beats/backbone.py

# --------------------------------------------------------
# BEATs: Audio Pre-Training with Acoustic Tokenizers (https://arxiv.org/abs/2212.09058)
# Github source: https://github.com/microsoft/unilm/tree/master/beats
# Copyright (c) 2022 Microsoft
# Licensed under The MIT License [see LICENSE for details]
# Based on fairseq code bases
# https://github.com/pytorch/fairseq
# --------------------------------------------------------

import math
import numpy as np
from typing import Dict, Optional, Tuple
import torch
from torch import Tensor, nn
import torch.nn.functional as F
from torch.nn import LayerNorm, Parameter
from .modules import (
    GradMultiply,
    SamePad,
    get_activation_fn,
    GLU_Linear,
    quant_noise,
)


class TransformerEncoder(nn.Module):
    def __init__(self, args):
        super().__init__()

        self.dropout = args.dropout
        self.embedding_dim = args.encoder_embed_dim

        self.pos_conv = nn.Conv1d(
            self.embedding_dim,
            self.embedding_dim,
            kernel_size=args.conv_pos,
            padding=args.conv_pos // 2,
            groups=args.conv_pos_groups,
        )
        dropout = 0
        std = math.sqrt((4 * (1.0 - dropout)) / (args.conv_pos * self.embedding_dim))
        nn.init.normal_(self.pos_conv.weight, mean=0, std=std)
        nn.init.constant_(self.pos_conv.bias, 0)

        self.pos_conv = nn.utils.weight_norm(self.pos_conv, name="weight", dim=2)
        self.pos_conv = nn.Sequential(self.pos_conv, SamePad(args.conv_pos), nn.GELU())

        if hasattr(args, "relative_position_embedding"):
            self.relative_position_embedding = args.relative_position_embedding
            self.num_buckets = args.num_buckets
            self.max_distance = args.max_distance
        else:
            self.relative_position_embedding = False
            self.num_buckets = 0
            self.max_distance = 0

        self.layers = nn.ModuleList(
            [
                TransformerSentenceEncoderLayer(
                    embedding_dim=self.embedding_dim,
                    ffn_embedding_dim=args.encoder_ffn_embed_dim,
                    num_attention_heads=args.encoder_attention_heads,
                    dropout=self.dropout,
                    attention_dropout=args.attention_dropout,
                    activation_dropout=args.activation_dropout,
                    activation_fn=args.activation_fn,
                    layer_norm_first=args.layer_norm_first,
                    deep_norm=args.deep_norm,
                    has_relative_attention_bias=self.relative_position_embedding,
                    num_buckets=self.num_buckets,
                    max_distance=self.max_distance,
                    gru_rel_pos=args.gru_rel_pos,
                    encoder_layers=args.encoder_layers,
                )
                for i in range(args.encoder_layers)
            ]
        )
        if self.relative_position_embedding:
            for i in range(1, args.encoder_layers):
                del self.layers[i].self_attn.relative_attention_bias
                self.layers[i].self_attn.relative_attention_bias = self.layers[0].self_attn.relative_attention_bias

        self.layer_norm_first = args.layer_norm_first
        self.layer_norm = LayerNorm(self.embedding_dim)
        self.layerdrop = args.encoder_layerdrop

        self.apply(init_bert_params)

        if args.deep_norm:
            deep_norm_beta = math.pow(8 * args.encoder_layers, -1 / 4)
            for i in range(args.encoder_layers):
                nn.init.xavier_normal_(self.layers[i].self_attn.k_proj.weight, gain=1)
                nn.init.xavier_normal_(self.layers[i].self_attn.v_proj.weight, gain=deep_norm_beta)
                nn.init.xavier_normal_(self.layers[i].self_attn.q_proj.weight, gain=1)
                nn.init.xavier_normal_(self.layers[i].self_attn.out_proj.weight, gain=deep_norm_beta)
                nn.init.xavier_normal_(self.layers[i].fc1.weight, gain=deep_norm_beta)
                nn.init.xavier_normal_(self.layers[i].fc2.weight, gain=deep_norm_beta)

