src/axolotl/monkeypatch/mixtral/modeling_mixtral.py

"""
Mixtral modeling for multipack
"""
# pylint: disable=missing-module-docstring,unused-argument,protected-access,pointless-string-statement,duplicate-code
import logging
import warnings
from typing import List, Optional, Tuple, Union

import torch
from einops import rearrange
from flash_attn import flash_attn_varlen_qkvpacked_func
from transformers import Cache, DynamicCache
from transformers.modeling_attn_mask_utils import _prepare_4d_causal_attention_mask
from transformers.modeling_outputs import MoeModelOutputWithPast
from transformers.models.mixtral.modeling_mixtral import (
    MixtralFlashAttention2,
    apply_rotary_pos_emb,
    repeat_kv,
)

from axolotl.monkeypatch.utils import get_cu_seqlens_from_pos_ids

LOG = logging.getLogger("axolotl.monkeypatch.mixtral")


class MixtralMultipackFlashAttention2(MixtralFlashAttention2):
    """
    Custom multipack implementation w flash attention 2
    """

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self._flash_attn_uses_top_left_mask = True

    def forward(
        self,
        hidden_states: torch.Tensor,
        attention_mask: Optional[torch.Tensor] = None,
        position_ids: Optional[torch.LongTensor] = None,
        past_key_value: Optional[Cache] = None,
        output_attentions: bool = False,
        use_cache: bool = False,
        cu_seqlens: Optional[torch.Tensor] = None,
        max_seqlen: Optional[torch.Tensor] = None,
        **kwargs,
    ) -> Tuple[torch.Tensor, Optional[torch.Tensor], Optional[Tuple[torch.Tensor]]]:
        if "padding_mask" in kwargs:
            warnings.warn(
                "Passing `padding_mask` is deprecated and will be removed in v4.37. Please make sure use `attention_mask` instead.`"
            )
        bsz, q_len, _ = hidden_states.size()

        query_states = self.q_proj(hidden_states)
        key_states = self.k_proj(hidden_states)
        value_states = self.v_proj(hidden_states)

        query_states = query_states.view(
            bsz, q_len, self.num_heads, self.head_dim
        ).transpose(1, 2)
        key_states = key_states.view(
            bsz, q_len, self.num_key_value_heads, self.head_dim
        ).transpose(1, 2)
        value_states = value_states.view(
            bsz, q_len, self.num_key_value_heads, self.head_dim
        ).transpose(1, 2)

        kv_seq_len = key_states.shape[-2]
        if past_key_value is not None:
            if self.layer_idx is None:
                raise ValueError(
                    f"The cache structure has changed since version v4.36. If you are using {self.__class__.__name__} "
                    "for auto-regressive decoding with k/v caching, please make sure to initialize the attention class "
                    "with a layer index."
                )
            kv_seq_len += past_key_value.get_usable_length(kv_seq_len, self.layer_idx)
        cos, sin = self.rotary_emb(value_states, seq_len=kv_seq_len)
        query_states, key_states = apply_rotary_pos_emb(
            query_states, key_states, cos, sin, position_ids
        )

        if past_key_value is not None:
            cache_kwargs = {"sin": sin, "cos": cos}  # Specific to RoPE models
            key_states, value_states = past_key_value.update(
                key_states, value_states, self.layer_idx, cache_kwargs
            )

        # repeat k/v heads if n_kv_heads < n_heads
        key_states = repeat_kv(key_states, self.num_key_value_groups)
        value_states = repeat_kv(value_states, self.num_key_value_groups)

        if cu_seqlens is not None and max_seqlen is not None and cu_seqlens.dim() == 1:
            # special handling using sample packing
            qkv = torch.stack(
                [query_states, key_states, value_states], dim=2
            )  # [bsz, nh, 3, q_len, hd]
            qkv = qkv.transpose(1, 3)  # [bsz, q_len, 3, nh, hd]
            qkv = rearrange(qkv, "b s ... -> (b s) ...")

