update

docs/source/en/_toctree.yml

@@ -266,6 +266,8 @@
         title: LatteTransformer3DModel
       - local: api/models/lumina_nextdit2d
         title: LuminaNextDiT2DModel
+      - local: api/models/mochi_transformer3d
+        title: MochiTransformer3DModel
       - local: api/models/pixart_transformer2d
         title: PixArtTransformer2DModel
       - local: api/models/prior_transformer

docs/source/en/api/models/mochi_transformer3d.md

@@ -0,0 +1,30 @@
+<!-- Copyright 2024 The HuggingFace Team. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+the License. You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+an "AS IS" BASIS, 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. -->
+
+# MochiTransformer3DModel
+
+A Diffusion Transformer model for 3D video-like data was introduced in [Mochi-1 Preview](https://huggingface.co/genmo/mochi-1-preview) by Genmo.
+
+The model can be loaded with the following code snippet.
+
+```python
+from diffusers import MochiTransformer3DModel
+
+vae = MochiTransformer3DModel.from_pretrained("genmo/mochi-1-preview", subfolder="transformer", torch_dtype=torch.float16).to("cuda")
+```
+
+## MochiTransformer3DModel
+
+[[autodoc]] MochiTransformer3DModel
+
+## Transformer2DModelOutput
+
+[[autodoc]] models.modeling_outputs.Transformer2DModelOutput

