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ssd.py
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import torch.nn as nn
import torch
import numpy as np
from typing import List, Tuple
import torch.nn.functional as F
from ..utils import box_utils
from collections import namedtuple
GraphPath = namedtuple("GraphPath", ['s0', 'name', 's1']) #
class SSD(nn.Module):
def __init__(self, num_classes: int, base_net: nn.ModuleList, source_layer_indexes: List[int],
extras: nn.ModuleList, classification_headers: nn.ModuleList,
regression_headers: nn.ModuleList, is_test=False, config=None, device=None):
"""Compose a SSD model using the given components.
"""
super(SSD, self).__init__()
self.num_classes = num_classes
self.base_net = base_net
self.source_layer_indexes = source_layer_indexes
self.extras = extras
self.classification_headers = classification_headers
self.regression_headers = regression_headers
self.is_test = is_test
self.config = config
# register layers in source_layer_indexes by adding them to a module list
self.source_layer_add_ons = nn.ModuleList([t[1] for t in source_layer_indexes
if isinstance(t, tuple) and not isinstance(t, GraphPath)])
if device:
self.device = device
else:
self.device = torch.device("cuda:0" if torch.cuda.is_available() else "cpu")
if is_test:
self.config = config
self.priors = config.priors.to(self.device)
def forward(self, x: torch.Tensor) -> Tuple[torch.Tensor, torch.Tensor]:
confidences = []
locations = []
start_layer_index = 0
header_index = 0
for end_layer_index in self.source_layer_indexes:
if isinstance(end_layer_index, GraphPath):
path = end_layer_index
end_layer_index = end_layer_index.s0
added_layer = None
elif isinstance(end_layer_index, tuple):
added_layer = end_layer_index[1]
end_layer_index = end_layer_index[0]
path = None
else:
added_layer = None
path = None
for layer in self.base_net[start_layer_index: end_layer_index]:
x = layer(x)
if added_layer:
y = added_layer(x)
else:
y = x
if path:
sub = getattr(self.base_net[end_layer_index], path.name)
for layer in sub[:path.s1]:
x = layer(x)
y = x
for layer in sub[path.s1:]:
x = layer(x)
end_layer_index += 1
start_layer_index = end_layer_index
confidence, location = self.compute_header(header_index, y)
header_index += 1
confidences.append(confidence)
locations.append(location)
for layer in self.base_net[end_layer_index:]:
x = layer(x)
for layer in self.extras:
x = layer(x)
confidence, location = self.compute_header(header_index, x)
header_index += 1
confidences.append(confidence)
locations.append(location)
confidences = torch.cat(confidences, 1)
locations = torch.cat(locations, 1)
if self.is_test:
confidences = F.softmax(confidences, dim=2)
boxes = box_utils.convert_locations_to_boxes(
locations, self.priors, self.config.center_variance, self.config.size_variance
)
boxes = box_utils.center_form_to_corner_form(boxes)
return confidences, boxes
else:
return confidences, locations
def compute_header(self, i, x):
confidence = self.classification_headers[i](x)
confidence = confidence.permute(0, 2, 3, 1).contiguous()
confidence = confidence.view(confidence.size(0), -1, self.num_classes)
location = self.regression_headers[i](x)
location = location.permute(0, 2, 3, 1).contiguous()
location = location.view(location.size(0), -1, 4)
return confidence, location
def init_from_base_net(self, model):
self.base_net.load_state_dict(torch.load(model, map_location=lambda storage, loc: storage), strict=True)
self.source_layer_add_ons.apply(_xavier_init_)
self.extras.apply(_xavier_init_)
self.classification_headers.apply(_xavier_init_)
self.regression_headers.apply(_xavier_init_)
def init_from_pretrained_ssd(self, model):
state_dict = torch.load(model, map_location=lambda storage, loc: storage)
state_dict = {k: v for k, v in state_dict.items() if not (k.startswith("classification_headers") or k.startswith("regression_headers"))}
model_dict = self.state_dict()
model_dict.update(state_dict)
self.load_state_dict(model_dict)
self.classification_headers.apply(_xavier_init_)
self.regression_headers.apply(_xavier_init_)
def init(self):
self.base_net.apply(_xavier_init_)
self.source_layer_add_ons.apply(_xavier_init_)
self.extras.apply(_xavier_init_)
self.classification_headers.apply(_xavier_init_)
self.regression_headers.apply(_xavier_init_)
def load(self, model):
self.load_state_dict(torch.load(model, map_location=lambda storage, loc: storage))
def save(self, model_path):
torch.save(self.state_dict(), model_path)
class MatchPrior(object):
def __init__(self, center_form_priors, center_variance, size_variance, iou_threshold):
self.center_form_priors = center_form_priors
self.corner_form_priors = box_utils.center_form_to_corner_form(center_form_priors)
self.center_variance = center_variance
self.size_variance = size_variance
self.iou_threshold = iou_threshold
def __call__(self, gt_boxes, gt_labels):
if type(gt_boxes) is np.ndarray:
gt_boxes = torch.from_numpy(gt_boxes)
if type(gt_labels) is np.ndarray:
gt_labels = torch.from_numpy(gt_labels)
boxes, labels = box_utils.assign_priors(gt_boxes, gt_labels,
self.corner_form_priors, self.iou_threshold)
boxes = box_utils.corner_form_to_center_form(boxes)
locations = box_utils.convert_boxes_to_locations(boxes, self.center_form_priors, self.center_variance, self.size_variance)
return locations, labels
def _xavier_init_(m: nn.Module):
if isinstance(m, nn.Conv2d):
nn.init.xavier_uniform_(m.weight)