        self.layer_wise_gradient_decay_ratio = getattr(args, "layer_wise_gradient_decay_ratio", 1)

    def forward(self, x, padding_mask=None, layer=None):
        x, layer_results = self.extract_features(x, padding_mask, layer)

        if self.layer_norm_first and layer is None:
            x = self.layer_norm(x)

        return x, layer_results

    def extract_features(self, x, padding_mask=None, tgt_layer=None):

        if padding_mask is not None:
            x[padding_mask] = 0

        x_conv = self.pos_conv(x.transpose(1, 2))
        x_conv = x_conv.transpose(1, 2)
        x = x + x_conv

        if not self.layer_norm_first:
            x = self.layer_norm(x)

        x = F.dropout(x, p=self.dropout, training=self.training)

        # B x T x C -> T x B x C
        x = x.transpose(0, 1)

        layer_results = []
        z = None
        if tgt_layer is not None:
            layer_results.append((x, z))
        r = None
        pos_bias = None
        for i, layer in enumerate(self.layers):
            if self.layer_wise_gradient_decay_ratio != 1.0:
                x = GradMultiply.apply(x, self.layer_wise_gradient_decay_ratio)
            dropout_probability = np.random.random()
            if not self.training or (dropout_probability > self.layerdrop):
                x, z, pos_bias = layer(x, self_attn_padding_mask=padding_mask, need_weights=False, pos_bias=pos_bias)
            if tgt_layer is not None:
                layer_results.append((x, z))
            if i == tgt_layer:
                r = x
                break

        if r is not None:
            x = r

        # T x B x C -> B x T x C
        x = x.transpose(0, 1)

        return x, layer_results


class TransformerSentenceEncoderLayer(nn.Module):
    def __init__(
            self,
            embedding_dim: float = 768,
            ffn_embedding_dim: float = 3072,
            num_attention_heads: float = 8,
            dropout: float = 0.1,
            attention_dropout: float = 0.1,
            activation_dropout: float = 0.1,
            activation_fn: str = "relu",
            layer_norm_first: bool = False,
            deep_norm: bool = False,
            has_relative_attention_bias: bool = False,
            num_buckets: int = 0,
            max_distance: int = 0,
            rescale_init: bool = False,
            gru_rel_pos: bool = False,
            encoder_layers: int = 0,
    ) -> None:

        super().__init__()
        self.embedding_dim = embedding_dim
        self.dropout = dropout
        self.activation_dropout = activation_dropout

        self.activation_name = activation_fn
        self.activation_fn = get_activation_fn(activation_fn)
        self.self_attn = MultiheadAttention(
            self.embedding_dim,
            num_attention_heads,
            dropout=attention_dropout,
            self_attention=True,
            has_relative_attention_bias=has_relative_attention_bias,
            num_buckets=num_buckets,
            max_distance=max_distance,
            rescale_init=rescale_init,
            gru_rel_pos=gru_rel_pos,
        )

        self.dropout1 = nn.Dropout(dropout)
        self.dropout2 = nn.Dropout(self.activation_dropout)
        self.dropout3 = nn.Dropout(dropout)

        self.layer_norm_first = layer_norm_first

        self.self_attn_layer_norm = LayerNorm(self.embedding_dim)

        if self.activation_name == "glu":
            self.fc1 = GLU_Linear(self.embedding_dim, ffn_embedding_dim, "swish")
        else:
            self.fc1 = nn.Linear(self.embedding_dim, ffn_embedding_dim)
        self.fc2 = nn.Linear(ffn_embedding_dim, self.embedding_dim)

        self.final_layer_norm = LayerNorm(self.embedding_dim)

        self.deep_norm = deep_norm
        if self.deep_norm:
            self.deep_norm_alpha = math.pow(2 * encoder_layers, 1 / 4)
        else:
            self.deep_norm_alpha = 1

    def forward(
            self,
            x: torch.Tensor,
            self_attn_mask: torch.Tensor = None,
            self_attn_padding_mask: torch.Tensor = None,
            need_weights: bool = False,
            pos_bias=None
    ):
        residual = x

