Added support for finetuning OmniGen2.

extensions_built_in/diffusion_models/omnigen2/src/models/attention_processor.py

@@ -0,0 +1,357 @@
+"""
+OmniGen2 Attention Processor Module
+
+Copyright 2025 BAAI, The OmniGen2 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.
+"""
+
+import warnings
+import math
+from typing import Optional, Tuple, Dict, Any
+
+import torch
+import torch.nn.functional as F
+from einops import repeat
+
+from ..utils.import_utils import is_flash_attn_available
+
+if is_flash_attn_available():
+    from flash_attn import flash_attn_varlen_func
+    from flash_attn.bert_padding import index_first_axis, pad_input, unpad_input
+else:
+    warnings.warn("Cannot import flash_attn, install flash_attn to use Flash2Varlen attention for better performance")
+
+
+from diffusers.models.attention_processor import Attention
+from .embeddings import apply_rotary_emb
+
+
+class OmniGen2AttnProcessorFlash2Varlen:
+    """
+    Processor for implementing scaled dot-product attention with flash attention and variable length sequences.
+    
+    This processor implements:
+    - Flash attention with variable length sequences
+    - Rotary position embeddings (RoPE)
+    - Query-Key normalization
+    - Proportional attention scaling
+    
+    Args:
+        None
+    """
+
+    def __init__(self) -> None:
+        """Initialize the attention processor."""
+        if not is_flash_attn_available():
+            raise ImportError(
+                "OmniGen2AttnProcessorFlash2Varlen requires flash_attn. "
+                "Please install flash_attn."
+            )
+
+    def _upad_input(
+        self,
+        query_layer: torch.Tensor,
+        key_layer: torch.Tensor,
+        value_layer: torch.Tensor,
+        attention_mask: torch.Tensor,
+        query_length: int,
+        num_heads: int,
+    ) -> Tuple[torch.Tensor, torch.Tensor, torch.Tensor, torch.Tensor, Tuple[torch.Tensor, torch.Tensor], Tuple[int, int]]:
+        """
+        Unpad the input tensors for flash attention.
+
+        Args:
+            query_layer: Query tensor of shape (batch_size, seq_len, num_heads, head_dim)
+            key_layer: Key tensor of shape (batch_size, seq_len, num_kv_heads, head_dim)
+            value_layer: Value tensor of shape (batch_size, seq_len, num_kv_heads, head_dim)
+            attention_mask: Attention mask tensor of shape (batch_size, seq_len)
+            query_length: Length of the query sequence
+            num_heads: Number of attention heads
+
+        Returns:
+            Tuple containing:
+                - Unpadded query tensor
+                - Unpadded key tensor
+                - Unpadded value tensor
+                - Query indices
+                - Tuple of cumulative sequence lengths for query and key
+                - Tuple of maximum sequence lengths for query and key
+        """
+        def _get_unpad_data(attention_mask: torch.Tensor) -> Tuple[torch.Tensor, torch.Tensor, int]:
+            """Helper function to get unpadding data from attention mask."""
+            seqlens_in_batch = attention_mask.sum(dim=-1, dtype=torch.int32)
+            indices = torch.nonzero(attention_mask.flatten(), as_tuple=False).flatten()
+            max_seqlen_in_batch = seqlens_in_batch.max().item()
+            cu_seqlens = F.pad(torch.cumsum(seqlens_in_batch, dim=0, dtype=torch.int32), (1, 0))
+            return indices, cu_seqlens, max_seqlen_in_batch
+
+        indices_k, cu_seqlens_k, max_seqlen_in_batch_k = _get_unpad_data(attention_mask)
+        batch_size, kv_seq_len, num_key_value_heads, head_dim = key_layer.shape
+
+        # Unpad key and value layers
+        key_layer = index_first_axis(
+            key_layer.reshape(batch_size * kv_seq_len, num_key_value_heads, head_dim),
+            indices_k,
+        )
+        value_layer = index_first_axis(
+            value_layer.reshape(batch_size * kv_seq_len, num_key_value_heads, head_dim),
+            indices_k,
+        )
+
+        # Handle different query length cases
+        if query_length == kv_seq_len:
+            query_layer = index_first_axis(
+                query_layer.reshape(batch_size * kv_seq_len, num_heads, head_dim),
+                indices_k,
+            )
+            cu_seqlens_q = cu_seqlens_k
+            max_seqlen_in_batch_q = max_seqlen_in_batch_k
+            indices_q = indices_k
+        elif query_length == 1:
+            max_seqlen_in_batch_q = 1
+            cu_seqlens_q = torch.arange(
+                batch_size + 1, dtype=torch.int32, device=query_layer.device
+            )
+            indices_q = cu_seqlens_q[:-1]
+            query_layer = query_layer.squeeze(1)
+        else:
+            attention_mask = attention_mask[:, -query_length:]
+            query_layer, indices_q, cu_seqlens_q, max_seqlen_in_batch_q = unpad_input(query_layer, attention_mask)
+
+        return (
+            query_layer,
+            key_layer,
+            value_layer,
+            indices_q,
+            (cu_seqlens_q, cu_seqlens_k),
+            (max_seqlen_in_batch_q, max_seqlen_in_batch_k),
+        )
+            
+    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,
+        base_sequence_length: Optional[int] = None,
+    ) -> torch.Tensor:
+        """
+        Process attention computation with flash attention.
+
+        Args:
+            attn: Attention module
+            hidden_states: Hidden states tensor of shape (batch_size, seq_len, hidden_dim)
+            encoder_hidden_states: Encoder hidden states tensor
+            attention_mask: Optional attention mask tensor
+            image_rotary_emb: Optional rotary embeddings for image tokens
+            base_sequence_length: Optional base sequence length for proportional attention
+
+        Returns:
+            torch.Tensor: Processed hidden states after attention computation
+        """
+        batch_size, sequence_length, _ = hidden_states.shape
+
+        # Get Query-Key-Value Pair
+        query = attn.to_q(hidden_states)
+        key = attn.to_k(encoder_hidden_states)
+        value = attn.to_v(encoder_hidden_states)
+
+        query_dim = query.shape[-1]
+        inner_dim = key.shape[-1]
+        head_dim = query_dim // attn.heads
+        dtype = query.dtype
+
+        # Get key-value heads
+        kv_heads = inner_dim // head_dim
+
+        # Reshape tensors for attention computation
+        query = query.view(batch_size, -1, attn.heads, head_dim)
+        key = key.view(batch_size, -1, kv_heads, head_dim)
+        value = value.view(batch_size, -1, kv_heads, head_dim)
+
+        # Apply Query-Key normalization
+        if attn.norm_q is not None:
+            query = attn.norm_q(query)
+        if attn.norm_k is not None:
+            key = attn.norm_k(key)
+
+        # Apply Rotary Position Embeddings
+        if image_rotary_emb is not None:
+            query = apply_rotary_emb(query, image_rotary_emb, use_real=False)
+            key = apply_rotary_emb(key, image_rotary_emb, use_real=False)
+
+        query, key = query.to(dtype), key.to(dtype)
+
+        # Calculate attention scale
+        if base_sequence_length is not None:
+            softmax_scale = math.sqrt(math.log(sequence_length, base_sequence_length)) * attn.scale
+        else:
+            softmax_scale = attn.scale
+
+        # Unpad input for flash attention
+        (
+            query_states,
+            key_states,
+            value_states,
+            indices_q,
+            cu_seq_lens,
+            max_seq_lens,
+        ) = self._upad_input(query, key, value, attention_mask, sequence_length, attn.heads)
+
+        cu_seqlens_q, cu_seqlens_k = cu_seq_lens
+        max_seqlen_in_batch_q, max_seqlen_in_batch_k = max_seq_lens
+
+        # Handle different number of heads
+        if kv_heads < attn.heads:
+            key_states = repeat(key_states, "l h c -> l (h k) c", k=attn.heads // kv_heads)
+            value_states = repeat(value_states, "l h c -> l (h k) c", k=attn.heads // kv_heads)
+
+        # Apply flash attention
+        attn_output_unpad = flash_attn_varlen_func(
+            query_states,
+            key_states,
+            value_states,
+            cu_seqlens_q=cu_seqlens_q,
+            cu_seqlens_k=cu_seqlens_k,
+            max_seqlen_q=max_seqlen_in_batch_q,
+            max_seqlen_k=max_seqlen_in_batch_k,
+            dropout_p=0.0,
+            causal=False,
+            softmax_scale=softmax_scale,
+        )
+
+        # Pad output and apply final transformations
+        hidden_states = pad_input(attn_output_unpad, indices_q, batch_size, sequence_length)
+        hidden_states = hidden_states.flatten(-2)
+        hidden_states = hidden_states.type_as(query)
+
+        # Apply output projection
+        hidden_states = attn.to_out[0](hidden_states)
+        hidden_states = attn.to_out[1](hidden_states)
+        
+        return hidden_states
+
+
+class OmniGen2AttnProcessor:
+    """
+    Processor for implementing scaled dot-product attention with flash attention and variable length sequences.