scripts/convert_mochi_to_diffusers.py

@@ -0,0 +1,187 @@
+import argparse
+from contextlib import nullcontext
+
+import torch
+from accelerate import init_empty_weights
+from safetensors.torch import load_file
+
+# from transformers import T5EncoderModel, T5Tokenizer
+from diffusers import MochiTransformer3DModel
+from diffusers.utils.import_utils import is_accelerate_available
+
+
+CTX = init_empty_weights if is_accelerate_available else nullcontext
+
+TOKENIZER_MAX_LENGTH = 256
+
+parser = argparse.ArgumentParser()
+parser.add_argument("--transformer_checkpoint_path", default=None, type=str)
+# parser.add_argument("--vae_checkpoint_path", default=None, type=str)
+parser.add_argument("--output_path", required=True, type=str)
+parser.add_argument("--push_to_hub", action="store_true", default=False, help="Whether to push to HF Hub after saving")
+parser.add_argument("--text_encoder_cache_dir", type=str, default=None, help="Path to text encoder cache directory")
+parser.add_argument("--dtype", type=str, default=None)
+
+args = parser.parse_args()
+
+
+# This is specific to `AdaLayerNormContinuous`:
+# Diffusers implementation split the linear projection into the scale, shift while Mochi split it into shift, scale
+def swap_scale_shift(weight, dim):
+    shift, scale = weight.chunk(2, dim=0)
+    new_weight = torch.cat([scale, shift], dim=0)
+    return new_weight
+
+
+def convert_mochi_transformer_checkpoint_to_diffusers(ckpt_path):
+    original_state_dict = load_file(ckpt_path, device="cpu")
+    new_state_dict = {}
+
+    # Convert patch_embed
+    new_state_dict["patch_embed.proj.weight"] = original_state_dict.pop("x_embedder.proj.weight")
+    new_state_dict["patch_embed.proj.bias"] = original_state_dict.pop("x_embedder.proj.bias")
+
+    # Convert time_embed
+    new_state_dict["time_embed.timestep_embedder.linear_1.weight"] = original_state_dict.pop("t_embedder.mlp.0.weight")
+    new_state_dict["time_embed.timestep_embedder.linear_1.bias"] = original_state_dict.pop("t_embedder.mlp.0.bias")
+    new_state_dict["time_embed.timestep_embedder.linear_2.weight"] = original_state_dict.pop("t_embedder.mlp.2.weight")
+    new_state_dict["time_embed.timestep_embedder.linear_2.bias"] = original_state_dict.pop("t_embedder.mlp.2.bias")
+    new_state_dict["time_embed.pooler.to_kv.weight"] = original_state_dict.pop("t5_y_embedder.to_kv.weight")
+    new_state_dict["time_embed.pooler.to_kv.bias"] = original_state_dict.pop("t5_y_embedder.to_kv.bias")
+    new_state_dict["time_embed.pooler.to_q.weight"] = original_state_dict.pop("t5_y_embedder.to_q.weight")
+    new_state_dict["time_embed.pooler.to_q.bias"] = original_state_dict.pop("t5_y_embedder.to_q.bias")
+    new_state_dict["time_embed.pooler.to_out.weight"] = original_state_dict.pop("t5_y_embedder.to_out.weight")
+    new_state_dict["time_embed.pooler.to_out.bias"] = original_state_dict.pop("t5_y_embedder.to_out.bias")
+    new_state_dict["time_embed.caption_proj.weight"] = original_state_dict.pop("t5_yproj.weight")
+    new_state_dict["time_embed.caption_proj.bias"] = original_state_dict.pop("t5_yproj.bias")
+
+    # Convert transformer blocks
+    num_layers = 48
+    for i in range(num_layers):
+        block_prefix = f"transformer_blocks.{i}."
+        old_prefix = f"blocks.{i}."
+
+        # norm1
+        new_state_dict[block_prefix + "norm1.linear.weight"] = original_state_dict.pop(old_prefix + "mod_x.weight")
+        new_state_dict[block_prefix + "norm1.linear.bias"] = original_state_dict.pop(old_prefix + "mod_x.bias")
+        if i < num_layers - 1:
+            new_state_dict[block_prefix + "norm1_context.linear.weight"] = original_state_dict.pop(
+                old_prefix + "mod_y.weight"
+            )
+            new_state_dict[block_prefix + "norm1_context.linear.bias"] = original_state_dict.pop(
+                old_prefix + "mod_y.bias"
+            )
+        else:
+            new_state_dict[block_prefix + "norm1_context.linear_1.weight"] = original_state_dict.pop(
+                old_prefix + "mod_y.weight"
+            )
+            new_state_dict[block_prefix + "norm1_context.linear_1.bias"] = original_state_dict.pop(
+                old_prefix + "mod_y.bias"
+            )
+
+        # Visual attention
+        qkv_weight = original_state_dict.pop(old_prefix + "attn.qkv_x.weight")
+        q, k, v = qkv_weight.chunk(3, dim=0)
+
+        new_state_dict[block_prefix + "attn1.to_q.weight"] = q
+        new_state_dict[block_prefix + "attn1.to_k.weight"] = k
+        new_state_dict[block_prefix + "attn1.to_v.weight"] = v
+        new_state_dict[block_prefix + "attn1.norm_q.weight"] = original_state_dict.pop(
+            old_prefix + "attn.q_norm_x.weight"
+        )
+        new_state_dict[block_prefix + "attn1.norm_k.weight"] = original_state_dict.pop(
+            old_prefix + "attn.k_norm_x.weight"
+        )
+        new_state_dict[block_prefix + "attn1.to_out.0.weight"] = original_state_dict.pop(
+            old_prefix + "attn.proj_x.weight"
+        )
+        new_state_dict[block_prefix + "attn1.to_out.0.bias"] = original_state_dict.pop(old_prefix + "attn.proj_x.bias")
+
+        # Context attention
+        qkv_weight = original_state_dict.pop(old_prefix + "attn.qkv_y.weight")
+        q, k, v = qkv_weight.chunk(3, dim=0)
+
+        new_state_dict[block_prefix + "attn1.add_q_proj.weight"] = q
+        new_state_dict[block_prefix + "attn1.add_k_proj.weight"] = k
+        new_state_dict[block_prefix + "attn1.add_v_proj.weight"] = v
+        new_state_dict[block_prefix + "attn1.norm_added_q.weight"] = original_state_dict.pop(
+            old_prefix + "attn.q_norm_y.weight"
+        )
+        new_state_dict[block_prefix + "attn1.norm_added_k.weight"] = original_state_dict.pop(
+            old_prefix + "attn.k_norm_y.weight"
+        )
+        if i < num_layers - 1:
+            new_state_dict[block_prefix + "attn1.to_add_out.weight"] = original_state_dict.pop(
+                old_prefix + "attn.proj_y.weight"
+            )
+            new_state_dict[block_prefix + "attn1.to_add_out.bias"] = original_state_dict.pop(
+                old_prefix + "attn.proj_y.bias"
+            )
+
+        # MLP
+        new_state_dict[block_prefix + "ff.net.0.proj.weight"] = original_state_dict.pop(old_prefix + "mlp_x.w1.weight")
+        new_state_dict[block_prefix + "ff.net.2.weight"] = original_state_dict.pop(old_prefix + "mlp_x.w2.weight")
+        if i < num_layers - 1:
+            new_state_dict[block_prefix + "ff_context.net.0.proj.weight"] = original_state_dict.pop(
+                old_prefix + "mlp_y.w1.weight"
+            )
+            new_state_dict[block_prefix + "ff_context.net.2.weight"] = original_state_dict.pop(
+                old_prefix + "mlp_y.w2.weight"
+            )
+
+    # Output layers
+    new_state_dict["norm_out.linear.weight"] = swap_scale_shift(original_state_dict.pop("final_layer.mod.weight"), dim=0)
+    new_state_dict["norm_out.linear.bias"] = swap_scale_shift(original_state_dict.pop("final_layer.mod.bias"), dim=0)
+    new_state_dict["proj_out.weight"] = original_state_dict.pop("final_layer.linear.weight")
+    new_state_dict["proj_out.bias"] = original_state_dict.pop("final_layer.linear.bias")
+
+    new_state_dict["pos_frequencies"] = original_state_dict.pop("pos_frequencies")
+
+    print("Remaining Keys:", original_state_dict.keys())
+
+    return new_state_dict
+
+
+# def convert_mochi_vae_checkpoint_to_diffusers(ckpt_path, vae_config):
+#     original_state_dict = torch.load(ckpt_path, map_location="cpu")["state_dict"]
+#     return convert_ldm_vae_checkpoint(original_state_dict, vae_config)
+
+
+def main(args):
+    if args.dtype is None:
+        dtype = None
+    if args.dtype == "fp16":
+        dtype = torch.float16
+    elif args.dtype == "bf16":
+        dtype = torch.bfloat16
+    elif args.dtype == "fp32":
+        dtype = torch.float32
+    else:
+        raise ValueError(f"Unsupported dtype: {args.dtype}")
+
+    transformer = None
+    # vae = None
+
+    if args.transformer_checkpoint_path is not None:
+        converted_transformer_state_dict = convert_mochi_transformer_checkpoint_to_diffusers(
+            args.transformer_checkpoint_path
+        )
+        transformer = MochiTransformer3DModel()
+        transformer.load_state_dict(converted_transformer_state_dict, strict=True)
+        if dtype is not None:
+            # Original checkpoint data type will be preserved
+            transformer = transformer.to(dtype=dtype)
+
+    # text_encoder_id = "google/t5-v1_1-xxl"
+    # tokenizer = T5Tokenizer.from_pretrained(text_encoder_id, model_max_length=TOKENIZER_MAX_LENGTH)
+    # text_encoder = T5EncoderModel.from_pretrained(text_encoder_id, cache_dir=args.text_encoder_cache_dir)
+
+    # # Apparently, the conversion does not work anymore without this :shrug:
+    # for param in text_encoder.parameters():
+    #     param.data = param.data.contiguous()
+
+    transformer.save_pretrained("/raid/aryan/mochi-diffusers", subfolder="transformer")
+
+
+if __name__ == "__main__":
+    main(args)

