image-match/python/py/Lib/site-packages/transformers/modeling_attn_mask_utils.py

# Copyright 2023 The HuggingFace Team. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""
IMPORTANT NOTICE: Every class and function in this file is deprecated in favor of using the much more general
`masking_utils.py` primitives. New code should not rely on it, it is only kept for backward compatibility for now,
and will be removed in the future.
"""

import warnings
from dataclasses import dataclass
from typing import Union

import torch

from .utils.import_utils import is_torchdynamo_compiling, is_tracing


DEPRECATION_MESSAGE = (
    "The attention mask API under `transformers.modeling_attn_mask_utils` (`AttentionMaskConverter`) "
    "is deprecated and will be removed in Transformers v5.10. Please use the new API in `transformers.masking_utils`."
)


@dataclass
class AttentionMaskConverter:
    """
    A utility attention mask class that allows one to:
        - Create a causal 4d mask
        - Create a causal 4d mask with slided window
        - Convert a 2d attention mask (batch_size, query_length) to a 4d attention mask (batch_size, 1, query_length,
          key_value_length) that can be multiplied with attention scores

    Examples:

    ```python
    >>> import torch
    >>> from transformers.modeling_attn_mask_utils import AttentionMaskConverter

    >>> converter = AttentionMaskConverter(True)
    >>> converter.to_4d(torch.tensor([[0, 0, 0, 1, 1]]), 5, key_value_length=5, dtype=torch.float32)
    tensor([[[[-3.4028e+38, -3.4028e+38, -3.4028e+38, -3.4028e+38, -3.4028e+38],
            [-3.4028e+38, -3.4028e+38, -3.4028e+38, -3.4028e+38, -3.4028e+38],
            [-3.4028e+38, -3.4028e+38, -3.4028e+38, -3.4028e+38, -3.4028e+38],
            [-3.4028e+38, -3.4028e+38, -3.4028e+38,  0.0000e+00, -3.4028e+38],
            [-3.4028e+38, -3.4028e+38, -3.4028e+38,  0.0000e+00,  0.0000e+00]]]])
    ```

    Parameters:
        is_causal (`bool`):
            Whether the attention mask should be a uni-directional (causal) or bi-directional mask.

        sliding_window (`int`, *optional*):
            Optionally, the sliding window masks can be created if `sliding_window` is defined to a positive integer.
    """

    is_causal: bool
    sliding_window: int

    def __init__(self, is_causal: bool, sliding_window: int | None = None):
        warnings.warn(DEPRECATION_MESSAGE, FutureWarning)

        self.is_causal = is_causal
        self.sliding_window = sliding_window

        if self.sliding_window is not None and self.sliding_window <= 0:
            raise ValueError(
                f"Make sure that when passing `sliding_window` that its value is a strictly positive integer, not `{self.sliding_window}`"
            )

    def to_causal_4d(
        self,
        batch_size: int,
        query_length: int,
        key_value_length: int,
        dtype: torch.dtype,
        device: Union[torch.device, "str"] = "cpu",
    ) -> torch.Tensor | None:
        """
        Creates a causal 4D mask of (bsz, head_dim=1, query_length, key_value_length) shape and adds large negative
        bias to upper right hand triangular matrix (causal mask).
        """
        if not self.is_causal:
            raise ValueError(f"Please use `to_causal_4d` only if {self.__class__} has `is_causal` set to True.")

        # If shape is not cached, create a new causal mask and cache it
        input_shape = (batch_size, query_length)
        past_key_values_length = key_value_length - query_length

        # create causal mask
        # [bsz, seq_len] -> [bsz, 1, tgt_seq_len, src_seq_len]
        causal_4d_mask = None
        if input_shape[-1] > 1 or self.sliding_window is not None:
            causal_4d_mask = self._make_causal_mask(
                input_shape,
                dtype,
                device=device,
                past_key_values_length=past_key_values_length,
                sliding_window=self.sliding_window,
            )

        return causal_4d_mask

    def to_4d(
        self,
        attention_mask_2d: torch.Tensor,
        query_length: int,
        dtype: torch.dtype,
        key_value_length: int | None = None,
    ) -> torch.Tensor:
        """
        Converts 2D attention mask to 4D attention mask by expanding mask to (bsz, head_dim=1, query_length,
        key_value_length) shape and by adding a large negative bias to not-attended positions. If attention_mask is
        causal, a causal mask will be added.
        """
        input_shape = (attention_mask_2d.shape[0], query_length)

