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# References:
# Lightning-DiT: https://github.com/hustvl/LightningDiT
# --------------------------------------------------------
from math import pi
import torch
from torch import nn
import numpy as np
from einops import rearrange, repeat
def broadcat(tensors, dim = -1):
num_tensors = len(tensors)
shape_lens = set(list(map(lambda t: len(t.shape), tensors)))
assert len(shape_lens) == 1, 'tensors must all have the same number of dimensions'
shape_len = list(shape_lens)[0]
dim = (dim + shape_len) if dim < 0 else dim
dims = list(zip(*map(lambda t: list(t.shape), tensors)))
expandable_dims = [(i, val) for i, val in enumerate(dims) if i != dim]
assert all([*map(lambda t: len(set(t[1])) <= 2, expandable_dims)]), 'invalid dimensions for broadcastable concatentation'
max_dims = list(map(lambda t: (t[0], max(t[1])), expandable_dims))
expanded_dims = list(map(lambda t: (t[0], (t[1],) * num_tensors), max_dims))
expanded_dims.insert(dim, (dim, dims[dim]))
expandable_shapes = list(zip(*map(lambda t: t[1], expanded_dims)))
tensors = list(map(lambda t: t[0].expand(*t[1]), zip(tensors, expandable_shapes)))
return torch.cat(tensors, dim = dim)
def rotate_half(x):
x = rearrange(x, '... (d r) -> ... d r', r = 2)
x1, x2 = x.unbind(dim = -1)
x = torch.stack((-x2, x1), dim = -1)
return rearrange(x, '... d r -> ... (d r)')
class VisionRotaryEmbedding(nn.Module):
def __init__(
self,
dim,
pt_seq_len,
ft_seq_len=None,
custom_freqs = None,
freqs_for = 'lang',
theta = 10000,
max_freq = 10,
num_freqs = 1,
):
super().__init__()
if custom_freqs:
freqs = custom_freqs
elif freqs_for == 'lang':
freqs = 1. / (theta ** (torch.arange(0, dim, 2)[:(dim // 2)].float() / dim))
elif freqs_for == 'pixel':
freqs = torch.linspace(1., max_freq / 2, dim // 2) * pi
elif freqs_for == 'constant':
freqs = torch.ones(num_freqs).float()
else:
raise ValueError(f'unknown modality {freqs_for}')
if ft_seq_len is None: ft_seq_len = pt_seq_len
t = torch.arange(ft_seq_len) / ft_seq_len * pt_seq_len
freqs_h = torch.einsum('..., f -> ... f', t, freqs)
freqs_h = repeat(freqs_h, '... n -> ... (n r)', r = 2)
freqs_w = torch.einsum('..., f -> ... f', t, freqs)
freqs_w = repeat(freqs_w, '... n -> ... (n r)', r = 2)
freqs = broadcat((freqs_h[:, None, :], freqs_w[None, :, :]), dim = -1)
self.register_buffer("freqs_cos", freqs.cos())
self.register_buffer("freqs_sin", freqs.sin())
def forward(self, t, start_index = 0):
rot_dim = self.freqs_cos.shape[-1]
end_index = start_index + rot_dim
assert rot_dim <= t.shape[-1], f'feature dimension {t.shape[-1]} is not of sufficient size to rotate in all the positions {rot_dim}'
t_left, t, t_right = t[..., :start_index], t[..., start_index:end_index], t[..., end_index:]
t = (t * self.freqs_cos) + (rotate_half(t) * self.freqs_sin)
return torch.cat((t_left, t, t_right), dim = -1)
class VisionRotaryEmbeddingFast(nn.Module):
def __init__(
self,
dim,
pt_seq_len=16,
ft_seq_len=None,
custom_freqs = None,
freqs_for = 'lang',
theta = 10000,
max_freq = 10,
num_freqs = 1,
num_cls_token = 0
):
super().__init__()
if custom_freqs:
freqs = custom_freqs
elif freqs_for == 'lang':
freqs = 1. / (theta ** (torch.arange(0, dim, 2)[:(dim // 2)].float() / dim))
elif freqs_for == 'pixel':
