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c9ef531 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 | # Copyright (c) Meta Platforms, Inc. and affiliates. All Rights Reserved
# pyre-unsafe
import math
from typing import Optional
import torch
from torch import nn
class PositionEmbeddingSine(nn.Module):
"""
This is a more standard version of the position embedding, very similar to the one
used by the Attention is all you need paper, generalized to work on images.
"""
def __init__(
self,
num_pos_feats,
temperature: int = 10000,
normalize: bool = True,
scale: Optional[float] = None,
precompute_resolution: Optional[int] = None,
):
super().__init__()
assert num_pos_feats % 2 == 0, "Expecting even model width"
self.num_pos_feats = num_pos_feats // 2
self.temperature = temperature
self.normalize = normalize
if scale is not None and normalize is False:
raise ValueError("normalize should be True if scale is passed")
if scale is None:
scale = 2 * math.pi
self.scale = scale
self.cache = {}
# Precompute positional encodings under `precompute_resolution` to fill the cache
# and avoid symbolic shape tracing errors in torch.compile in PyTorch 2.4 nightly.
if precompute_resolution is not None:
# We precompute pos enc for all strides used by both DualViTDetNeck and
# TriViTDetNeck (scale_factors 4.0, 2.0, 1.0, 0.5 applied to backbone
# output at stride 14 from 1008px input → 72x72).
precompute_sizes = [
(int(precompute_resolution // 3.5), int(precompute_resolution // 3.5)),
(precompute_resolution // 4, precompute_resolution // 4),
(int(precompute_resolution // 7), int(precompute_resolution // 7)),
(precompute_resolution // 8, precompute_resolution // 8),
(int(precompute_resolution // 14), int(precompute_resolution // 14)),
(precompute_resolution // 16, precompute_resolution // 16),
(int(precompute_resolution // 28), int(precompute_resolution // 28)),
(precompute_resolution // 32, precompute_resolution // 32),
]
for size in precompute_sizes:
tensors = torch.zeros((1, 1) + size, device="cuda")
self.forward(tensors)
# further clone and detach it in the cache (just to be safe)
self.cache[size] = self.cache[size].clone().detach()
def _encode_xy(self, x, y):
# The positions are expected to be normalized
assert len(x) == len(y) and x.ndim == y.ndim == 1
x_embed = x * self.scale
y_embed = y * self.scale
dim_t = torch.arange(self.num_pos_feats, dtype=torch.float32, device=x.device)
dim_t = self.temperature ** (2 * (dim_t // 2) / self.num_pos_feats)
pos_x = x_embed[:, None] / dim_t
pos_y = y_embed[:, None] / dim_t
pos_x = torch.stack(
(pos_x[:, 0::2].sin(), pos_x[:, 1::2].cos()), dim=2
).flatten(1)
pos_y = torch.stack(
(pos_y[:, 0::2].sin(), pos_y[:, 1::2].cos()), dim=2
).flatten(1)
return pos_x, pos_y
@torch.no_grad()
def encode_boxes(self, x, y, w, h):
pos_x, pos_y = self._encode_xy(x, y)
pos = torch.cat((pos_y, pos_x, h[:, None], w[:, None]), dim=1)
return pos
encode = encode_boxes # Backwards compatibility
@torch.no_grad()
def encode_points(self, x, y, labels):
(bx, nx), (by, ny), (bl, nl) = x.shape, y.shape, labels.shape
assert bx == by and nx == ny and bx == bl and nx == nl
pos_x, pos_y = self._encode_xy(x.flatten(), y.flatten())
pos_x, pos_y = pos_x.reshape(bx, nx, -1), pos_y.reshape(by, ny, -1)
pos = torch.cat((pos_y, pos_x, labels[:, :, None]), dim=2)
return pos
@torch.no_grad()
def forward(self, x):
cache_key = None
cache_key = (x.shape[-2], x.shape[-1])
if cache_key in self.cache:
return self.cache[cache_key][None].repeat(x.shape[0], 1, 1, 1)
y_embed = (
torch.arange(1, x.shape[-2] + 1, dtype=torch.float32, device=x.device)
.view(1, -1, 1)
.repeat(x.shape[0], 1, x.shape[-1])
)
x_embed = (
torch.arange(1, x.shape[-1] + 1, dtype=torch.float32, device=x.device)
.view(1, 1, -1)
.repeat(x.shape[0], x.shape[-2], 1)
)
if self.normalize:
eps = 1e-6
y_embed = y_embed / (y_embed[:, -1:, :] + eps) * self.scale
x_embed = x_embed / (x_embed[:, :, -1:] + eps) * self.scale
dim_t = torch.arange(self.num_pos_feats, dtype=torch.float32, device=x.device)
dim_t = self.temperature ** (2 * (dim_t // 2) / self.num_pos_feats)
pos_x = x_embed[:, :, :, None] / dim_t
pos_y = y_embed[:, :, :, None] / dim_t
pos_x = torch.stack(
(pos_x[:, :, :, 0::2].sin(), pos_x[:, :, :, 1::2].cos()), dim=4
).flatten(3)
pos_y = torch.stack(
(pos_y[:, :, :, 0::2].sin(), pos_y[:, :, :, 1::2].cos()), dim=4
).flatten(3)
pos = torch.cat((pos_y, pos_x), dim=3).permute(0, 3, 1, 2)
if cache_key is not None:
self.cache[cache_key] = pos[0]
return pos
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