestepEmbedding, Timesteps
-from .unet_blocks import UNetMidBlock2DCrossAttn, get_down_block, get_up_block
+from .unet_blocks import (
+    CrossAttnDownBlock2D,
+    CrossAttnUpBlock2D,
+    DownBlock2D,
+    UNetMidBlock2DCrossAttn,
+    UpBlock2D,
+    get_down_block,
+    get_up_block,
+)
 
 
 @dataclass
@@ -54,6 +63,8 @@ class UNet2DConditionModel(ModelMixin, ConfigMixin):
         attention_head_dim (`int`, *optional*, defaults to 8): The dimension of the attention heads.
     """
 
+    _supports_gradient_checkpointing = True
+
     @register_to_config
     def __init__(
         self,
@@ -188,6 +199,10 @@ class UNet2DConditionModel(ModelMixin, ConfigMixin):
             if hasattr(block, "attentions") and block.attentions is not None:
                 block.set_attention_slice(slice_size)
 
+    def _set_gradient_checkpointing(self, module, value=False):
+        if isinstance(module, (CrossAttnDownBlock2D, DownBlock2D, CrossAttnUpBlock2D, UpBlock2D)):
+            module.gradient_checkpointing = value
+
     def forward(
         self,
         sample: torch.FloatTensor,
@@ -234,7 +249,9 @@ class UNet2DConditionModel(ModelMixin, ConfigMixin):
         for downsample_block in self.down_blocks:
             if hasattr(downsample_block, "attentions") and downsample_block.attentions is not None:
                 sample, res_samples = downsample_block(
-                    hidden_states=sample, temb=emb, encoder_hidden_states=encoder_hidden_states
+                    hidden_states=sample,
+                    temb=emb,
+                    encoder_hidden_states=encoder_hidden_states,
                 )
             else:
                 sample, res_samples = downsample_block(hidden_states=sample, temb=emb)

src/diffusers/models/unet_blocks.py

@@ -527,6 +527,8 @@ class CrossAttnDownBlock2D(nn.Module):
         else:
             self.downsamplers = None
 
+        self.gradient_checkpointing = False
+
     def set_attention_slice(self, slice_size):
         if slice_size is not None and self.attn_num_head_channels % slice_size != 0:
             raise ValueError(
@@ -546,8 +548,22 @@ class CrossAttnDownBlock2D(nn.Module):
         output_states = ()
 
         for resnet, attn in zip(self.resnets, self.attentions):
+            if self.training and self.gradient_checkpointing:
+
+                def create_custom_forward(module):
+                    def custom_forward(*inputs):
+                        return module(*inputs)
+
+                    return custom_forward
+
+                hidden_states = torch.utils.checkpoint.checkpoint(create_custom_forward(resnet), hidden_states, temb)
+                hidden_states = torch.utils.checkpoint.checkpoint(
+                    create_custom_forward(attn), hidden_states, encoder_hidden_states
+                )
+            else:
                 hidden_states = resnet(hidden_states, temb)
                 hidden_states = attn(hidden_states, context=encoder_hidden_states)
+
             output_states += (hidden_states,)
 
         if self.downsamplers is not None:
@@ -609,11 +625,24 @@ class DownBlock2D(nn.Module):
         else:
             self.downsamplers = None
 
+        self.gradient_checkpointing = False
+
     def forward(self, hidden_states, temb=None):
         output_states = ()
 
         for resnet in self.resnets:
+            if self.training and self.gradient_checkpointing:
+
+                def create_custom_forward(module):
+                    def custom_forward(*inputs):
+                        return module(*inputs)
+
+                    return custom_forward
+
+                hidden_states = torch.utils.checkpoint.checkpoint(create_custom_forward(resnet), hidden_states, temb)
+            else:
                 hidden_states = resnet(hidden_states, temb)
+
             output_states += (hidden_states,)
 
         if self.downsamplers is not None:
@@ -1072,6 +1101,8 @@ class CrossAttnUpBlock2D(nn.Module):
         else:
             self.upsamplers = None
 
