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modeling_molmo.py

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+import logging
+import math
+from copy import deepcopy
+from dataclasses import fields, dataclass, replace
+from enum import Enum
+from typing import List, Optional, Tuple, Union, Dict, Any, Sequence, Callable, cast, MutableMapping
+
+import torch
+from einops import einsum, einops
+from transformers import PreTrainedModel, GenerationConfig
+from transformers.cache_utils import Cache
+from transformers.modeling_outputs import CausalLMOutputWithPast, ModelOutput
+from transformers.models.auto import AutoModelForCausalLM
+from torch import nn
+
+from .config_molmo import MolmoConfig
+from torch.nn import functional as F
+
+
+log = logging.getLogger(__name__)
+
+
+class BufferCache(dict, MutableMapping[str, torch.Tensor]):
+    """
+    Cache for attention biases and other things that would normally be stored as buffers.
+    We avoid using buffers because we've run into various issues doing so with FSDP.
+    In general it appears the way FSDP handles buffers is not well-defined.
+    It doesn't shard them but apparently it does synchronize them across processes, which we want to avoid
+    since (A) it isn't necessary, and (B) we sometimes have `-inf` in these biases which might get turned into
+    NaNs when they're synchronized due to casting or some other issue.
+    """
+
+
+class StrEnum(str, Enum):
+    def __str__(self) -> str:
+        return self.value
+
+    def __repr__(self) -> str:
+        return f"'{str(self)}'"
+
+
+class ImageProjectType(StrEnum):
+    mlp = "mlp"
+    mlpx2 = "2mlp"
+    linear = "linear"
+
+
+class ImagePooling2DType(StrEnum):
+    attention = "attention"
+    attention_meanq = "attention-meanq"
+    attention_2wide = "attention_2wide"
+    attention_v2 = "attention-v2"
+    none = "none"
+    stack = "stack"
+
+
+class ActivationType(StrEnum):
+    quick_gelu = "quick_gelu"
+    gelu = "gelu"
+    gelu_tanh = "gelu_tanh"
+    relu = "relu"
+    silu = "silu"
+    llama_geglu = "llama_geglu"
+    llama_geglu_tanh = "llama_geglu_tanh"
+    llama_swiglu = "llama_swiglu"
+    swiglu = "swiglu"
+
+
+def ensure_finite_(x: torch.Tensor, check_neg_inf: bool = True, check_pos_inf: bool = False):
+    """
+    Modify ``x`` in place to replace ``float("-inf")`` with the minimum value of the dtype when ``check_neg_inf``
+    is ``True`` and to replace ``float("inf")`` with the maximum value of the dtype when ``check_pos_inf`` is ``True``.
+    """
+    if check_neg_inf:
+        x.masked_fill_(x == float("-inf"), torch.finfo(x.dtype).min)
+    if check_pos_inf:
+        x.masked_fill_(x == float("inf"), torch.finfo(x.dtype).max)
+
+
+class MolmoConfigurationError(Exception):
+    pass
+
+
+def _non_meta_init_device(config) -> torch.device:
+    if config.init_device is not None and config.init_device != "meta":
+        return torch.device(config.init_device)
+    else:
+        return torch.device("cuda" if torch.cuda.is_available() else "cpu")
+
+
+class RotaryEmbedding(nn.Module):
+    """
+    [Rotary positional embeddings (RoPE)](https://arxiv.org/abs/2104.09864).
+    """
+
+    def __init__(self, config: MolmoConfig, cache: BufferCache):
+        super().__init__()
+        self.config = config
+        self.__cache = cache
+        # Warm up cache.
+        self.get_rotary_embedding(
+            config.max_position_embeddings or config.max_sequence_length,
+            _non_meta_init_device(config)
+        )
+
+    def get_rotary_embedding(self, seq_len: int, device: torch.device) -> Tuple[torch.Tensor, torch.Tensor]:
+        if (
+            (pos_sin := self.__cache.get("rope_pos_sin")) is not None
+            and (pos_cos := self.__cache.get("rope_pos_cos")) is not None
+            and pos_sin.shape[-2] >= seq_len
+            and pos_cos.shape[-2] >= seq_len
+        ):
+            if pos_sin.device != device:
+                pos_sin = pos_sin.to(device)
+                self.__cache["rope_pos_sin"] = pos_sin
+            if pos_cos.device != device:
+                pos_cos = pos_cos.to(device)
+                self.__cache["rope_pos_cos"] = pos_cos
+            return pos_sin[:, :, :seq_len, :], pos_cos[:, :, :seq_len, :]
+
+        with torch.autocast(device.type, enabled=False):
+            dim = self.config.d_model // self.config.n_heads
+            inv_freq = 1.0 / (self.config.rope_theta ** (torch.arange(0, dim, 2, device=device, dtype=torch.float) / dim))
+            seq = torch.arange(seq_len, device=device, dtype=torch.float)
+            freqs = torch.einsum("i , j -> i j", seq, inv_freq)
+            if self.config.rope_impl == "interleave":
+                positions = freqs.repeat_interleave(2, dim=-1)
+            else:
+                positions = torch.cat((freqs, freqs), dim=-1)
+            pos_sin, pos_cos = positions.sin()[None, None, :, :], positions.cos()[None, None, :, :]
+        self.__cache["rope_pos_sin"] = pos_sin
+        self.__cache["rope_pos_cos"] = pos_cos
+        return pos_sin, pos_cos
+
+    def rotate_half(self, x: torch.Tensor) -> torch.Tensor:
+        B, nh, T, hs = x.size()
+        x = x.view(B, nh, T, 2, hs // 2)
+        x1, x2 = x.unbind(dim=-2)
+        return torch.cat((-x2, x1), dim=-1)
+
+    def rotate_every_two(self, x: torch.Tensor) -> torch.Tensor:
+        B, nh, T, hs = x.size()
+        x = x.view(B, nh, T, hs // 2, 2)
+        x1, x2 = x.unbind(dim=-1)
+        x = torch.stack((-x2, x1), dim=-1)
+        return x.view(B, nh, T, hs)
+
+    def apply_rotary_pos_emb(self, pos_sin: torch.Tensor, pos_cos: torch.Tensor, t: torch.Tensor) -> torch.Tensor:
+        if self.config.rope_impl == "interleave":
+            return ((t * pos_cos) + (self.rotate_every_two(t) * pos_sin)).to(t.dtype)
+        else:
+            return ((t * pos_cos) + (self.rotate_half(t) * pos_sin)).to(t.dtype)
+
+    def forward(
+        self,
+        q: torch.Tensor,
+        k: torch.Tensor,
+        position_ids: Optional[torch.Tensor] = None
+    ) -> Tuple[torch.Tensor, torch.Tensor]:
+        if self.config.rope_full_precision:
+            q_, k_ = q.float(), k.float()
+        else:
+            q_, k_ = q, k
+
+        with torch.autocast(q.device.type, enabled=False):
+            batch_size = q_.shape[0]
+            query_len, key_len = q_.shape[-2], k_.shape[-2]  # could be different if layer_past not None
+            if position_ids is not None:
+                freqs_cis_len = (self.config.max_position_embeddings or self.config.max_sequence_length)
+            else:
+                freqs_cis_len = key_len
+            pos_sin, pos_cos = self.get_rotary_embedding(freqs_cis_len, q_.device)
+            pos_sin = pos_sin.type_as(q_)
+            pos_cos = pos_cos.type_as(q_)
+            if position_ids is not None:
+                assert query_len == key_len, "Query and key lengths must be equal when using position IDs."
+                pos_sin = pos_sin[0, 0][position_ids].view(
+                    (batch_size, 1, key_len, pos_sin.shape[-1])
+                )
+                pos_cos = pos_cos[0, 0][position_ids].view(
+                    (batch_size, 1, key_len, pos_cos.shape[-1])
+                )
+            q_ = self.apply_rotary_pos_emb(
+                pos_sin[:, :, key_len - query_len : key_len, :],
+                pos_cos[:, :, key_len - query_len : key_len, :],
+                q_,
+            )
+            k_ = self.apply_rotary_pos_emb(pos_sin, pos_cos, k_)
+        return q_.type_as(q), k_.type_as(k)
+
+
+class MolmoBlock(nn.Module):
+    """
+    A base class for transformer block implementations.
+    """
+
+    def __init__(self, layer_id: int, config: MolmoConfig, cache: BufferCache):
+        super().__init__()
+        self.layer_id = layer_id
+        self.config = config
+        self.hidden_size = (
+            config.mlp_hidden_size if config.mlp_hidden_size is not None else config.mlp_ratio * config.d_model
+        )
+        self.__cache = cache
+        self._activation_checkpoint_fn = None
+
+        # Dropout.
+        self.dropout = Dropout(config.residual_dropout)
+
+        # Layer norms.
+        self.k_norm: Optional[LayerNormBase] = None
+        self.q_norm: Optional[LayerNormBase] = None
+        if config.attention_layer_norm:
+            assert config.effective_n_kv_heads is not None
+            self.k_norm = LayerNormBase.build(
+                config,
+                size=(config.d_model // config.n_heads) * config.effective_n_kv_heads,
+                elementwise_affine=config.attention_layer_norm_with_affine,
+            )
+            self.q_norm = LayerNormBase.build(config, elementwise_affine=config.attention_layer_norm_with_affine)
+
+        # Make sure QKV clip coefficient is positive, otherwise it's not well-defined.
+        if config.clip_qkv is not None:
+            assert config.clip_qkv > 0
+
+        # Activation function.
+        self.act = Activation.build(config)
+        assert (self.act.output_multiplier * self.hidden_size) % 1 == 0
+
+        # Attention output projection.
+        input_dim = config.d_model
+        self.attn_out = nn.Linear(
+            input_dim, config.d_model,
+            bias=config.include_bias,
+            device=config.init_device
+        )
+
+        # Feed-forward output projection.
+        self.ff_out = nn.Linear(
+            int(self.act.output_multiplier * self.hidden_size),
+            config.d_model,
+            bias=config.include_bias,
+            device=config.init_device,
+        )
+        self.ff_out._is_residual = True  # type: ignore
+
+        # Rotary embeddings.
+        if self.config.rope:
+            self.rotary_emb = RotaryEmbedding(config, self.__cache)
+
+        self.flash_attn_func = None
+        if config.attention_type == "flash":
+            try:
+                from flash_attn import flash_attn_func  # type: ignore
+
+                self.flash_attn_func = flash_attn_func
+            except ModuleNotFoundError:
+                pass
+
+    def reset_parameters(self):
+        if self.k_norm is not None:
+            self.k_norm.reset_parameters()
+        if self.q_norm is not None:
+            self.q_norm.reset_parameters()
+        init_weights(
+            self.config,
+            self.attn_out,
+            d=self.config.d_model,
+            layer_id=self.layer_id,
+            type_of_module=ModuleType.out_module,
+        )
+        init_weights(
+            self.config,
+            self.ff_out,
+            d=self.ff_out.in_features,
+            layer_id=self.layer_id,
+            type_of_module=ModuleType.out_module,
+        )
+
+    @classmethod
+    def _cast_attn_bias(cls, bias: torch.Tensor, input_dtype: torch.dtype) -> torch.Tensor:
+        target_dtype = input_dtype
+        # NOTE: `is_autocast_enabled()` only checks for CUDA autocast, so we use the separate function
+        # `is_autocast_cpu_enabled()` for CPU autocast.
+        # See https://github.com/pytorch/pytorch/issues/110966.
+        if bias.device.type == "cuda" and torch.is_autocast_enabled():
+            target_dtype = torch.get_autocast_gpu_dtype()
+        elif bias.device.type == "cpu" and torch.is_autocast_cpu_enabled():
+            target_dtype = torch.get_autocast_cpu_dtype()
+        if bias.dtype != target_dtype:
+            bias = bias.to(target_dtype)
+            ensure_finite_(bias, check_neg_inf=True, check_pos_inf=False)
+        return bias
+
+    def _scaled_dot_product_attention(
+        self,
+        q: torch.Tensor,
+        k: torch.Tensor,
+        v: torch.Tensor,
+        attn_mask: Optional[torch.Tensor] = None,
+        dropout_p: float = 0.0,
+        response_dropout_p: float = 0.0,
+        is_causal: bool = False,
+    ) -> torch.Tensor:
+        """
+        Computes scaled dot product attention on query, key and value tensors, using an optional
+        attention mask if passed, and applying dropout if a probability greater than 0.0 is specified.