        # create causal mask
        # [bsz, seq_len] -> [bsz, 1, tgt_seq_len, src_seq_len]
        causal_4d_mask = None
        if (input_shape[-1] > 1 or self.sliding_window is not None) and self.is_causal:
            if key_value_length is None:
                raise ValueError(
                    "This attention mask converter is causal. Make sure to pass `key_value_length` to correctly create a causal mask."
                )

            past_key_values_length = key_value_length - query_length
            causal_4d_mask = self._make_causal_mask(
                input_shape,
                dtype,
                device=attention_mask_2d.device,
                past_key_values_length=past_key_values_length,
                sliding_window=self.sliding_window,
            )
        elif self.sliding_window is not None:
            raise NotImplementedError("Sliding window is currently only implemented for causal masking")

        # [bsz, seq_len] -> [bsz, 1, tgt_seq_len, src_seq_len]
        expanded_attn_mask = self._expand_mask(attention_mask_2d, dtype, tgt_len=input_shape[-1]).to(
            attention_mask_2d.device
        )

        if causal_4d_mask is not None:
            expanded_attn_mask = causal_4d_mask.masked_fill(expanded_attn_mask.bool(), torch.finfo(dtype).min)

        # expanded_attn_mask + causal_4d_mask can cause some overflow
        expanded_4d_mask = expanded_attn_mask

        return expanded_4d_mask

    @staticmethod
    def _make_causal_mask(
        input_ids_shape: torch.Size,
        dtype: torch.dtype,
        device: torch.device,
        past_key_values_length: int = 0,
        sliding_window: int | None = None,
    ):
        """
        Make causal mask used for bi-directional self-attention.
        """
        warnings.warn(DEPRECATION_MESSAGE, FutureWarning)

        bsz, tgt_len = input_ids_shape
        mask = torch.full((tgt_len, tgt_len), torch.finfo(dtype).min, device=device)
        mask_cond = torch.arange(mask.size(-1), device=device)
        mask.masked_fill_(mask_cond < (mask_cond + 1).view(mask.size(-1), 1), 0)

        mask = mask.to(dtype)

        if past_key_values_length > 0:
            mask = torch.cat([torch.zeros(tgt_len, past_key_values_length, dtype=dtype, device=device), mask], dim=-1)

        # add lower triangular sliding window mask if necessary
        if sliding_window is not None:
            diagonal = past_key_values_length - sliding_window - 1

            context_mask = torch.tril(torch.ones_like(mask, dtype=torch.bool), diagonal=diagonal)
            # Recent changes in PyTorch prevent mutations on tensors converted with aten::_to_copy
            # See https://github.com/pytorch/pytorch/issues/127571
            if is_torchdynamo_compiling():
                mask = mask.clone()
            mask.masked_fill_(context_mask, torch.finfo(dtype).min)

        return mask[None, None, :, :].expand(bsz, 1, tgt_len, tgt_len + past_key_values_length)

    @staticmethod
    def _expand_mask(mask: torch.Tensor, dtype: torch.dtype, tgt_len: int | None = None):
        """
        Expands attention_mask from `[bsz, seq_len]` to `[bsz, 1, tgt_seq_len, src_seq_len]`.
        """
        warnings.warn(DEPRECATION_MESSAGE, FutureWarning)

        bsz, src_len = mask.size()
        tgt_len = tgt_len if tgt_len is not None else src_len

        expanded_mask = mask[:, None, None, :].expand(bsz, 1, tgt_len, src_len).to(dtype)

        inverted_mask = torch.tensor(1.0, dtype=dtype) - expanded_mask

        return inverted_mask.masked_fill(inverted_mask.to(torch.bool), torch.finfo(dtype).min)

    @staticmethod
    def _unmask_unattended(
        expanded_mask: torch.FloatTensor,
        min_dtype: float,
    ):
        # fmt: off
        """
        Attend to all tokens in masked rows from the expanded attention mask, for example the relevant first rows when
        using left padding. This is required by F.scaled_dot_product_attention memory-efficient attention path.
        Details: https://github.com/pytorch/pytorch/issues/110213

        `expanded_mask` is [bsz, num_masks, tgt_seq_len, src_seq_len] or [bsz, tgt_seq_len, src_seq_len].
        `attention_mask` is [bsz, src_seq_len].