+    
+    This processor is optimized for PyTorch 2.0 and implements:
+    - Flash attention with variable length sequences
+    - Rotary position embeddings (RoPE)
+    - Query-Key normalization
+    - Proportional attention scaling
+    
+    Args:
+        None
+        
+    Raises:
+        ImportError: If PyTorch version is less than 2.0
+    """
+
+    def __init__(self) -> None:
+        """Initialize the attention processor."""
+        if not hasattr(F, "scaled_dot_product_attention"):
+            raise ImportError(
+                "OmniGen2AttnProcessorFlash2Varlen requires PyTorch 2.0. "
+                "Please upgrade PyTorch to version 2.0 or later."
+            )
+
+    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,
+        base_sequence_length: Optional[int] = None,
+    ) -> torch.Tensor:
+        """
+        Process attention computation with flash attention.
+
+        Args:
+            attn: Attention module
+            hidden_states: Hidden states tensor of shape (batch_size, seq_len, hidden_dim)
+            encoder_hidden_states: Encoder hidden states tensor
+            attention_mask: Optional attention mask tensor
+            image_rotary_emb: Optional rotary embeddings for image tokens
+            base_sequence_length: Optional base sequence length for proportional attention
+
+        Returns:
+            torch.Tensor: Processed hidden states after attention computation
+        """
+        batch_size, sequence_length, _ = hidden_states.shape
+
+        # Get Query-Key-Value Pair
+        query = attn.to_q(hidden_states)
+        key = attn.to_k(encoder_hidden_states)
+        value = attn.to_v(encoder_hidden_states)
+
+        query_dim = query.shape[-1]
+        inner_dim = key.shape[-1]
+        head_dim = query_dim // attn.heads
+        dtype = query.dtype
+
+        # Get key-value heads
+        kv_heads = inner_dim // head_dim
+
+        # Reshape tensors for attention computation
+        query = query.view(batch_size, -1, attn.heads, head_dim)
+        key = key.view(batch_size, -1, kv_heads, head_dim)
+        value = value.view(batch_size, -1, kv_heads, head_dim)
+
+        # Apply Query-Key normalization
+        if attn.norm_q is not None:
+            query = attn.norm_q(query)
+        if attn.norm_k is not None:
+            key = attn.norm_k(key)
+
+        # Apply Rotary Position Embeddings
+        if image_rotary_emb is not None:
+            query = apply_rotary_emb(query, image_rotary_emb, use_real=False)
+            key = apply_rotary_emb(key, image_rotary_emb, use_real=False)
+
+        query, key = query.to(dtype), key.to(dtype)
+
+        # Calculate attention scale
+        if base_sequence_length is not None:
+            softmax_scale = math.sqrt(math.log(sequence_length, base_sequence_length)) * attn.scale
+        else:
+            softmax_scale = attn.scale
+
+        # scaled_dot_product_attention expects attention_mask shape to be
+        # (batch, heads, source_length, target_length)
+        if attention_mask is not None:
+            attention_mask = attention_mask.bool().view(batch_size, 1, 1, -1)
+
+        query = query.transpose(1, 2)
+        key = key.transpose(1, 2)
+        value = value.transpose(1, 2)
+        
+        # explicitly repeat key and value to match query length, otherwise using enable_gqa=True results in MATH backend of sdpa in our test of pytorch2.6
+        key = key.repeat_interleave(query.size(-3) // key.size(-3), -3)
+        value = value.repeat_interleave(query.size(-3) // value.size(-3), -3)
+
+        hidden_states = F.scaled_dot_product_attention(
+            query, key, value, attn_mask=attention_mask, scale=softmax_scale
+        )
+        hidden_states = hidden_states.transpose(1, 2).reshape(batch_size, -1, attn.heads * head_dim)
+        hidden_states = hidden_states.type_as(query)
+
+        # Apply output projection
+        hidden_states = attn.to_out[0](hidden_states)
+        hidden_states = attn.to_out[1](hidden_states)
+        
+        return hidden_states

extensions_built_in/diffusion_models/omnigen2/src/models/embeddings.py

@@ -0,0 +1,126 @@
+# 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.
+from typing import List, Optional, Tuple, Union
+
+import torch
+from torch import nn
+
+
+from diffusers.models.activations import get_activation
+
+
+class TimestepEmbedding(nn.Module):
+    def __init__(
+        self,
+        in_channels: int,
+        time_embed_dim: int,
+        act_fn: str = "silu",
+        out_dim: int = None,
+        post_act_fn: Optional[str] = None,
+        cond_proj_dim=None,
+        sample_proj_bias=True,
+    ):
+        super().__init__()
+
+        self.linear_1 = nn.Linear(in_channels, time_embed_dim, sample_proj_bias)
+
+        if cond_proj_dim is not None:
+            self.cond_proj = nn.Linear(cond_proj_dim, in_channels, bias=False)
+        else:
+            self.cond_proj = None
+
+        self.act = get_activation(act_fn)
+
+        if out_dim is not None:
+            time_embed_dim_out = out_dim
+        else:
+            time_embed_dim_out = time_embed_dim
+        self.linear_2 = nn.Linear(time_embed_dim, time_embed_dim_out, sample_proj_bias)
+
+        if post_act_fn is None:
+            self.post_act = None
+        else:
+            self.post_act = get_activation(post_act_fn)
+
+        self.initialize_weights()
+        
+    def initialize_weights(self):
+        nn.init.normal_(self.linear_1.weight, std=0.02)
+        nn.init.zeros_(self.linear_1.bias)
+        nn.init.normal_(self.linear_2.weight, std=0.02)
+        nn.init.zeros_(self.linear_2.bias)
+        
+    def forward(self, sample, condition=None):
+        if condition is not None:
+            sample = sample + self.cond_proj(condition)
+        sample = self.linear_1(sample)
+
+        if self.act is not None:
+            sample = self.act(sample)
+
+        sample = self.linear_2(sample)
+
+        if self.post_act is not None:
+            sample = self.post_act(sample)
+        return sample
+
+
+def apply_rotary_emb(
+    x: torch.Tensor,
+    freqs_cis: Union[torch.Tensor, Tuple[torch.Tensor]],
+    use_real: bool = True,
+    use_real_unbind_dim: int = -1,
+) -> Tuple[torch.Tensor, torch.Tensor]:
+    """
+    Apply rotary embeddings to input tensors using the given frequency tensor. This function applies rotary embeddings
+    to the given query or key 'x' tensors using the provided frequency tensor 'freqs_cis'. The input tensors are
+    reshaped as complex numbers, and the frequency tensor is reshaped for broadcasting compatibility. The resulting
+    tensors contain rotary embeddings and are returned as real tensors.
