#
# For licensing see accompanying LICENSE file.
# Copyright (C) 2023 Apple Inc. All Rights Reserved.
#
import argparse
from typing import Dict, List, Optional, Tuple
from torch import nn
from cvnets.layers import ConvLayer2d, Dropout, GlobalPool, LinearLayer
from cvnets.models import MODEL_REGISTRY
from cvnets.models.classification.base_image_encoder import BaseImageEncoder
from cvnets.models.classification.config.mobilenetv2 import get_configuration
from cvnets.modules import InvertedResidual
from utils.math_utils import bound_fn, make_divisible
[docs]@MODEL_REGISTRY.register(name="mobilenetv2", type="classification")
class MobileNetV2(BaseImageEncoder):
"""
This class defines the `MobileNetv2 architecture <https://arxiv.org/abs/1801.04381>`_
"""
[docs] def __init__(self, opts, *args, **kwargs) -> None:
width_mult = getattr(
opts, "model.classification.mobilenetv2.width_multiplier", 1.0
)
num_classes = getattr(opts, "model.classification.n_classes", 1000)
cfg = get_configuration(opts=opts)
image_channels = 3
input_channels = 32
last_channel = 1280
classifier_dropout = getattr(
opts, "model.classification.classifier_dropout", 0.0
)
if classifier_dropout == 0.0 or classifier_dropout is None:
val = round(0.2 * width_mult, 3)
classifier_dropout = bound_fn(min_val=0.0, max_val=0.2, value=val)
super().__init__(opts, *args, **kwargs)
last_channel = make_divisible(
last_channel * max(1.0, width_mult), self.round_nearest
)
self.model_conf_dict = dict()
self.conv_1 = ConvLayer2d(
opts=opts,
in_channels=image_channels,
out_channels=input_channels,
kernel_size=3,
stride=2,
use_norm=True,
use_act=True,
)
self.model_conf_dict["conv1"] = {"in": image_channels, "out": input_channels}
self.layer_1, out_channels = self._make_layer(
opts=opts,
mv2_config=cfg["layer1"],
width_mult=width_mult,
input_channel=input_channels,
)
self.model_conf_dict["layer1"] = {"in": input_channels, "out": out_channels}
input_channels = out_channels
self.layer_2, out_channels = self._make_layer(
opts=opts,
mv2_config=cfg["layer2"],
width_mult=width_mult,
input_channel=input_channels,
)
self.model_conf_dict["layer2"] = {"in": input_channels, "out": out_channels}
input_channels = out_channels
self.layer_3, out_channels = self._make_layer(
opts=opts,
mv2_config=cfg["layer3"],
width_mult=width_mult,
input_channel=input_channels,
)
self.model_conf_dict["layer3"] = {"in": input_channels, "out": out_channels}
input_channels = out_channels
self.layer_4, out_channels = self._make_layer(
opts=opts,
mv2_config=[cfg["layer4"], cfg["layer4_a"]],
width_mult=width_mult,
input_channel=input_channels,
dilate=self.dilate_l4,
)
self.model_conf_dict["layer4"] = {"in": input_channels, "out": out_channels}
input_channels = out_channels
self.layer_5, out_channels = self._make_layer(
opts=opts,
mv2_config=[cfg["layer5"], cfg["layer5_a"]],
width_mult=width_mult,
input_channel=input_channels,
dilate=self.dilate_l5,
)
self.model_conf_dict["layer5"] = {"in": input_channels, "out": out_channels}
input_channels = out_channels
self.conv_1x1_exp = ConvLayer2d(
opts=opts,
in_channels=input_channels,
out_channels=last_channel,
kernel_size=1,
stride=1,
use_act=True,
use_norm=True,
)
self.model_conf_dict["exp_before_cls"] = {
"in": input_channels,
"out": last_channel,
}
pool_type = getattr(opts, "model.layer.global_pool", "mean")
self.classifier = nn.Sequential()
self.classifier.add_module(
name="global_pool", module=GlobalPool(pool_type=pool_type, keep_dim=False)
)
if 0.0 < classifier_dropout < 1.0:
self.classifier.add_module(
name="classifier_dropout", module=Dropout(p=classifier_dropout)
)
self.classifier.add_module(
name="classifier_fc",
module=LinearLayer(
in_features=last_channel, out_features=num_classes, bias=True
),
)
self.model_conf_dict["cls"] = {"in": last_channel, "out": num_classes}
# check model
self.check_model()
# weight initialization
self.reset_parameters(opts=opts)
[docs] @classmethod
def add_arguments(cls, parser: argparse.ArgumentParser) -> argparse.ArgumentParser:
group = parser.add_argument_group(title=cls.__name__)
group.add_argument(
"--model.classification.mobilenetv2.width-multiplier",
type=float,
default=1.0,
help="Width multiplier for MobileNetv2. Default: 1.0",
)
return parser
def _make_layer(
self,
opts,
mv2_config: Dict or List,
width_mult: float,
input_channel: int,
dilate: Optional[bool] = False,
*args,
**kwargs
) -> Tuple[nn.Module, int]:
prev_dilation = self.dilation
mv2_block = nn.Sequential()
count = 0
if isinstance(mv2_config, Dict):
mv2_config = [mv2_config]
for cfg in mv2_config:
t = cfg.get("expansion_ratio")
c = cfg.get("out_channels")
n = cfg.get("num_blocks")
s = cfg.get("stride")
output_channel = make_divisible(c * width_mult, self.round_nearest)
for block_idx in range(n):
stride = s if block_idx == 0 else 1
block_name = "mv2_block_{}".format(count)
if dilate and count == 0:
self.dilation *= stride
stride = 1
layer = InvertedResidual(
opts=opts,
in_channels=input_channel,
out_channels=output_channel,
stride=stride,
expand_ratio=t,
dilation=prev_dilation if count == 0 else self.dilation,
)
mv2_block.add_module(name=block_name, module=layer)
count += 1
input_channel = output_channel
return mv2_block, input_channel