+        """
+        if attn_mask is not None:
+            attn_mask = attn_mask.to(q.device)
+
+        if self.flash_attn_func is not None and attn_mask is None:
+            r = self.flash_attn_func(
+                q.transpose(1, 2), k.transpose(1, 2), v.transpose(1, 2), dropout_p=dropout_p, causal=is_causal
+            )
+            return r.transpose(1, 2)
+        else:
+            # torch's sdpa doesn't support GQA, so we're doing this
+            assert k.size(1) == v.size(1)
+            num_kv_heads = k.size(1)
+            num_q_heads = q.size(1)
+            if num_q_heads != num_kv_heads:
+                assert num_q_heads % num_kv_heads == 0
+                k = k.repeat_interleave(num_q_heads // num_kv_heads, dim=1, output_size=num_q_heads)
+                v = v.repeat_interleave(num_q_heads // num_kv_heads, dim=1, output_size=num_q_heads)
+
+            return F.scaled_dot_product_attention(
+                q,
+                k,
+                v,
+                attn_mask=attn_mask,
+                dropout_p=dropout_p,
+                is_causal=is_causal,
+            )
+
+    def attention(
+        self,
+        q: torch.Tensor,
+        k: torch.Tensor,
+        v: torch.Tensor,
+        attention_bias: Optional[torch.Tensor] = None,
+        position_ids: Optional[torch.Tensor] = None,
+        layer_past: Optional[Tuple[torch.Tensor, torch.Tensor]] = None,
+        use_cache: bool = False,
+    ) -> Tuple[torch.Tensor, Optional[Tuple[torch.Tensor, torch.Tensor]]]:
+        B, T, C = q.size()  # batch size, sequence length, d_model
+        dtype = k.dtype
+
+        # Optionally apply layer norm to keys and queries.
+        if self.q_norm is not None and self.k_norm is not None:
+            q = self.q_norm(q).to(dtype=dtype)
+            k = self.k_norm(k).to(dtype=dtype)
+
+        # Move head forward to be next to the batch dim.
+        # shape: (B, nh, T, hs)
+        q = q.view(B, T, self.config.n_heads, C // self.config.n_heads).transpose(1, 2)
+        # shape: (B, n_kv_h, T, hs)
+        k = k.view(B, T, self.config.effective_n_kv_heads, C // self.config.n_heads).transpose(1, 2)
+        # shape: (B, n_kv_h, T, hs)
+        v = v.view(B, T, self.config.effective_n_kv_heads, C // self.config.n_heads).transpose(1, 2)
+
+        if self.config.use_position_ids and self.config.rope:
+            # Apply rotary embeddings
+            q, k = self.rotary_emb(q, k, position_ids=position_ids)
+
+        if layer_past is not None:
+            past_key, past_value = layer_past
+            k = torch.cat((past_key.to(k.device), k), dim=-2)
+            v = torch.cat((past_value.to(v.device), v), dim=-2)
+
+        present = (k, v) if use_cache else None
+        query_len, key_len = q.shape[-2], k.shape[-2]  # could be different if layer_past not None
+
+        if not self.config.use_position_ids and self.config.rope:
+            # Apply rotary embeddings
+            q, k = self.rotary_emb(q, k)
+
+        if attention_bias is not None:
+            # Resize and cast attention bias.
+            # The current dtype of the attention bias might not match the dtype that the SDP attn function will
+            # run in if AMP is enabled, and this can be a problem if some tokens are masked out due to padding
+            # as down-casting the attention bias to the autocast precision will result in -infs, which will
+            # cause the SDP attn function to produce NaNs.
+            attention_bias = self._cast_attn_bias(
+                attention_bias[:, :, key_len - query_len : key_len, :key_len], dtype
+            )
+
+        # Get the attention scores.
+        # shape: (B, nh, T, hs)
+        att = self._scaled_dot_product_attention(
+            q,
+            k,
+            v,
+            attn_mask=attention_bias,
+            dropout_p=0.0 if not self.training else self.config.attention_dropout,
+            response_dropout_p=0.0 if not self.training else self.config.response_attention_dropout,
+            is_causal=attention_bias is None,
+        )
+
+        # Re-assemble all head outputs side-by-side.
+        att = att.transpose(1, 2).contiguous().view(B, T, C)
+
+        # Apply output projection.
+        return self.attn_out(att), present
+
+    def forward(
+        self,
+        x: torch.Tensor,
+        attention_bias: Optional[torch.FloatTensor] = None,
+        position_ids: Optional[torch.Tensor] = None,
+        layer_past: Optional[Tuple[torch.Tensor, torch.Tensor]] = None,
+        use_cache: bool = False,
+    ) -> Tuple[torch.Tensor, Optional[Tuple[torch.Tensor, torch.Tensor]]]:
+        raise NotImplementedError
+
+    @classmethod
+    def build(cls, layer_id: int, config: MolmoConfig, cache: BufferCache):
+        return MolmoSequentialBlock(layer_id, config, cache)
+
+
+class MolmoSequentialBlock(MolmoBlock):
+    """
+    This is a typical transformer block where the output is computed as ``MLP(LN(x + Attention(LN(x))))``
+    (plus another skip connection).
+    """
+
+    def __init__(self, layer_id: int, config: MolmoConfig, cache: BufferCache):
+        super().__init__(layer_id, config, cache)
+        # Layer norms.
+        self.attn_norm = LayerNorm.build(config)
+        self.ff_norm = LayerNorm.build(config)
+        # Attention input projection. Projects x -> (q, k, v)
+
+        head_dim = config.d_model // config.n_heads
+        self.fused_dims = (
+            config.d_model,
+            config.effective_n_kv_heads * head_dim,
+            config.effective_n_kv_heads * head_dim,
+        )
+        self.att_proj = nn.Linear(
+            config.d_model, sum(self.fused_dims),
+            bias=config.include_bias or config.qkv_bias,
+            device=config.init_device
+        )
+        # Feed-forward input projection.
+        self.ff_proj = nn.Linear(
+            config.d_model, self.hidden_size, bias=config.include_bias, device=config.init_device
+        )
+
+    def reset_parameters(self):
+        super().reset_parameters()
+        self.attn_norm.reset_parameters()
+        self.ff_norm.reset_parameters()
+        # NOTE: the standard deviation for these weights does not depend on the layer.
+        init_weights(
+            self.config, self.att_proj, d=self.config.d_model, layer_id=None, type_of_module=ModuleType.in_module
+        )
+        init_weights(
+            self.config, self.ff_proj, d=self.config.d_model, layer_id=None, type_of_module=ModuleType.in_module
+        )
+
+    def forward(
+        self,
+        x: torch.Tensor,
+        attention_bias: Optional[torch.Tensor] = None,
+        position_ids: Optional[torch.Tensor] = None,
+        layer_past: Optional[Tuple[torch.Tensor, torch.Tensor]] = None,
+        use_cache: bool = False,
+    ) -> Tuple[torch.Tensor, Optional[Tuple[torch.Tensor, torch.Tensor]]]:
+        # Get query, key, value projections.
+        # shape:
+        #  - for regular attn q, k, v: (batch_size, seq_len, d_model)
+        #  - for multi-query attn q: (batch_size, seq_len, d_model)
+        #                      k, v: (batch_size, seq_len, d_model // n_heads)
+        #  - for group query attn q: (batch_size, seq_len, d_model)
+        #                      k, v: (batch_size, seq_len, d_model // n_kv_heads)
+
+        if not self.config.norm_after:
+            if self._activation_checkpoint_fn is not None:
+                atten_in = self._activation_checkpoint_fn(self.attn_norm, x)
+            else:
+                atten_in = self.attn_norm(x)
+        else:
+            atten_in = x
+        qkv = self.att_proj(atten_in)
+
+        if self.config.clip_qkv is not None:
+            qkv.clamp_(min=-self.config.clip_qkv, max=self.config.clip_qkv)
+
+        q, k, v = qkv.split(self.fused_dims, dim=-1)
+
+        # Get attention scores.
+        if self._activation_checkpoint_fn is not None:
+            att, cache = self._activation_checkpoint_fn(  # type: ignore
+                self.attention, q, k, v, attention_bias, position_ids=position_ids, layer_past=layer_past, use_cache=use_cache
+            )
+        else:
+            att, cache = self.attention(q, k, v, attention_bias, position_ids=position_ids, layer_past=layer_past, use_cache=use_cache)
+
+        if self.config.norm_after:
+            if self._activation_checkpoint_fn is not None:
+                att = self._activation_checkpoint_fn(self.attn_norm, att)
+            else:
+                att = self.attn_norm(att)
+
+        # Add attention scores.
+        # shape: (B, T, C)
+        x = x + self.dropout(att)
+
+        # Add feed-forward projection.
+        # shape: (batch_size, seq_len, d_model)
+        og_x = x
+
+        if not self.config.norm_after:
+            if self._activation_checkpoint_fn is not None:
+                x = self._activation_checkpoint_fn(self.ff_norm, x)  # type: ignore
+            else:
+                x = self.ff_norm(x)
+
+        x = self.ff_proj(x)
+        if self._activation_checkpoint_fn is not None:
+            x = self._activation_checkpoint_fn(self.act, x)  # type: ignore
+        else:
+            x = self.act(x)
+        x = self.ff_out(x)
+
+        if self.config.norm_after:
+            if self._activation_checkpoint_fn is not None:
+                x = self._activation_checkpoint_fn(self.ff_norm, x)  # type: ignore
+            else:
+                x = self.ff_norm(x)
+
+        x = self.dropout(x)
+        x = og_x + x
+
+        return x, cache
+
+
+class Embedding(nn.Module):
+    def __init__(
+        self,
+        num_embeddings: int,
+        num_new_embeddings: int,
+        features: int,
+        device: Union[str, torch.device],
+        initializer_range: float = 0.02,
+        new_embed_initializer_range: float = 0.02,
+    ):
+        super().__init__()
+        self.initializer_range = initializer_range
+        self.new_embed_initializer_range = new_embed_initializer_range
+        self.embedding = nn.Parameter(
+            torch.zeros(num_embeddings, features, device=device),
+        )
+        self.new_embedding = nn.Parameter(
+            torch.zeros(num_new_embeddings, features, device=device),
+        )
+
+    def reset_parameters(self):
+        nn.init.normal_(self.embedding, std=self.initializer_range)
+        nn.init.normal_(self.new_embedding, std=self.new_embed_initializer_range)
+
+    def forward(self, x: torch.Tensor) -> torch.Tensor:
+        return F.embedding(x, torch.cat([self.embedding, self.new_embedding], dim=0))
+
+
+class Dropout(nn.Dropout):
+    def __init__(
+        self,
+        p: float = 0.5,
+        inplace: bool = False,
+        mask_p: float = 0,
+        broadcast_dims: Sequence[int] = (),
+    ):
+        super().__init__(p, inplace)
+        self.mask_p = mask_p
+        self.broadcast_dims = broadcast_dims
+
+    def forward(self, input: torch.Tensor) -> torch.Tensor:
+        """
+        :param input: A tensor of shape `(batch_size, seq_len, embed_dim)`
+        """
+        if self.p == 0.0 and (self.mask_p is None or self.mask_p == 0.0):
+            return input
+        else:
+            if self.p > 0. and len(self.broadcast_dims) > 0 and self.training:
+                keep_prob = 1.0 - self.p
+                dropout_shape = list(input.shape)
+                for dim in self.broadcast_dims:
+                    dropout_shape[dim] = 1
+                keep = input.new_empty(dropout_shape).bernoulli_(keep_prob)
+                multiplier = keep.broadcast_to(input.shape)
+                multiplier.div_(keep_prob)
+                input = input * multiplier
+            else:
+                return F.dropout(input, self.p, self.training, self.inplace)
+
+
+@dataclass
+class VisionBackboneConfig:
+    image_default_input_size: Tuple[int, int] = (336, 336)
+    image_patch_size: int = 14
+    image_pos_patch_size: int = 14
+    image_emb_dim: int = 1024
+    image_num_heads: int = 16
+    image_num_key_value_heads: int = 16
+    image_num_layers: int = 24
+    image_head_dim: int = 64
+    image_mlp_dim: int = 4096
+    image_mlp_activations: str = "gelu"
+    image_dropout_rate: float = 0.0
+    image_num_pos: int = 577
+    image_norm_eps: float = 1e-5
+    attention_dropout: float = 0.0
+    residual_dropout: float = 0.0
+    initializer_range: float = 0.02
+    fsdp_wrap: bool = False
+    resize_mode: str = "default"
+
+    def __post_init__(self):
+        self.image_default_input_size = tuple(self.image_default_input_size)  # type: ignore[assignment]
+
+    @property
+    def image_num_patch(self):
+        h, w = self.image_default_input_size
+        return h // self.image_patch_size, w // self.image_patch_size
+
+
+@dataclass
+class FullMolmoConfig:
+    d_model: int = 768
+    n_heads: int = 12
+    n_kv_heads: Optional[int] = None
+    qkv_bias: bool = False
+    clip_qkv: Optional[float] = None
+    n_layers: int = 12
+    mlp_ratio: int = 4
+    mlp_hidden_size: Optional[int] = None
+    activation_type: str = "swiglu"
+    block_group_size: int = 1
+    rope: bool = True
+    rope_full_precision: bool = True
+    rope_theta: float = 10000.