            attn_output = flash_attn_varlen_qkvpacked_func(
                qkv,
                cu_seqlens,
                max_seqlen,
                dropout_p=self.attention_dropout,
                softmax_scale=None,
                causal=True,
            )
            attn_output = rearrange(attn_output, "(b s) ... -> b s ...", b=bsz)

        attn_output = attn_output.reshape(bsz, q_len, self.hidden_size).contiguous()
        attn_output = self.o_proj(attn_output)

        if not output_attentions:
            attn_weights = None

        return attn_output, attn_weights, past_key_value


def mixtral_decoder_layer_forward(
    self,
    hidden_states: torch.Tensor,
    attention_mask: Optional[torch.Tensor] = None,
    position_ids: Optional[torch.LongTensor] = None,
    past_key_value: Optional[Tuple[torch.Tensor]] = None,
    output_attentions: Optional[bool] = False,
    output_router_logits: Optional[bool] = False,
    use_cache: Optional[bool] = False,
    cu_seqlens: Optional[torch.Tensor] = None,
    max_seqlen: Optional[torch.Tensor] = None,
    **kwargs,
) -> Tuple[torch.FloatTensor, Optional[Tuple[torch.FloatTensor, torch.FloatTensor]]]:
    if "padding_mask" in kwargs:
        warnings.warn(
            "Passing `padding_mask` is deprecated and will be removed in v4.37. Please make sure use `attention_mask` instead.`"
        )
    """
    Args:
        hidden_states (`torch.FloatTensor`): input to the layer of shape `(batch, seq_len, embed_dim)`
        attention_mask (`torch.FloatTensor`, *optional*): attention mask of size
            `(batch, sequence_length)` where padding elements are indicated by 0.
        past_key_value (`Tuple(torch.FloatTensor)`, *optional*): cached past key and value projection states
        output_attentions (`bool`, *optional*):
            Whether or not to return the attentions tensors of all attention layers. See `attentions` under
            returned tensors for more detail.
        output_router_logits (`bool`, *optional*):
            Whether or not to return the logits of all the routers. They are useful for computing the router loss, and
            should not be returned during inference.
        use_cache (`bool`, *optional*):
            If set to `True`, `past_key_values` key value states are returned and can be used to speed up decoding
            (see `past_key_values`).
    """

    residual = hidden_states

    hidden_states = self.input_layernorm(hidden_states)

    # Self Attention
    hidden_states, self_attn_weights, present_key_value = self.self_attn(
        hidden_states=hidden_states,
        attention_mask=attention_mask,
        position_ids=position_ids,
        past_key_value=past_key_value,
        output_attentions=output_attentions,
        use_cache=use_cache,
        cu_seqlens=cu_seqlens,
        max_seqlen=max_seqlen,
    )
    hidden_states = residual + hidden_states

    # Fully Connected
    residual = hidden_states
    hidden_states = self.post_attention_layernorm(hidden_states)
    hidden_states, router_logits = self.block_sparse_moe(hidden_states)
    hidden_states = residual + hidden_states

    outputs = (hidden_states,)

    if output_attentions:
        outputs += (self_attn_weights,)

    if use_cache:
        outputs += (present_key_value,)

    if output_router_logits:
        outputs += (router_logits,)

    return outputs


def mixtral_model_forward(
    self,
    input_ids: torch.LongTensor = None,
    attention_mask: Optional[torch.Tensor] = None,
    position_ids: Optional[torch.LongTensor] = None,
    past_key_values: Optional[List[torch.FloatTensor]] = None,
    inputs_embeds: Optional[torch.FloatTensor] = None,
    use_cache: Optional[bool] = None,
    output_attentions: Optional[bool] = None,
    output_hidden_states: Optional[bool] = None,
    output_router_logits: Optional[bool] = None,
    return_dict: Optional[bool] = None,
) -> Union[Tuple, MoeModelOutputWithPast]:
    output_attentions = (
        output_attentions
        if output_attentions is not None
        else self.config.output_attentions
    )
    output_router_logits = (
        output_router_logits
        if output_router_logits is not None
        else self.config.output_router_logits
    )
    output_hidden_states = (
        output_hidden_states
        if output_hidden_states is not None
        else self.config.output_hidden_states
    )
    use_cache = use_cache if use_cache is not None else self.config.use_cache

    return_dict = (
        return_dict if return_dict is not None else self.config.use_return_dict
    )