        if self.layer_norm_first:
            x = self.self_attn_layer_norm(x)
            x, attn, pos_bias = self.self_attn(
                query=x,
                key=x,
                value=x,
                key_padding_mask=self_attn_padding_mask,
                need_weights=False,
                attn_mask=self_attn_mask,
                position_bias=pos_bias
            )
            x = self.dropout1(x)
            x = residual + x

            residual = x
            x = self.final_layer_norm(x)
            if self.activation_name == "glu":
                x = self.fc1(x)
            else:
                x = self.activation_fn(self.fc1(x))
            x = self.dropout2(x)
            x = self.fc2(x)
            x = self.dropout3(x)
            x = residual + x
        else:
            x, attn, pos_bias = self.self_attn(
                query=x,
                key=x,
                value=x,
                key_padding_mask=self_attn_padding_mask,
                need_weights=need_weights,
                attn_mask=self_attn_mask,
                position_bias=pos_bias
            )

            x = self.dropout1(x)
            x = residual * self.deep_norm_alpha + x

            x = self.self_attn_layer_norm(x)

            residual = x
            if self.activation_name == "glu":
                x = self.fc1(x)
            else:
                x = self.activation_fn(self.fc1(x))
            x = self.dropout2(x)
            x = self.fc2(x)
            x = self.dropout3(x)
            x = residual * self.deep_norm_alpha + x
            x = self.final_layer_norm(x)

        return x, attn, pos_bias


class MultiheadAttention(nn.Module):
    """Multi-headed attention.

    See "Attention Is All You Need" for more details.
    """

    def __init__(
            self,
            embed_dim,
            num_heads,
            kdim=None,
            vdim=None,
            dropout=0.0,
            bias=True,
            add_bias_kv=False,
            add_zero_attn=False,
            self_attention=False,
            encoder_decoder_attention=False,
            q_noise=0.0,
            qn_block_size=8,
            has_relative_attention_bias=False,
            num_buckets=32,
            max_distance=128,
            gru_rel_pos=False,
            rescale_init=False,
    ):
        super().__init__()
        self.embed_dim = embed_dim
        self.kdim = kdim if kdim is not None else embed_dim
        self.vdim = vdim if vdim is not None else embed_dim
        self.qkv_same_dim = self.kdim == embed_dim and self.vdim == embed_dim

        self.num_heads = num_heads
        self.dropout_module = nn.Dropout(dropout)

        self.has_relative_attention_bias = has_relative_attention_bias
        self.num_buckets = num_buckets
        self.max_distance = max_distance
        if self.has_relative_attention_bias:
            self.relative_attention_bias = nn.Embedding(num_buckets, num_heads)

        self.head_dim = embed_dim // num_heads
        self.q_head_dim = self.head_dim
        self.k_head_dim = self.head_dim
        assert (
                self.head_dim * num_heads == self.embed_dim
        ), "embed_dim must be divisible by num_heads"
        self.scaling = self.head_dim ** -0.5

        self.self_attention = self_attention
        self.encoder_decoder_attention = encoder_decoder_attention

        assert not self.self_attention or self.qkv_same_dim, (
            "Self-attention requires query, key and " "value to be of the same size"
        )

        k_bias = True
        if rescale_init:
            k_bias = False

        k_embed_dim = embed_dim
        q_embed_dim = embed_dim

        self.k_proj = quant_noise(
            nn.Linear(self.kdim, k_embed_dim, bias=k_bias), q_noise, qn_block_size
        )
        self.v_proj = quant_noise(
            nn.Linear(self.vdim, embed_dim, bias=bias), q_noise, qn_block_size
        )
        self.q_proj = quant_noise(
            nn.Linear(embed_dim, q_embed_dim, bias=bias), q_noise, qn_block_size
        )

        self.out_proj = quant_noise(
            nn.Linear(embed_dim, embed_dim, bias=bias), q_noise, qn_block_size
        )

        if add_bias_kv:
            self.bias_k = Parameter(torch.Tensor(1, 1, embed_dim))
            self.bias_v = Parameter(torch.Tensor(1, 1, embed_dim))
        else:
            self.bias_k = self.bias_v = None