+    rope_impl: str = "interleave"
+    vision_backbone: Optional[VisionBackboneConfig] = None
+    attention_type: str = "sdpa"
+    float32_attention: bool = True
+    attention_dropout: float = 0.1
+    response_attention_dropout: float = 0.0
+    multi_query_attention: Optional[bool] = None
+    attention_layer_norm: bool = False
+    residual_dropout: float = 0.1
+    embedding_dropout: float = 0.1
+    layer_norm_type: str = "default"
+    layer_norm_with_affine: bool = True
+    layer_norm_eps: Optional[float] = None
+    attention_layer_norm_with_affine: bool = True
+    max_sequence_length: int = 1024
+    max_position_embeddings: Optional[int] = None
+    include_bias: bool = True
+    bias_for_layer_norm: Optional[bool] = None
+    scale_logits: bool = False
+    vocab_size: int = 50257
+    embedding_size: Optional[int] = 50304
+    additional_vocab_size: Optional[int] = None
+    new_embedding_init_range: float = 0.02
+    weight_tying: bool = True
+    pad_token_id: int = -1
+    init_device: Optional[str] = None
+    init_std: float = 0.02
+    init_cutoff_factor: Optional[float] = None
+    norm_after: bool = False
+    precision: Optional[str] = None
+    image_padding_embed: Optional[str] = None
+    vit_layers: Tuple = (-1,)
+    image_pooling_h: int = 2
+    image_pooling_w: int = 2
+    image_pooling_2d: str = "attention"
+    image_projector: str = "mlp"
+    image_feature_dropout: float = 0.0
+    initializer_range: float = 0.02
+    normalize_input_embeds: bool = False
+    use_position_ids: bool = True
+
+    @property
+    def effective_n_kv_heads(self) -> int:
+        if self.n_kv_heads is None:
+            if self.multi_query_attention is True:
+                return 1
+            else:
+                return self.n_heads
+        else:
+            if self.multi_query_attention is None:
+                return self.n_kv_heads
+            if self.multi_query_attention:
+                n_kv_heads_should_be = 1
+            else:
+                n_kv_heads_should_be = self.n_heads
+            if self.n_kv_heads == n_kv_heads_should_be:
+                return n_kv_heads_should_be
+            else:
+                raise MolmoConfigurationError(
+                    "You can't set `multi_query_attention` and `n_kv_heads` at the same time."
+                )
+
+    @property
+    def image_num_patch(self):
+        assert self.vision_backbone is not None
+        return self.vision_backbone.image_num_patch
+
+    @property
+    def image_patch_size(self):
+        assert self.vision_backbone is not None
+        return self.visoin_backbone.image_patch_size
+
+    def llm_patches_per_crop(self):
+        h, w = self.image_num_patch
+        # Round up in case we need to pad the image features for pooling
+        h = (h + self.image_pooling_h - 1) // self.image_pooling_h
+        w = (w + self.image_pooling_w - 1) // self.image_pooling_w
+        return h, w
+
+
+def _expand_token(token, batch_size: int):
+    return token.view(1, 1, -1).expand(batch_size, -1, -1)
+
+
+class LayerNormFp32(nn.LayerNorm):
+    """Subclass torch's LayerNorm to handle fp16 (by casting to float32 and back).
+    Derived from https://github.com/mlfoundations/open_clip/blob/main/src/open_clip/transformer.py.
+    """
+
+    def forward(self, x: torch.Tensor) -> torch.Tensor:
+        orig_type = x.dtype
+        x = F.layer_norm(x.to(torch.float32), self.normalized_shape, self.weight, self.bias, self.eps)
+        return x.to(orig_type)
+
+
+class ViTMLP(nn.Module):
+    def __init__(self, config: FullMolmoConfig):
+        super().__init__()
+        self.config = config
+        v_cfg = config.vision_backbone
+
+        self.w1 = nn.Linear(
+            v_cfg.image_emb_dim,
+            v_cfg.image_mlp_dim,
+            bias=True,
+            device=config.init_device,
+        )
+        # Activation function.
+        cfg = deepcopy(config)
+        cfg.activation_type = v_cfg.image_mlp_activations
+        self.act = Activation.build(cfg)
+        self.w2 = nn.Linear(
+            v_cfg.image_mlp_dim,
+            v_cfg.image_emb_dim,
+            bias=True,
+            device=config.init_device,
+        )
+
+    def reset_parameters(self):
+        v_cfg = self.config.vision_backbone
+        nn.init.trunc_normal_(self.w1.weight, std=math.sqrt(1 / v_cfg.image_emb_dim), a=-2.0, b=2.0)
+        nn.init.trunc_normal_(self.w2.weight, std=math.sqrt(1 / v_cfg.image_mlp_dim), a=-2.0, b=2.0)
+        nn.init.zeros_(self.w1.bias)
+        nn.init.zeros_(self.w2.bias)
+
+    def forward(self, x: torch.Tensor) -> torch.Tensor:
+        x = self.w1(x)
+        x = self.act(x)
+        x = self.w2(x)
+        return x
+
+
+
+class ResidualAttentionBlock(nn.Module):
+
+    def __init__(self, config: FullMolmoConfig):
+        super().__init__()
+        self.config = config
+
+        v_cfg = config.vision_backbone
+        self.attention = MultiHeadDotProductAttention(config)
+        self.feed_forward = ViTMLP(config)
+        self.attention_norm = nn.LayerNorm(
+            v_cfg.image_emb_dim,
+            eps=v_cfg.image_norm_eps,
+            device=config.init_device,
+        )
+        self.ffn_norm = nn.LayerNorm(
+            v_cfg.image_emb_dim,
+            eps=v_cfg.image_norm_eps,
+            device=config.init_device,
+        )
+
+    def reset_parameters(self):
+        self.attention.reset_parameters()
+        self.feed_forward.reset_parameters()
+        self.attention_norm.reset_parameters()
+        self.ffn_norm.reset_parameters()
+
+    def forward(self, x: torch.Tensor) -> torch.Tensor:
+        x = x + self.attention(self.attention_norm(x))
+        x = x + self.feed_forward(self.ffn_norm(x))
+        return x
+
+
+class BlockCollection(nn.Module):
+
+    def __init__(self, config: FullMolmoConfig):
+        super().__init__()
+        self.config = config
+        self.grad_checkpointing: bool = False
+
+        v_cfg = config.vision_backbone
+        self.resblocks = nn.ModuleList([
+            ResidualAttentionBlock(config) for _ in range(v_cfg.image_num_layers)
+        ])
+
+    def reset_parameters(self):
+        for r in self.resblocks:
+            r.reset_parameters()
+
+    def forward(self, x: torch.Tensor) -> List[torch.Tensor]:
+        hidden_states = []
+        for r in self.resblocks:
+            x = r(x)
+            hidden_states.append(x)
+        return hidden_states
+
+
+class VisionTransformer(nn.Module):
+
+    def __init__(self, config: FullMolmoConfig):
+        super().__init__()
+        self.config = config
+
+        v_cfg = config.vision_backbone
+        # class embeddings and positional embeddings
+        self.scale = v_cfg.image_emb_dim ** -0.5
+        self.class_embedding = nn.Parameter(
+            torch.zeros(v_cfg.image_emb_dim, device=config.init_device),
+        )
+        self.num_prefix_tokens: int = 1
+        self.positional_embedding = nn.Parameter(
+            torch.zeros(v_cfg.image_num_pos, v_cfg.image_emb_dim, device=config.init_device),
+        )
+
+        image_patch_size = v_cfg.image_patch_size
+        self.patch_embedding = nn.Linear(
+            image_patch_size * image_patch_size * 3,
+            v_cfg.image_emb_dim,
+            bias=False,
+            device=config.init_device,
+            )
+
+        self.pre_ln = LayerNormFp32(
+            v_cfg.image_emb_dim,
+            eps=v_cfg.image_norm_eps,
+            device=config.init_device,
+        )
+
+        self.transformer = BlockCollection(config)
+
+    @torch.jit.ignore
+    def set_grad_checkpointing(self, enable=True):
+        self.transformer.grad_checkpointing = enable
+
+    def reset_parameters(self):
+        nn.init.normal_(self.class_embedding, std=self.scale)
+        nn.init.normal_(self.positional_embedding, std=self.scale)
+        nn.init.normal_(self.patch_embedding.weight, std=0.02)
+        self.pre_ln.reset_parameters()
+        self.transformer.reset_parameters()
+
+    def add_pos_emb(self, x: torch.Tensor, patch_num: int) -> torch.Tensor:
+        cls_emb = self.positional_embedding[0:1]
+        pos_emb = self.positional_embedding[1:]
+
+        pos_emb = pos_emb.reshape(
+            (int(math.sqrt(pos_emb.shape[0])), int(math.sqrt(pos_emb.shape[0])), pos_emb.shape[1])
+        )
+
+        (patch_num_0, patch_num_1) = patch_num
+
+        if pos_emb.shape[0] != patch_num_0 or pos_emb.shape[1] != patch_num_1:
+            # Dervied from https://github.com/facebookresearch/mae/blob/main/util/pos_embed.py
+            # antialias: default True in jax.image.resize
+            pos_emb = pos_emb.unsqueeze(0).permute(0, 3, 1, 2)
+            pos_emb = F.interpolate(
+                pos_emb, size=(patch_num_0, patch_num_1), mode="bicubic", align_corners=False, antialias=True,
+            )
+            pos_emb = pos_emb.permute(0, 2, 3, 1).squeeze(0)
+
+        pos_emb = pos_emb.reshape(-1, pos_emb.shape[-1])
+        x = x + torch.cat([cls_emb[None, :, :], pos_emb[None, :, :]], dim=1).to(x.dtype)
+        return x
+
+    def forward(self, x: torch.Tensor, patch_num: int = None) -> List[torch.Tensor]:
+        """
+        : param x: (batch_size, num_patch, n_pixels)
+        """
+        if patch_num is None:
+            patch_num = self.config.vision_backbone.image_num_patch
+        B, N, D = x.shape
+        
+        x = self.patch_embedding(x)
+
+        # class embeddings and positional embeddings
+        x = torch.cat([_expand_token(self.class_embedding, x.shape[0]).to(x.dtype), x], dim=1)
+        x = self.add_pos_emb(x, patch_num)
+
+        x = self.pre_ln(x)
+
+        hidden_states = self.transformer(x)
+        return hidden_states
+
+
+class MultiHeadDotProductAttention(nn.Module):
+    def __init__(self, config: FullMolmoConfig, use_bias: bool = True, is_vit_layer: Optional[bool] = True):
+        super().__init__()
+        self.config = config
+        self.use_bias = use_bias
+
+        v_cfg = config.vision_backbone
+        self.embed_dim = v_cfg.image_emb_dim
+        self.num_heads = v_cfg.image_num_heads
+        self.head_dim = v_cfg.image_head_dim
+        self.num_key_value_heads = v_cfg.image_num_key_value_heads
+        self.num_key_value_groups = self.num_heads // self.num_key_value_heads
+        self.initializer_range = v_cfg.initializer_range
+        self.is_vit_layer = is_vit_layer
+
+        nlayers = 1 if (is_vit_layer or config.vit_layers is None) else len(config.vit_layers)