freqs = torch.linspace(1., max_freq / 2, dim // 2) * pi
elif freqs_for == 'constant':
freqs = torch.ones(num_freqs).float()
else:
raise ValueError(f'unknown modality {freqs_for}')
if ft_seq_len is None: ft_seq_len = pt_seq_len
t = torch.arange(ft_seq_len) / ft_seq_len * pt_seq_len
freqs = torch.einsum('..., f -> ... f', t, freqs)
freqs = repeat(freqs, '... n -> ... (n r)', r = 2)
freqs = broadcat((freqs[:, None, :], freqs[None, :, :]), dim = -1)
if num_cls_token > 0:
freqs_flat = freqs.view(-1, freqs.shape[-1]) # [N_img, D]
cos_img = freqs_flat.cos()
sin_img = freqs_flat.sin()
# prepend in-context cls token
N_img, D = cos_img.shape
cos_pad = torch.ones(num_cls_token, D, dtype=cos_img.dtype, device=cos_img.device)
sin_pad = torch.zeros(num_cls_token, D, dtype=sin_img.dtype, device=sin_img.device)
self.freqs_cos = torch.cat([cos_pad, cos_img], dim=0).cuda() # [N_cls+N_img, D]
self.freqs_sin = torch.cat([sin_pad, sin_img], dim=0).cuda()
else:
self.freqs_cos = freqs.cos().view(-1, freqs.shape[-1]).cuda()
self.freqs_sin = freqs.sin().view(-1, freqs.shape[-1]).cuda()
def forward(self, t): return (t * self.freqs_cos + rotate_half(t) * self.freqs_sin).to(t.dtype)
class RMSNorm(nn.Module):
def __init__(self, hidden_size, eps=1e-6):
"""
LlamaRMSNorm is equivalent to T5LayerNorm
"""
super().__init__()
self.weight = nn.Parameter(torch.ones(hidden_size))
self.variance_epsilon = eps
def forward(self, hidden_states):
input_dtype = hidden_states.dtype
hidden_states = hidden_states.to(torch.float32)
variance = hidden_states.pow(2).mean(-1, keepdim=True)
hidden_states = hidden_states * torch.rsqrt(variance + self.variance_epsilon)
return (self.weight * hidden_states).to(input_dtype)
def get_2d_sincos_pos_embed(embed_dim, grid_size, cls_token=False, extra_tokens=0):
"""
grid_size: int of the grid height and width
return:
pos_embed: [grid_size*grid_size, embed_dim] or [1+grid_size*grid_size, embed_dim] (w/ or w/o cls_token)
"""
grid_h = np.arange(grid_size, dtype=np.float32)
grid_w = np.arange(grid_size, dtype=np.float32)
grid = np.meshgrid(grid_w, grid_h) # here w goes first
grid = np.stack(grid, axis=0)
grid = grid.reshape([2, 1, grid_size, grid_size])
pos_embed = get_2d_sincos_pos_embed_from_grid(embed_dim, grid)
if cls_token and extra_tokens > 0:
pos_embed = np.concatenate([np.zeros([extra_tokens, embed_dim]), pos_embed], axis=0)
return pos_embed
def get_2d_sincos_pos_embed_from_grid(embed_dim, grid):
assert embed_dim % 2 == 0
# use half of dimensions to encode grid_h
emb_h = get_1d_sincos_pos_embed_from_grid(embed_dim // 2, grid[0]) # (H*W, D/2)
emb_w = get_1d_sincos_pos_embed_from_grid(embed_dim // 2, grid[1]) # (H*W, D/2)
emb = np.concatenate([emb_h, emb_w], axis=1) # (H*W, D)
return emb
def get_1d_sincos_pos_embed_from_grid(embed_dim, pos):
"""
embed_dim: output dimension for each position
pos: a list of positions to be encoded: size (M,)
out: (M, D)
"""
assert embed_dim % 2 == 0
omega = np.arange(embed_dim // 2, dtype=np.float64)
omega /= embed_dim / 2.
omega = 1. / 10000**omega # (D/2,)
pos = pos.reshape(-1) # (M,)
out = np.einsum('m,d->md', pos, omega) # (M, D/2), outer product
emb_sin = np.sin(out) # (M, D/2)
emb_cos = np.cos(out) # (M, D/2)
emb = np.concatenate([emb_sin, emb_cos], axis=1) # (M, D)
return emb |