""" EfficientNet, MobileNetV3, etc Builder
Assembles EfficieNet and related network feature blocks from string definitions.
Handles stride, dilation calculations, and selects feature extraction points.
Hacked together by / Copyright 2020 Ross Wightman
"""
import logging
import math
import re
from copy import deepcopy
import torch.nn as nn
from .efficientnet_blocks import *
from .layers import CondConv2d, get_condconv_initializer
__all__ = ["EfficientNetBuilder", "decode_arch_def", "efficientnet_init_weights"]
_logger = logging.getLogger(__name__)
def _log_info_if(msg, condition):
if condition:
_logger.info(msg)
def _parse_ksize(ss):
if ss.isdigit():
return int(ss)
else:
return [int(k) for k in ss.split('.')]
def _decode_block_str(block_str):
""" Decode block definition string
Gets a list of block arg (dicts) through a string notation of arguments.
E.g. ir_r2_k3_s2_e1_i32_o16_se0.25_noskip
All args can exist in any order with the exception of the leading string which
is assumed to indicate the block type.
leading string - block type (
ir = InvertedResidual, ds = DepthwiseSep, dsa = DeptwhiseSep with pw act, cn = ConvBnAct)
r - number of repeat blocks,
k - kernel size,
s - strides (1-9),
e - expansion ratio,
c - output channels,
se - squeeze/excitation ratio
n - activation fn ('re', 'r6', 'hs', or 'sw')
Args:
block_str: a string representation of block arguments.
Returns:
A list of block args (dicts)
Raises:
ValueError: if the string def not properly specified (TODO)
"""
assert isinstance(block_str, str)
ops = block_str.split('_')
block_type = ops[0] # take the block type off the front
ops = ops[1:]
options = {}
noskip = False
for op in ops:
# string options being checked on individual basis, combine if they grow
if op == 'noskip':
noskip = True
elif op.startswith('n'):
# activation fn
key = op[0]
v = op[1:]
if v == 're':
value = get_act_layer('relu')
elif v == 'r6':
value = get_act_layer('relu6')
elif v == 'hs':
value = get_act_layer('hard_swish')
elif v == 'sw':
value = get_act_layer('swish')
else:
continue
options[key] = value
else:
# all numeric options
splits = re.split(r'(\d.*)', op)
if len(splits) >= 2:
key, value = splits[:2]
options[key] = value
# if act_layer is None, the model default (passed to model init) will be used
act_layer = options['n'] if 'n' in options else None
exp_kernel_size = _parse_ksize(options['a']) if 'a' in options else 1
pw_kernel_size = _parse_ksize(options['p']) if 'p' in options else 1
fake_in_chs = int(options['fc']) if 'fc' in options else 0 # FIXME hack to deal with in_chs issue in TPU def
num_repeat = int(options['r'])
# each type of block has different valid arguments, fill accordingly
if block_type == 'ir':
block_args = dict(
block_type=block_type,
dw_kernel_size=_parse_ksize(options['k']),
exp_kernel_size=exp_kernel_size,
pw_kernel_size=pw_kernel_size,
out_chs=int(options['c']),
exp_ratio=float(options['e']),
se_ratio=float(options['se']) if 'se' in options else None,
stride=int(options['s']),
act_layer=act_layer,
noskip=noskip,
)
if 'cc' in options:
block_args['num_experts'] = int(options['cc'])
elif block_type == 'ds' or block_type == 'dsa':
block_args = dict(
block_type=block_type,
dw_kernel_size=_parse_ksize(options['k']),
pw_kernel_size=pw_kernel_size,
out_chs=int(options['c']),
se_ratio=float(options['se']) if 'se' in options else None,
stride=int(options['s']),
act_layer=act_layer,
pw_act=block_type == 'dsa',
noskip=block_type == 'dsa' or noskip,
)
elif block_type == 'er':
block_args = dict(
block_type=block_type,
exp_kernel_size=_parse_ksize(options['k']),
pw_kernel_size=pw_kernel_size,
out_chs=int(options['c']),
exp_ratio=float(options['e']),
fake_in_chs=fake_in_chs,
se_ratio=float(options['se']) if 'se' in options else None,
stride=int(options['s']),
act_layer=act_layer,
noskip=noskip,
)
elif block_type == 'cn':
block_args = dict(
block_type=block_type,
kernel_size=int(options['k']),
out_chs=int(options['c']),
stride=int(options['s']),
act_layer=act_layer,
)
else:
assert False, 'Unknown block type (%s)' % block_type
return block_args, num_repeat
def _scale_stage_depth(stack_args, repeats, depth_multiplier=1.0, depth_trunc='ceil'):
""" Per-stage depth scaling
Scales the block repeats in each stage. This depth scaling impl maintains
compatibility with the EfficientNet scaling method, while allowing sensible
scaling for other models that may have multiple block arg definitions in each stage.