        The dimension num_masks of `expanded_mask` is most often 1, but it can also be the number of heads in the case of alibi attention bias.

        For example, if `expanded_mask` is (e.g. here left-padding case)
        ```
        [[[[0, 0, 0],
           [0, 0, 0],
           [0, 0, 1]]],
         [[[1, 0, 0],
           [1, 1, 0],
           [1, 1, 1]]],
         [[[0, 0, 0],
           [0, 1, 0],
           [0, 1, 1]]]]
        ```
        then the modified `expanded_mask` will be
        ```
        [[[[1, 1, 1],   <-- modified
           [1, 1, 1],   <-- modified
           [0, 0, 1]]],
         [[[1, 0, 0],
           [1, 1, 0],
           [1, 1, 1]]],
         [[[1, 1, 1],   <-- modified
           [0, 1, 0],
           [0, 1, 1]]]]
        ```
        """
        warnings.warn(DEPRECATION_MESSAGE, FutureWarning)

        # fmt: on
        if expanded_mask.dtype == torch.bool:
            raise ValueError(
                "AttentionMaskConverter._unmask_unattended expects a float `expanded_mask`, got a BoolTensor."
            )

        return expanded_mask.mul(~torch.all(expanded_mask == min_dtype, dim=-1, keepdim=True))

    @staticmethod
    def _ignore_causal_mask_sdpa(
        attention_mask: torch.Tensor | None,
        inputs_embeds: torch.Tensor,
        past_key_values_length: int,
        sliding_window: int | None = None,
        is_training: bool = False,
    ) -> bool:
        """
        Detects whether the optional user-specified attention_mask & the automatically created causal mask can be
        ignored in case PyTorch's SDPA is used, rather relying on SDPA's `is_causal` argument.

        In case no token is masked in the `attention_mask` argument, if `query_length == 1` or
        `key_value_length == query_length`, we rather rely on SDPA `is_causal` argument to use causal/non-causal masks,
        allowing to dispatch to the flash attention kernel (that can otherwise not be used if a custom `attn_mask` is
        passed).
        """
        warnings.warn(DEPRECATION_MESSAGE, FutureWarning)

        _, query_length = inputs_embeds.shape[0], inputs_embeds.shape[1]
        key_value_length = query_length + past_key_values_length

        is_tracing_ = is_tracing(inputs_embeds)

        ignore_causal_mask = False

        if attention_mask is None:
            # TODO: When tracing with TorchDynamo with fullgraph=True, the model is recompiled depending on the input
            # shape, thus SDPA's `is_causal` argument is rightfully updated
            # (see https://gist.github.com/fxmarty/1313f39037fc1c112508989628c57363). However, when using
            # `torch.export` or `torch.onnx.dynamo_export`, we must pass an example input, and `is_causal` behavior is
            # hard-coded. If a user exports a model with q_len > 1, the exported model will hard-code `is_causal=True`
            # which is in general wrong (see https://github.com/pytorch/pytorch/issues/108108).
            # Thus, we only set `ignore_causal_mask = True` if the model is set to training.
            #
            # Besides, jit.trace can not handle the `q_len > 1` condition for `is_causal`
            # ("TypeError: scaled_dot_product_attention(): argument 'is_causal' must be bool, not Tensor").
            if (
                (is_training or not is_tracing_)
                and (query_length == 1 or key_value_length == query_length)
                and (sliding_window is None or key_value_length < sliding_window)
            ):
                ignore_causal_mask = True
        elif sliding_window is None or key_value_length < sliding_window:
            if len(attention_mask.shape) == 4:
                return False
            elif not is_tracing_ and torch.all(attention_mask == 1):
                if query_length == 1 or key_value_length == query_length:
                    # For query_length == 1, causal attention and bi-directional attention are the same.
                    ignore_causal_mask = True