+
+    Args:
+        x (`torch.Tensor`):
+            Query or key tensor to apply rotary embeddings. [B, H, S, D] xk (torch.Tensor): Key tensor to apply
+        freqs_cis (`Tuple[torch.Tensor]`): Precomputed frequency tensor for complex exponentials. ([S, D], [S, D],)
+
+    Returns:
+        Tuple[torch.Tensor, torch.Tensor]: Tuple of modified query tensor and key tensor with rotary embeddings.
+    """
+    if use_real:
+        cos, sin = freqs_cis  # [S, D]
+        cos = cos[None, None]
+        sin = sin[None, None]
+        cos, sin = cos.to(x.device), sin.to(x.device)
+
+        if use_real_unbind_dim == -1:
+            # Used for flux, cogvideox, hunyuan-dit
+            x_real, x_imag = x.reshape(*x.shape[:-1], -1, 2).unbind(-1)  # [B, S, H, D//2]
+            x_rotated = torch.stack([-x_imag, x_real], dim=-1).flatten(3)
+        elif use_real_unbind_dim == -2:
+            # Used for Stable Audio, OmniGen and CogView4
+            x_real, x_imag = x.reshape(*x.shape[:-1], 2, -1).unbind(-2)  # [B, S, H, D//2]
+            x_rotated = torch.cat([-x_imag, x_real], dim=-1)
+        else:
+            raise ValueError(f"`use_real_unbind_dim={use_real_unbind_dim}` but should be -1 or -2.")
+
+        out = (x.float() * cos + x_rotated.float() * sin).to(x.dtype)
+
+        return out
+    else:
+        # used for lumina
+        # x_rotated = torch.view_as_complex(x.float().reshape(*x.shape[:-1], -1, 2))
+        x_rotated = torch.view_as_complex(x.float().reshape(*x.shape[:-1], x.shape[-1] // 2, 2))
+        freqs_cis = freqs_cis.unsqueeze(2)
+        x_out = torch.view_as_real(x_rotated * freqs_cis).flatten(3)
+
+        return x_out.type_as(x)

extensions_built_in/diffusion_models/omnigen2/src/models/transformers/__init__.py

@@ -0,0 +1,3 @@
+from .transformer_omnigen2 import OmniGen2Transformer2DModel
+
+__all__ = ["OmniGen2Transformer2DModel"]

extensions_built_in/diffusion_models/omnigen2/src/models/transformers/block_lumina2.py

@@ -0,0 +1,218 @@
+
+# Copyright 2024 Alpha-VLLM Authors 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.
+
+import warnings
+from typing import Optional, Tuple
+
+import torch
+import torch.nn as nn
+
+from diffusers.models.embeddings import Timesteps
+from ..embeddings import TimestepEmbedding
+
+from ...utils.import_utils import is_flash_attn_available, is_triton_available
+
+if is_triton_available():
+    from ...ops.triton.layer_norm import RMSNorm
+else:
+    from torch.nn import RMSNorm
+    warnings.warn("Cannot import triton, install triton to use fused RMSNorm for better performance")
+    
+if is_flash_attn_available():
+    from flash_attn.ops.activations import swiglu
+else:
+    from .components import swiglu
+    warnings.warn("Cannot import flash_attn, install flash_attn to use fused SwiGLU for better performance")
+
+# try:
+#     from flash_attn.ops.activations import swiglu as fused_swiglu
+#     FUSEDSWIGLU_AVALIBLE = True
+# except ImportError:
+    
+#     FUSEDSWIGLU_AVALIBLE = False
+#     warnings.warn("Cannot import apex RMSNorm, switch to vanilla implementation")
+        
+class LuminaRMSNormZero(nn.Module):
+    """
+    Norm layer adaptive RMS normalization zero.
+
+    Parameters:
+        embedding_dim (`int`): The size of each embedding vector.
+    """
+
+    def __init__(
+        self,
+        embedding_dim: int,
+        norm_eps: float,
+        norm_elementwise_affine: bool,
+    ):
+        super().__init__()
+        self.silu = nn.SiLU()
+        self.linear = nn.Linear(
+            min(embedding_dim, 1024),
+            4 * embedding_dim,
+            bias=True,
+        )
+        
+        self.norm = RMSNorm(embedding_dim, eps=norm_eps)
+
+    def forward(
+        self,
+        x: torch.Tensor,
+        emb: Optional[torch.Tensor] = None,
+    ) -> 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)
+        x = self.norm(x) * (1 + scale_msa[:, None])
+        return x, gate_msa, scale_mlp, gate_mlp
+    
+
+class LuminaLayerNormContinuous(nn.Module):
+    def __init__(
+        self,
+        embedding_dim: int,
+        conditioning_embedding_dim: int,
+        # NOTE: It is a bit weird that the norm layer can be configured to have scale and shift parameters
+        # because the output is immediately scaled and shifted by the projected conditioning embeddings.
+        # Note that AdaLayerNorm does not let the norm layer have scale and shift parameters.
+        # However, this is how it was implemented in the original code, and it's rather likely you should
+        # set `elementwise_affine` to False.
+        elementwise_affine=True,
+        eps=1e-5,
+        bias=True,
+        norm_type="layer_norm",
+        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 = nn.LayerNorm(embedding_dim, eps, elementwise_affine, bias)
+        elif norm_type == "rms_norm":
+            self.norm = RMSNorm(embedding_dim, eps=eps, elementwise_affine=elementwise_affine)
+        else:
+            raise ValueError(f"unknown norm_type {norm_type}")
+
+        self.linear_2 = None
+        if out_dim is not None:
+            self.linear_2 = nn.Linear(embedding_dim, out_dim, bias=bias)
+
+    def forward(
+        self,
+        x: torch.Tensor,
+        conditioning_embedding: torch.Tensor,
+    ) -> torch.Tensor:
+        # convert back to the original dtype in case `conditioning_embedding`` is upcasted to float32 (needed for hunyuanDiT)
+        emb = self.linear_1(self.silu(conditioning_embedding).to(x.dtype))
+        scale = emb
+        x = self.norm(x) * (1 + scale)[:, None, :]
+
+        if self.linear_2 is not None:
+            x = self.linear_2(x)
+
+        return x
+    
+
+class LuminaFeedForward(nn.Module):
+    r"""
+    A feed-forward layer.
