text: """ 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, get_act_layer, make_divisible
  
  __all__ = ["EfficientNetBuilder", "decode_arch_def", "efficientnet_init_weights",
             'resolve_bn_args', 'resolve_act_layer', 'round_channels', 'BN_MOMENTUM_TF_DEFAULT', 'BN_EPS_TF_DEFAULT']
  
  _logger = logging.getLogger(__name__)
  
  
  _DEBUG_BUILDER = False
  
  # Defaults used for Google/Tensorflow training of mobile networks /w RMSprop as per
  # papers and TF reference implementations. PT momentum equiv for TF decay is (1 - TF decay)
  # NOTE: momentum varies btw .99 and .9997 depending on source
  # .99 in official TF TPU impl
  # .9997 (/w .999 in search space) for paper
  BN_MOMENTUM_TF_DEFAULT = 1 - 0.99
  BN_EPS_TF_DEFAULT = 1e-3
  _BN_ARGS_TF = dict(momentum=BN_MOMENTUM_TF_DEFAULT, eps=BN_EPS_TF_DEFAULT)
  
  
  def get_bn_args_tf():
      return _BN_ARGS_TF.copy()
  
  
  def resolve_bn_args(kwargs):
      bn_args = get_bn_args_tf() if kwargs.pop('bn_tf', False) else {}
      bn_momentum = kwargs.pop('bn_momentum', None)
      if bn_momentum is not None:
          bn_args['momentum'] = bn_momentum
      bn_eps = kwargs.pop('bn_eps', None)
      if bn_eps is not None:
          bn_args['eps'] = bn_eps
      return bn_args
  
  
  def resolve_act_layer(kwargs, default='relu'):
      return get_act_layer(kwargs.pop('act_layer', default))
  
  
  def round_channels(channels, multiplier=1.0, divisor=8, channel_min=None, round_limit=0.9):
      """Round number of filters based on depth multiplier."""
      if not multiplier:
          return channels
      return make_divisible(channels * multiplier, divisor, channel_min, round_limit=round_limit)
  
  
  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 = {}
      skip = None
      for op in ops:
          # string options being checked on individual basis, combine if they grow
          if op == 'noskip':
              skip = False  # force no skip connection
          elif op == 'skip':
              skip = True  # force a skip connection
          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
      force_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 0.,
              stride=int(options['s']),
              act_layer=act_layer,
              noskip=skip is False,
          )
          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 0.,
              stride=int(options['s']),
              act_layer=act_layer,
              pw_act=block_type == 'dsa',
              noskip=block_type == 'dsa' or skip is False,
          )
      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']),
              force_in_chs=force_in_chs,
              se_ratio=float(options['se']) if 'se' in options else 0.,
              stride=int(options['s']),
              act_layer=act_layer,
              noskip=skip is False,
          )
      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,
              skip=skip is True,
          )
      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 = []
      if isinstance(depth_multiplier, tuple):
          assert len(depth_multiplier) == len(arch_def)
      else:
          depth_multiplier = (depth_multiplier,) * len(arch_def)
      for stack_idx, (block_strings, multiplier) in enumerate(zip(arch_def, depth_multiplier)):
          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, 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, output_stride=32, pad_type='', round_chs_fn=round_channels,
                   act_layer=None, norm_layer=None, se_layer=None, drop_path_rate=0., feature_location=''):
          self.output_stride = output_stride
          self.pad_type = pad_type
          self.round_chs_fn = round_chs_fn
          self.act_layer = act_layer
          self.norm_layer = norm_layer
          self.se_layer = se_layer
          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 = _DEBUG_BUILDER
  
          # state updated during build, consumed by model
          self.in_chs = None
          self.features = []
  
      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_chs_fn(ba['out_chs'])
          if 'force_in_chs' in ba and ba['force_in_chs']:
              # NOTE this is a hack to work around mismatch in TF EdgeEffNet impl
              ba['force_in_chs'] = self.round_chs_fn(ba['force_in_chs'])
          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
          ba['norm_layer'] = self.norm_layer
          if bt != 'cn':
              ba['se_layer'] = self.se_layer
              ba['drop_path_rate'] = drop_path_rate
  
          if bt == 'ir':
              _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':
              _log_info_if('  DepthwiseSeparable {}, Args: {}'.format(block_idx, str(ba)), self.verbose)
              block = DepthwiseSeparableConv(**ba)
          elif bt == 'er':
              _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)
  
  