+
+        self.wq = nn.Linear(
+            nlayers * self.embed_dim,
+            self.num_heads * self.head_dim,
+            bias=use_bias,
+            device=config.init_device,
+            )
+        self.wk = nn.Linear(
+            nlayers * self.embed_dim,
+            self.num_key_value_heads * self.head_dim,
+            bias=use_bias,
+            device=config.init_device,
+            )
+        self.wv = nn.Linear(
+            nlayers * self.embed_dim,
+            self.num_key_value_heads * self.head_dim,
+            bias=use_bias,
+            device=config.init_device,
+            )
+        self.wo = nn.Linear(
+            self.num_heads * self.head_dim,
+            self.embed_dim,
+            bias=use_bias,
+            device=config.init_device,
+            )
+        self.attention_dropout: Optional[Dropout] = None
+        if v_cfg.attention_dropout > 0:
+            self.attention_dropout = Dropout(v_cfg.attention_dropout, broadcast_dims=(0, 1))
+        self.residual_dropout = Dropout(v_cfg.residual_dropout)
+
+    def reset_parameters(self):
+        nn.init.normal_(self.wq.weight, std=self.initializer_range)
+        nn.init.normal_(self.wk.weight, std=self.initializer_range)
+        nn.init.normal_(self.wv.weight, std=self.initializer_range)
+        nn.init.normal_(self.wo.weight, std=self.initializer_range)
+        if self.use_bias:
+            nn.init.constant_(self.wq.bias, 0)
+            nn.init.constant_(self.wk.bias, 0)
+            nn.init.constant_(self.wv.bias, 0)
+            nn.init.constant_(self.wo.bias, 0)
+
+    def _split_heads(self, hidden_states, num_heads) -> torch.Tensor:
+        return hidden_states.reshape(hidden_states.shape[:2] + (num_heads, self.head_dim))
+
+    def _merge_heads(self, hidden_states) -> torch.Tensor:
+        return hidden_states.reshape(hidden_states.shape[:2] + (self.embed_dim,))
+
+    def forward(self, inputs_q: torch.Tensor, inputs_kv: Optional[torch.Tensor] = None) -> torch.Tensor:
+
+        if inputs_kv is not None:
+            inputs_k = inputs_kv
+            inputs_v = inputs_kv
+        else:
+            inputs_k = inputs_q
+            inputs_v = inputs_q
+
+        xq, xk, xv = self.wq(inputs_q), self.wk(inputs_k), self.wv(inputs_v)
+
+        xq = self._split_heads(xq, self.num_heads)
+        xk = self._split_heads(xk, self.num_key_value_heads)
+        xv = self._split_heads(xv, self.num_key_value_heads)
+
+        if self.num_heads != self.num_key_value_heads:
+            xk = xk.repeat_interleave(self.num_key_value_groups, dim=2, output_size=self.num_heads)
+            xv = xv.repeat_interleave(self.num_key_value_groups, dim=2, output_size=self.num_heads)
+
+        og_dtype = xq.dtype
+
+        if self.config.float32_attention:
+            xq = xq.to(torch.float)
+            xk = xk.to(torch.float)
+
+        if self.config.attention_type == "direct":
+            attn_weights = torch.einsum("...qhd,...khd->...hqk", xq / math.sqrt(xq.size(-1)), xk)
+            attn_weights = F.softmax(attn_weights, dim=-1, dtype=torch.float32).to(xq.dtype)
+            if self.attention_dropout is not None:
+                attn_weights = self.attention_dropout(attn_weights)
+            attn_output = torch.einsum("...hqk,...khd->...qhd", attn_weights.to(xv.dtype), xv)
+
+        elif self.config.attention_type == "sdpa":
+            attn_output = F.scaled_dot_product_attention(
+                xq.transpose(1, 2).contiguous(),
+                xk.transpose(1, 2).contiguous(),
+                xv.transpose(1, 2).contiguous(),
+                is_causal=False,
+                dropout_p=self.config.vision_backbone.attention_dropout
+            ).transpose(1, 2)
+        else:
+            raise NotImplementedError(self.config.attention_type)
+        attn_output = attn_output.to(og_dtype)
+        attn_output = self._merge_heads(attn_output)
+        attn_output = self.wo(attn_output)
+        attn_output = self.residual_dropout(attn_output)
+
+        return attn_output
+
+
+class MultiHeadAttentionPool(nn.Module):
+    def __init__(
+        self,
+        config: FullMolmoConfig,
+        factor: int = 1,
+        use_bias: bool = True,
+        dropout: bool = True,
+        output_layer: bool = True,
+        mean_residual: bool = False,
+        query: str = "mean",
+        is_vit_layer: Optional[bool] = True
+    ):
+        super().__init__()
+        self.config = config
+        self.factor = factor
+        self.use_bias = use_bias
+        self.dropout = dropout
+        self.output_layer = output_layer
+        self.mean_residual = mean_residual
+        self.query = query
+
+        v_cfg = config.vision_backbone
+        input_dim = v_cfg.image_emb_dim
+        self.embed_dim = v_cfg.image_emb_dim * factor
+        self.num_heads = v_cfg.image_num_heads
+        self.head_dim = v_cfg.image_head_dim * factor
+        self.num_key_value_heads = v_cfg.image_num_key_value_heads
+        self.num_key_value_groups = self.num_heads // self.num_key_value_heads
+        self.initializer_range = v_cfg.initializer_range
+
+        nlayers = 1 if (is_vit_layer or config.vit_layers is None) else len(config.vit_layers)
+
+        if query != "vector":
+            self.wq = nn.Linear(
+                nlayers * input_dim,
+                self.num_heads * self.head_dim,
+                bias=use_bias,
+                device=config.init_device,
+                )
+        self.wk = nn.Linear(
+            nlayers * input_dim,
+            self.num_key_value_heads * self.head_dim,
+            bias=use_bias,
+            device=config.init_device,
+            )
+        self.wv = nn.Linear(
+            nlayers * input_dim,
+            self.num_key_value_heads * self.head_dim,
+            bias=use_bias,
+            device=config.init_device,
+            )
+
+        if query == "vector":
+            self.attention_query = nn.Parameter(
+                torch.zeros(
+                    1, self.num_key_value_heads * self.head_dim, device=config.init_device,
+                       ),
+            )
+
+        if output_layer:
+            self.wo = nn.Linear(
+                self.num_heads * self.head_dim,
+                self.embed_dim,
+                bias=use_bias,
+                device=config.init_device,
+                )
+        self.attention_dropout = Dropout(v_cfg.attention_dropout, broadcast_dims=(0, 1))
+        if dropout:
+            self.residual_dropout = Dropout(v_cfg.residual_dropout)
+
+    def reset_parameters(self):
+        if self.query != "vector":
+            nn.init.normal_(self.wq.weight, std=self.initializer_range)
+        nn.init.normal_(self.wk.weight, std=self.initializer_range)
+        nn.init.normal_(self.wv.weight, std=self.initializer_range)
+        if self.output_layer:
+            nn.init.normal_(self.wo.weight, std=self.initializer_range)
+        if self.use_bias:
+            if self.query != "vector":
+                nn.init.constant_(self.wq.bias, 0)
+            nn.init.constant_(self.wk.bias, 0)
+            nn.init.constant_(self.wv.bias, 0)
+            if self.output_layer:
+                nn.init.constant_(self.wo.bias, 0)
+        if self.query == "vector":
+            nn.init.normal_(self.attention_query, std=self.initializer_range)
+
+    def _split_heads(self, hidden_states, num_heads):
+        return hidden_states.reshape(hidden_states.shape[:2] + (num_heads, self.head_dim))
+
+    def _merge_heads(self, hidden_states):
+        return hidden_states.reshape(hidden_states.shape[:2] + (self.embed_dim,))
+
+    def forward(self, inputs_kv: torch.Tensor) -> torch.Tensor:
+
+        xk, xv = self.wk(inputs_kv), self.wv(inputs_kv)
+
+        if self.query == "mean":
+            inputs_q = inputs_kv.mean(dim=1, keepdim=True)
+            xq = self.wq(inputs_q)
+        elif self.query == "first":
+            inputs_q = inputs_kv[:, :1]
+            xq = self.wq(inputs_q)
+        elif self.query == "vector":
+            xq = self.attention_query.expand(inputs_kv.size(0), -1, -1)
+        elif self.query == "constant":
+            inputs_q = torch.ones_like(inputs_kv[:, :1]) / math.sqrt(inputs_kv.shape[-1])
+            xq = self.wq(inputs_q)
+        else:
+            raise ValueError(f"Unknown query type: {self.query}")
+
+        xq = self._split_heads(xq, self.num_heads)
+        xk = self._split_heads(xk, self.num_key_value_heads)
+        xv = self._split_heads(xv, self.num_key_value_heads)
+
+        if self.num_heads != self.num_key_value_heads:
+            xk = xk.repeat_interleave(self.num_key_value_groups, dim=2, output_size=self.num_heads)
+            xv = xv.repeat_interleave(self.num_key_value_groups, dim=2, output_size=self.num_heads)
+
+        xq = xq.to(torch.float)
+        xk = xk.to(torch.float)
+
+        xq = xq / math.sqrt(xq.size(-1))
+        attn_weights = torch.einsum("...qhd,...khd->...hqk", xq, xk)
+
+        attn_weights = F.softmax(attn_weights, dim=-1).to(xq.dtype)
+
+        attn_weights = self.attention_dropout(attn_weights).to(xv.dtype)
+
+        attn_output = torch.einsum("...hqk,...khd->...qhd", attn_weights, xv)
+        attn_output = self._merge_heads(attn_output)
+        if self.output_layer:
+            attn_output = self.wo(attn_output)
+        if self.dropout:
+            attn_output = self.residual_dropout(attn_output)
+        if self.mean_residual:
+            attn_output += inputs_kv.mean(dim=1, keepdim=True)
+
+        return attn_output
+
+
+class MLP(nn.Module):
+    def __init__(self, config: FullMolmoConfig, input_dim: int, dropout: float = 0.0):
+        super().__init__()
+        self.config = config
+        self.hidden_size = (
+            config.mlp_hidden_size if config.mlp_hidden_size is not None else config.mlp_ratio * config.d_model
+        )
+        self.initializer_range = config.initializer_range
+
+        self.w1 = nn.Linear(
+            input_dim,
+            self.hidden_size // 2,
+            bias=False,
+            device=config.init_device,
+            )
+        self.w2 = nn.Linear(
+            self.hidden_size // 2,
+            config.d_model,
+            bias=False,
+            device=config.init_device,
+            )
+        self.w3 = nn.Linear(
+            input_dim,
+            self.hidden_size // 2,
+            bias=False,
+            device=config.init_device,
+            )
+        # Activation function.