"""
# We scale the total repeat count for each stage, there may be multiple
# block arg defs per stage so we need to sum.
num_repeat = sum(repeats)
if depth_trunc == 'round':
# Truncating to int by rounding allows stages with few repeats to remain
# proportionally smaller for longer. This is a good choice when stage definitions
# include single repeat stages that we'd prefer to keep that way as long as possible
num_repeat_scaled = max(1, round(num_repeat * depth_multiplier))
else:
# The default for EfficientNet truncates repeats to int via 'ceil'.
# Any multiplier > 1.0 will result in an increased depth for every stage.
num_repeat_scaled = int(math.ceil(num_repeat * depth_multiplier))
# Proportionally distribute repeat count scaling to each block definition in the stage.
# Allocation is done in reverse as it results in the first block being less likely to be scaled.
# The first block makes less sense to repeat in most of the arch definitions.
repeats_scaled = []
for r in repeats[::-1]:
rs = max(1, round((r / num_repeat * num_repeat_scaled)))
repeats_scaled.append(rs)
num_repeat -= r
num_repeat_scaled -= rs
repeats_scaled = repeats_scaled[::-1]
# Apply the calculated scaling to each block arg in the stage
sa_scaled = []
for ba, rep in zip(stack_args, repeats_scaled):
sa_scaled.extend([deepcopy(ba) for _ in range(rep)])
return sa_scaled
def decode_arch_def(arch_def, depth_multiplier=1.0, depth_trunc='ceil', experts_multiplier=1, fix_first_last=False):
arch_args = []
for stack_idx, block_strings in enumerate(arch_def):
assert isinstance(block_strings, list)
stack_args = []
repeats = []
for block_str in block_strings:
assert isinstance(block_str, str)
ba, rep = _decode_block_str(block_str)
if ba.get('num_experts', 0) > 0 and experts_multiplier > 1:
ba['num_experts'] *= experts_multiplier
stack_args.append(ba)
repeats.append(rep)
if fix_first_last and (stack_idx == 0 or stack_idx == len(arch_def) - 1):
arch_args.append(_scale_stage_depth(stack_args, repeats, 1.0, depth_trunc))
else:
arch_args.append(_scale_stage_depth(stack_args, repeats, depth_multiplier, depth_trunc))
return arch_args
class EfficientNetBuilder:
""" Build Trunk Blocks
This ended up being somewhat of a cross between
https://github.com/tensorflow/tpu/blob/master/models/official/mnasnet/mnasnet_models.py
and
https://github.com/facebookresearch/maskrcnn-benchmark/blob/master/maskrcnn_benchmark/modeling/backbone/fbnet_builder.py
"""
def __init__(self, channel_multiplier=1.0, channel_divisor=8, channel_min=None,
output_stride=32, pad_type='', act_layer=None, se_kwargs=None,
norm_layer=nn.BatchNorm2d, norm_kwargs=None, drop_path_rate=0., feature_location='',
verbose=False):
self.channel_multiplier = channel_multiplier
self.channel_divisor = channel_divisor
self.channel_min = channel_min
self.output_stride = output_stride
self.pad_type = pad_type
self.act_layer = act_layer
self.se_kwargs = se_kwargs
self.norm_layer = norm_layer
self.norm_kwargs = norm_kwargs
self.drop_path_rate = drop_path_rate
if feature_location == 'depthwise':
# old 'depthwise' mode renamed 'expansion' to match TF impl, old expansion mode didn't make sense
_logger.warning("feature_location=='depthwise' is deprecated, using 'expansion'")