    # retrieve input_ids and inputs_embeds
    if input_ids is not None and inputs_embeds is not None:
        raise ValueError(
            "You cannot specify both decoder_input_ids and decoder_inputs_embeds at the same time"
        )
    if input_ids is not None:
        batch_size, seq_length = input_ids.shape
    elif inputs_embeds is not None:
        batch_size, seq_length, _ = inputs_embeds.shape
    else:
        raise ValueError(
            "You have to specify either decoder_input_ids or decoder_inputs_embeds"
        )

    past_key_values_length = 0

    if use_cache:
        use_legacy_cache = not isinstance(past_key_values, Cache)
        if use_legacy_cache:
            past_key_values = DynamicCache.from_legacy_cache(past_key_values)
        past_key_values_length = past_key_values.get_usable_length(seq_length)

    cu_seqlens = None
    max_seqlen = None
    if position_ids is None:
        device = input_ids.device if input_ids is not None else inputs_embeds.device
        position_ids = torch.arange(
            past_key_values_length,
            seq_length + past_key_values_length,
            dtype=torch.long,
            device=device,
        )
        position_ids = position_ids.unsqueeze(0).view(-1, seq_length)
    else:
        position_ids = position_ids.view(-1, seq_length).long()
        cu_seqlens, max_seqlen = get_cu_seqlens_from_pos_ids(position_ids)
        cu_seqlens = cu_seqlens.squeeze()

    if inputs_embeds is None:
        inputs_embeds = self.embed_tokens(input_ids)

    if (
        attention_mask is not None
        and self._attn_implementation == "flash_attention_2"
        and use_cache
    ):
        is_padding_right = attention_mask[:, -1].sum().item() != batch_size
        if is_padding_right:
            raise ValueError(
                "You are attempting to perform batched generation with padding_side='right'"
                " this may lead to unexpected behaviour for Flash Attention version of Mixtral. Make sure to "
                " call `tokenizer.padding_side  = 'left'` before tokenizing the input. "
            )

    if self._attn_implementation == "flash_attention_2":
        # 2d mask is passed through the layers
        attention_mask = (
            attention_mask
            if (attention_mask is not None and 0 in attention_mask)
            else None
        )
    else:
        # 4d mask is passed through the layers
        attention_mask = _prepare_4d_causal_attention_mask(
            attention_mask,
            (batch_size, seq_length),
            inputs_embeds,
            past_key_values_length,
            sliding_window=self.config.sliding_window,
        )

    hidden_states = inputs_embeds

    if self.gradient_checkpointing and self.training:
        if use_cache:
            LOG.warning_once(
                "`use_cache=True` is incompatible with gradient checkpointing. Setting `use_cache=False`..."
            )
            use_cache = False

    # decoder layers
    all_hidden_states = () if output_hidden_states else None
    all_self_attns = () if output_attentions else None
    all_router_logits = () if output_router_logits else None
    next_decoder_cache = None

    for decoder_layer in self.layers:
        if output_hidden_states:
            all_hidden_states += (hidden_states,)

        if self.gradient_checkpointing and self.training:
            layer_outputs = self._gradient_checkpointing_func(
                decoder_layer.__call__,
                hidden_states,
                attention_mask,
                position_ids,
                past_key_values,
                output_attentions,
                output_router_logits,
                use_cache,
                cu_seqlens,
                max_seqlen,
            )
        else:
            layer_outputs = decoder_layer(
                hidden_states,
                attention_mask=attention_mask,
                position_ids=position_ids,
                past_key_value=past_key_values,
                output_attentions=output_attentions,
                output_router_logits=output_router_logits,
                use_cache=use_cache,
                cu_seqlens=cu_seqlens,
                max_seqlen=max_seqlen,
            )

        hidden_states = layer_outputs[0]

        if use_cache:
            next_decoder_cache = layer_outputs[2 if output_attentions else 1]

        if output_attentions:
            all_self_attns += (layer_outputs[1],)

        if output_router_logits:
            all_router_logits += (layer_outputs[-1],)

    hidden_states = self.norm(hidden_states)

    # add hidden states from the last decoder layer
    if output_hidden_states:
        all_hidden_states += (hidden_states,)

    next_cache = None
    if use_cache:
        next_cache = (
            next_decoder_cache.to_legacy_cache()
            if use_legacy_cache
            else next_decoder_cache
        )

    if not return_dict:
        return tuple(
            v
            for v in [
                hidden_states,
                next_cache,
                all_hidden_states,
                all_self_attns,
                all_router_logits,
            ]
            if v is not None
        )

    return MoeModelOutputWithPast(
        last_hidden_state=hidden_states,
        past_key_values=next_cache,
        hidden_states=all_hidden_states,
        attentions=all_self_attns,
        router_logits=all_router_logits,
    )