+        self.act = Activation.build(config)
+        self.dropout = Dropout(dropout)
+
+    def reset_parameters(self):
+        nn.init.normal_(self.w1.weight, std=self.initializer_range)
+        nn.init.normal_(self.w2.weight, std=self.initializer_range)
+        nn.init.normal_(self.w3.weight, std=self.initializer_range)
+
+    def forward(self, x: torch.Tensor) -> torch.Tensor:
+        x = self.w2(self.act(self.w1(x), self.w3(x)))
+        x = self.dropout(x)
+        return x
+
+
+class Residual(nn.Module):
+    def __init__(self, submodule: nn.Module):
+        super().__init__()
+        self.submodule = submodule
+
+    def reset_parameters(self):
+        self.submodule.reset_parameters()
+
+    def forward(self, x: torch.Tensor) -> torch.Tensor:
+        return x + self.submodule(x)
+
+
+class OLMoVisionBackbone(nn.Module):
+    def __init__(self, config: FullMolmoConfig):
+        super().__init__()
+        self.config = config
+        self.image_vit = VisionTransformer(config)
+
+        input_dim: int = None
+        self.image_pooling_2d: nn.Module = None
+        if config.image_pooling_2d in {ImagePooling2DType.attention, ImagePooling2DType.attention_meanq}:
+            self.image_pooling_2d = MultiHeadDotProductAttention(config, is_vit_layer=False)
+            input_dim = config.vision_backbone.image_emb_dim
+        elif config.image_pooling_2d == ImagePooling2DType.attention_2wide:
+            cfg = deepcopy(config)
+            cfg.vision_backbone.image_emb_dim *= 2
+            cfg.vision_backbone.image_head_dim *= 2
+            self.image_pooling_2d = MultiHeadDotProductAttention(cfg, is_vit_layer=False)
+            input_dim = cfg.vision_backbone.image_emb_dim
+        elif config.image_pooling_2d == ImagePooling2DType.attention_v2:
+            assert config.vit_layers is not None
+            use_bias = True
+            dropout = True
+            output_layer = True
+            query = "mean"
+            mean_residual = False
+            factor = len(config.vit_layers)
+            self.image_pooling_2d = MultiHeadAttentionPool(
+                config,
+                factor=factor,
+                use_bias=use_bias,
+                dropout=dropout,
+                output_layer=output_layer,
+                mean_residual=mean_residual,
+                query=query,
+                is_vit_layer=False,
+            )
+            input_dim = config.vision_backbone.image_emb_dim * factor
+        elif config.image_pooling_2d in [ImagePooling2DType.none, ImagePooling2DType.stack]:
+            self.image_pooling_2d = None
+            nlayers = 1 if config.vit_layers is None else len(config.vit_layers)
+            input_dim = nlayers * config.vision_backbone.image_emb_dim
+        else:
+            raise NotImplementedError(f"Unknown image pooling 2D method: {config.image_pooling_2d}")
+
+        self.input_dim = input_dim
+
+        # `MLP` assume the activation takes two inputs, so it must be a 'llama' version
+        if config.activation_type == ActivationType.swiglu:
+            mlp_config = replace(config, activation_type=ActivationType.llama_swiglu)
+        elif config.activation_type == ActivationType.gelu:
+            mlp_config = replace(config, activation_type=ActivationType.llama_geglu)
+        else:
+            mlp_config = config
+        if config.image_projector == ImageProjectType.mlpx2:
+            self.image_projector = nn.ModuleList(
+                [MLP(mlp_config, input_dim), Residual(MLP(config, input_dim))]
+            )
+        elif config.image_projector == ImageProjectType.mlp:
+            self.image_projector = MLP(mlp_config, input_dim)
+        elif config.image_projector == ImageProjectType.linear:
+            self.image_projector = nn.Linear(
+                input_dim,
+                config.d_model,
+                bias=False,
+                device=config.init_device,
+            )
+        else:
+            raise NotImplementedError(f"Unknown image projector: {config.image_projector}")
+
+        self.image_feature_dropout = Dropout(config.image_feature_dropout)
+
+    def reset_parameters(self):
+        if self.image_pooling_2d is not None:
+            self.image_pooling_2d.reset_parameters()
+        if self.config.image_projector == "2mlp":
+            for module in self.image_projector:
+                module.reset_parameters()
+        elif self.config.image_projector == "linear":
+            nn.init.xavier_uniform_(self.image_projector.weight)
+        else:
+            self.image_projector.reset_parameters()
+
+    def forward(self, images: torch.Tensor, image_masks: torch.Tensor) -> Tuple[torch.Tensor, Optional[torch.Tensor]]:
+        raise NotImplementedError
+
+
+class OLMoPretrainedVisionBackbone(OLMoVisionBackbone):
+    def __init__(self, config: FullMolmoConfig):
+        super().__init__(config)
+        v_cfg = self.config.vision_backbone
+        self.grad_checkpointing = False
+
+        self.num_prefix_tokens = self.image_vit.num_prefix_tokens
+        assert self.num_prefix_tokens in {0, 1}, "Only 0 or 1 prefix tokens are supported"
+
+        self.pad_embed = None
+        if config.image_padding_embed:
+            image_dim = v_cfg.image_emb_dim*len(self.config.vit_layers)
+            if config.image_padding_embed in ["pad_embed", "regress"]:
+                self.pad_embed = nn.Parameter(
+                    torch.zeros((image_dim,), device=config.init_device))
+            elif config.image_padding_embed == "pad_and_partial_pad":
+                self.pad_embed = nn.Parameter(
+                    torch.zeros((2, image_dim), device=config.init_device))
+            else:
+                raise ValueError(config.image_padding_embed)
+
+    def reset_parameters(self):
+        super().reset_parameters()
+        self.image_vit.reset_parameters()
+
+    def encode_image(self, images: torch.Tensor) -> torch.Tensor:
+        """
+        : param images: (batch_size, num_crops, num_patch, n_pixels)
+        """
+        cfg = self.config
+        v_cfg = self.config.vision_backbone
+        B, T, N, D = images.shape
+
+        mask = ~torch.all(images.view(B * T, N, D) == -1, dim=(1, 2), keepdim=True)
+
+        # Output all hidden states
+        # n_layers x (batch_num_crops, (1+)n_tokens, image_emb_dim)
+        images = images.view(B * T, N, D)
+        image_features = self.image_vit(images)
+
+        if cfg.vit_layers is not None:
+            features = []
+            for layer in cfg.vit_layers:
+                features.append(image_features[layer])
+            image_features = torch.cat(features, dim=-1)
+        else:
+            image_features = image_features[-1]
+
+        cls_embed: torch.Tensor = None
+        if self.num_prefix_tokens > 0:
+            cls_embed = image_features[:, 0]
+            image_features = image_features[:, 1:]
+
+        image_features = image_features * mask
+        image_features = image_features.view(B, T, N, -1)
+
+        cls_embed = cls_embed.view(B, T, -1) if cls_embed is not None else None
+
+        return image_features, cls_embed
+
+    def forward(self, images: torch.Tensor, image_masks: torch.Tensor) -> Tuple[torch.Tensor, Optional[torch.Tensor]]:
+        cfg = self.config
+
+        # image_features: (batch_size, num_crops(=num_image), num_patch, nximage_emb_dim)
+        batch_size, num_image = images.shape[:2]
+        image_features, cls_embed = self.encode_image(images)
+
+        if cfg.image_padding_embed:
+            assert image_masks is not None
+            if cfg.image_padding_embed == "pad_embed":
+                all_pad = (image_masks == 0).to(dtype=torch.float32)
+                pad_embed = self.pad_embed[None, None, None, :]
+                image_features = image_features + pad_embed * torch.unsqueeze(all_pad, -1)
+            elif cfg.image_padding_embed == "regress":
+                pad_embed = self.pad_embed[None, None, None, :]
+                image_features = image_features + pad_embed * torch.unsqueeze(torch.maximum(image_masks, torch.zeros_like(image_masks)), -1)
+            elif cfg.image_padding_embed == "pad_and_partial_pad":
+                pad_embed = self.pad_embed[:, None, None, None, :]
+                all_pad = image_masks == 0
+                partial_pad = torch.logical_and(image_masks < 1, torch.logical_not(all_pad)).to(dtype=torch.float32)
+                all_pad = all_pad.to(dtype=torch.float32)
+                image_features = image_features + pad_embed[0] * torch.unsqueeze(all_pad, -1)
+                image_features = image_features + pad_embed[1] * torch.unsqueeze(partial_pad, -1)
+            else:
+                raise ValueError(cfg.image_padding_embed)
+
+        image_features = self.image_feature_dropout(image_features)
+        if cls_embed is not None:
+            cls_embed = self.image_feature_dropout(cls_embed)
+
+        image_features = image_features.reshape(
+            (batch_size, num_image) + cfg.image_num_patch + (-1,),
+            )
+
+        if cfg.image_num_patch[0] % cfg.image_pooling_h == 1:
+            # Pad so we can still pool 2x2 patches
+            image_features = F.pad(
+                image_features,
+                (0, 0, 0, 1, 0, 1, 0, 0, 0, 0),
+            )
+
+        # image pooling
+        image_features = einops.rearrange(
+            image_features,
+            'b n (h dh) (w dw) c -> (b n h w) (dh dw) c',
+            dh=cfg.image_pooling_h,
+            dw=cfg.image_pooling_w,
+        )
+
+        if cfg.image_pooling_2d == ImagePooling2DType.attention_meanq:
+            query = image_features.mean(-2, keepdim=True)
+            image_features = self.image_pooling_2d(query, image_features)
+        elif cfg.image_pooling_2d not in {ImagePooling2DType.none, ImagePooling2DType.stack}:
+            if self.grad_checkpointing:
+                from torch.utils.checkpoint import checkpoint
+                image_features = checkpoint(self.image_pooling_2d, image_features[:, :1, :], image_features, use_reentrant=False)
+            else:
+                image_features = self.image_pooling_2d(image_features[:, :1, :], image_features)
+
+        h, w = cfg.llm_patches_per_crop()
+        image_features = image_features.reshape(batch_size, num_image, h * w, -1)
+
+        # MLP layer to map the feature.
