rvc/layers/attentions.py

import math
from typing import Optional

import torch
from torch import nn
from torch.nn import functional as F


class MultiHeadAttention(nn.Module):
    def __init__(
        self,
        channels: int,
        out_channels: int,
        n_heads: int,
        p_dropout: float = 0.0,
        window_size: Optional[int] = None,
        heads_share: bool = True,
        block_length: Optional[int] = None,
        proximal_bias: bool = False,
        proximal_init: bool = False,
    ):
        super(MultiHeadAttention, self).__init__()
        assert channels % n_heads == 0

        self.channels = channels
        self.out_channels = out_channels
        self.n_heads = n_heads
        self.p_dropout = p_dropout
        self.window_size = window_size
        self.heads_share = heads_share
        self.block_length = block_length
        self.proximal_bias = proximal_bias
        self.proximal_init = proximal_init
        self.attn = None

        self.k_channels = channels // n_heads
        self.conv_q = nn.Conv1d(channels, channels, 1)
        self.conv_k = nn.Conv1d(channels, channels, 1)
        self.conv_v = nn.Conv1d(channels, channels, 1)
        self.conv_o = nn.Conv1d(channels, out_channels, 1)
        self.drop = nn.Dropout(p_dropout)

        if window_size is not None:
            n_heads_rel = 1 if heads_share else n_heads
            rel_stddev = self.k_channels**-0.5
            self.emb_rel_k = nn.Parameter(
                torch.randn(n_heads_rel, window_size * 2 + 1, self.k_channels)
                * rel_stddev
            )
            self.emb_rel_v = nn.Parameter(
                torch.randn(n_heads_rel, window_size * 2 + 1, self.k_channels)
                * rel_stddev
            )

        nn.init.xavier_uniform_(self.conv_q.weight)
        nn.init.xavier_uniform_(self.conv_k.weight)
        nn.init.xavier_uniform_(self.conv_v.weight)
        if proximal_init:
            with torch.no_grad():
                self.conv_k.weight.copy_(self.conv_q.weight)
                self.conv_k.bias.copy_(self.conv_q.bias)

    def __call__(
        self,
        x: torch.Tensor,
        c: torch.Tensor,
        attn_mask: Optional[torch.Tensor] = None,
    ) -> torch.Tensor:
        return super().__call__(x, c, attn_mask=attn_mask)

    def forward(
        self,
        x: torch.Tensor,
        c: torch.Tensor,
        attn_mask: Optional[torch.Tensor] = None,
    ) -> torch.Tensor:
        q = self.conv_q(x)
        k = self.conv_k(c)
        v = self.conv_v(c)

        x, _ = self._attention(q, k, v, mask=attn_mask)

        x = self.conv_o(x)
        return x

    def _attention(
        self,
        query: torch.Tensor,
        key: torch.Tensor,
        value: torch.Tensor,
        mask: Optional[torch.Tensor] = None,
    ):
        # reshape [b, d, t] -> [b, n_h, t, d_k]
        b, d, t_s = key.size()
        t_t = query.size(2)
        query = query.view(b, self.n_heads, self.k_channels, t_t).transpose(2, 3)
        key = key.view(b, self.n_heads, self.k_channels, t_s).transpose(2, 3)
        value = value.view(b, self.n_heads, self.k_channels, t_s).transpose(2, 3)

        scores = torch.matmul(query / math.sqrt(self.k_channels), key.transpose(-2, -1))
        if self.window_size is not None:
            assert (
                t_s == t_t
            ), "Relative attention is only available for self-attention."
            key_relative_embeddings = self._get_relative_embeddings(self.emb_rel_k, t_s)
            rel_logits = self._matmul_with_relative_keys(
                query / math.sqrt(self.k_channels), key_relative_embeddings
            )
            scores_local = self._relative_position_to_absolute_position(rel_logits)
            scores = scores + scores_local
        if self.proximal_bias:
            assert t_s == t_t, "Proximal bias is only available for self-attention."
            scores = scores + self._attention_bias_proximal(t_s).to(
                device=scores.device, dtype=scores.dtype
            )
        if mask is not None:
            scores = scores.masked_fill(mask == 0, -1e4)
            if self.block_length is not None:
                assert (
                    t_s == t_t
                ), "Local attention is only available for self-attention."
                block_mask = (
                    torch.ones_like(scores)
                    .triu(-self.block_length)
                    .tril(self.block_length)
                )
                scores = scores.masked_fill(block_mask == 0, -1e4)
        p_attn = F.softmax(scores, dim=-1)  # [b, n_h, t_t, t_s]
        p_attn = self.drop(p_attn)
        output = torch.matmul(p_attn, value)
        if self.window_size is not None:
            relative_weights = self._absolute_position_to_relative_position(p_attn)
            value_relative_embeddings = self._get_relative_embeddings(
                self.emb_rel_v, t_s
            )
            output = output + self._matmul_with_relative_values(
                relative_weights, value_relative_embeddings
            )
        output = (
            output.transpose(2, 3).contiguous().view(b, d, t_t)
        )  # [b, n_h, t_t, d_k] -> [b, d, t_t]
        return output, p_attn

    def _matmul_with_relative_values(self, x, y):
        """
        x: [b, h, l, m]
        y: [h or 1, m, d]
        ret: [b, h, l, d]
        """
        ret = torch.matmul(x, y.unsqueeze(0))
        return ret

