model.py

import torch
import torch.nn as nn
from operations import *
from torch.autograd import Variable
from utils import drop_path


class Cell(nn.Module):

	def __init__(self, genotype, C_prev_prev, C_prev, C, reduction, reduction_prev):
		super(Cell, self).__init__()
		print(C_prev_prev, C_prev, C)

		if reduction_prev:
			self.preprocess0 = FactorizedReduce(C_prev_prev, C)
		else:
			self.preprocess0 = ReLUConvBN(C_prev_prev, C, 1, 1, 0)
		self.preprocess1 = ReLUConvBN(C_prev, C, 1, 1, 0)

		if reduction:
			op_names, indices = zip(*genotype.reduce)
			concat = genotype.reduce_concat
		else:
			op_names, indices = zip(*genotype.normal)
			concat = genotype.normal_concat
		self._compile(C, op_names, indices, concat, reduction)

	def _compile(self, C, op_names, indices, concat, reduction):
		assert len(op_names) == len(indices)
		self._steps = len(op_names) // 2
		self._concat = concat
		self.multiplier = len(concat)

		self._ops = nn.ModuleList()
		for name, index in zip(op_names, indices):
			stride = 2 if reduction and index < 2 else 1
			op = OPS[name](C, stride, True)
			self._ops += [op]
		self._indices = indices

	def forward(self, s0, s1, drop_prob):
		s0 = self.preprocess0(s0)
		s1 = self.preprocess1(s1)

		states = [s0, s1]
		for i in range(self._steps):
			h1 = states[self._indices[2*i]]
			h2 = states[self._indices[2*i+1]]
			op1 = self._ops[2*i]
			op2 = self._ops[2*i+1]
			h1 = op1(h1)
			h2 = op2(h2)
			if self.training and drop_prob > 0.:
				if not isinstance(op1, Identity):
					h1 = drop_path(h1, drop_prob)
				if not isinstance(op2, Identity):
					h2 = drop_path(h2, drop_prob)
			s = h1 + h2
			states += [s]
		return torch.cat([states[i] for i in self._concat], dim=1)


class AuxiliaryHeadCIFAR(nn.Module):

	def __init__(self, C, num_classes):
		"""assuming input size 8x8"""
		super(AuxiliaryHeadCIFAR, self).__init__()
		self.features = nn.Sequential(
			nn.ReLU(inplace=True),
			nn.AvgPool2d(5, stride=3, padding=0, count_include_pad=False), # image size = 2 x 2
			nn.Conv2d(C, 128, 1, bias=False),
			nn.BatchNorm2d(128),
			nn.ReLU(inplace=True),
			nn.Conv2d(128, 768, 2, bias=False),
			nn.BatchNorm2d(768),
			nn.ReLU(inplace=True)
		)
		self.classifier = nn.Linear(768, num_classes)

	def forward(self, x):
		x = self.features(x)
		x = self.classifier(x.view(x.size(0),-1))
		return x


class AuxiliaryHeadImageNet(nn.Module):

	def __init__(self, C, num_classes):
		"""assuming input size 14x14"""
		super(AuxiliaryHeadImageNet, self).__init__()
		self.features = nn.Sequential(
			nn.ReLU(inplace=True),
			nn.AvgPool2d(5, stride=2, padding=0, count_include_pad=False),
			nn.Conv2d(C, 128, 1, bias=False),
			nn.BatchNorm2d(128),
			nn.ReLU(inplace=True),
			nn.Conv2d(128, 768, 2, bias=False),
			# nn.BatchNorm2d(768),
			nn.ReLU(inplace=True)
		)
		self.classifier = nn.Linear(768, num_classes)

	def forward(self, x):
		x = self.features(x)
		x = self.classifier(x.view(x.size(0),-1))
		return x


class NetworkCIFAR(nn.Module):
	def __init__(self, C, num_classes, layers, auxiliary, genotype):
		super(NetworkCIFAR, self).__init__()
		self._layers = layers
		self._auxiliary = auxiliary

		stem_multiplier = 3
		C_curr = stem_multiplier*C
		self.stem = nn.Sequential(
			nn.Conv2d(3, C_curr, 3, padding=1, bias=False),
			nn.BatchNorm2d(C_curr)
		)