feature_location = 'expansion'
self.feature_location = feature_location
assert feature_location in ('bottleneck', 'expansion', '')
self.verbose = verbose
# state updated during build, consumed by model
self.in_chs = None
self.features = []
def _round_channels(self, chs):
return round_channels(chs, self.channel_multiplier, self.channel_divisor, self.channel_min)
def _make_block(self, ba, block_idx, block_count):
drop_path_rate = self.drop_path_rate * block_idx / block_count
bt = ba.pop('block_type')
ba['in_chs'] = self.in_chs
ba['out_chs'] = self._round_channels(ba['out_chs'])
if 'fake_in_chs' in ba and ba['fake_in_chs']:
# FIXME this is a hack to work around mismatch in origin impl input filters
ba['fake_in_chs'] = self._round_channels(ba['fake_in_chs'])
ba['norm_layer'] = self.norm_layer
ba['norm_kwargs'] = self.norm_kwargs
ba['pad_type'] = self.pad_type
# block act fn overrides the model default
ba['act_layer'] = ba['act_layer'] if ba['act_layer'] is not None else self.act_layer
assert ba['act_layer'] is not None
if bt == 'ir':
ba['drop_path_rate'] = drop_path_rate
ba['se_kwargs'] = self.se_kwargs
_log_info_if(' InvertedResidual {}, Args: {}'.format(block_idx, str(ba)), self.verbose)
if ba.get('num_experts', 0) > 0:
block = CondConvResidual(**ba)
else:
block = InvertedResidual(**ba)
elif bt == 'ds' or bt == 'dsa':
ba['drop_path_rate'] = drop_path_rate
ba['se_kwargs'] = self.se_kwargs
_log_info_if(' DepthwiseSeparable {}, Args: {}'.format(block_idx, str(ba)), self.verbose)
block = DepthwiseSeparableConv(**ba)
elif bt == 'er':
ba['drop_path_rate'] = drop_path_rate
ba['se_kwargs'] = self.se_kwargs
_log_info_if(' EdgeResidual {}, Args: {}'.format(block_idx, str(ba)), self.verbose)
block = EdgeResidual(**ba)
elif bt == 'cn':
_log_info_if(' ConvBnAct {}, Args: {}'.format(block_idx, str(ba)), self.verbose)
block = ConvBnAct(**ba)
else:
assert False, 'Uknkown block type (%s) while building model.' % bt
self.in_chs = ba['out_chs'] # update in_chs for arg of next block
return block
def __call__(self, in_chs, model_block_args):
""" Build the blocks
Args:
in_chs: Number of input-channels passed to first block
model_block_args: A list of lists, outer list defines stages, inner
list contains strings defining block configuration(s)
Return:
List of block stacks (each stack wrapped in nn.Sequential)
"""
_log_info_if('Building model trunk with %d stages...' % len(model_block_args), self.verbose)
self.in_chs = in_chs
total_block_count = sum([len(x) for x in model_block_args])
total_block_idx = 0
current_stride = 2
current_dilation = 1
stages = []
if model_block_args[0][0]['stride'] > 1:
# if the first block starts with a stride, we need to extract first level feat from stem
feature_info = dict(
module='act1', num_chs=in_chs, stage=0, reduction=current_stride,
hook_type='forward' if self.feature_location != 'bottleneck' else '')
self.features.append(feature_info)
# outer list of block_args defines the stacks
for stack_idx, stack_args in enumerate(model_block_args):
last_stack = stack_idx + 1 == len(model_block_args)
_log_info_if('Stack: {}'.format(stack_idx), self.verbose)
assert isinstance(stack_args, list)
blocks = []
# each stack (stage of blocks) contains a list of block arguments
for block_idx, block_args in enumerate(stack_args):