+
+    Parameters:
+        hidden_size (`int`):
+            The dimensionality of the hidden layers in the model. This parameter determines the width of the model's
+            hidden representations.
+        intermediate_size (`int`): The intermediate dimension of the feedforward layer.
+        multiple_of (`int`, *optional*): Value to ensure hidden dimension is a multiple
+            of this value.
+        ffn_dim_multiplier (float, *optional*): Custom multiplier for hidden
+            dimension. Defaults to None.
+    """
+
+    def __init__(
+        self,
+        dim: int,
+        inner_dim: int,
+        multiple_of: Optional[int] = 256,
+        ffn_dim_multiplier: Optional[float] = None,
+    ):
+        super().__init__()
+        self.swiglu = swiglu
+        
+        # custom hidden_size factor multiplier
+        if ffn_dim_multiplier is not None:
+            inner_dim = int(ffn_dim_multiplier * inner_dim)
+        inner_dim = multiple_of * ((inner_dim + multiple_of - 1) // multiple_of)
+
+        self.linear_1 = nn.Linear(
+            dim,
+            inner_dim,
+            bias=False,
+        )
+        self.linear_2 = nn.Linear(
+            inner_dim,
+            dim,
+            bias=False,
+        )
+        self.linear_3 = nn.Linear(
+            dim,
+            inner_dim,
+            bias=False,
+        )
+
+    def forward(self, x):
+        h1, h2 = self.linear_1(x), self.linear_3(x)
+        return self.linear_2(self.swiglu(h1, h2))
+
+
+class Lumina2CombinedTimestepCaptionEmbedding(nn.Module):
+    def __init__(
+        self,
+        hidden_size: int = 4096,
+        text_feat_dim: int = 2048,
+        frequency_embedding_size: int = 256,
+        norm_eps: float = 1e-5,
+        timestep_scale: float = 1.0,
+    ) -> None:
+        super().__init__()
+
+        self.time_proj = Timesteps(
+            num_channels=frequency_embedding_size, flip_sin_to_cos=True, downscale_freq_shift=0.0, scale=timestep_scale
+        )
+
+        self.timestep_embedder = TimestepEmbedding(
+            in_channels=frequency_embedding_size, time_embed_dim=min(hidden_size, 1024)
+        )
+
+        self.caption_embedder = nn.Sequential(
+            RMSNorm(text_feat_dim, eps=norm_eps),
+            nn.Linear(text_feat_dim, hidden_size, bias=True),
+        )
+        
+        self._initialize_weights()
+
+    def _initialize_weights(self):
+        nn.init.trunc_normal_(self.caption_embedder[1].weight, std=0.02)
+        nn.init.zeros_(self.caption_embedder[1].bias)
+
+    def forward(
+        self, timestep: torch.Tensor, text_hidden_states: torch.Tensor, dtype: torch.dtype
+    ) -> Tuple[torch.Tensor, torch.Tensor]:
+        timestep_proj = self.time_proj(timestep).to(dtype=dtype)
+        time_embed = self.timestep_embedder(timestep_proj)
+        caption_embed = self.caption_embedder(text_hidden_states)
+        return time_embed, caption_embed

extensions_built_in/diffusion_models/omnigen2/src/models/transformers/components.py

@@ -0,0 +1,4 @@
+import torch.nn.functional as F
+
+def swiglu(x, y):
+    return F.silu(x.float(), inplace=False).to(x.dtype) * y

extensions_built_in/diffusion_models/omnigen2/src/models/transformers/repo.py

@@ -0,0 +1,135 @@
+from typing import List, Tuple
+
+import torch
+import torch.nn as nn
+
+from einops import repeat
+from diffusers.models.embeddings import get_1d_rotary_pos_embed
+
+class OmniGen2RotaryPosEmbed(nn.Module):
+    def __init__(self, theta: int,
+                 axes_dim: Tuple[int, int, int],
+                 axes_lens: Tuple[int, int, int] = (300, 512, 512),
+                 patch_size: int = 2):
+        super().__init__()
+        self.theta = theta
+        self.axes_dim = axes_dim
+        self.axes_lens = axes_lens
+        self.patch_size = patch_size
+
+    @staticmethod
+    def get_freqs_cis(axes_dim: Tuple[int, int, int],
+                      axes_lens: Tuple[int, int, int],
+                      theta: int) -> List[torch.Tensor]:
+        freqs_cis = []
+        freqs_dtype = torch.float32 if torch.backends.mps.is_available() else torch.float64
+        for i, (d, e) in enumerate(zip(axes_dim, axes_lens)):
+            emb = get_1d_rotary_pos_embed(d, e, theta=theta, freqs_dtype=freqs_dtype)
+            freqs_cis.append(emb)
+        return freqs_cis
+
+    def _get_freqs_cis(self, freqs_cis, ids: torch.Tensor) -> torch.Tensor:
+        device = ids.device
+        if ids.device.type == "mps":
+            ids = ids.to("cpu")
+
+        result = []
+        for i in range(len(self.axes_dim)):
+            freqs = freqs_cis[i].to(ids.device)
+            index = ids[:, :, i : i + 1].repeat(1, 1, freqs.shape[-1]).to(torch.int64)
+            result.append(torch.gather(freqs.unsqueeze(0).repeat(index.shape[0], 1, 1), dim=1, index=index))
+        return torch.cat(result, dim=-1).to(device)
+
+    def forward(
+        self,
+        freqs_cis,
+        attention_mask,
+        l_effective_ref_img_len,
+        l_effective_img_len,
+        ref_img_sizes,
+        img_sizes,
+        device
+    ):
+        batch_size = len(attention_mask)
+        p = self.patch_size
+
+        encoder_seq_len = attention_mask.shape[1]
+        l_effective_cap_len = attention_mask.sum(dim=1).tolist()
+
+        seq_lengths = [cap_len + sum(ref_img_len) + img_len for cap_len, ref_img_len, img_len in zip(l_effective_cap_len, l_effective_ref_img_len, l_effective_img_len)]
+
+        max_seq_len = int(max(seq_lengths))
+        max_ref_img_len = max([sum(ref_img_len) for ref_img_len in l_effective_ref_img_len])
+        max_img_len = max(l_effective_img_len)
+
+        # Create position IDs
+        position_ids = torch.zeros(batch_size, max_seq_len, 3, dtype=torch.int32, device=device)
+
+        for i, (cap_seq_len, seq_len) in enumerate(zip(l_effective_cap_len, seq_lengths)):
+            cap_seq_len = int(cap_seq_len)
+            seq_len = int(seq_len)
+            # add text position ids
+            position_ids[i, :cap_seq_len] = repeat(torch.arange(cap_seq_len, dtype=torch.int32, device=device), "l -> l 3")
+
+            pe_shift = cap_seq_len
+            pe_shift_len = cap_seq_len
+
+            if ref_img_sizes[i] is not None:
+                for ref_img_size, ref_img_len in zip(ref_img_sizes[i], l_effective_ref_img_len[i]):
+                    H, W = ref_img_size
+                    ref_H_tokens, ref_W_tokens = H // p, W // p
+                    assert ref_H_tokens * ref_W_tokens == ref_img_len
+                    # add image position ids
+
+                    row_ids = repeat(torch.arange(ref_H_tokens, dtype=torch.int32, device=device), "h -> h w", w=ref_W_tokens).flatten()