                # Unfortunately, for query_length > 1 and key_value_length != query_length, we cannot generally ignore
                # the attention mask, as SDPA causal mask generation may be wrong. We will set `is_causal=False` in
                # SDPA and rely on Transformers attention_mask instead, hence not setting it to None here.
                # Reference: https://github.com/pytorch/pytorch/issues/108108
                # TODO: maybe revisit this with https://github.com/pytorch/pytorch/pull/114823 in PyTorch 2.3.

        return ignore_causal_mask


def _prepare_4d_causal_attention_mask(
    attention_mask: torch.Tensor | None,
    input_shape: torch.Size | tuple | list,
    inputs_embeds: torch.Tensor,
    past_key_values_length: int,
    sliding_window: int | None = None,
):
    """
    Creates a causal 4D mask of shape `(batch_size, 1, query_length, key_value_length)` from a 2D mask of shape
    `(batch_size, key_value_length)`

    Args:
        attention_mask (`torch.Tensor` or `None`):
            A 2D attention mask of shape `(batch_size, key_value_length)`
        input_shape (`tuple(int)` or `list(int)` or `torch.Size`):
            The input shape should be a tuple that defines `(batch_size, query_length)`.
        inputs_embeds (`torch.Tensor`):
            The embedded inputs as a torch Tensor.
        past_key_values_length (`int`):
            The length of the key value cache.
        sliding_window (`int`, *optional*):
            If the model uses windowed attention, a sliding window should be passed.
    """
    attn_mask_converter = AttentionMaskConverter(is_causal=True, sliding_window=sliding_window)

    key_value_length = input_shape[-1] + past_key_values_length

    # 4d mask is passed through the layers
    if attention_mask is not None and len(attention_mask.shape) == 2:
        attention_mask = attn_mask_converter.to_4d(
            attention_mask, input_shape[-1], key_value_length=key_value_length, dtype=inputs_embeds.dtype
        )
    elif attention_mask is not None and len(attention_mask.shape) == 4:
        expected_shape = (input_shape[0], 1, input_shape[1], key_value_length)
        if tuple(attention_mask.shape) != expected_shape:
            raise ValueError(
                f"Incorrect 4D attention_mask shape: {tuple(attention_mask.shape)}; expected: {expected_shape}."
            )
        else:
            # if the 4D mask has correct shape - invert it and fill with negative infinity
            inverted_mask = 1.0 - attention_mask
            attention_mask = inverted_mask.masked_fill(
                inverted_mask.to(torch.bool), torch.finfo(inputs_embeds.dtype).min
            )
    else:
        attention_mask = attn_mask_converter.to_causal_4d(
            input_shape[0], input_shape[-1], key_value_length, dtype=inputs_embeds.dtype, device=inputs_embeds.device
        )

    return attention_mask


# Adapted from _prepare_4d_causal_attention_mask
def _prepare_4d_causal_attention_mask_for_sdpa(
    attention_mask: torch.Tensor | None,
    input_shape: torch.Size | tuple | list,
    inputs_embeds: torch.Tensor,
    past_key_values_length: int,
    sliding_window: int | None = None,
):
    """
    Prepares the correct `attn_mask` argument to be used by `torch.nn.functional.scaled_dot_product_attention`.

    In case no token is masked in the `attention_mask` argument, we simply set it to `None` for the cases `query_length == 1` and
    `key_value_length == query_length`, and rely instead on SDPA `is_causal` argument to use causal/non-causal masks,
    allowing to dispatch to the flash attention kernel (that can otherwise not be used if a custom `attn_mask` is passed).
    """
    attn_mask_converter = AttentionMaskConverter(is_causal=True, sliding_window=sliding_window)

    key_value_length = input_shape[-1] + past_key_values_length

    # torch.jit.trace, symbolic_trace and torchdynamo with fullgraph=True are unable to capture the controlflow `is_causal=attention_mask is None and q_len > 1`
    # used as an SDPA argument. We keep compatibility with these tracing tools by always using SDPA's `attn_mask` argument in case we are tracing.
    # TODO: For dynamo, rather use a check on fullgraph=True once this is possible (https://github.com/pytorch/pytorch/pull/120400).
    is_tracing_ = is_tracing(inputs_embeds)