src/diffusers/__init__.py

@@ -100,6 +100,7 @@ else:
             "Kandinsky3UNet",
             "LatteTransformer3DModel",
             "LuminaNextDiT2DModel",
+            "MochiTransformer3DModel",
             "ModelMixin",
             "MotionAdapter",
             "MultiAdapter",
@@ -579,6 +580,7 @@ if TYPE_CHECKING or DIFFUSERS_SLOW_IMPORT:
             Kandinsky3UNet,
             LatteTransformer3DModel,
             LuminaNextDiT2DModel,
+            MochiTransformer3DModel,
             ModelMixin,
             MotionAdapter,
             MultiAdapter,

src/diffusers/models/__init__.py

@@ -56,6 +56,7 @@ if is_torch_available():
     _import_structure["transformers.transformer_2d"] = ["Transformer2DModel"]
     _import_structure["transformers.transformer_cogview3plus"] = ["CogView3PlusTransformer2DModel"]
     _import_structure["transformers.transformer_flux"] = ["FluxTransformer2DModel"]
+    _import_structure["transformers.transformer_mochi"] = ["MochiTransformer3DModel"]
     _import_structure["transformers.transformer_sd3"] = ["SD3Transformer2DModel"]
     _import_structure["transformers.transformer_temporal"] = ["TransformerTemporalModel"]
     _import_structure["unets.unet_1d"] = ["UNet1DModel"]
@@ -106,6 +107,7 @@ if TYPE_CHECKING or DIFFUSERS_SLOW_IMPORT:
             HunyuanDiT2DModel,
             LatteTransformer3DModel,
             LuminaNextDiT2DModel,
+            MochiTransformer3DModel,
             PixArtTransformer2DModel,
             PriorTransformer,
             SD3Transformer2DModel,

src/diffusers/models/activations.py

@@ -134,14 +134,18 @@ class SwiGLU(nn.Module):
         bias (`bool`, defaults to True): Whether to use a bias in the linear layer.
     """
 
-    def __init__(self, dim_in: int, dim_out: int, bias: bool = True):
+    def __init__(self, dim_in: int, dim_out: int, bias: bool = True, flip_gate: bool = False):
         super().__init__()
+        self.flip_gate = flip_gate
+
         self.proj = nn.Linear(dim_in, dim_out * 2, bias=bias)
         self.activation = nn.SiLU()
 
     def forward(self, hidden_states):
         hidden_states = self.proj(hidden_states)
         hidden_states, gate = hidden_states.chunk(2, dim=-1)
+        if self.flip_gate:
+            hidden_states, gate = gate, hidden_states
         return hidden_states * self.activation(gate)
 
 

src/diffusers/models/attention.py

@@ -1206,6 +1206,7 @@ class FeedForward(nn.Module):
         final_dropout: bool = False,
         inner_dim=None,
         bias: bool = True,
+        flip_gate: bool = False,
     ):
         super().__init__()
         if inner_dim is None:
@@ -1221,7 +1222,7 @@ class FeedForward(nn.Module):
         elif activation_fn == "geglu-approximate":
             act_fn = ApproximateGELU(dim, inner_dim, bias=bias)
         elif activation_fn == "swiglu":
-            act_fn = SwiGLU(dim, inner_dim, bias=bias)
+            act_fn = SwiGLU(dim, inner_dim, bias=bias, flip_gate=flip_gate)
 
         self.net = nn.ModuleList([])
         # project in

src/diffusers/models/attention_processor.py

@@ -120,6 +120,7 @@ class Attention(nn.Module):
         _from_deprecated_attn_block: bool = False,
         processor: Optional["AttnProcessor"] = None,
         out_dim: int = None,
+        out_context_dim: int = None,
         context_pre_only=None,
         pre_only=False,
         elementwise_affine: bool = True,
@@ -142,6 +143,7 @@ class Attention(nn.Module):
         self.dropout = dropout
         self.fused_projections = False
         self.out_dim = out_dim if out_dim is not None else query_dim
+        self.out_context_dim = out_context_dim if out_context_dim is not None else query_dim
         self.context_pre_only = context_pre_only
         self.pre_only = pre_only
 
@@ -241,7 +243,7 @@ class Attention(nn.Module):
             self.to_out.append(nn.Dropout(dropout))
 
         if self.context_pre_only is not None and not self.context_pre_only:
-            self.to_add_out = nn.Linear(self.inner_dim, self.out_dim, bias=out_bias)
+            self.to_add_out = nn.Linear(self.inner_dim, self.out_context_dim, bias=out_bias)
 
         if qk_norm is not None and added_kv_proj_dim is not None:
             if qk_norm == "fp32_layer_norm":
@@ -1792,6 +1794,7 @@ class FluxAttnProcessor2_0:
             hidden_states = attn.to_out[0](hidden_states)
             # dropout
             hidden_states = attn.to_out[1](hidden_states)
+
             encoder_hidden_states = attn.to_add_out(encoder_hidden_states)
 
             return hidden_states, encoder_hidden_states
@@ -3078,6 +3081,94 @@ class LuminaAttnProcessor2_0:
         return hidden_states
 
