207 lines
6.3 KiB
Python
207 lines
6.3 KiB
Python
import math
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import torch
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import torch.nn as nn
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import torch.nn.functional as F
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from craftsman.utils.typing import *
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from craftsman.utils.checkpoint import checkpoint
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from .utils import init_linear, MLP
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class MultiheadAttention(nn.Module):
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def __init__(
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self,
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*,
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n_ctx: int,
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width: int,
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heads: int,
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init_scale: float,
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qkv_bias: bool,
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use_flash: bool = False
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):
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super().__init__()
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self.n_ctx = n_ctx
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self.width = width
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self.heads = heads
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self.c_qkv = nn.Linear(width, width * 3, bias=qkv_bias)
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self.c_proj = nn.Linear(width, width)
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self.attention = QKVMultiheadAttention(heads=heads, n_ctx=n_ctx, use_flash=use_flash)
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init_linear(self.c_qkv, init_scale)
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init_linear(self.c_proj, init_scale)
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def forward(self, x):
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x = self.c_qkv(x)
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x = checkpoint(self.attention, (x,), (), True)
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x = self.c_proj(x)
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return x
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class QKVMultiheadAttention(nn.Module):
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def __init__(self, *, heads: int, n_ctx: int, use_flash: bool = False):
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super().__init__()
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self.heads = heads
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self.n_ctx = n_ctx
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self.use_flash = use_flash
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def forward(self, qkv):
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bs, n_ctx, width = qkv.shape
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attn_ch = width // self.heads // 3
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scale = 1 / math.sqrt(math.sqrt(attn_ch))
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qkv = qkv.view(bs, n_ctx, self.heads, -1)
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q, k, v = torch.split(qkv, attn_ch, dim=-1)
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if self.use_flash:
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q = q.permute(0, 2, 1, 3)
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k = k.permute(0, 2, 1, 3)
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v = v.permute(0, 2, 1, 3)
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out = F.scaled_dot_product_attention(q, k, v).permute(0, 2, 1, 3).reshape(bs, n_ctx, -1)
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else:
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weight = torch.einsum(
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"bthc,bshc->bhts", q * scale, k * scale
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) # More stable with f16 than dividing afterwards
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wdtype = weight.dtype
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weight = torch.softmax(weight.float(), dim=-1).type(wdtype)
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out = torch.einsum("bhts,bshc->bthc", weight, v).reshape(bs, n_ctx, -1)
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return out
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class ResidualAttentionBlock(nn.Module):
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def __init__(
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self,
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*,
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n_ctx: int,
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width: int,
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heads: int,
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init_scale: float = 1.0,
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qkv_bias: bool = True,
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use_flash: bool = False,
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use_checkpoint: bool = False
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):
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super().__init__()
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self.use_checkpoint = use_checkpoint
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self.attn = MultiheadAttention(
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n_ctx=n_ctx,
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width=width,
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heads=heads,
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init_scale=init_scale,
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qkv_bias=qkv_bias,
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use_flash=use_flash
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)
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self.ln_1 = nn.LayerNorm(width)
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self.mlp = MLP(width=width, init_scale=init_scale)
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self.ln_2 = nn.LayerNorm(width)
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def _forward(self, x: torch.Tensor):
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x = x + self.attn(self.ln_1(x))
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x = x + self.mlp(self.ln_2(x))
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return x
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def forward(self, x: torch.Tensor):
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return checkpoint(self._forward, (x,), self.parameters(), self.use_checkpoint)
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class MultiheadCrossAttention(nn.Module):
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def __init__(
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self,
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*,
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width: int,
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heads: int,
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init_scale: float,
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qkv_bias: bool = True,
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use_flash: bool = False,
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n_data: Optional[int] = None,
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data_width: Optional[int] = None,
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):
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super().__init__()
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self.n_data = n_data
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self.width = width
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self.heads = heads
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self.data_width = width if data_width is None else data_width
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self.c_q = nn.Linear(width, width, bias=qkv_bias)
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self.c_kv = nn.Linear(self.data_width, width * 2, bias=qkv_bias)
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self.c_proj = nn.Linear(width, width)
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self.attention = QKVMultiheadCrossAttention(
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heads=heads, n_data=n_data, use_flash=use_flash
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)
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init_linear(self.c_q, init_scale)
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init_linear(self.c_kv, init_scale)
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init_linear(self.c_proj, init_scale)
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def forward(self, x, data):
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x = self.c_q(x)
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data = self.c_kv(data)
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x = checkpoint(self.attention, (x, data), (), True)
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x = self.c_proj(x)
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return x
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class QKVMultiheadCrossAttention(nn.Module):
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def __init__(self, *, heads: int, use_flash: bool = False, n_data: Optional[int] = None):
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super().__init__()
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self.heads = heads
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self.n_data = n_data
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self.use_flash = use_flash
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def forward(self, q, kv):
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_, n_ctx, _ = q.shape
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bs, n_data, width = kv.shape
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attn_ch = width // self.heads // 2
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scale = 1 / math.sqrt(math.sqrt(attn_ch))
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q = q.view(bs, n_ctx, self.heads, -1)
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kv = kv.view(bs, n_data, self.heads, -1)
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k, v = torch.split(kv, attn_ch, dim=-1)
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if self.use_flash:
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q = q.permute(0, 2, 1, 3)
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k = k.permute(0, 2, 1, 3)
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v = v.permute(0, 2, 1, 3)
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out = F.scaled_dot_product_attention(q, k, v).permute(0, 2, 1, 3).reshape(bs, n_ctx, -1)
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else:
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weight = torch.einsum(
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"bthc,bshc->bhts", q * scale, k * scale
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) # More stable with f16 than dividing afterwards
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wdtype = weight.dtype
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weight = torch.softmax(weight.float(), dim=-1).type(wdtype)
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out = torch.einsum("bhts,bshc->bthc", weight, v).reshape(bs, n_ctx, -1)
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return out
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class ResidualCrossAttentionBlock(nn.Module):
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def __init__(
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self,
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*,
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n_data: Optional[int] = None,
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width: int,
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heads: int,
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data_width: Optional[int] = None,
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init_scale: float = 0.25,
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qkv_bias: bool = True,
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use_flash: bool = False
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):
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super().__init__()
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if data_width is None:
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data_width = width
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self.attn = MultiheadCrossAttention(
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n_data=n_data,
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width=width,
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heads=heads,
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data_width=data_width,
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init_scale=init_scale,
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qkv_bias=qkv_bias,
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use_flash=use_flash,
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)
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self.ln_1 = nn.LayerNorm(width)
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self.ln_2 = nn.LayerNorm(data_width)
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self.mlp = MLP(width=width, init_scale=init_scale)
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self.ln_3 = nn.LayerNorm(width)
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def forward(self, x: torch.Tensor, data: torch.Tensor):
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x = x + self.attn(self.ln_1(x), self.ln_2(data))
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x = x + self.mlp(self.ln_3(x))
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return x |