    def _matmul_with_relative_keys(self, x, y):
        """
        x: [b, h, l, d]
        y: [h or 1, m, d]
        ret: [b, h, l, m]
        """
        ret = torch.matmul(x, y.unsqueeze(0).transpose(-2, -1))
        return ret

    def _get_relative_embeddings(self, relative_embeddings, length: int):
        # max_relative_position = 2 * self.window_size + 1
        # Pad first before slice to avoid using cond ops.
        pad_length: int = max(length - (self.window_size + 1), 0)
        slice_start_position = max((self.window_size + 1) - length, 0)
        slice_end_position = slice_start_position + 2 * length - 1
        if pad_length > 0:
            padded_relative_embeddings = F.pad(
                relative_embeddings,
                [0, 0, pad_length, pad_length, 0, 0],
            )
        else:
            padded_relative_embeddings = relative_embeddings
        used_relative_embeddings = padded_relative_embeddings[
            :, slice_start_position:slice_end_position
        ]
        return used_relative_embeddings

    def _relative_position_to_absolute_position(self, x):
        """
        x: [b, h, l, 2*l-1]
        ret: [b, h, l, l]
        """
        batch, heads, length, _ = x.size()
        # Concat columns of pad to shift from relative to absolute indexing.
        x = F.pad(
            x,
            [0, 1, 0, 0, 0, 0, 0, 0],
        )

        # Concat extra elements so to add up to shape (len+1, 2*len-1).
        x_flat = x.view([batch, heads, length * 2 * length])
        x_flat = F.pad(x_flat, [0, length - 1, 0, 0, 0, 0])

        # Reshape and slice out the padded elements.
        x_final = x_flat.view([batch, heads, length + 1, 2 * length - 1])[
            :, :, :length, length - 1 :
        ]
        return x_final

    def _absolute_position_to_relative_position(self, x):
        """
        x: [b, h, l, l]
        ret: [b, h, l, 2*l-1]
        """
        batch, heads, length, _ = x.size()
        # padd along column
        x = F.pad(x, [0, length - 1, 0, 0, 0, 0, 0, 0])
        x_flat = x.view([batch, heads, (length**2) + (length * (length - 1))])
        # add 0's in the beginning that will skew the elements after reshape
        x_flat = F.pad(x_flat, [length, 0, 0, 0, 0, 0])
        x_final = x_flat.view([batch, heads, length, 2 * length])[:, :, :, 1:]
        return x_final

    def _attention_bias_proximal(self, length: int):
        """Bias for self-attention to encourage attention to close positions.
        Args:
          length: an integer scalar.
        Returns:
          a Tensor with shape [1, 1, length, length]
        """
        r = torch.arange(length, dtype=torch.float32)
        diff = torch.unsqueeze(r, 0) - torch.unsqueeze(r, 1)
        return torch.unsqueeze(torch.unsqueeze(-torch.log1p(torch.abs(diff)), 0), 0)


class FFN(nn.Module):
    """
    Feed-Forward Network
    """

    def __init__(
        self,
        in_channels: int,
        out_channels: int,
        filter_channels: int,
        kernel_size: int,
        p_dropout: float = 0.0,
        activation: Optional[str] = None,
        causal: bool = False,
    ):
        super(FFN, self).__init__()
        self.in_channels = in_channels
        self.out_channels = out_channels
        self.filter_channels = filter_channels
        self.kernel_size = kernel_size
        self.p_dropout = p_dropout
        self.activation = activation
        self.causal = causal
        self.is_activation = True if activation == "gelu" else False

        self.conv_1 = nn.Conv1d(in_channels, filter_channels, kernel_size)
        self.conv_2 = nn.Conv1d(filter_channels, out_channels, kernel_size)
        self.drop = nn.Dropout(p_dropout)

    def __call__(self, x: torch.Tensor, x_mask: torch.Tensor) -> torch.Tensor:
        return super().__call__(x, x_mask)

    def forward(self, x: torch.Tensor, x_mask: torch.Tensor) -> torch.Tensor:
        x = self.conv_1(self._padding(x, x_mask))
        if self.is_activation:
            x = x * torch.sigmoid(1.702 * x)
        else:
            x = torch.relu(x)
        x = self.drop(x)

        x = self.conv_2(self._padding(x, x_mask))
        return x * x_mask

    def _padding(self, x: torch.Tensor, x_mask: torch.Tensor) -> torch.Tensor:
        if self.causal:
            return self._causal_padding(x * x_mask)
        return self._same_padding(x * x_mask)

    def _causal_padding(self, x):
        if self.kernel_size == 1:
            return x
        pad_l: int = self.kernel_size - 1
        pad_r: int = 0
        # padding = [[0, 0], [0, 0], [pad_l, pad_r]]
        x = F.pad(x, [pad_l, pad_r, 0, 0, 0, 0])
        return x

    def _same_padding(self, x):
        if self.kernel_size == 1:
            return x
        pad_l: int = (self.kernel_size - 1) // 2
        pad_r: int = self.kernel_size // 2
        # padding = [[0, 0], [0, 0], [pad_l, pad_r]]
        x = F.pad(x, [pad_l, pad_r, 0, 0, 0, 0])
        return x