+        if self.grad_checkpointing:
+            from torch.utils.checkpoint import checkpoint
+            image_features = checkpoint(self.image_projector, image_features, use_reentrant=False)
+        else:
+            image_features = self.image_projector(image_features)
+
+        # image_features: (batch_size, num_image, num_patch, d_model)
+        # cls_embed: (batch_size, num_image, d_model)
+        return image_features, cls_embed
+
+
+class ModuleType(str, Enum):
+    in_module = "in"
+    out_module = "out"
+    emb = "emb"
+    final_out = "final_out"
+
+
+def init_weights(
+    config: FullMolmoConfig,
+    module: Union[nn.Linear, nn.Embedding],
+    d: Optional[int] = None,
+    layer_id: Optional[int] = None,
+    std_factor: float = 1.0,
+    type_of_module: Optional[ModuleType] = None,
+) -> None:
+    d = d if d is not None else config.d_model
+    std = config.init_std * std_factor
+    if config.init_cutoff_factor is not None:
+        cutoff_value = config.init_cutoff_factor * std
+        nn.init.trunc_normal_(module.weight, mean=0.0, std=std, a=-cutoff_value, b=cutoff_value)
+    else:
+        nn.init.normal_(module.weight, mean=0.0, std=std)
+
+
+class LlamaSwiGLU(nn.Module):
+    def forward(self, x1: torch.Tensor, x2: torch.Tensor) -> torch.Tensor:
+        return F.silu(x1) * x2
+
+    @property
+    def output_multiplier(self) -> float:
+        return 0.5
+
+
+class SwiGLU(nn.Module):
+    def forward(self, x: torch.Tensor) -> torch.Tensor:
+        x, gate = x.chunk(2, dim=-1)
+        return F.silu(gate) * x
+
+    @property
+    def output_multiplier(self) -> float:
+        return 0.5
+
+
+class Activation(nn.Module):
+    def __init__(self, config: FullMolmoConfig):
+        super().__init__()
+        self.config = config
+
+    def forward(self, x: torch.Tensor) -> torch.Tensor:
+        raise NotImplementedError
+
+    @property
+    def output_multiplier(self) -> float:
+        raise NotImplementedError
+
+    @classmethod
+    def build(cls, config: FullMolmoConfig) -> 'Activation':
+        if config.activation_type == "quick_gelu":
+            return QuickGELU(config)
+        elif config.activation_type == "gelu":
+            return cast(Activation, GELU(approximate="none"))
+        elif config.activation_type == "gelu_tanh":
+            return cast(Activation, GELU(approximate="tanh"))
+        elif config.activation_type == "relu":
+            return cast(Activation, ReLU(inplace=False))
+        elif config.activation_type == "silu":
+            return cast(Activation, SiLU(inplace=False))
+        # elif config.activation_type == "llama_geglu":
+        #     return LlamaGEGLU(config)
+        # elif config.activation_type == "llama_geglu_tanh":
+        #     return LlamaGEGLUTanh(config)
+        elif config.activation_type == "llama_swiglu":
+            return LlamaSwiGLU()
+        elif config.activation_type == "swiglu":
+            return SwiGLU()
+        else:
+            raise NotImplementedError(f"Unknown activation: '{config.activation_type}'")
+
+
+class QuickGELU(Activation):
+    def forward(self, x: torch.Tensor) -> torch.Tensor:
+        return x * torch.sigmoid(1.702 * x)
+
+    @property
+    def output_multiplier(self) -> float:
+        return 1.0
+
+
+class GELU(nn.GELU):
+    @property
+    def output_multiplier(self) -> float:
+        return 1.0
+
+
+class ReLU(nn.ReLU):
+    @property
+    def output_multiplier(self) -> float:
+        return 1.0
+
+
+class SiLU(nn.SiLU):
+    @property
+    def output_multiplier(self) -> float:
+        return 1.0
+
+
+def causal_attention_bias(seq_len: int, device: torch.device) -> torch.FloatTensor:
+    att_bias = torch.triu(
+        torch.ones(seq_len, seq_len, device=device, dtype=torch.float),
+        diagonal=1,
+    )
+    att_bias.masked_fill_(att_bias == 1, torch.finfo(att_bias.dtype).min)
+    return att_bias.view(1, 1, seq_len, seq_len)  # type: ignore
+
+
+def get_causal_attention_bias(cache: BufferCache, seq_len: int, device: torch.device) -> torch.Tensor:
+    if (causal_bias := cache.get("causal_attention_bias")) is not None and causal_bias.shape[-1] >= seq_len:
+        if causal_bias.device != device:
+            causal_bias = causal_bias.to(device)
+            cache["causal_attention_bias"] = causal_bias
+        return causal_bias
+    with torch.autocast(device.type, enabled=False):
+        causal_bias = causal_attention_bias(seq_len, device)
+    cache["causal_attention_bias"] = causal_bias
+    return causal_bias
+
+
+class LayerNormBase(nn.Module):
+    def __init__(
+        self,
+        config: MolmoConfig,
+        *,
+        size: Optional[int] = None,
+        elementwise_affine: Optional[bool] = True,
+        eps: float = 1e-05,
+        weight_initializer: Optional[Callable] = torch.ones,
+        bias_initializer: Optional[Callable] = torch.zeros,
+    ):
+        super().__init__()
+        self.config = config
+        self.eps = self.config.layer_norm_eps or eps
+        self.normalized_shape = (size or config.d_model,)
+        if elementwise_affine or (elementwise_affine is None and self.config.layer_norm_with_affine):
+            self.weight = nn.Parameter(weight_initializer(self.normalized_shape, device=config.init_device))
+            use_bias = self.config.bias_for_layer_norm
+            if use_bias is None:
+                use_bias = self.config.include_bias
+            if use_bias:
+                self.bias = nn.Parameter(bias_initializer(self.normalized_shape, device=config.init_device))
+            else:
+                self.register_parameter("bias", None)
+        else:
+            self.register_parameter("bias", None)
+            self.register_parameter("weight", None)
+
+    @classmethod
+    def build(cls, config: FullMolmoConfig, size: Optional[int] = None, **kwargs):
+        if config.layer_norm_type == "default":
+            return LayerNorm(config, size=size, low_precision=False, **kwargs)
+        elif config.layer_norm_type == "low_precision":
+            return LayerNorm(config, size=size, low_precision=True, **kwargs)
+        elif config.layer_norm_type == "rms":
+            return RMSLayerNorm(config, size=size, **kwargs)
+        else:
+            raise NotImplementedError(f"Unknown LayerNorm type: '{config.layer_norm_type}'")
+
+
+class RMSLayerNorm(LayerNormBase):
+    """
+    RMS layer norm, a simplified :class:`LayerNorm` implementation
+    """
+
+    def __init__(
+        self,
+        config: FullMolmoConfig,
+        size: Optional[int] = None,
+        elementwise_affine: Optional[bool] = None,
+        eps: float = 1e-5,
+    ):
+        super().__init__(config, size=size, elementwise_affine=elementwise_affine, eps=eps)
+
+    def forward(self, x: torch.Tensor) -> torch.Tensor:
+        with torch.autocast(enabled=False, device_type=x.device.type):
+            og_dtype = x.dtype
+            x = x.to(torch.float32)
+            variance = x.pow(2).mean(-1, keepdim=True)
+            x = x * torch.rsqrt(variance + self.eps)
+            x = x.to(og_dtype)
+
+        if self.weight is not None:
+            if self.bias is not None:
+                return self.weight * x + self.bias
+            else:
+                return self.weight * x
+        else:
+            return x
+
+
+class LayerNorm(LayerNormBase):
+    """
+    The default :class:`LayerNorm` implementation which can optionally run in low precision.
+    """
+
+    def __init__(
+        self,
+        config: FullMolmoConfig,
+        size: Optional[int] = None,
+        low_precision: bool = False,
+        elementwise_affine: Optional[bool] = None,
+        eps: float = 1e-05,
+    ):
+        super().__init__(config, size=size, elementwise_affine=elementwise_affine, eps=eps)
+        self.low_precision = low_precision
+
+    def forward(self, x: torch.Tensor) -> torch.Tensor:
+        if self.low_precision:
+            module_device = x.device
+            downcast_x = self._cast_if_autocast_enabled(x)
+            downcast_weight = (
+                self._cast_if_autocast_enabled(self.weight) if self.weight is not None else self.weight
+            )
+            downcast_bias = self._cast_if_autocast_enabled(self.bias) if self.bias is not None else self.bias
+            with torch.autocast(enabled=False, device_type=module_device.type):
+                return F.layer_norm(
+                    downcast_x, self.normalized_shape, weight=downcast_weight, bias=downcast_bias, eps=self.eps
+                )
+        else:
+            return F.layer_norm(x, self.normalized_shape, weight=self.weight, bias=self.bias, eps=self.eps)
+
+
+class Molmo(nn.Module):
+    def __init__(self, config: FullMolmoConfig, init_params: bool = True):
+        super().__init__()
+        self.config = config
+        self.__cache = BufferCache()
+
+        # Validate config.
+        if self.config.embedding_size is not None and self.config.embedding_size != self.config.vocab_size:
+            if self.config.embedding_size < self.config.vocab_size:
+                raise MolmoConfigurationError("embedding size should be at least as big as vocab size")
+            elif self.config.embedding_size % 128 != 0:
+                import warnings
+
+                warnings.warn(
+                    "Embedding size is not a multiple of 128! This could hurt throughput performance.", UserWarning
+                )
+        torch.backends.cuda.enable_flash_sdp(True)
+        torch.backends.cuda.enable_mem_efficient_sdp(False)  # this is super slow so make sure torch won't use it
+
+        wte = None
+        if self.config.additional_vocab_size is not None:
+            wte = Embedding(
+                config.embedding_size or config.vocab_size,
+                config.additional_vocab_size,
+                config.d_model,
+                device=config.init_device,
+                initializer_range=config.initializer_range,
+                new_embed_initializer_range=config.new_embedding_init_range
+            )
+        else:
+            wte=nn.Embedding(
+                config.embedding_size or config.vocab_size, config.d_model, device=config.init_device
+            )
+
+        self.transformer = nn.ModuleDict(
+            dict(
+                wte=wte,
+                emb_drop=Dropout(config.embedding_dropout),
+                ln_f=LayerNorm.build(config),
+            )
+        )
+
+        blocks = [MolmoBlock.build(i, config, self.__cache) for i in range(config.n_layers)]
+        if self.config.block_group_size > 1:
+            raise NotImplementedError()
+        else:
+            self.transformer.update({"blocks": nn.ModuleList(blocks)})
+
+        if not self.config.rope:
+            self.transformer.update(
+                {"wpe": nn.Embedding(config.max_sequence_length, config.d_model, device=config.init_device)}
+            )
+        if not config.weight_tying:
+            self.transformer.update(
+                {
+                    "ff_out": nn.Linear(
+                        config.d_model,
+                        config.embedding_size or config.vocab_size,
+                        bias=config.include_bias,
+                        device=config.init_device,
+                        )
+                }
+            )
+
+        self.vision_backbone: Optional[OLMoVisionBackbone] = None
+        if config.vision_backbone is not None:
+            self.vision_backbone = OLMoPretrainedVisionBackbone(config)
+
+        self.__num_fwd_flops: Optional[int] = None
+
+    def reset_parameters(self):
+        if self.vision_backbone is not None:
+            self.vision_backbone.reset_parameters()
+        self.reset_non_vision_parameters()
+
+    def reset_non_vision_parameters(self):
+        self.transformer.wte.reset_parameters()
+        if hasattr(self.transformer.wte, "new_embedding"):
+            nn.init.normal_(self.transformer.wte.new_embedding, std=self.config.new_embedding_init_range)
+
+        if hasattr(self.transformer, "wpe"):
+            nn.init.normal_(self.transformer.wpe, mean=0.0, std=1.0)
+
+        self.transformer.ln_f.reset_parameters()  # type: ignore
+
+        if hasattr(self.transformer, "ff_out"):
+            nn.init.normal_(self.transformer.ff_out, mean=0.0, std=0.02)
+
+        if self.config.block_group_size == 1:
+            for block in self.transformer.blocks:
+                block.reset_parameters()
+        else:
+            for block_group in self.transformer.block_groups:
+                block_group.reset_parameters()
+
+    def forward(
+        self,
+        input_ids: torch.LongTensor,
+        input_embeddings: Optional[torch.FloatTensor] = None,
+        attention_mask: Optional[torch.Tensor] = None,
+        attention_bias: Optional[torch.Tensor] = None,
+        response_mask: Optional[torch.Tensor] = None,
+        images: Optional[torch.Tensor] = None,
+        image_masks: Optional[torch.Tensor] = None,
+        image_input_idx: Optional[torch.Tensor] = None,
+        subsegment_ids: Optional[torch.Tensor] = None,
+        position_ids: Optional[torch.Tensor] = None,
+        past_key_values: Optional[Sequence[Tuple[torch.Tensor, torch.Tensor]]] = None,
+        use_cache: bool = False,
+        last_logits_only: bool = False,
+        output_hidden_states: Optional[bool] = None,
+        append_last_valid_logits: Optional[torch.Tensor] = None,
+    ) -> ModelOutput:
+        """
+        :param input_ids: A tensor of shape `(batch_size, seq_len)`.
+        :param input_embeddings: A tensor of shape `(batch_size, seq_len, d_model)` with input
+            embeddings. When provided, it is treated as the output of the input embedding layer.
+        :param attention_mask: A tensor of shape `(batch_size, seq_len)` that indicates
+            which input IDs are masked. A `1` value in the mask means that
+            the corresponding input ID should *not* be ignored. A `0` means
+            that the corresponding input ID is masked.
+
+            This has the same meaning as the `attention_mask` in HuggingFace's `transformers`
+            library.
+        :param attention_bias: A tensor of shape `(batch_size, 1, seq_len, seq_len)`,
+            `(1, 1, seq_len, seq_len)`, or `(seq_len, seq_len)`. This is used
+            to introduce causal or other biases.
+
+            If the tensor is a bool or byte tensor, a `True` or `1` at `attention_bias[:, :, i, j]`
+            indicates that the i-th element in the sequence is allowed to attend to the j-th
+            element in the sequence.
+
+            If the tensor is a float tensor, it will just be added to the attention
+            scores before the softmax.