        self.add_zero_attn = add_zero_attn

        self.gru_rel_pos = gru_rel_pos
        if self.gru_rel_pos:
            self.grep_linear = nn.Linear(self.q_head_dim, 8)
            self.grep_a = nn.Parameter(torch.ones(1, num_heads, 1, 1))

        self.reset_parameters()

    def reset_parameters(self):
        if self.qkv_same_dim:
            # Empirically observed the convergence to be much better with
            # the scaled initialization
            nn.init.xavier_uniform_(self.k_proj.weight, gain=1 / math.sqrt(2))
            nn.init.xavier_uniform_(self.v_proj.weight, gain=1 / math.sqrt(2))
            nn.init.xavier_uniform_(self.q_proj.weight, gain=1 / math.sqrt(2))
        else:
            nn.init.xavier_uniform_(self.k_proj.weight)
            nn.init.xavier_uniform_(self.v_proj.weight)
            nn.init.xavier_uniform_(self.q_proj.weight)

        nn.init.xavier_uniform_(self.out_proj.weight)
        if self.out_proj.bias is not None:
            nn.init.constant_(self.out_proj.bias, 0.0)
        if self.bias_k is not None:
            nn.init.xavier_normal_(self.bias_k)
        if self.bias_v is not None:
            nn.init.xavier_normal_(self.bias_v)
        if self.has_relative_attention_bias:
            nn.init.xavier_normal_(self.relative_attention_bias.weight)

    def _relative_positions_bucket(self, relative_positions, bidirectional=True):
        num_buckets = self.num_buckets
        max_distance = self.max_distance
        relative_buckets = 0

        if bidirectional:
            num_buckets = num_buckets // 2
            relative_buckets += (relative_positions > 0).to(torch.long) * num_buckets
            relative_positions = torch.abs(relative_positions)
        else:
            relative_positions = -torch.min(relative_positions, torch.zeros_like(relative_positions))

        max_exact = num_buckets // 2
        is_small = relative_positions < max_exact

        relative_postion_if_large = max_exact + (
                torch.log(relative_positions.float() / max_exact)
                / math.log(max_distance / max_exact)
                * (num_buckets - max_exact)
        ).to(torch.long)
        relative_postion_if_large = torch.min(
            relative_postion_if_large, torch.full_like(relative_postion_if_large, num_buckets - 1)
        )

        relative_buckets += torch.where(is_small, relative_positions, relative_postion_if_large)
        return relative_buckets

    def compute_bias(self, query_length, key_length):
        context_position = torch.arange(query_length, dtype=torch.long)[:, None]
        memory_position = torch.arange(key_length, dtype=torch.long)[None, :]
        relative_position = memory_position - context_position
        relative_position_bucket = self._relative_positions_bucket(
            relative_position,
            bidirectional=True
        )
        relative_position_bucket = relative_position_bucket.to(self.relative_attention_bias.weight.device)
        values = self.relative_attention_bias(relative_position_bucket)
        values = values.permute([2, 0, 1])
        return values

    def forward(
            self,
            query,
            key: Optional[Tensor],
            value: Optional[Tensor],
            key_padding_mask: Optional[Tensor] = None,
            incremental_state: Optional[Dict[str, Dict[str, Optional[Tensor]]]] = None,
            need_weights: bool = True,
            static_kv: bool = False,
            attn_mask: Optional[Tensor] = None,
            before_softmax: bool = False,
            need_head_weights: bool = False,
            position_bias: Optional[Tensor] = None
    ) -> Tuple[Tensor, Optional[Tensor], Optional[Tensor]]:
        """Input shape: Time x Batch x Channel