+                    col_ids = repeat(torch.arange(ref_W_tokens, dtype=torch.int32, device=device), "w -> h w", h=ref_H_tokens).flatten()
+                    position_ids[i, pe_shift_len:pe_shift_len + ref_img_len, 0] = pe_shift
+                    position_ids[i, pe_shift_len:pe_shift_len + ref_img_len, 1] = row_ids
+                    position_ids[i, pe_shift_len:pe_shift_len + ref_img_len, 2] = col_ids
+
+                    pe_shift += max(ref_H_tokens, ref_W_tokens)
+                    pe_shift_len += ref_img_len
+
+            H, W = img_sizes[i]
+            H_tokens, W_tokens = H // p, W // p
+            assert H_tokens * W_tokens == l_effective_img_len[i]
+
+            row_ids = repeat(torch.arange(H_tokens, dtype=torch.int32, device=device), "h -> h w", w=W_tokens).flatten()
+            col_ids = repeat(torch.arange(W_tokens, dtype=torch.int32, device=device), "w -> h w", h=H_tokens).flatten()
+
+            assert pe_shift_len + l_effective_img_len[i] == seq_len
+            position_ids[i, pe_shift_len: seq_len, 0] = pe_shift
+            position_ids[i, pe_shift_len: seq_len, 1] = row_ids
+            position_ids[i, pe_shift_len: seq_len, 2] = col_ids
+
+        # Get combined rotary embeddings
+        freqs_cis = self._get_freqs_cis(freqs_cis, position_ids)
+        
+        # create separate rotary embeddings for captions and images
+        cap_freqs_cis = torch.zeros(
+            batch_size, encoder_seq_len, freqs_cis.shape[-1], device=device, dtype=freqs_cis.dtype
+        )
+        ref_img_freqs_cis = torch.zeros(
+            batch_size, max_ref_img_len, freqs_cis.shape[-1], device=device, dtype=freqs_cis.dtype
+        )
+        img_freqs_cis = torch.zeros(
+            batch_size, max_img_len, freqs_cis.shape[-1], device=device, dtype=freqs_cis.dtype
+        )
+
+        for i, (cap_seq_len, ref_img_len, img_len, seq_len) in enumerate(zip(l_effective_cap_len, l_effective_ref_img_len, l_effective_img_len, seq_lengths)):
+            cap_seq_len = int(cap_seq_len)
+            sum_ref_img_len = int(sum(ref_img_len))
+            img_len = int(img_len)
+            seq_len = int(seq_len)
+            cap_freqs_cis[i, :cap_seq_len] = freqs_cis[i, :cap_seq_len]
+            ref_img_freqs_cis[i, :sum_ref_img_len] = freqs_cis[i, cap_seq_len:cap_seq_len + sum_ref_img_len]
+            img_freqs_cis[i, :img_len] = freqs_cis[i, cap_seq_len + sum_ref_img_len:cap_seq_len + sum_ref_img_len + img_len]
+
+        return (
+            cap_freqs_cis,
+            ref_img_freqs_cis,
+            img_freqs_cis,
+            freqs_cis,
+            l_effective_cap_len,
+            seq_lengths,
+        )

extensions_built_in/diffusion_models/omnigen2/src/models/transformers/transformer_omnigen2.py

@@ -0,0 +1,621 @@
+import warnings
+import itertools
+from typing import Any, Dict, List, Optional, Tuple, Union
+
+import torch
+import torch.nn as nn
+
+from einops import rearrange
+
+from diffusers.configuration_utils import ConfigMixin, register_to_config
+from diffusers.loaders import PeftAdapterMixin
+from diffusers.loaders.single_file_model import FromOriginalModelMixin
+from diffusers.utils import USE_PEFT_BACKEND, logging, scale_lora_layers, unscale_lora_layers
+from diffusers.models.attention_processor import Attention
+from diffusers.models.modeling_outputs import Transformer2DModelOutput
+from diffusers.models.modeling_utils import ModelMixin
+
+from ..attention_processor import OmniGen2AttnProcessorFlash2Varlen, OmniGen2AttnProcessor
+from .repo import OmniGen2RotaryPosEmbed
+from .block_lumina2 import LuminaLayerNormContinuous, LuminaRMSNormZero, LuminaFeedForward, Lumina2CombinedTimestepCaptionEmbedding
+
+from ...utils.import_utils import is_triton_available, is_flash_attn_available
+
+if is_triton_available():
+    from ...ops.triton.layer_norm import RMSNorm
+else:
+    from torch.nn import RMSNorm
+
+logger = logging.get_logger(__name__)
+
+
+class OmniGen2TransformerBlock(nn.Module):
+    """
+    Transformer block for OmniGen2 model.
+    
+    This block implements a transformer layer with:
+    - Multi-head attention with flash attention
+    - Feed-forward network with SwiGLU activation
+    - RMS normalization
+    - Optional modulation for conditional generation
+    
+    Args:
+        dim: Dimension of the input and output tensors
+        num_attention_heads: Number of attention heads
+        num_kv_heads: Number of key-value heads
+        multiple_of: Multiple of which the hidden dimension should be
+        ffn_dim_multiplier: Multiplier for the feed-forward network dimension
+        norm_eps: Epsilon value for normalization layers
+        modulation: Whether to use modulation for conditional generation
+        use_fused_rms_norm: Whether to use fused RMS normalization
+        use_fused_swiglu: Whether to use fused SwiGLU activation
+    """
+
+    def __init__(
+        self,
+        dim: int,
+        num_attention_heads: int,
+        num_kv_heads: int,
+        multiple_of: int,
+        ffn_dim_multiplier: float,
+        norm_eps: float,
+        modulation: bool = True,
+    ) -> None:
+        """Initialize the transformer block."""
+        super().__init__()
+        self.head_dim = dim // num_attention_heads
+        self.modulation = modulation
+
+        try:
+            processor = OmniGen2AttnProcessorFlash2Varlen()
+        except ImportError:
+            processor = OmniGen2AttnProcessor()
+
+        # Initialize attention layer
+        self.attn = Attention(
+            query_dim=dim,
+            cross_attention_dim=None,
+            dim_head=dim // num_attention_heads,
+            qk_norm="rms_norm",
+            heads=num_attention_heads,
+            kv_heads=num_kv_heads,
+            eps=1e-5,
+            bias=False,
+            out_bias=False,
+            processor=processor,
+        )
+
+        # Initialize feed-forward network
+        self.feed_forward = LuminaFeedForward(
+            dim=dim,
+            inner_dim=4 * dim,
+            multiple_of=multiple_of,
+            ffn_dim_multiplier=ffn_dim_multiplier
+        )
+
+        # Initialize normalization layers
+        if modulation:
+            self.norm1 = LuminaRMSNormZero(
+                embedding_dim=dim,
+                norm_eps=norm_eps,
+                norm_elementwise_affine=True
+            )
+        else:
+            self.norm1 = RMSNorm(dim, eps=norm_eps)
+
+        self.ffn_norm1 = RMSNorm(dim, eps=norm_eps)
+        self.norm2 = RMSNorm(dim, eps=norm_eps)
+        self.ffn_norm2 = RMSNorm(dim, eps=norm_eps)
+
+        self.initialize_weights()
+
+    def initialize_weights(self) -> None:
+        """
+        Initialize the weights of the transformer block.