+
+            The default is causal, which corresponds to a lower-diagonal byte matrix of ones.
+        :param response_mask: A tensor of shape `(batch_size, seq_len)` that indicates
+            the response mask. A `1` value in the mask means that the corresponding token
+            is a response token. A `0` means that the corresponding token is not
+            a response token.
+        :param past_key_values: Pre-computed keys and values for each attention block.
+            Can be used to speed up sequential decoding. The `input_ids` which have
+            their past given to this model should not be passed as `input_ids` as they have already been computed.
+        :param use_cache: If `True`, return key and value tensors for each block.
+        :param last_logits_only: If `True`, only compute the logits for the last token of each sequence.
+            This can speed up decoding when you only care about the next token.
+        """
+        output_hidden_states = output_hidden_states if output_hidden_states is not None else False
+
+        if past_key_values:
+            assert len(past_key_values) == self.config.n_layers
+
+        has_image = images is not None
+
+        assert not (has_image and input_embeddings is not None), "Cannot provide both images and input embeddings."
+        assert not (has_image and past_key_values is not None), "Cached key and values should not be used with images."
+
+        batch_size, seq_len = input_ids.size() if input_embeddings is None else input_embeddings.size()[:2]
+        if past_key_values is None:
+            past_length = 0
+        else:
+            past_length = past_key_values[0][0].size(-2)
+
+        if self.config.use_position_ids and attention_mask is None:
+            attention_mask = input_ids != -1
+
+        if subsegment_ids is not None:
+            assert not use_cache, "Subsegment_ids cannot be used with cache."
+            subsegment_mask = subsegment_ids.unsqueeze(2) <= subsegment_ids.unsqueeze(1)
+            attention_mask = (
+                subsegment_mask.to(attention_mask.dtype) *
+                attention_mask.unsqueeze(2) *
+                attention_mask.unsqueeze(1))
+            if position_ids is None:
+                raise ValueError(f"Positioned ids must be given if using subsegment_ids")
+        else:
+            if self.config.use_position_ids and position_ids is None:
+                position_ids = torch.clamp(
+                    torch.cumsum(attention_mask.to(torch.int32), dim=-1) - 1,
+                    min=0,
+                    ).broadcast_to((batch_size, attention_mask.shape[-1]))
+
+        # Get embeddings of input.
+        # shape: (batch_size, seq_len, d_model)
+        if input_ids is not None:
+            input_ids = input_ids * (input_ids != -1).to(input_ids.dtype)
+        x = self.transformer.wte(input_ids) if input_embeddings is None else input_embeddings  # type: ignore
+
+        num_image: Optional[int] = None
+        if images is not None:
+            # shape: (batch_size, num_image, num_patch, d_model)
+            # cls_embed: (batch_size, num_image, d_model)
+            image_features, cls_embed = self.vision_backbone(images, image_masks)
+            num_image, num_patch = image_features.shape[1:3]
+            assert image_input_idx.shape == (batch_size, num_image, num_patch)
+
+            # inster the image feature into the embedding.
+            image_features = image_features.view(batch_size, num_image * num_patch, -1)
+            image_input_idx = image_input_idx.view(batch_size, num_image * num_patch)
+
+            valid = image_input_idx >= 0
+            batch_idx = torch.arange(batch_size, device=x.device)
+            batch_idx = torch.tile(batch_idx[:, None], [1, image_features.shape[1]])
+
+            # For hf demo/endpoint
+            image_features = image_features.to(x.device)
+
+            x[batch_idx[valid], image_input_idx[valid]] += image_features[valid]
+
+        if not self.config.rope:
+            # Get positional embeddings.
+            # shape: (1, seq_len)
+            pos = torch.arange(past_length, past_length + seq_len, dtype=torch.long, device=x.device).unsqueeze(0)
+            # shape: (1, seq_len, d_model)
+            pos_emb = self.transformer.wpe(pos)  # type: ignore
+            x = pos_emb + x
+
+        # Add input + positional embeddings and apply dropout.
+        # shape: (batch_size, seq_len, d_model)
+        x = self.transformer.emb_drop(x)  # type: ignore
+
+        # normalized
+        if self.config.normalize_input_embeds:
+            x = x * (self.config.d_model ** 0.5)
+
+        # Transform the attention mask into what the blocks expect.
+        if attention_mask is not None:
+            # shape: (batch_size, 1, 1, seq_len)
+            if len(attention_mask.shape) == 2:
+                attention_mask = attention_mask[:, :past_length + seq_len]
+                attention_mask = attention_mask.to(dtype=torch.float).view(batch_size, -1)[:, None, None, :]
+            else:
+                attention_mask = attention_mask.unsqueeze(1).to(dtype=torch.float)
+            attention_mask = (1.0 - attention_mask) * torch.finfo(attention_mask.dtype).min
+
+        # Merge attention mask with attention bias.
+        if (
+            attention_bias is not None
+            or attention_mask is not None
+            # NOTE (epwalsh): we need to initialize the attn bias in order for attn to work properly
+            # with key+value cache. Otherwise `F.scaled_dot_product_attention()` doesn't seem to compute
+            # scores correctly.
+            or past_key_values is not None
+        ):
+            if attention_bias is None:
+                attention_bias = get_causal_attention_bias(self.__cache, past_length + seq_len, x.device)
+            elif attention_bias.dtype in (torch.int8, torch.bool):
+                attention_bias = attention_bias.to(dtype=torch.float)
+                attention_bias.masked_fill_(attention_bias == 0.0, torch.finfo(attention_bias.dtype).min)
+
+            # Transform to the right shape and data type.
+            mask_len = seq_len
+            if attention_mask is not None:
+                mask_len = attention_mask.shape[-1]
+            elif past_key_values is not None:
+                mask_len = past_key_values[0][0].shape[-2] + seq_len
+            attention_bias = attention_bias[:, :, :mask_len, :mask_len].to(dtype=torch.float)
+
+            # Add in the masking bias.
+            if attention_mask is not None:
+                attention_bias = attention_bias + attention_mask
+                # Might get -infs after adding attention mask, since dtype.min + dtype.min = -inf.
+                # `F.scaled_dot_product_attention()` doesn't handle -inf like you'd expect, instead
+                # it can produce NaNs.
+                ensure_finite_(attention_bias, check_neg_inf=True, check_pos_inf=False)
+
+        attn_key_values: Optional[List[Tuple[torch.Tensor, torch.Tensor]]] = [] if use_cache else None
+
+        # decoder layers
+        all_hidden_states = []
+
+        # Apply blocks one-by-one.
+        if self.config.block_group_size == 1:
+            for block_idx, block in enumerate(self.transformer.blocks):
+                if output_hidden_states:
+                    # add hidden states
+                    all_hidden_states.append(x)
+
+                layer_past = None if past_key_values is None else past_key_values[block_idx]
+                x, cache = block(x, attention_bias=attention_bias, position_ids=position_ids, layer_past=layer_past, use_cache=use_cache)
+
+                if attn_key_values is not None:
+                    assert cache is not None
+                    attn_key_values.append(cache)
+        else:
+            for group_idx, block_group in enumerate(self.transformer.block_groups):
+                if output_hidden_states:
+                    # add hidden states
+                    all_hidden_states.append(x)
+
+                layers_past = (
+                    None
+                    if past_key_values is None
+                    else past_key_values[
+                         group_idx * self.config.block_group_size : (group_idx + 1) * self.config.block_group_size
+                         ]
+                )
+                x, cache = block_group(
+                    x, attention_bias=attention_bias, position_ids=position_ids, layers_past=layers_past, use_cache=use_cache
+                )
+                if attn_key_values is not None:
+                    assert cache is not None
+                    attn_key_values.extend(cache)
+
+        if last_logits_only:
+            # shape: (batch_size, 1, d_model)
+            if append_last_valid_logits is not None:
+                last_valid_output = x[
+                    torch.arange(x.shape[0], device=x.device), append_last_valid_logits.to(x.device)]
+                x = last_valid_output.unsqueeze(1)
+            else:
+                x = x[:, -1, :].unsqueeze(1)
+
+        # Apply final layer norm.
+        # shape: (batch_size, seq_len or 1, d_model)
+        x = self.transformer.ln_f(x)  # type: ignore
+        if output_hidden_states:
+            # add final hidden state post-final-layernorm, following HuggingFace's convention
+            all_hidden_states.append(x)
+
+        # Get logits.
+        # shape: (batch_size, seq_len or 1, vocab_size)
+        if self.config.weight_tying:
+            logits = F.linear(x, self.transformer.wte.weight, None)  # type: ignore
+        else:
+            logits = self.transformer.ff_out(x)  # type: ignore
+        if self.config.scale_logits:
+            logits.mul_(1 / math.sqrt(self.config.d_model))
+
+        if not last_logits_only and append_last_valid_logits is not None:
+            last_valid_logit = logits[
+                torch.arange(logits.shape[0], device=logits.device), append_last_valid_logits]
+            logits = torch.cat([logits[:, :-1], last_valid_logit[:, None]], dim=1)
+
+        return ModelOutput(logits=logits, attn_key_values=attn_key_values, hidden_states=tuple(all_hidden_states) if output_hidden_states else None)  # type: ignore[arg-type]
+
+
+class MolmoForCausalLM(PreTrainedModel):
+    config_class = MolmoConfig
+    base_model_prefix = "model"
+    _no_split_modules = ["MolmoBlock"]
+
+    def __init__(self, config: MolmoConfig, model: Optional[Molmo] = None, init_params: bool = False):
+        super().__init__(config)
+
+        if not model:
+            full_config = FullMolmoConfig(
+                image_padding_embed="pad_and_partial_pad",
+                image_pooling_2d="attention-meanq",
+                attention_layer_norm=config.attention_layer_norm,
+                rope_impl="llama",
+                vocab_size=config.vocab_size,
+                max_sequence_length=config.max_position_embeddings,
+                qkv_bias=config.qkv_bias,
+                norm_after=config.norm_after,
+                embedding_size=config.embedding_size,
+                attention_type="sdpa",
+                embedding_dropout=0,
+                attention_dropout=0,
+                residual_dropout=0,
+                rope=True,
+                weight_tying=False,
+                include_bias=False,
+                d_model=config.hidden_size,
+                mlp_hidden_size=config.intermediate_size,
+                n_layers=config.num_hidden_layers,
+                additional_vocab_size=128,
+                n_heads=config.num_attention_heads,
+                n_kv_heads=config.num_key_value_heads,
+                rope_theta=config.rope_theta,
+                layer_norm_eps=config.layer_norm_eps,
+                layer_norm_type=config.layer_norm_type,
+                vit_layers=[-2, -9],
+                vision_backbone=VisionBackboneConfig(
+                    image_default_input_size=(336, 336),
+                    image_patch_size=14,
+                    image_pos_patch_size=14,
+                    image_emb_dim=1024,
+                    image_num_heads=16,
+                    image_num_key_value_heads=16,
+                    image_num_layers=23,
+                    image_head_dim=64,
+                    image_mlp_dim=4096,
+                    image_mlp_activations="quick_gelu",
+                    image_dropout_rate=0.0,
+                    image_num_pos=577,
+                    image_norm_eps=1e-5,
+                    attention_dropout=0.0,
+                    residual_dropout=0.0,
+                    initializer_range=0.02,
+                )
+            )
+            self.model = Molmo(full_config, init_params=init_params)
+        else:
+            self.model = model
+
+    def forward(
+        self,
+        input_ids: torch.LongTensor = None,
+        inputs_embeds: Optional[torch.FloatTensor] = None,
+        attention_mask: Optional[torch.Tensor] = None,
+        attention_bias: Optional[torch.Tensor] = None,
+        response_mask: Optional[torch.Tensor] = None,
+        images: Optional[torch.Tensor] = None,
+        image_masks: Optional[torch.Tensor] = None,
+        image_input_idx: Optional[torch.Tensor] = None,
+        subsegment_ids: Optional[torch.Tensor] = None,