        Args:
            key_padding_mask (ByteTensor, optional): mask to exclude
                keys that are pads, of shape `(batch, src_len)`, where
                padding elements are indicated by 1s.
            need_weights (bool, optional): return the attention weights,
                averaged over heads (default: False).
            attn_mask (ByteTensor, optional): typically used to
                implement causal attention, where the mask prevents the
                attention from looking forward in time (default: None).
            before_softmax (bool, optional): return the raw attention
                weights and values before the attention softmax.
            need_head_weights (bool, optional): return the attention
                weights for each head. Implies *need_weights*. Default:
                return the average attention weights over all heads.
        """
        if need_head_weights:
            need_weights = True

        is_tpu = query.device.type == "xla"

        tgt_len, bsz, embed_dim = query.size()
        src_len = tgt_len
        assert embed_dim == self.embed_dim
        assert list(query.size()) == [tgt_len, bsz, embed_dim]
        if key is not None:
            src_len, key_bsz, _ = key.size()
            if not torch.jit.is_scripting():
                assert key_bsz == bsz
                assert value is not None
                assert src_len, bsz == value.shape[:2]

        if self.has_relative_attention_bias and position_bias is None:
            position_bias = self.compute_bias(tgt_len, src_len)
            position_bias = position_bias.unsqueeze(0).repeat(bsz, 1, 1, 1).view(bsz * self.num_heads, tgt_len, src_len)

        if incremental_state is not None:
            saved_state = self._get_input_buffer(incremental_state)
            if saved_state is not None and "prev_key" in saved_state:
                # previous time steps are cached - no need to recompute
                # key and value if they are static
                if static_kv:
                    assert self.encoder_decoder_attention and not self.self_attention
                    key = value = None
        else:
            saved_state = None

        if self.self_attention:
            q = self.q_proj(query)
            k = self.k_proj(query)
            v = self.v_proj(query)
        elif self.encoder_decoder_attention:
            # encoder-decoder attention
            q = self.q_proj(query)
            if key is None:
                assert value is None
                k = v = None
            else:
                k = self.k_proj(key)
                v = self.v_proj(key)

        else:
            assert key is not None and value is not None
            q = self.q_proj(query)
            k = self.k_proj(key)
            v = self.v_proj(value)
        q *= self.scaling
        alpha = 32
        q *= 1 / alpha

        if self.bias_k is not None:
            assert self.bias_v is not None
            k = torch.cat([k, self.bias_k.repeat(1, bsz, 1)])
            v = torch.cat([v, self.bias_v.repeat(1, bsz, 1)])
            if attn_mask is not None:
                attn_mask = torch.cat(
                    [attn_mask, attn_mask.new_zeros(attn_mask.size(0), 1)], dim=1
                )
            if key_padding_mask is not None:
                key_padding_mask = torch.cat(
                    [
                        key_padding_mask,
                        key_padding_mask.new_zeros(key_padding_mask.size(0), 1),
                    ],
                    dim=1,
                )

        q = (
            q.contiguous()
                .view(tgt_len, bsz * self.num_heads, self.q_head_dim)
                .transpose(0, 1)
        )
        if k is not None:
            k = (
                k.contiguous()
                    .view(-1, bsz * self.num_heads, self.k_head_dim)
                    .transpose(0, 1)
            )
        if v is not None:
            v = (
                v.contiguous()
                    .view(-1, bsz * self.num_heads, self.head_dim)
                    .transpose(0, 1)
            )

        if saved_state is not None:
            # saved states are stored with shape (bsz, num_heads, seq_len, head_dim)
            if "prev_key" in saved_state:
                _prev_key = saved_state["prev_key"]
                assert _prev_key is not None
                prev_key = _prev_key.view(bsz * self.num_heads, -1, self.head_dim)
                if static_kv:
                    k = prev_key
                else:
                    assert k is not None
                    k = torch.cat([prev_key, k], dim=1)
                src_len = k.size(1)
            if "prev_value" in saved_state:
                _prev_value = saved_state["prev_value"]
                assert _prev_value is not None
                prev_value = _prev_value.view(bsz * self.num_heads, -1, self.head_dim)
                if static_kv:
                    v = prev_value
                else:
                    assert v is not None
                    v = torch.cat([prev_value, v], dim=1)
            prev_key_padding_mask: Optional[Tensor] = None
            if "prev_key_padding_mask" in saved_state:
                prev_key_padding_mask = saved_state["prev_key_padding_mask"]
            assert k is not None and v is not None
            key_padding_mask = MultiheadAttention._append_prev_key_padding_mask(
                key_padding_mask=key_padding_mask,
                prev_key_padding_mask=prev_key_padding_mask,
                batch_size=bsz,
                src_len=k.size(1),
                static_kv=static_kv,
            )

            saved_state["prev_key"] = k.view(bsz, self.num_heads, -1, self.head_dim)
            saved_state["prev_value"] = v.view(bsz, self.num_heads, -1, self.head_dim)
            saved_state["prev_key_padding_mask"] = key_padding_mask
            # In this branch incremental_state is never None
            assert incremental_state is not None
            incremental_state = self._set_input_buffer(incremental_state, saved_state)
        assert k is not None
        assert k.size(1) == src_len