		C_prev_prev, C_prev, C_curr = C_curr, C_curr, C
		self.cells = nn.ModuleList()
		reduction_prev = False
		for i in range(layers):
			if i in [layers//3, 2*layers//3]:
				C_curr *= 2
				reduction = True
			else:
				reduction = False
			cell = Cell(genotype, C_prev_prev, C_prev, C_curr, reduction, reduction_prev)
			reduction_prev = reduction
			self.cells += [cell]
			C_prev_prev, C_prev = C_prev, cell.multiplier*C_curr
			if i == 2*layers//3:
				C_to_auxiliary = C_prev

		if auxiliary:
			self.auxiliary_head = AuxiliaryHeadCIFAR(C_to_auxiliary, num_classes)
		self.global_pooling = nn.AdaptiveAvgPool2d(1)
		self.classifier = nn.Linear(C_prev, num_classes)

	def forward(self, input):
		logits_aux = None
		s0 = s1 = self.stem(input)
		for i, cell in enumerate(self.cells):
			s0, s1 = s1, cell(s0, s1, self.drop_path_prob)
			if i == 2*self._layers//3:
				if self._auxiliary and self.training:
					logits_aux = self.auxiliary_head(s1)
		out = self.global_pooling(s1)
		logits = self.classifier(out.view(out.size(0),-1))
		return logits, logits_aux


class NetworkImageNet(nn.Module):

	def __init__(self, C, num_classes, layers, auxiliary, genotype):
		super(NetworkImageNet, self).__init__()
		self._layers = layers
		self._auxiliary = auxiliary

		self.stem0 = nn.Sequential(
			nn.Conv2d(3, C // 2, kernel_size=3, stride=2, padding=1, bias=False),
			nn.BatchNorm2d(C // 2),
			nn.ReLU(inplace=True),
			nn.Conv2d(C // 2, C, 3, stride=2, padding=1, bias=False),
			nn.BatchNorm2d(C),
		)

		self.stem1 = nn.Sequential(
			nn.ReLU(inplace=True),
			nn.Conv2d(C, C, 3, stride=2, padding=1, bias=False),
			nn.BatchNorm2d(C),
		)

		C_prev_prev, C_prev, C_curr = C, C, C

		self.cells = nn.ModuleList()
		reduction_prev = True
		for i in range(layers):
			if i in [layers // 3, 2 * layers // 3]:
				C_curr *= 2
				reduction = True
			else:
				reduction = False
			cell = Cell(genotype, C_prev_prev, C_prev, C_curr, reduction, reduction_prev)
			reduction_prev = reduction
			self.cells += [cell]
			C_prev_prev, C_prev = C_prev, cell.multiplier * C_curr
			if i == 2 * layers // 3:
				C_to_auxiliary = C_prev

		if auxiliary:
			self.auxiliary_head = AuxiliaryHeadImageNet(C_to_auxiliary, num_classes)
		self.global_pooling = nn.AvgPool2d(7)
		self.classifier = nn.Linear(C_prev, num_classes)

	def forward(self, input):
		logits_aux = None
		s0 = self.stem0(input)
		s1 = self.stem1(s0)
		for i, cell in enumerate(self.cells):
			s0, s1 = s1, cell(s0, s1, self.drop_path_prob)
			if i == 2 * self._layers // 3:
				if self._auxiliary and self.training:
					logits_aux = self.auxiliary_head(s1)
		out = self.global_pooling(s1)
		logits = self.classifier(out.view(out.size(0), -1))
		return logits, logits_aux