 
+class MochiAttnProcessor2_0:
+    """Attention processor used in Mochi."""
+
+    def __init__(self):
+        if not hasattr(F, "scaled_dot_product_attention"):
+            raise ImportError("MochiAttnProcessor2_0 requires PyTorch 2.0. To use it, please upgrade PyTorch to 2.0.")
+
+    def __call__(
+        self,
+        attn: Attention,
+        hidden_states: torch.Tensor,
+        encoder_hidden_states: torch.Tensor,
+        attention_mask: Optional[torch.Tensor] = None,
+        image_rotary_emb: Optional[torch.Tensor] = None,
+    ) -> torch.Tensor:
+        query = attn.to_q(hidden_states)
+        key = attn.to_k(hidden_states)
+        value = attn.to_v(hidden_states)
+
+        query = query.unflatten(2, (attn.heads, -1))
+        key = key.unflatten(2, (attn.heads, -1))
+        value = value.unflatten(2, (attn.heads, -1))
+
+        if attn.norm_q is not None:
+            query = attn.norm_q(query)
+        if attn.norm_k is not None:
+            key = attn.norm_k(key)
+
+        encoder_query = attn.add_q_proj(encoder_hidden_states)
+        encoder_key = attn.add_k_proj(encoder_hidden_states)
+        encoder_value = attn.add_v_proj(encoder_hidden_states)
+
+        encoder_query = encoder_query.unflatten(2, (attn.heads, -1))
+        encoder_key = encoder_key.unflatten(2, (attn.heads, -1))
+        encoder_value = encoder_value.unflatten(2, (attn.heads, -1))
+
+        if attn.norm_added_q is not None:
+            encoder_query = attn.norm_added_q(encoder_query)
+        if attn.norm_added_k is not None:
+            encoder_key = attn.norm_added_k(encoder_key)
+
+        if image_rotary_emb is not None:
+
+            def apply_rotary_emb(x, freqs_cos, freqs_sin):
+                x_even = x[..., 0::2].float()
+                x_odd = x[..., 1::2].float()
+
+                cos = (x_even * freqs_cos - x_odd * freqs_sin).to(x.dtype)
+                sin = (x_even * freqs_sin + x_odd * freqs_cos).to(x.dtype)
+
+                return torch.stack([cos, sin], dim=-1).flatten(-2)
+
+            query = apply_rotary_emb(query, *image_rotary_emb)
+            key = apply_rotary_emb(key, *image_rotary_emb)
+
+        query, key, value = query.transpose(1, 2), key.transpose(1, 2), value.transpose(1, 2)
+        encoder_query, encoder_key, encoder_value = (
+            encoder_query.transpose(1, 2),
+            encoder_key.transpose(1, 2),
+            encoder_value.transpose(1, 2),
+        )
+
+        sequence_length = query.size(2)
+        encoder_sequence_length = encoder_query.size(2)
+
+        query = torch.cat([query, encoder_query], dim=2)
+        key = torch.cat([key, encoder_key], dim=2)
+        value = torch.cat([value, encoder_value], dim=2)
+
+        hidden_states = F.scaled_dot_product_attention(query, key, value, dropout_p=0.0, is_causal=False)
+        hidden_states = hidden_states.transpose(1, 2).flatten(2, 3)
+        hidden_states = hidden_states.to(query.dtype)
+
+        hidden_states, encoder_hidden_states = hidden_states.split_with_sizes(
+            (sequence_length, encoder_sequence_length), dim=1
+        )
+
+        # linear proj
+        hidden_states = attn.to_out[0](hidden_states)
+        # dropout
+        hidden_states = attn.to_out[1](hidden_states)
+
+        if hasattr(attn, "to_add_out"):
+            encoder_hidden_states = attn.to_add_out(encoder_hidden_states)
+
+        return hidden_states, encoder_hidden_states
+
+
 class FusedAttnProcessor2_0:
     r"""
     Processor for implementing scaled dot-product attention (enabled by default if you're using PyTorch 2.0). It uses

src/diffusers/models/embeddings.py

@@ -1302,6 +1302,41 @@ class LuminaCombinedTimestepCaptionEmbedding(nn.Module):
         return conditioning
 
 
+class MochiCombinedTimestepCaptionEmbedding(nn.Module):
+    def __init__(
+        self,
+        embedding_dim: int,
+        pooled_projection_dim: int,
+        text_embed_dim: int,
+        time_embed_dim: int = 256,
+        num_attention_heads: int = 8,
+    ) -> None:
+        super().__init__()
+
+        self.time_proj = Timesteps(num_channels=time_embed_dim, flip_sin_to_cos=True, downscale_freq_shift=0.0)
+        self.timestep_embedder = TimestepEmbedding(in_channels=time_embed_dim, time_embed_dim=embedding_dim)
+        self.pooler = MochiAttentionPool(
+            num_attention_heads=num_attention_heads, embed_dim=text_embed_dim, output_dim=embedding_dim
+        )
+        self.caption_proj = nn.Linear(text_embed_dim, pooled_projection_dim)
+
+    def forward(
+        self,
+        timestep: torch.LongTensor,
+        encoder_hidden_states: torch.Tensor,
+        encoder_attention_mask: torch.Tensor,
+        hidden_dtype: Optional[torch.dtype] = None,
+    ):
+        time_proj = self.time_proj(timestep)
+        time_emb = self.timestep_embedder(time_proj.to(dtype=hidden_dtype))
+
+        pooled_projections = self.pooler(encoder_hidden_states, encoder_attention_mask)
+        caption_proj = self.caption_proj(encoder_hidden_states)
+
+        conditioning = time_emb + pooled_projections
+        return conditioning, caption_proj
+
+
 class TextTimeEmbedding(nn.Module):
     def __init__(self, encoder_dim: int, time_embed_dim: int, num_heads: int = 64):
         super().__init__()
@@ -1430,6 +1465,88 @@ class AttentionPooling(nn.Module):
         return a[:, 0, :]  # cls_token
 