        # This is part of a workaround to get around fork/join parallelism
        # not supporting Optional types.
        if key_padding_mask is not None and key_padding_mask.dim() == 0:
            key_padding_mask = None

        if key_padding_mask is not None:
            assert key_padding_mask.size(0) == bsz
            assert key_padding_mask.size(1) == src_len

        if self.add_zero_attn:
            assert v is not None
            src_len += 1
            k = torch.cat([k, k.new_zeros((k.size(0), 1) + k.size()[2:])], dim=1)
            v = torch.cat([v, v.new_zeros((v.size(0), 1) + v.size()[2:])], dim=1)
            if attn_mask is not None:
                attn_mask = torch.cat(
                    [attn_mask, attn_mask.new_zeros(attn_mask.size(0), 1)], dim=1
                )
            if key_padding_mask is not None:
                key_padding_mask = torch.cat(
                    [
                        key_padding_mask,
                        torch.zeros(key_padding_mask.size(0), 1).type_as(
                            key_padding_mask
                        ),
                    ],
                    dim=1,
                )

        attn_weights = torch.bmm(q, k.transpose(1, 2))
        attn_weights = (attn_weights - attn_weights.max(dim=-1, keepdim=True)[0]) * alpha
        attn_weights = self.apply_sparse_mask(attn_weights, tgt_len, src_len, bsz)

        assert list(attn_weights.size()) == [bsz * self.num_heads, tgt_len, src_len]

        if attn_mask is not None:
            attn_mask = attn_mask.unsqueeze(0)
            attn_weights += attn_mask

        if key_padding_mask is not None:
            # don't attend to padding symbols
            attn_weights = attn_weights.view(bsz, self.num_heads, tgt_len, src_len)
            if not is_tpu:
                attn_weights = attn_weights.masked_fill(
                    key_padding_mask.unsqueeze(1).unsqueeze(2).to(torch.bool),
                    float("-inf"),
                )
            else:
                attn_weights = attn_weights.transpose(0, 2)
                attn_weights = attn_weights.masked_fill(key_padding_mask, float("-inf"))
                attn_weights = attn_weights.transpose(0, 2)
            attn_weights = attn_weights.view(bsz * self.num_heads, tgt_len, src_len)

        if before_softmax:
            return attn_weights, v, position_bias

        if position_bias is not None:
            attn_mask_rel_pos = position_bias
            if self.gru_rel_pos == 1:
                query_layer = q.view(bsz, self.num_heads, tgt_len, self.q_head_dim) * alpha / self.scaling
                _B, _H, _L, __ = query_layer.size()
                gate_a, gate_b = torch.sigmoid(self.grep_linear(query_layer).view(
                    _B, _H, _L, 2, 4).sum(-1, keepdim=False)).chunk(2, dim=-1)
                gate_a_1 = gate_a * (gate_b * self.grep_a - 1.0) + 2.0
                attn_mask_rel_pos = gate_a_1.view(bsz * self.num_heads, tgt_len, 1) * position_bias

            attn_mask_rel_pos = attn_mask_rel_pos.view(attn_weights.size())

            attn_weights = attn_weights + attn_mask_rel_pos

        attn_weights_float = F.softmax(
            attn_weights, dim=-1
        )
        attn_weights = attn_weights_float.type_as(attn_weights)
        attn_probs = self.dropout_module(attn_weights)