+        
+        Uses Xavier uniform initialization for linear layers and zero initialization for biases.
+        """
+        nn.init.xavier_uniform_(self.attn.to_q.weight)
+        nn.init.xavier_uniform_(self.attn.to_k.weight)
+        nn.init.xavier_uniform_(self.attn.to_v.weight)
+        nn.init.xavier_uniform_(self.attn.to_out[0].weight)
+
+        nn.init.xavier_uniform_(self.feed_forward.linear_1.weight)
+        nn.init.xavier_uniform_(self.feed_forward.linear_2.weight)
+        nn.init.xavier_uniform_(self.feed_forward.linear_3.weight)
+        
+        if self.modulation:
+            nn.init.zeros_(self.norm1.linear.weight)
+            nn.init.zeros_(self.norm1.linear.bias)
+
+    def forward(
+        self,
+        hidden_states: torch.Tensor,
+        attention_mask: torch.Tensor,
+        image_rotary_emb: torch.Tensor,
+        temb: Optional[torch.Tensor] = None,
+    ) -> torch.Tensor:
+        """
+        Forward pass of the transformer block.
+
+        Args:
+            hidden_states: Input hidden states tensor
+            attention_mask: Attention mask tensor
+            image_rotary_emb: Rotary embeddings for image tokens
+            temb: Optional timestep embedding tensor
+
+        Returns:
+            torch.Tensor: Output hidden states after transformer block processing
+        """
+        import time
+        if self.modulation:
+            if temb is None:
+                raise ValueError("temb must be provided when modulation is enabled")
+                
+            norm_hidden_states, gate_msa, scale_mlp, gate_mlp = self.norm1(hidden_states, temb)
+            attn_output = self.attn(
+                hidden_states=norm_hidden_states,
+                encoder_hidden_states=norm_hidden_states,
+                attention_mask=attention_mask,
+                image_rotary_emb=image_rotary_emb,
+            )
+            hidden_states = hidden_states + gate_msa.unsqueeze(1).tanh() * self.norm2(attn_output)
+            mlp_output = self.feed_forward(self.ffn_norm1(hidden_states) * (1 + scale_mlp.unsqueeze(1)))
+            hidden_states = hidden_states + gate_mlp.unsqueeze(1).tanh() * self.ffn_norm2(mlp_output)
+        else:
+            norm_hidden_states = self.norm1(hidden_states)
+            attn_output = self.attn(
+                hidden_states=norm_hidden_states,
+                encoder_hidden_states=norm_hidden_states,
+                attention_mask=attention_mask,
+                image_rotary_emb=image_rotary_emb,
+            )
+            hidden_states = hidden_states + self.norm2(attn_output)
+            mlp_output = self.feed_forward(self.ffn_norm1(hidden_states))
+            hidden_states = hidden_states + self.ffn_norm2(mlp_output)
+
+        return hidden_states
+
+
+class OmniGen2Transformer2DModel(ModelMixin, ConfigMixin, PeftAdapterMixin, FromOriginalModelMixin):
+    """
+    OmniGen2 Transformer 2D Model.
+    
+    A transformer-based diffusion model for image generation with:
+    - Patch-based image processing
+    - Rotary position embeddings
+    - Multi-head attention
+    - Conditional generation support
+    
+    Args:
+        patch_size: Size of image patches
+        in_channels: Number of input channels
+        out_channels: Number of output channels (defaults to in_channels)
+        hidden_size: Size of hidden layers
+        num_layers: Number of transformer layers
+        num_refiner_layers: Number of refiner layers
+        num_attention_heads: Number of attention heads
+        num_kv_heads: Number of key-value heads
+        multiple_of: Multiple of which the hidden dimension should be
+        ffn_dim_multiplier: Multiplier for feed-forward network dimension
+        norm_eps: Epsilon value for normalization layers
+        axes_dim_rope: Dimensions for rotary position embeddings
+        axes_lens: Lengths for rotary position embeddings
+        text_feat_dim: Dimension of text features
+        timestep_scale: Scale factor for timestep embeddings
+        use_fused_rms_norm: Whether to use fused RMS normalization
+        use_fused_swiglu: Whether to use fused SwiGLU activation
+    """
+
+    _supports_gradient_checkpointing = True
+    _no_split_modules = ["Omnigen2TransformerBlock"]
+    _skip_layerwise_casting_patterns = ["x_embedder", "norm"]
+
+    @register_to_config
+    def __init__(
+        self,
+        patch_size: int = 2,
+        in_channels: int = 16,
+        out_channels: Optional[int] = None,
+        hidden_size: int = 2304,
+        num_layers: int = 26,
+        num_refiner_layers: int = 2,
+        num_attention_heads: int = 24,
+        num_kv_heads: int = 8,
+        multiple_of: int = 256,
+        ffn_dim_multiplier: Optional[float] = None,
+        norm_eps: float = 1e-5,
+        axes_dim_rope: Tuple[int, int, int] = (32, 32, 32),
+        axes_lens: Tuple[int, int, int] = (300, 512, 512),
+        text_feat_dim: int = 1024,
+        timestep_scale: float = 1.0
+    ) -> None:
+        """Initialize the OmniGen2 transformer model."""
+        super().__init__()
+
+        # Validate configuration
+        if (hidden_size // num_attention_heads) != sum(axes_dim_rope):
+            raise ValueError(
+                f"hidden_size // num_attention_heads ({hidden_size // num_attention_heads}) "
+                f"must equal sum(axes_dim_rope) ({sum(axes_dim_rope)})"
+            )
+        
+        self.out_channels = out_channels or in_channels
+
+        # Initialize embeddings
+        self.rope_embedder = OmniGen2RotaryPosEmbed(
+            theta=10000,
+            axes_dim=axes_dim_rope,
+            axes_lens=axes_lens,
+            patch_size=patch_size,
+        )
+
+        self.x_embedder = nn.Linear(
+            in_features=patch_size * patch_size * in_channels,
+            out_features=hidden_size,
+        )
+
+        self.ref_image_patch_embedder = nn.Linear(
+            in_features=patch_size * patch_size * in_channels,
+            out_features=hidden_size,
+        )
+
+        self.time_caption_embed = Lumina2CombinedTimestepCaptionEmbedding(
+            hidden_size=hidden_size,
+            text_feat_dim=text_feat_dim,
+            norm_eps=norm_eps,
+            timestep_scale=timestep_scale
+        )
+
+        # Initialize transformer blocks
+        self.noise_refiner = nn.ModuleList([
+            OmniGen2TransformerBlock(
+                hidden_size,
+                num_attention_heads,
+                num_kv_heads,
+                multiple_of,
+                ffn_dim_multiplier,
+                norm_eps,
+                modulation=True
+            )
+            for _ in range(num_refiner_layers)
+        ])
+
+        self.ref_image_refiner = nn.ModuleList([
+            OmniGen2TransformerBlock(
+                hidden_size,
+                num_attention_heads,
+                num_kv_heads,
+                multiple_of,
+                ffn_dim_multiplier,
+                norm_eps,
+                modulation=True
+            )
+            for _ in range(num_refiner_layers)
+        ])
+
+        self.context_refiner = nn.ModuleList(
+            [
+                OmniGen2TransformerBlock(
+                    hidden_size,
+                    num_attention_heads,
+                    num_kv_heads,
+                    multiple_of,
+                    ffn_dim_multiplier,
+                    norm_eps,
+                    modulation=False
+                )
+                for _ in range(num_refiner_layers)
+            ]
+        )
+
+        # 3. Transformer blocks
+        self.layers = nn.ModuleList(
+            [
+                OmniGen2TransformerBlock(
+                    hidden_size,
+                    num_attention_heads,
+                    num_kv_heads,
+                    multiple_of,
+                    ffn_dim_multiplier,
+                    norm_eps,
+                    modulation=True
+                )
+                for _ in range(num_layers)
+            ]
+        )
+
+        # 4. Output norm & projection
+        self.norm_out = LuminaLayerNormContinuous(
+            embedding_dim=hidden_size,
+            conditioning_embedding_dim=min(hidden_size, 1024),
+            elementwise_affine=False,
+            eps=1e-6,
+            bias=True,
+            out_dim=patch_size * patch_size * self.out_channels
+        )
+        
+        # Add learnable embeddings to distinguish different images
+        self.image_index_embedding = nn.Parameter(torch.randn(5, hidden_size)) # support max 5 ref images
+
+        self.gradient_checkpointing = False
+
+        self.initialize_weights()
+
+    def initialize_weights(self) -> None:
+        """
+        Initialize the weights of the model.