+        self.gradient_checkpointing = False
+
     def set_attention_slice(self, slice_size):
         if slice_size is not None and self.attn_num_head_channels % slice_size != 0:
             raise ValueError(
@@ -1087,13 +1118,34 @@ class CrossAttnUpBlock2D(nn.Module):
         for attn in self.attentions:
             attn._set_attention_slice(slice_size)
 
-    def forward(self, hidden_states, res_hidden_states_tuple, temb=None, encoder_hidden_states=None):
+        self.gradient_checkpointing = False
+
+    def forward(
+        self,
+        hidden_states,
+        res_hidden_states_tuple,
+        temb=None,
+        encoder_hidden_states=None,
+    ):
         for resnet, attn in zip(self.resnets, self.attentions):
             # pop res hidden states
             res_hidden_states = res_hidden_states_tuple[-1]
             res_hidden_states_tuple = res_hidden_states_tuple[:-1]
             hidden_states = torch.cat([hidden_states, res_hidden_states], dim=1)
 
+            if self.training and self.gradient_checkpointing:
+
+                def create_custom_forward(module):
+                    def custom_forward(*inputs):
+                        return module(*inputs)
+
+                    return custom_forward
+
+                hidden_states = torch.utils.checkpoint.checkpoint(create_custom_forward(resnet), hidden_states, temb)
+                hidden_states = torch.utils.checkpoint.checkpoint(
+                    create_custom_forward(attn), hidden_states, encoder_hidden_states
+                )
+            else:
                 hidden_states = resnet(hidden_states, temb)
                 hidden_states = attn(hidden_states, context=encoder_hidden_states)
 
@@ -1150,6 +1202,8 @@ class UpBlock2D(nn.Module):
         else:
             self.upsamplers = None
 
+        self.gradient_checkpointing = False
+
     def forward(self, hidden_states, res_hidden_states_tuple, temb=None):
         for resnet in self.resnets:
             # pop res hidden states
@@ -1157,6 +1211,16 @@ class UpBlock2D(nn.Module):
             res_hidden_states_tuple = res_hidden_states_tuple[:-1]
             hidden_states = torch.cat([hidden_states, res_hidden_states], dim=1)
 
+            if self.training and self.gradient_checkpointing:
+
+                def create_custom_forward(module):
+                    def custom_forward(*inputs):
+                        return module(*inputs)
+
+                    return custom_forward
+
+                hidden_states = torch.utils.checkpoint.checkpoint(create_custom_forward(resnet), hidden_states, temb)
+            else:
                 hidden_states = resnet(hidden_states, temb)
 
         if self.upsamplers is not None:

src/diffusers/pipelines/latent_diffusion/pipeline_latent_diffusion.py

@@ -478,7 +478,7 @@ class LDMBertEncoderLayer(nn.Module):
 class LDMBertPreTrainedModel(PreTrainedModel):
     config_class = LDMBertConfig
     base_model_prefix = "model"
-    supports_gradient_checkpointing = True
+    _supports_gradient_checkpointing = True
     _keys_to_ignore_on_load_unexpected = [r"encoder\.version", r"decoder\.version"]
 
     def _init_weights(self, module):

tests/test_modeling_common.py

@@ -246,3 +246,21 @@ class ModelTesterMixin:
             outputs_tuple = model(**inputs_dict, return_dict=False)
 
         recursive_check(outputs_tuple, outputs_dict)
+
+    def test_enable_disable_gradient_checkpointing(self):
+        if not self.model_class._supports_gradient_checkpointing:
+            return  # Skip test if model does not support gradient checkpointing
+
+        init_dict, _ = self.prepare_init_args_and_inputs_for_common()
+
+        # at init model should have gradient checkpointing disabled
+        model = self.model_class(**init_dict)
+        self.assertFalse(model.is_gradient_checkpointing)
+
+        # check enable works
+        model.enable_gradient_checkpointing()
+        self.assertTrue(model.is_gradient_checkpointing)
+
+        # check disable works
+        model.disable_gradient_checkpointing()
+        self.assertFalse(model.is_gradient_checkpointing)