 
+class MochiAttentionPool(nn.Module):
+    def __init__(
+        self,
+        num_attention_heads: int,
+        embed_dim: int,
+        output_dim: Optional[int] = None,
+    ) -> None:
+        super().__init__()
+
+        self.output_dim = output_dim or embed_dim
+        self.num_attention_heads = num_attention_heads
+
+        self.to_kv = nn.Linear(embed_dim, 2 * embed_dim)
+        self.to_q = nn.Linear(embed_dim, embed_dim)
+        self.to_out = nn.Linear(embed_dim, self.output_dim)
+
+    @staticmethod
+    def pool_tokens(x: torch.Tensor, mask: torch.Tensor, *, keepdim=False) -> torch.Tensor:
+        """
+        Pool tokens in x using mask.
+
+        NOTE: We assume x does not require gradients.
+
+        Args:
+            x: (B, L, D) tensor of tokens.
+            mask: (B, L) boolean tensor indicating which tokens are not padding.
+
+        Returns:
+            pooled: (B, D) tensor of pooled tokens.
+        """
+        assert x.size(1) == mask.size(1)  # Expected mask to have same length as tokens.
+        assert x.size(0) == mask.size(0)  # Expected mask to have same batch size as tokens.
+        mask = mask[:, :, None].to(dtype=x.dtype)
+        mask = mask / mask.sum(dim=1, keepdim=True).clamp(min=1)
+        pooled = (x * mask).sum(dim=1, keepdim=keepdim)
+        return pooled
+
+    def forward(self, x: torch.Tensor, mask: torch.BoolTensor) -> torch.Tensor:
+        r"""
+        Args:
+            x (`torch.Tensor`):
+                Tensor of shape `(B, S, D)` of input tokens.
+            mask (`torch.Tensor`):
+                Boolean ensor of shape `(B, S)` indicating which tokens are not padding.
+
+        Returns:
+            `torch.Tensor`:
+                `(B, D)` tensor of pooled tokens.
+        """
+        D = x.size(2)
+
+        # Construct attention mask, shape: (B, 1, num_queries=1, num_keys=1+L).
+        attn_mask = mask[:, None, None, :].bool()  # (B, 1, 1, L).
+        attn_mask = F.pad(attn_mask, (1, 0), value=True)  # (B, 1, 1, 1+L).
+
+        # Average non-padding token features. These will be used as the query.
+        x_pool = self.pool_tokens(x, mask, keepdim=True)  # (B, 1, D)
+
+        # Concat pooled features to input sequence.
+        x = torch.cat([x_pool, x], dim=1)  # (B, L+1, D)
+
+        # Compute queries, keys, values. Only the mean token is used to create a query.
+        kv = self.to_kv(x)  # (B, L+1, 2 * D)
+        q = self.to_q(x[:, 0])  # (B, D)
+
+        # Extract heads.
+        head_dim = D // self.num_attention_heads
+        kv = kv.unflatten(2, (2, self.num_attention_heads, head_dim))  # (B, 1+L, 2, H, head_dim)
+        kv = kv.transpose(1, 3)  # (B, H, 2, 1+L, head_dim)
+        k, v = kv.unbind(2)  # (B, H, 1+L, head_dim)
+        q = q.unflatten(1, (self.num_attention_heads, head_dim))  # (B, H, head_dim)
+        q = q.unsqueeze(2)  # (B, H, 1, head_dim)
+
+        # Compute attention.
+        x = F.scaled_dot_product_attention(q, k, v, attn_mask=attn_mask, dropout_p=0.0)  # (B, H, 1, head_dim)
+
+        # Concatenate heads and run output.
+        x = x.squeeze(2).flatten(1, 2)  # (B, D = H * head_dim)
+        x = self.to_out(x)
+        return x
+
+
 def get_fourier_embeds_from_boundingbox(embed_dim, box):
     """
     Args:

src/diffusers/models/normalization.py

@@ -237,6 +237,33 @@ class LuminaRMSNormZero(nn.Module):
         return x, gate_msa, scale_mlp, gate_mlp
 
 
+class MochiRMSNormZero(nn.Module):
+    r"""
+    Adaptive RMS Norm used in Mochi.
+
+    Parameters:
+        embedding_dim (`int`): The size of each embedding vector.
+    """
+
+    def __init__(
+        self, embedding_dim: int, hidden_dim: int, eps: float = 1e-5, elementwise_affine: bool = False
+    ) -> None:
+        super().__init__()
+
+        self.silu = nn.SiLU()
+        self.linear = nn.Linear(embedding_dim, hidden_dim)
+        self.norm = RMSNorm(embedding_dim, eps=eps, elementwise_affine=elementwise_affine)
+
+    def forward(
+        self, hidden_states: torch.Tensor, emb: torch.Tensor
+    ) -> Tuple[torch.Tensor, torch.Tensor, torch.Tensor, torch.Tensor]:
+        emb = self.linear(self.silu(emb))
+        scale_msa, gate_msa, scale_mlp, gate_mlp = emb.chunk(4, dim=1)
+        hidden_states = self.norm(hidden_states) * (1 + scale_msa[:, None])
+
+        return hidden_states, gate_msa, scale_mlp, gate_mlp
+
+
 class AdaLayerNormSingle(nn.Module):
     r"""
     Norm layer adaptive layer norm single (adaLN-single).
@@ -358,20 +385,21 @@ class LuminaLayerNormContinuous(nn.Module):
         out_dim: Optional[int] = None,
     ):
         super().__init__()
+
         # AdaLN
         self.silu = nn.SiLU()
         self.linear_1 = nn.Linear(conditioning_embedding_dim, embedding_dim, bias=bias)
+
         if norm_type == "layer_norm":
             self.norm = LayerNorm(embedding_dim, eps, elementwise_affine, bias)
+        if norm_type == "rms_norm":
+            self.norm = RMSNorm(embedding_dim, eps=eps, elementwise_affine=elementwise_affine)
         else:
             raise ValueError(f"unknown norm_type {norm_type}")
-        # linear_2
+
+        self.linear_2 = None
         if out_dim is not None:
-            self.linear_2 = nn.Linear(
-                embedding_dim,
-                out_dim,
-                bias=bias,
-            )
+            self.linear_2 = nn.Linear(embedding_dim, out_dim, bias=bias)
 