+        
+        Uses Xavier uniform initialization for linear layers.
+        """
+        nn.init.xavier_uniform_(self.x_embedder.weight)
+        nn.init.constant_(self.x_embedder.bias, 0.0)
+
+        nn.init.xavier_uniform_(self.ref_image_patch_embedder.weight)
+        nn.init.constant_(self.ref_image_patch_embedder.bias, 0.0)
+
+        nn.init.zeros_(self.norm_out.linear_1.weight)
+        nn.init.zeros_(self.norm_out.linear_1.bias)
+        nn.init.zeros_(self.norm_out.linear_2.weight)
+        nn.init.zeros_(self.norm_out.linear_2.bias)
+        
+        nn.init.normal_(self.image_index_embedding, std=0.02)
+
+    def img_patch_embed_and_refine(
+        self,
+        hidden_states,
+        ref_image_hidden_states,
+        padded_img_mask,
+        padded_ref_img_mask,
+        noise_rotary_emb,
+        ref_img_rotary_emb,
+        l_effective_ref_img_len,
+        l_effective_img_len,
+        temb
+    ):
+        batch_size = len(hidden_states)
+        max_combined_img_len = max([img_len + sum(ref_img_len) for img_len, ref_img_len in zip(l_effective_img_len, l_effective_ref_img_len)])
+    
+        hidden_states = self.x_embedder(hidden_states)
+        ref_image_hidden_states = self.ref_image_patch_embedder(ref_image_hidden_states)
+        
+        for i in range(batch_size):
+            shift = 0
+            for j, ref_img_len in enumerate(l_effective_ref_img_len[i]):
+                ref_image_hidden_states[i, shift:shift + ref_img_len, :] = ref_image_hidden_states[i, shift:shift + ref_img_len, :] + self.image_index_embedding[j]
+                shift += ref_img_len
+
+        for layer in self.noise_refiner:
+            hidden_states = layer(hidden_states, padded_img_mask, noise_rotary_emb, temb)
+
+        flat_l_effective_ref_img_len = list(itertools.chain(*l_effective_ref_img_len))
+        num_ref_images = len(flat_l_effective_ref_img_len)
+        max_ref_img_len = max(flat_l_effective_ref_img_len)
+
+        batch_ref_img_mask = ref_image_hidden_states.new_zeros(num_ref_images, max_ref_img_len, dtype=torch.bool)
+        batch_ref_image_hidden_states = ref_image_hidden_states.new_zeros(num_ref_images, max_ref_img_len, self.config.hidden_size)
+        batch_ref_img_rotary_emb = hidden_states.new_zeros(num_ref_images, max_ref_img_len, ref_img_rotary_emb.shape[-1], dtype=ref_img_rotary_emb.dtype)
+        batch_temb = temb.new_zeros(num_ref_images, *temb.shape[1:], dtype=temb.dtype)
+
+        # sequence of ref imgs to batch
+        idx = 0
+        for i in range(batch_size):
+            shift = 0
+            for ref_img_len in l_effective_ref_img_len[i]:
+                batch_ref_img_mask[idx, :ref_img_len] = True
+                batch_ref_image_hidden_states[idx, :ref_img_len] = ref_image_hidden_states[i, shift:shift + ref_img_len]
+                batch_ref_img_rotary_emb[idx, :ref_img_len] = ref_img_rotary_emb[i, shift:shift + ref_img_len]
+                batch_temb[idx] = temb[i]
+                shift += ref_img_len
+                idx += 1
+
+        # refine ref imgs separately
+        for layer in self.ref_image_refiner:
+            batch_ref_image_hidden_states = layer(batch_ref_image_hidden_states, batch_ref_img_mask, batch_ref_img_rotary_emb, batch_temb)
+
+        # batch of ref imgs to sequence
+        idx = 0
+        for i in range(batch_size):
+            shift = 0
+            for ref_img_len in l_effective_ref_img_len[i]:
+                ref_image_hidden_states[i, shift:shift + ref_img_len] = batch_ref_image_hidden_states[idx, :ref_img_len]
+                shift += ref_img_len
+                idx += 1
+            
+        combined_img_hidden_states = hidden_states.new_zeros(batch_size, max_combined_img_len, self.config.hidden_size)
+        for i, (ref_img_len, img_len) in enumerate(zip(l_effective_ref_img_len, l_effective_img_len)):
+            combined_img_hidden_states[i, :sum(ref_img_len)] = ref_image_hidden_states[i, :sum(ref_img_len)]
+            combined_img_hidden_states[i, sum(ref_img_len):sum(ref_img_len) + img_len] = hidden_states[i, :img_len]
+
+        return combined_img_hidden_states
+
+    def flat_and_pad_to_seq(self, hidden_states, ref_image_hidden_states):
+        batch_size = len(hidden_states)
+        p = self.config.patch_size
+        device = hidden_states[0].device
+
+        img_sizes = [(img.size(1), img.size(2)) for img in hidden_states]
+        l_effective_img_len = [(H // p) * (W // p) for (H, W) in img_sizes]
+
+        if ref_image_hidden_states is not None:
+            ref_img_sizes = [[(img.size(1), img.size(2)) for img in imgs] if imgs is not None else None for imgs in ref_image_hidden_states]
+            l_effective_ref_img_len = [[(ref_img_size[0] // p) * (ref_img_size[1] // p) for ref_img_size in _ref_img_sizes] if _ref_img_sizes is not None else [0] for _ref_img_sizes in ref_img_sizes]
+        else:
+            ref_img_sizes = [None for _ in range(batch_size)]
+            l_effective_ref_img_len = [[0] for _ in range(batch_size)]
+
+        max_ref_img_len = max([sum(ref_img_len) for ref_img_len in l_effective_ref_img_len])
+        max_img_len = max(l_effective_img_len)
+
+        # ref image patch embeddings
+        flat_ref_img_hidden_states = []
+        for i in range(batch_size):
+            if ref_img_sizes[i] is not None:
+                imgs = []
+                for ref_img in ref_image_hidden_states[i]:
+                    C, H, W = ref_img.size()
+                    ref_img = rearrange(ref_img, 'c (h p1) (w p2) -> (h w) (p1 p2 c)', p1=p, p2=p)
+                    imgs.append(ref_img)
+
+                img = torch.cat(imgs, dim=0)
+                flat_ref_img_hidden_states.append(img)
+            else:
+                flat_ref_img_hidden_states.append(None)
+
+        # image patch embeddings
+        flat_hidden_states = []
+        for i in range(batch_size):
+            img = hidden_states[i]
+            C, H, W = img.size()
+            
+            img = rearrange(img, 'c (h p1) (w p2) -> (h w) (p1 p2 c)', p1=p, p2=p)
+            flat_hidden_states.append(img)
+        