tests/test_models_unet.py

@@ -18,7 +18,7 @@ import unittest
 
 import torch
 
-from diffusers import UNet2DModel
+from diffusers import UNet2DConditionModel, UNet2DModel
 from diffusers.testing_utils import floats_tensor, slow, torch_device
 
 from .test_modeling_common import ModelTesterMixin
@@ -159,6 +159,82 @@ class UNetLDMModelTests(ModelTesterMixin, unittest.TestCase):
         self.assertTrue(torch.allclose(output_slice, expected_output_slice, rtol=1e-3))
 
 
+class UNet2DConditionModelTests(ModelTesterMixin, unittest.TestCase):
+    model_class = UNet2DConditionModel
+
+    @property
+    def dummy_input(self):
+        batch_size = 4
+        num_channels = 4
+        sizes = (32, 32)
+
+        noise = floats_tensor((batch_size, num_channels) + sizes).to(torch_device)
+        time_step = torch.tensor([10]).to(torch_device)
+        encoder_hidden_states = floats_tensor((batch_size, 4, 32)).to(torch_device)
+
+        return {"sample": noise, "timestep": time_step, "encoder_hidden_states": encoder_hidden_states}
+
+    @property
+    def input_shape(self):
+        return (4, 32, 32)
+
+    @property
+    def output_shape(self):
+        return (4, 32, 32)
+
+    def prepare_init_args_and_inputs_for_common(self):
+        init_dict = {
+            "block_out_channels": (32, 64),
+            "down_block_types": ("CrossAttnDownBlock2D", "DownBlock2D"),
+            "up_block_types": ("UpBlock2D", "CrossAttnUpBlock2D"),
+            "cross_attention_dim": 32,
+            "attention_head_dim": 8,
+            "out_channels": 4,
+            "in_channels": 4,
+            "layers_per_block": 2,
+            "sample_size": 32,
+        }
+        inputs_dict = self.dummy_input
+        return init_dict, inputs_dict
+
+    def test_gradient_checkpointing(self):
+        init_dict, inputs_dict = self.prepare_init_args_and_inputs_for_common()
+        model = self.model_class(**init_dict)
+        model.to(torch_device)
+
+        out = model(**inputs_dict).sample
+        # run the backwards pass on the model. For backwards pass, for simplicity purpose,
+        # we won't calculate the loss and rather backprop on out.sum()
+        model.zero_grad()
+        out.sum().backward()
+
+        # now we save the output and parameter gradients that we will use for comparison purposes with
+        # the non-checkpointed run.
+        output_not_checkpointed = out.data.clone()
+        grad_not_checkpointed = {}
+        for name, param in model.named_parameters():
+            grad_not_checkpointed[name] = param.grad.data.clone()
+
+        model.enable_gradient_checkpointing()
+        out = model(**inputs_dict).sample
+        # run the backwards pass on the model. For backwards pass, for simplicity purpose,
+        # we won't calculate the loss and rather backprop on out.sum()
+        model.zero_grad()
+        out.sum().backward()
+
+        # now we save the output and parameter gradients that we will use for comparison purposes with
+        # the non-checkpointed run.
+        output_checkpointed = out.data.clone()
+        grad_checkpointed = {}
+        for name, param in model.named_parameters():
+            grad_checkpointed[name] = param.grad.data.clone()
+
+        # compare the output and parameters gradients
+        self.assertTrue((output_checkpointed == output_not_checkpointed).all())
+        for name in grad_checkpointed:
+            self.assertTrue(torch.allclose(grad_checkpointed[name], grad_not_checkpointed[name], atol=5e-5))
+
+
 #    TODO(Patrick) - Re-add this test after having cleaned up LDM
 #    def test_output_pretrained_spatial_transformer(self):
 #        model = UNetLDMModel.from_pretrained("fusing/unet-ldm-dummy-spatial")