+        position_ids: Optional[torch.Tensor] = None,
+        past_key_values: Optional[List[torch.FloatTensor]] = None,
+        labels: Optional[torch.LongTensor] = None,
+        loss_masks: Optional[torch.Tensor] = None,
+        use_cache: Optional[bool] = None,
+        last_logits_only: Optional[bool] = None,
+        output_attentions: Optional[bool] = None,
+        output_hidden_states: Optional[bool] = None,
+        append_last_valid_logits: Optional[torch.Tensor] = None,
+        return_dict: Optional[bool] = None,
+        cache_position: Optional[
+            Cache
+        ] = None,  # This is a hack mitigation of an issue in transformers `4.39.x` https://github.com/huggingface/transformers/issues/29426
+    ) -> Union[Tuple, CausalLMOutputWithPast]:
+        if use_cache is None:
+            use_cache = self.config.use_cache
+
+        if output_attentions:
+            raise ValueError("output_attentions is not yet supported in Molmo")
+
+        return_dict = return_dict if return_dict is not None else self.config.use_return_dict
+
+        # decoder outputs consists of (dec_features, layer_state, dec_hidden, dec_attn)
+        outputs = self.model.forward(
+            input_ids=input_ids,
+            input_embeddings=inputs_embeds,
+            attention_mask=attention_mask,
+            attention_bias=attention_bias,
+            response_mask=response_mask,
+            images=images,
+            image_masks=image_masks,
+            image_input_idx=image_input_idx,
+            subsegment_ids=subsegment_ids,
+            position_ids=position_ids,
+            past_key_values=past_key_values,
+            use_cache=use_cache,
+            last_logits_only=last_logits_only,
+            output_hidden_states=output_hidden_states,
+            append_last_valid_logits=append_last_valid_logits,
+        )
+
+        logits = outputs.logits
+        hidden_states = outputs.hidden_states
+
+        loss = None
+        if labels is not None:
+            if loss_masks is not None:
+                loss_masks = loss_masks * (loss_masks > 0)
+                batch_size_in_tokens = max(loss_masks.sum().item(), 1)
+                labels = labels.long()
+                labels.masked_fill_(~(loss_masks > 0), -100)
+                labels = labels.view(-1)
+                logits_for_loss = logits.to(torch.float32).view(-1, logits.size(-1))
+                loss_fct = torch.nn.CrossEntropyLoss(ignore_index=-100, reduction='none')
+                loss = loss_fct(logits_for_loss, labels)
+                loss = loss.view(input_ids.shape[0], -1)
+                loss = loss * loss_masks
+                loss = loss.sum() / batch_size_in_tokens
+                use_zloss = getattr(self.config, "softmax_auxiliary_loss", False)
+                if use_zloss:
+                    z_squared = logits_for_loss.logsumexp(-1).pow(2)
+                    z_loss = self.config.softmax_auxiliary_loss_scale * z_squared
+                    z_loss = z_loss.view(input_ids.shape[0], -1)
+                    z_loss = z_loss * loss_masks
+                    z_loss = z_loss.sum() / batch_size_in_tokens
+                    loss += z_loss
+            else:
+                # Shift so that tokens < n predict n
+                shift_logits = logits[..., :-1, :].contiguous()
+                shift_labels = labels[..., 1:].contiguous()
+                # Flatten the tokens
+                loss_fct = torch.nn.CrossEntropyLoss()
+                shift_logits = shift_logits.view(-1, self.config.embedding_size)
+                shift_labels = shift_labels.view(-1)
+                # Enable model parallelism
+                shift_labels = shift_labels.to(shift_logits.device)
+                loss = loss_fct(shift_logits, shift_labels)
+
+        if not return_dict:
+            output = (logits,) + outputs[1:]
+            return (loss,) + output if loss is not None else output
+
+        return CausalLMOutputWithPast(
+            loss=loss,
+            logits=logits,
+            past_key_values=outputs.attn_key_values,
+            hidden_states=hidden_states,
+        )
+
+    def can_generate(self) -> bool:
+        return True
+
+    @torch.no_grad()
+    def generate_from_batch(
+        self,
+        batch: Dict[str, Any],
+        generation_config: Optional[GenerationConfig] = None,
+        **kwargs,
+    ):
+        if generation_config is not None:
+            assert generation_config.use_cache
+
+        images = batch.get("images")
+        image_masks = batch.get("image_masks")
+        image_input_idx = batch.get("image_input_idx")
+
+        # Validate inputs.
+        input_ids = batch["input_ids"]
+        batch_size, seq_len = input_ids.shape
+        attention_mask = batch.get("attention_mask", None)
+        max_new_tokens = generation_config.max_new_tokens
+        assert max_new_tokens is not None
+        mask_len = seq_len + max_new_tokens if self.config.use_position_ids else seq_len
+        position_ids: Optional[torch.Tensor] = None
+        append_last_valid_logits: Optional[torch.Tensor] = None
+        if self.config.use_position_ids and attention_mask is None:
+            attention_mask = input_ids != -1
+            position_ids = torch.clamp(
+                torch.cumsum(attention_mask.to(torch.int32), dim=-1) - 1,
+                min=0
+            )
+            append_last_valid_logits = attention_mask.long().sum(dim=-1) - 1
+            attention_mask = torch.cat(
+                [attention_mask, attention_mask.new_ones((batch_size, max_new_tokens))],
+                dim=1,
+            )
+        if attention_mask is not None:
+            assert attention_mask.shape == (batch_size, mask_len)
+
+        out = super().generate(
+            batch["input_ids"],
+            generation_config,
+            attention_mask=attention_mask,
+            images=images,
+            image_masks=image_masks,
+            image_input_idx=image_input_idx,
+            position_ids=position_ids,
+            append_last_valid_logits=append_last_valid_logits,
+            **kwargs,
+        )
+
+        return out
+
+    def prepare_inputs_for_generation(
+        self, input_ids: torch.LongTensor, past_key_values: Optional[List[Tuple]] = None, **kwargs
+    ):
+        if past_key_values:
+            # This is because we want the model to only process the last generated token.
+            input_ids = input_ids[:, -1:]
+
+        if self.config.use_position_ids:
+            attention_mask = kwargs.get("attention_mask")
+            images = kwargs.get("images")
+            image_masks = kwargs.get("image_masks")
+            image_input_idx = kwargs.get("image_input_idx")
+            position_ids = kwargs.get("position_ids")
+            append_last_valid_logits = kwargs.get("append_last_valid_logits")
+            model_inputs = {
+                "input_ids": input_ids,
+                "attention_mask": attention_mask,
+                "position_ids": position_ids,
+                "past_key_values": past_key_values,
+                "use_cache": True,
+                "last_logits_only": True,
+            }
+            if past_key_values is None:
+                model_inputs["images"] = images
+                model_inputs["image_masks"] = image_masks
+                model_inputs["image_input_idx"] = image_input_idx
+                model_inputs["append_last_valid_logits"] = append_last_valid_logits
+        else:
+            model_inputs = {"input_ids": input_ids, "past_key_values": past_key_values}
+
+            model_inputs.update(kwargs)
+            model_inputs["use_cache"] = kwargs.pop("use_cache", self.config.use_cache)
+        return model_inputs
+
+    def _update_model_kwargs_for_generation(
+        self,
+        outputs: ModelOutput,
+        model_kwargs: Dict[str, Any],
+        is_encoder_decoder: bool = False,
+        num_new_tokens: int = 1,
+    ) -> Dict[str, Any]:
+        if self.config.use_position_ids:
+            model_kwargs["position_ids"] = model_kwargs["position_ids"][:, -1:] + 1
+            if "append_last_valid_logits" in model_kwargs:
+                del model_kwargs["append_last_valid_logits"]
+            if "images" in model_kwargs:
+                del model_kwargs["images"]
+                del model_kwargs["image_masks"]
+                del model_kwargs["image_input_idx"]
+        cache_name, cache = super()._extract_past_from_model_output(outputs)
+        model_kwargs[cache_name] = cache
+        model_kwargs["cache_position"] = model_kwargs["cache_position"][-1:] + num_new_tokens
+        return model_kwargs
+
+    def get_input_embeddings(self) -> torch.nn.Module:
+        return self.model.transformer.wte
+
+    def set_input_embeddings(self, value: torch.nn.Module):
+        self.model.transformer.wte = value
+
+    def get_output_embeddings(self):
+        if self.config.weight_tying:
+            return self.model.transformer.wte
+        else:
+            return self.model.transformer.ff_out
+
+    def set_output_embeddings(self, value: torch.nn.Module):
+        if self.config.weight_tying:
+            self.model.transformer.wte = value
+        else:
+            self.model.transformer.ff_out = value
+
+    def tie_weights(self):
+        """
+        This function is intentionally left as a no-op.
+
+        Weight tying is handled as follows:
+        - When the model is initialized, the `ff_out` layer is conditionally defined based on the `weight_tying` configuration.
+        See: `if not config.weight_tying: self.transformer.update(...)` in `olmo/model.py`.
+        - When computing logits, the `wte` weights are used directly if `weight_tying` is enabled.
+        See: `if self.config.weight_tying: logits = F.linear(x, self.transformer.wte.weight, None)` in the `forward` method.
+
+        Therefore, there is no need to explicitly tie the weights in this function.
+        """
+        pass
+
+    def resize_token_embeddings(
+        self, new_num_tokens: Optional[int] = None, pad_to_multiple_of: Optional[int] = None
+    ) -> torch.nn.Embedding:
+        """
+        Resizes input token embeddings matrix of the model if `new_num_tokens != config.embedding_size`.
+
+        Takes care of tying weights embeddings afterwards if the model class has a `tie_weights()` method.
+
+        Arguments:
+            new_num_tokens (`int`, *optional*):
+                The new number of tokens in the embedding matrix. Increasing the size will add newly initialized
+                vectors at the end. Reducing the size will remove vectors from the end. If not provided or `None`, just
+                returns a pointer to the input tokens `torch.nn.Embedding` module of the model without doing anything.
+            pad_to_multiple_of (`int`, *optional*):
+                If set will pad the embedding matrix to a multiple of the provided value. If `new_num_tokens` is set to
+                `None` will just pad the embedding to a multiple of `pad_to_multiple_of`.
+
+                This is especially useful to enable the use of Tensor Cores on NVIDIA hardware with compute capability
+                `>= 7.5` (Volta), or on TPUs which benefit from having sequence lengths be a multiple of 128. For more
+                details about this, or help on choosing the correct value for resizing, refer to this guide:
+                https://docs.nvidia.com/deeplearning/performance/dl-performance-matrix-multiplication/index.html#requirements-tc
+
+        Return:
+            `torch.nn.Embedding`: Pointer to the input tokens Embeddings Module of the model.
+
+        Note:
+            This method differs from the base class implementation by resizing the `embedding_size` attribute of the
+            model configuration instead of the `vocab_size`. It also includes a warning if the resized `embedding_size`
+            is less than the `vocab_size`. In OLMo, `embedding_size` refers to the dimensionality of the model's token
+            embeddings, while `vocab_size` refers to the number of unique tokens in the vocabulary.
+        """
+        model_embeds = self._resize_token_embeddings(new_num_tokens, pad_to_multiple_of)
+        if new_num_tokens is None and pad_to_multiple_of is None:
+            return model_embeds
+
+        # Update base model and current model config
+        self.config.embedding_size = model_embeds.weight.shape[0]
+        self.model.config.embedding_size = model_embeds.weight.shape[0]
+
+        # Check if the embedding size is less than the vocab size
+        if self.config.embedding_size < self.config.vocab_size:
+            warning_message = (
+                f"Resizing token embeddings to size {self.config.embedding_size}, which is less than the vocab size "
+                f"{self.config.vocab_size} defined in the model configuration. Make sure your tokenizer's vocabulary "
+                "size is less than or equal to the new token embedding size."
+            )
+            log.warning(warning_message)
+
+        # Tie weights again if needed
+        self.tie_weights()
+
+        return model_embeds
+
+
+# Always register for multi-modal features
+AutoModelForCausalLM.register(MolmoConfig, MolmoForCausalLM)