xautodl/lib/models/cell_searchs/search_model_enas.py

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# Copyright (c) Xuanyi Dong [GitHub D-X-Y], 2019 #
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# Efficient Neural Architecture Search via Parameters Sharing, ICML 2018 #
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import torch
import torch.nn as nn
from copy import deepcopy
from ..cell_operations import ResNetBasicblock
from .search_cells     import NAS201SearchCell as SearchCell
from .genotypes        import Structure
from .search_model_enas_utils import Controller


class TinyNetworkENAS(nn.Module):

  def __init__(self, C, N, max_nodes, num_classes, search_space, affine, track_running_stats):
    super(TinyNetworkENAS, self).__init__()
    self._C        = C
    self._layerN   = N
    self.max_nodes = max_nodes
    self.stem = nn.Sequential(
                    nn.Conv2d(3, C, kernel_size=3, padding=1, bias=False),
                    nn.BatchNorm2d(C))
  
    layer_channels   = [C    ] * N + [C*2 ] + [C*2  ] * N + [C*4 ] + [C*4  ] * N    
    layer_reductions = [False] * N + [True] + [False] * N + [True] + [False] * N

    C_prev, num_edge, edge2index = C, None, None
    self.cells = nn.ModuleList()
    for index, (C_curr, reduction) in enumerate(zip(layer_channels, layer_reductions)):
      if reduction:
        cell = ResNetBasicblock(C_prev, C_curr, 2)
      else:
        cell = SearchCell(C_prev, C_curr, 1, max_nodes, search_space, affine, track_running_stats)
        if num_edge is None: num_edge, edge2index = cell.num_edges, cell.edge2index
        else: assert num_edge == cell.num_edges and edge2index == cell.edge2index, 'invalid {:} vs. {:}.'.format(num_edge, cell.num_edges)
      self.cells.append( cell )
      C_prev = cell.out_dim
    self.op_names   = deepcopy( search_space )
    self._Layer     = len(self.cells)
    self.edge2index = edge2index
    self.lastact    = nn.Sequential(nn.BatchNorm2d(C_prev), nn.ReLU(inplace=True))
    self.global_pooling = nn.AdaptiveAvgPool2d(1)
    self.classifier = nn.Linear(C_prev, num_classes)
    # to maintain the sampled architecture
    self.sampled_arch = None

  def update_arch(self, _arch):
    if _arch is None:
      self.sampled_arch = None
    elif isinstance(_arch, Structure):
      self.sampled_arch = _arch
    elif isinstance(_arch, (list, tuple)):
      genotypes = []
      for i in range(1, self.max_nodes):
        xlist = []
        for j in range(i):
          node_str = '{:}<-{:}'.format(i, j)
          op_index = _arch[ self.edge2index[node_str] ]
          op_name  = self.op_names[ op_index ]
          xlist.append((op_name, j))
        genotypes.append( tuple(xlist) )
      self.sampled_arch = Structure(genotypes)
    else:
      raise ValueError('invalid type of input architecture : {:}'.format(_arch))
    return self.sampled_arch
    
  def create_controller(self):
    return Controller(len(self.edge2index), len(self.op_names))

  def get_message(self):
    string = self.extra_repr()
    for i, cell in enumerate(self.cells):
      string += '\n {:02d}/{:02d} :: {:}'.format(i, len(self.cells), cell.extra_repr())
    return string

  def extra_repr(self):
    return ('{name}(C={_C}, Max-Nodes={max_nodes}, N={_layerN}, L={_Layer})'.format(name=self.__class__.__name__, **self.__dict__))

  def forward(self, inputs):

    feature = self.stem(inputs)
    for i, cell in enumerate(self.cells):
      if isinstance(cell, SearchCell):
        feature = cell.forward_dynamic(feature, self.sampled_arch)
      else: feature = cell(feature)

    out = self.lastact(feature)
    out = self.global_pooling( out )
    out = out.view(out.size(0), -1)
    logits = self.classifier(out)

    return out, logits