     def forward(
         self,

src/diffusers/models/transformers/__init__.py

@@ -16,5 +16,6 @@ if is_torch_available():
     from .transformer_2d import Transformer2DModel
     from .transformer_cogview3plus import CogView3PlusTransformer2DModel
     from .transformer_flux import FluxTransformer2DModel
+    from .transformer_mochi import MochiTransformer3DModel
     from .transformer_sd3 import SD3Transformer2DModel
     from .transformer_temporal import TransformerTemporalModel

src/diffusers/models/transformers/transformer_mochi.py

@@ -0,0 +1,323 @@
+# Copyright 2024 The Genmo team and The HuggingFace Team.
+# All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# 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.
+
+from typing import Any, Dict, Optional, Tuple
+
+import torch
+import torch.nn as nn
+
+from ...configuration_utils import ConfigMixin, register_to_config
+from ...utils import is_torch_version, logging
+from ...utils.torch_utils import maybe_allow_in_graph
+from ..attention import FeedForward
+from ..attention_processor import Attention, MochiAttnProcessor2_0
+from ..embeddings import MochiCombinedTimestepCaptionEmbedding, PatchEmbed
+from ..modeling_outputs import Transformer2DModelOutput
+from ..modeling_utils import ModelMixin
+from ..normalization import AdaLayerNormContinuous, LuminaLayerNormContinuous, MochiRMSNormZero, RMSNorm
+
+
+logger = logging.get_logger(__name__)  # pylint: disable=invalid-name
+
+
+@maybe_allow_in_graph
+class MochiTransformerBlock(nn.Module):
+    def __init__(
+        self,
+        dim: int,
+        num_attention_heads: int,
+        attention_head_dim: int,
+        pooled_projection_dim: int,
+        qk_norm: str = "rms_norm",
+        activation_fn: str = "swiglu",
+        context_pre_only: bool = True,
+        eps: float = 1e-6,
+    ) -> None:
+        super().__init__()
+
+        self.context_pre_only = context_pre_only
+        self.ff_inner_dim = (4 * dim * 2) // 3
+        self.ff_context_inner_dim = (4 * pooled_projection_dim * 2) // 3
+
+        self.norm1 = MochiRMSNormZero(dim, 4 * dim, eps=eps, elementwise_affine=False)
+
+        if not context_pre_only:
+            self.norm1_context = MochiRMSNormZero(dim, 4 * pooled_projection_dim, eps=eps, elementwise_affine=False)
+        else:
+            self.norm1_context = LuminaLayerNormContinuous(
+                embedding_dim=pooled_projection_dim,
+                conditioning_embedding_dim=dim,
+                eps=eps,
+                elementwise_affine=False,
+                norm_type="rms_norm",
+                out_dim=None,
+            )
+
+        self.attn1 = Attention(
+            query_dim=dim,
+            cross_attention_dim=None,
+            heads=num_attention_heads,
+            dim_head=attention_head_dim,
+            bias=False,
+            qk_norm=qk_norm,
+            added_kv_proj_dim=pooled_projection_dim,
+            added_proj_bias=False,
+            out_dim=dim,
+            out_context_dim=pooled_projection_dim,
+            context_pre_only=context_pre_only,
+            processor=MochiAttnProcessor2_0(),
+            eps=eps,
+            elementwise_affine=True,
+        )
+
+        self.norm2 = RMSNorm(dim, eps=eps, elementwise_affine=False)
+        self.norm2_context = RMSNorm(pooled_projection_dim, eps=eps, elementwise_affine=False)
+
+        self.norm3 = RMSNorm(dim, eps=eps, elementwise_affine=False)
+        self.norm3_context = RMSNorm(pooled_projection_dim, eps=eps, elementwise_affine=False)
+
+        self.ff = FeedForward(dim, inner_dim=self.ff_inner_dim, activation_fn=activation_fn, bias=False, flip_gate=True)
+        self.ff_context = None
+        if not context_pre_only:
+            self.ff_context = FeedForward(
+                pooled_projection_dim, inner_dim=self.ff_context_inner_dim, activation_fn=activation_fn, bias=False, flip_gate=True
+            )
+
+        self.norm4 = RMSNorm(dim, eps=eps, elementwise_affine=False)
+        self.norm4_context = RMSNorm(pooled_projection_dim, eps=eps, elementwise_affine=False)
+
+    def forward(
+        self,
+        hidden_states: torch.Tensor,
+        encoder_hidden_states: torch.Tensor,
+        temb: torch.Tensor,
+        image_rotary_emb: Optional[torch.Tensor] = None,
+    ) -> Tuple[torch.Tensor, torch.Tensor]:
+        norm_hidden_states, gate_msa, scale_mlp, gate_mlp = self.norm1(hidden_states, temb)
+
+        if not self.context_pre_only:
+            norm_encoder_hidden_states, enc_gate_msa, enc_scale_mlp, enc_gate_mlp = self.norm1_context(
+                encoder_hidden_states, temb
+            )
+        else:
+            norm_encoder_hidden_states = self.norm1_context(encoder_hidden_states, temb)
+
+        attn_hidden_states, context_attn_hidden_states = self.attn1(
+            hidden_states=norm_hidden_states,
+            encoder_hidden_states=norm_encoder_hidden_states,
+            image_rotary_emb=image_rotary_emb,
+        )
+
+        hidden_states = hidden_states + self.norm2(attn_hidden_states) * torch.tanh(gate_msa).unsqueeze(1)
+        norm_hidden_states = self.norm3(hidden_states) * (1 + scale_mlp.unsqueeze(1))
+        ff_output = self.ff(norm_hidden_states)
+        hidden_states = hidden_states + self.norm4(ff_output) * torch.tanh(gate_mlp).unsqueeze(1)
+
+        if not self.context_pre_only:
+            encoder_hidden_states = encoder_hidden_states + self.norm2_context(
+                context_attn_hidden_states
+            ) * torch.tanh(enc_gate_msa).unsqueeze(1)
+            norm_encoder_hidden_states = self.norm3_context(encoder_hidden_states) * (1 + enc_scale_mlp.unsqueeze(1))
+            context_ff_output = self.ff_context(norm_encoder_hidden_states)
+            encoder_hidden_states = encoder_hidden_states + self.norm4_context(context_ff_output) * torch.tanh(enc_gate_mlp).unsqueeze(1)
+
+        return hidden_states, encoder_hidden_states
+
+
+class MochiRoPE(nn.Module):
+    def __init__(self, base_height: int = 192, base_width: int = 192, theta: float = 10000.0) -> None:
+        super().__init__()
+
+        self.target_area = base_height * base_width
+
+    def _centers(self, start, stop, num, device, dtype) -> torch.Tensor:
+        edges = torch.linspace(start, stop, num + 1, device=device, dtype=dtype)
+        return (edges[:-1] + edges[1:]) / 2
+
+    def _get_positions(
+        self,
+        num_frames: int,
+        height: int,
+        width: int,