        assert v is not None
        attn = torch.bmm(attn_probs, v)
        assert list(attn.size()) == [bsz * self.num_heads, tgt_len, self.head_dim]
        attn = attn.transpose(0, 1).contiguous().view(tgt_len, bsz, embed_dim)
        attn = self.out_proj(attn)
        attn_weights: Optional[Tensor] = None
        if need_weights:
            attn_weights = attn_weights_float.view(
                bsz, self.num_heads, tgt_len, src_len
            ).transpose(1, 0)
            if not need_head_weights:
                # average attention weights over heads
                attn_weights = attn_weights.mean(dim=0)

        return attn, attn_weights, position_bias

    @staticmethod
    def _append_prev_key_padding_mask(
            key_padding_mask: Optional[Tensor],
            prev_key_padding_mask: Optional[Tensor],
            batch_size: int,
            src_len: int,
            static_kv: bool,
    ) -> Optional[Tensor]:
        # saved key padding masks have shape (bsz, seq_len)
        if prev_key_padding_mask is not None and static_kv:
            new_key_padding_mask = prev_key_padding_mask
        elif prev_key_padding_mask is not None and key_padding_mask is not None:
            new_key_padding_mask = torch.cat(
                [prev_key_padding_mask.float(), key_padding_mask.float()], dim=1
            )
        # During incremental decoding, as the padding token enters and
        # leaves the frame, there will be a time when prev or current
        # is None
        elif prev_key_padding_mask is not None:
            if src_len > prev_key_padding_mask.size(1):
                filler = torch.zeros(
                    (batch_size, src_len - prev_key_padding_mask.size(1)),
                    device=prev_key_padding_mask.device,
                )
                new_key_padding_mask = torch.cat(
                    [prev_key_padding_mask.float(), filler.float()], dim=1
                )
            else:
                new_key_padding_mask = prev_key_padding_mask.float()
        elif key_padding_mask is not None:
            if src_len > key_padding_mask.size(1):
                filler = torch.zeros(
                    (batch_size, src_len - key_padding_mask.size(1)),
                    device=key_padding_mask.device,
                )
                new_key_padding_mask = torch.cat(
                    [filler.float(), key_padding_mask.float()], dim=1
                )
            else:
                new_key_padding_mask = key_padding_mask.float()
        else:
            new_key_padding_mask = prev_key_padding_mask
        return new_key_padding_mask

    def _get_input_buffer(
            self, incremental_state: Optional[Dict[str, Dict[str, Optional[Tensor]]]]
    ) -> Dict[str, Optional[Tensor]]:
        result = self.get_incremental_state(incremental_state, "attn_state")
        if result is not None:
            return result
        else:
            empty_result: Dict[str, Optional[Tensor]] = {}
            return empty_result

    def _set_input_buffer(
            self,
            incremental_state: Dict[str, Dict[str, Optional[Tensor]]],
            buffer: Dict[str, Optional[Tensor]],
    ):
        return self.set_incremental_state(incremental_state, "attn_state", buffer)

    def apply_sparse_mask(self, attn_weights, tgt_len: int, src_len: int, bsz: int):
        return attn_weights


def init_bert_params(module):
    """
    Initialize the weights specific to the BERT Model.
    This overrides the default initializations depending on the specified arguments.
        1. If normal_init_linear_weights is set then weights of linear
           layer will be initialized using the normal distribution and
           bais will be set to the specified value.
        2. If normal_init_embed_weights is set then weights of embedding
           layer will be initialized using the normal distribution.
        3. If normal_init_proj_weights is set then weights of
           in_project_weight for MultiHeadAttention initialized using
           the normal distribution (to be validated).
    """

    def normal_(data):
        # with FSDP, module params will be on CUDA, so we cast them back to CPU
        # so that the RNG is consistent with and without FSDP
        data.copy_(
            data.cpu().normal_(mean=0.0, std=0.02).to(data.device)
        )

    if isinstance(module, nn.Linear):
        normal_(module.weight.data)
        if module.bias is not None:
            module.bias.data.zero_()
    if isinstance(module, nn.Embedding):
        normal_(module.weight.data)
        if module.padding_idx is not None:
            module.weight.data[module.padding_idx].zero_()
    if isinstance(module, MultiheadAttention):
        normal_(module.q_proj.weight.data)
        normal_(module.k_proj.weight.data)
        normal_(module.v_proj.weight.data)