+        padded_ref_img_hidden_states = torch.zeros(batch_size, max_ref_img_len, flat_hidden_states[0].shape[-1], device=device, dtype=flat_hidden_states[0].dtype)
+        padded_ref_img_mask = torch.zeros(batch_size, max_ref_img_len, dtype=torch.bool, device=device)
+        for i in range(batch_size):
+            if ref_img_sizes[i] is not None:
+                padded_ref_img_hidden_states[i, :sum(l_effective_ref_img_len[i])] = flat_ref_img_hidden_states[i]
+                padded_ref_img_mask[i, :sum(l_effective_ref_img_len[i])] = True
+
+        padded_hidden_states = torch.zeros(batch_size, max_img_len, flat_hidden_states[0].shape[-1], device=device, dtype=flat_hidden_states[0].dtype)
+        padded_img_mask = torch.zeros(batch_size, max_img_len, dtype=torch.bool, device=device)
+        for i in range(batch_size):
+            padded_hidden_states[i, :l_effective_img_len[i]] = flat_hidden_states[i]
+            padded_img_mask[i, :l_effective_img_len[i]] = True
+
+        return (
+            padded_hidden_states,
+            padded_ref_img_hidden_states,
+            padded_img_mask,
+            padded_ref_img_mask,
+            l_effective_ref_img_len,
+            l_effective_img_len,
+            ref_img_sizes,
+            img_sizes,
+        )
+    
+    def forward(
+        self,
+        hidden_states: Union[torch.Tensor, List[torch.Tensor]],
+        timestep: torch.Tensor,
+        text_hidden_states: torch.Tensor,
+        freqs_cis: torch.Tensor,
+        text_attention_mask: torch.Tensor,
+        ref_image_hidden_states: Optional[List[List[torch.Tensor]]] = None,
+        attention_kwargs: Optional[Dict[str, Any]] = None,
+        return_dict: bool = False,
+    ) -> Union[torch.Tensor, Transformer2DModelOutput]:
+        if attention_kwargs is not None:
+            attention_kwargs = attention_kwargs.copy()
+            lora_scale = attention_kwargs.pop("scale", 1.0)
+        else:
+            lora_scale = 1.0
+
+        if USE_PEFT_BACKEND:
+            # weight the lora layers by setting `lora_scale` for each PEFT layer
+            scale_lora_layers(self, lora_scale)
+        else:
+            if attention_kwargs is not None and attention_kwargs.get("scale", None) is not None:
+                logger.warning(
+                    "Passing `scale` via `attention_kwargs` when not using the PEFT backend is ineffective."
+                )
+
+        # 1. Condition, positional & patch embedding
+        batch_size = len(hidden_states)
+        is_hidden_states_tensor = isinstance(hidden_states, torch.Tensor)
+
+        if is_hidden_states_tensor:
+            assert hidden_states.ndim == 4
+            hidden_states = [_hidden_states for _hidden_states in hidden_states]
+
+        device = hidden_states[0].device
+
+        temb, text_hidden_states = self.time_caption_embed(timestep, text_hidden_states, hidden_states[0].dtype)
+
+        (
+            hidden_states,
+            ref_image_hidden_states,
+            img_mask,
+            ref_img_mask,
+            l_effective_ref_img_len,
+            l_effective_img_len,
+            ref_img_sizes,
+            img_sizes,
+        ) = self.flat_and_pad_to_seq(hidden_states, ref_image_hidden_states)
+        
+        (
+            context_rotary_emb,
+            ref_img_rotary_emb,
+            noise_rotary_emb,
+            rotary_emb,
+            encoder_seq_lengths,
+            seq_lengths,
+        ) = self.rope_embedder(
+            freqs_cis,
+            text_attention_mask,
+            l_effective_ref_img_len,
+            l_effective_img_len,
+            ref_img_sizes,
+            img_sizes,
+            device,
+        )
+
+        # 2. Context refinement
+        for layer in self.context_refiner:
+            text_hidden_states = layer(text_hidden_states, text_attention_mask, context_rotary_emb)
+        
+        combined_img_hidden_states = self.img_patch_embed_and_refine(
+            hidden_states,
+            ref_image_hidden_states,
+            img_mask,
+            ref_img_mask,
+            noise_rotary_emb,
+            ref_img_rotary_emb,
+            l_effective_ref_img_len,
+            l_effective_img_len,
+            temb,
+        )
+
+        # 3. Joint Transformer blocks
+        max_seq_len = int(max(seq_lengths))
+
+        attention_mask = hidden_states.new_zeros(batch_size, max_seq_len, dtype=torch.bool)
+        joint_hidden_states = hidden_states.new_zeros(batch_size, max_seq_len, self.config.hidden_size)
+        for i, (encoder_seq_len, seq_len) in enumerate(zip(encoder_seq_lengths, seq_lengths)):
+            encoder_seq_len = int(encoder_seq_len)
+            seq_len = int(seq_len)
+            attention_mask[i, :seq_len] = True
+            joint_hidden_states[i, :encoder_seq_len] = text_hidden_states[i, :encoder_seq_len]
+            joint_hidden_states[i, encoder_seq_len:seq_len] = combined_img_hidden_states[i, :seq_len - encoder_seq_len]
+
+        hidden_states = joint_hidden_states
+
+        for layer_idx, layer in enumerate(self.layers):
+            if torch.is_grad_enabled() and self.gradient_checkpointing:
+                hidden_states = self._gradient_checkpointing_func(
+                    layer, hidden_states, attention_mask, rotary_emb, temb
+                )
+            else:
+                hidden_states = layer(hidden_states, attention_mask, rotary_emb, temb)
+
+        # 4. Output norm & projection
+        hidden_states = self.norm_out(hidden_states, temb)
+
+        p = self.config.patch_size
+        output = []
+        for i, (img_size, img_len, seq_len) in enumerate(zip(img_sizes, l_effective_img_len, seq_lengths)):
+            img_len = int(img_len)
+            seq_len = int(seq_len)
+            height, width = img_size
+            output.append(rearrange(hidden_states[i][seq_len - img_len:seq_len], '(h w) (p1 p2 c) -> c (h p1) (w p2)', h=height // p, w=width // p, p1=p, p2=p))
+        if is_hidden_states_tensor:
+            output = torch.stack(output, dim=0)
+
+        if USE_PEFT_BACKEND:
+            # remove `lora_scale` from each PEFT layer
+            unscale_lora_layers(self, lora_scale)
+
+        if not return_dict:
+            return output
+        return Transformer2DModelOutput(sample=output)