last_block = block_idx + 1 == len(stack_args)
_log_info_if(' Block: {}'.format(block_idx), self.verbose)
assert block_args['stride'] in (1, 2)
if block_idx >= 1: # only the first block in any stack can have a stride > 1
block_args['stride'] = 1
extract_features = False
if last_block:
next_stack_idx = stack_idx + 1
extract_features = next_stack_idx >= len(model_block_args) or \
model_block_args[next_stack_idx][0]['stride'] > 1
next_dilation = current_dilation
if block_args['stride'] > 1:
next_output_stride = current_stride * block_args['stride']
if next_output_stride > self.output_stride:
next_dilation = current_dilation * block_args['stride']
block_args['stride'] = 1
_log_info_if(' Converting stride to dilation to maintain output_stride=={}'.format(
self.output_stride), self.verbose)
else:
current_stride = next_output_stride
block_args['dilation'] = current_dilation
if next_dilation != current_dilation:
current_dilation = next_dilation
# create the block
block = self._make_block(block_args, total_block_idx, total_block_count)
blocks.append(block)
# stash feature module name and channel info for model feature extraction
if extract_features:
feature_info = dict(
stage=stack_idx + 1, reduction=current_stride, **block.feature_info(self.feature_location))
module_name = f'blocks.{stack_idx}.{block_idx}'
leaf_name = feature_info.get('module', '')
feature_info['module'] = '.'.join([module_name, leaf_name]) if leaf_name else module_name
self.features.append(feature_info)
total_block_idx += 1 # incr global block idx (across all stacks)
stages.append(nn.Sequential(*blocks))
return stages
def _init_weight_goog(m, n='', fix_group_fanout=True):
""" Weight initialization as per Tensorflow official implementations.
Args:
m (nn.Module): module to init
n (str): module name
fix_group_fanout (bool): enable correct (matching Tensorflow TPU impl) fanout calculation w/ group convs
Handles layers in EfficientNet, EfficientNet-CondConv, MixNet, MnasNet, MobileNetV3, etc:
* https://github.com/tensorflow/tpu/blob/master/models/official/mnasnet/mnasnet_model.py
* https://github.com/tensorflow/tpu/blob/master/models/official/efficientnet/efficientnet_model.py
"""
if isinstance(m, CondConv2d):
fan_out = m.kernel_size[0] * m.kernel_size[1] * m.out_channels
if fix_group_fanout:
fan_out //= m.groups
init_weight_fn = get_condconv_initializer(
lambda w: w.data.normal_(0, math.sqrt(2.0 / fan_out)), m.num_experts, m.weight_shape)
init_weight_fn(m.weight)
if m.bias is not None:
m.bias.data.zero_()
elif isinstance(m, nn.Conv2d):
fan_out = m.kernel_size[0] * m.kernel_size[1] * m.out_channels
if fix_group_fanout:
fan_out //= m.groups
m.weight.data.normal_(0, math.sqrt(2.0 / fan_out))
if m.bias is not None:
m.bias.data.zero_()
elif isinstance(m, nn.BatchNorm2d):
m.weight.data.fill_(1.0)
m.bias.data.zero_()
elif isinstance(m, nn.Linear):
fan_out = m.weight.size(0) # fan-out
fan_in = 0
if 'routing_fn' in n:
fan_in = m.weight.size(1)
init_range = 1.0 / math.sqrt(fan_in + fan_out)
m.weight.data.uniform_(-init_range, init_range)
m.bias.data.zero_()
def efficientnet_init_weights(model: nn.Module, init_fn=None):
init_fn = init_fn or _init_weight_goog
for n, m in model.named_modules():
init_fn(m, n)