    ignore_causal_mask = AttentionMaskConverter._ignore_causal_mask_sdpa(
        attention_mask=attention_mask,
        inputs_embeds=inputs_embeds,
        past_key_values_length=past_key_values_length,
        sliding_window=sliding_window,
    )

    if ignore_causal_mask:
        expanded_4d_mask = None
    elif attention_mask is None:
        expanded_4d_mask = attn_mask_converter.to_causal_4d(
            input_shape[0], input_shape[-1], key_value_length, dtype=inputs_embeds.dtype, device=inputs_embeds.device
        )
    else:
        if attention_mask.dim() == 4:
            expanded_4d_mask = attention_mask
        else:
            expanded_4d_mask = attn_mask_converter.to_4d(
                attention_mask,
                input_shape[-1],
                dtype=inputs_embeds.dtype,
                key_value_length=key_value_length,
            )

        # Attend to all tokens in masked rows from the causal_mask, for example the relevant first rows when
        # using left padding. This is required by F.scaled_dot_product_attention memory-efficient attention path.
        # Details: https://github.com/pytorch/pytorch/issues/110213
        if not is_tracing_ and expanded_4d_mask.device.type in ["cuda", "xpu"]:
            expanded_4d_mask = AttentionMaskConverter._unmask_unattended(
                expanded_4d_mask, min_dtype=torch.finfo(inputs_embeds.dtype).min
            )

    return expanded_4d_mask


def _prepare_4d_attention_mask(mask: torch.Tensor, dtype: torch.dtype, tgt_len: int | None = None):
    """
    Creates a non-causal 4D mask of shape `(batch_size, 1, query_length, key_value_length)` from a 2D mask of shape
    `(batch_size, key_value_length)`

    Args:
        mask (`torch.Tensor`):
            A 2D attention mask of shape `(batch_size, key_value_length)`
        dtype (`torch.dtype`):
            The torch dtype the created mask shall have.
        tgt_len (`int`):
            The target length or query length the created mask shall have.
    """
    return AttentionMaskConverter._expand_mask(mask=mask, dtype=dtype, tgt_len=tgt_len)


def _prepare_4d_attention_mask_for_sdpa(mask: torch.Tensor, dtype: torch.dtype, tgt_len: int | None = None):
    """
    Creates a non-causal 4D mask of shape `(batch_size, 1, query_length, key_value_length)` from a 2D mask of shape
    `(batch_size, key_value_length)`

    Args:
        mask (`torch.Tensor`):
            A 2D attention mask of shape `(batch_size, key_value_length)`
        dtype (`torch.dtype`):
            The torch dtype the created mask shall have.
        tgt_len (`int`):
            The target length or query length the created mask shall have.
    """
    warnings.warn(DEPRECATION_MESSAGE, FutureWarning)

    _, key_value_length = mask.shape
    tgt_len = tgt_len if tgt_len is not None else key_value_length

    # torch.jit.trace, symbolic_trace and torchdynamo with fullgraph=True are unable to capture data-dependent controlflows.
    if not is_tracing(mask) and torch.all(mask == 1):
        return None
    else:
        return AttentionMaskConverter._expand_mask(mask=mask, dtype=dtype, tgt_len=tgt_len)


def _create_4d_causal_attention_mask(
    input_shape: torch.Size | tuple | list,
    dtype: torch.dtype,
    device: torch.device,
    past_key_values_length: int = 0,
    sliding_window: int | None = None,
) -> torch.Tensor | None:
    """
    Creates a causal 4D mask of shape `(batch_size, 1, query_length, key_value_length)`

    Args:
        input_shape (`tuple(int)` or `list(int)` or `torch.Size`):
            The input shape should be a tuple that defines `(batch_size, query_length)`.
        dtype (`torch.dtype`):
            The torch dtype the created mask shall have.
        device (`int`):
            The torch device the created mask shall have.
        sliding_window (`int`, *optional*):
            If the model uses windowed attention, a sliding window should be passed.
    """
    attn_mask_converter = AttentionMaskConverter(is_causal=True, sliding_window=sliding_window)

    key_value_length = past_key_values_length + input_shape[-1]
    attention_mask = attn_mask_converter.to_causal_4d(
        input_shape[0], input_shape[-1], key_value_length, dtype=dtype, device=device
    )

    return attention_mask