+        device: Optional[torch.device] = None,
+        dtype: Optional[torch.dtype] = None,
+    ) -> torch.Tensor:
+        scale = (self.target_area / (height * width)) ** 0.5
+
+        t = torch.arange(num_frames, device=device, dtype=dtype)
+        h = self._centers(-height * scale / 2, height * scale / 2, height, device, dtype)
+        w = self._centers(-width * scale / 2, width * scale / 2, width, device, dtype)
+
+        grid_t, grid_h, grid_w = torch.meshgrid(t, h, w, indexing="ij")
+
+        positions = torch.stack([grid_t, grid_h, grid_w], dim=-1).view(-1, 3)
+        return positions
+
+    def _create_rope(self, freqs: torch.Tensor, pos: torch.Tensor) -> torch.Tensor:
+        freqs = torch.einsum("nd,dhf->nhf", pos, freqs)
+        freqs_cos = torch.cos(freqs)
+        freqs_sin = torch.sin(freqs)
+        return freqs_cos, freqs_sin
+
+    def forward(
+        self,
+        pos_frequencies: torch.Tensor,
+        num_frames: int,
+        height: int,
+        width: int,
+        device: Optional[torch.device] = None,
+        dtype: Optional[torch.dtype] = None,
+    ) -> Tuple[torch.Tensor, torch.Tensor]:
+        pos = self._get_positions(num_frames, height, width, device, dtype)
+        rope_cos, rope_sin = self._create_rope(pos_frequencies, pos)
+        return rope_cos, rope_sin
+
+
+@maybe_allow_in_graph
+class MochiTransformer3DModel(ModelMixin, ConfigMixin):
+    _supports_gradient_checkpointing = True
+
+    @register_to_config
+    def __init__(
+        self,
+        patch_size: int = 2,
+        num_attention_heads: int = 24,
+        attention_head_dim: int = 128,
+        num_layers: int = 48,
+        pooled_projection_dim: int = 1536,
+        in_channels: int = 12,
+        out_channels: Optional[int] = None,
+        qk_norm: str = "rms_norm",
+        text_embed_dim: int = 4096,
+        time_embed_dim: int = 256,
+        activation_fn: str = "swiglu",
+        max_sequence_length: int = 256,
+    ) -> None:
+        super().__init__()
+
+        inner_dim = num_attention_heads * attention_head_dim
+        out_channels = out_channels or in_channels
+
+        self.patch_embed = PatchEmbed(
+            patch_size=patch_size,
+            in_channels=in_channels,
+            embed_dim=inner_dim,
+            pos_embed_type=None,
+        )
+
+        self.time_embed = MochiCombinedTimestepCaptionEmbedding(
+            embedding_dim=inner_dim,
+            pooled_projection_dim=pooled_projection_dim,
+            text_embed_dim=text_embed_dim,
+            time_embed_dim=time_embed_dim,
+            num_attention_heads=8,
+        )
+
+        self.pos_frequencies = nn.Parameter(torch.empty(3, num_attention_heads, attention_head_dim // 2))
+        self.rope = MochiRoPE()
+
+        self.transformer_blocks = nn.ModuleList(
+            [
+                MochiTransformerBlock(
+                    dim=inner_dim,
+                    num_attention_heads=num_attention_heads,
+                    attention_head_dim=attention_head_dim,
+                    pooled_projection_dim=pooled_projection_dim,
+                    qk_norm=qk_norm,
+                    activation_fn=activation_fn,
+                    context_pre_only=i == num_layers - 1,
+                )
+                for i in range(num_layers)
+            ]
+        )
+
+        self.norm_out = AdaLayerNormContinuous(
+            inner_dim, inner_dim, elementwise_affine=False, eps=1e-6, norm_type="layer_norm"
+        )
+        self.proj_out = nn.Linear(inner_dim, patch_size * patch_size * out_channels)
+
+        self.gradient_checkpointing = False
+
+    def _set_gradient_checkpointing(self, module, value=False):
+        if hasattr(module, "gradient_checkpointing"):
+            module.gradient_checkpointing = value
+
+    def forward(
+        self,
+        hidden_states: torch.Tensor,
+        encoder_hidden_states: torch.Tensor,
+        timestep: torch.LongTensor,
+        encoder_attention_mask: torch.Tensor,
+        return_dict: bool = True,
+    ) -> torch.Tensor:
+        batch_size, num_channels, num_frames, height, width = hidden_states.shape
+        p = self.config.patch_size
+
+        post_patch_height = height // p
+        post_patch_width = width // p
+
+        temb, encoder_hidden_states = self.time_embed(
+            timestep, encoder_hidden_states, encoder_attention_mask, hidden_dtype=hidden_states.dtype
+        )
+
+        hidden_states = hidden_states.permute(0, 2, 1, 3, 4).flatten(0, 1)
+        hidden_states = self.patch_embed(hidden_states)
+        hidden_states = hidden_states.unflatten(0, (batch_size, -1)).flatten(1, 2)
+
+        image_rotary_emb = self.rope(
+            self.pos_frequencies,
+            num_frames,
+            post_patch_height,
+            post_patch_width,
+            device=hidden_states.device,
+            dtype=torch.float32,
+        )
+
+        for i, block in enumerate(self.transformer_blocks):
+            if self.gradient_checkpointing:
+
+                def create_custom_forward(module):
+                    def custom_forward(*inputs):
+                        return module(*inputs)
+
+                    return custom_forward
+
+                ckpt_kwargs: Dict[str, Any] = {"use_reentrant": False} if is_torch_version(">=", "1.11.0") else {}
+                hidden_states, encoder_hidden_states = torch.utils.checkpoint.checkpoint(
+                    create_custom_forward(block),
+                    hidden_states,
+                    encoder_hidden_states,
+                    temb,
+                    image_rotary_emb,
+                    **ckpt_kwargs,
+                )
+            else:
+                hidden_states, encoder_hidden_states = block(
+                    hidden_states=hidden_states,
+                    encoder_hidden_states=encoder_hidden_states,
+                    temb=temb,
+                    image_rotary_emb=image_rotary_emb,
+                )
+
+        hidden_states = self.norm_out(hidden_states, temb)
+        hidden_states = self.proj_out(hidden_states)
+
+        hidden_states = hidden_states.reshape(batch_size, num_frames, post_patch_height, post_patch_width, p, p, -1)
+        hidden_states = hidden_states.permute(0, 6, 1, 2, 4, 3, 5)
+        output = hidden_states.reshape(batch_size, -1, num_frames, height, width)
+
+        if not return_dict:
+            return (output,)
+        return Transformer2DModelOutput(sample=output)

src/diffusers/utils/dummy_pt_objects.py

@@ -347,6 +347,21 @@ class LuminaNextDiT2DModel(metaclass=DummyObject):
         requires_backends(cls, ["torch"])
 
 
+class MochiTransformer3DModel(metaclass=DummyObject):
+    _backends = ["torch"]
+
+    def __init__(self, *args, **kwargs):
+        requires_backends(self, ["torch"])
+
+    @classmethod
+    def from_config(cls, *args, **kwargs):
+        requires_backends(cls, ["torch"])
+
+    @classmethod
+    def from_pretrained(cls, *args, **kwargs):
+        requires_backends(cls, ["torch"])
+
+
 class ModelMixin(metaclass=DummyObject):
     _backends = ["torch"]
 

tests/models/transformers/test_models_transformer_mochi.py

@@ -0,0 +1,80 @@
+# coding=utf-8
+# Copyright 2024 HuggingFace Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# 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 unittest
+
+import torch
+
+from diffusers import MochiTransformer3DModel
+from diffusers.utils.testing_utils import enable_full_determinism, torch_device
+
+from ..test_modeling_common import ModelTesterMixin
+
+
+enable_full_determinism()
+
+
+class MochiTransformerTests(ModelTesterMixin, unittest.TestCase):
+    model_class = MochiTransformer3DModel
+    main_input_name = "hidden_states"
+    uses_custom_attn_processor = True
+
+    @property
+    def dummy_input(self):
+        batch_size = 2
+        num_channels = 4
+        num_frames = 2
+        height = 16
+        width = 16
+        embedding_dim = 16
+        sequence_length = 16
+
+        hidden_states = torch.randn((batch_size, num_channels, num_frames, height, width)).to(torch_device)
+        encoder_hidden_states = torch.randn((batch_size, sequence_length, embedding_dim)).to(torch_device)
+        encoder_attention_mask = torch.ones((batch_size, sequence_length)).bool().to(torch_device)
+        timestep = torch.randint(0, 1000, size=(batch_size,)).to(torch_device)
+
+        return {
+            "hidden_states": hidden_states,
+            "encoder_hidden_states": encoder_hidden_states,
+            "timestep": timestep,
+            "encoder_attention_mask": encoder_attention_mask,
+        }
+
+    @property
+    def input_shape(self):
+        return (4, 2, 16, 16)
+
+    @property
+    def output_shape(self):
+        return (4, 2, 16, 16)
+
+    def prepare_init_args_and_inputs_for_common(self):
+        init_dict = {
+            "patch_size": 2,
+            "num_attention_heads": 2,
+            "attention_head_dim": 8,
+            "num_layers": 2,
+            "pooled_projection_dim": 16,
+            "in_channels": 4,
+            "out_channels": None,
+            "qk_norm": "rms_norm",
+            "text_embed_dim": 16,
+            "time_embed_dim": 4,
+            "activation_fn": "swiglu",
+            "max_sequence_length": 16,
+        }
+        inputs_dict = self.dummy_input
+        return init_dict, inputs_dict