File size: 4,438 Bytes
6e601ed
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
import torch
from copy import deepcopy


class FlattableModel(object):
    def __init__(self, model):
        self.model = deepcopy(model)
        self._original_model = model
        self._flat_model = None
        self._attr_names = self.get_attributes_name()

    def flatten_model(self):
        if self._flat_model is None:
            self._flat_model = self._flatten_model(self.model)
        return self._flat_model

    @staticmethod
    def _selection_method(module):
        return not (
            isinstance(module, torch.nn.Sequential)
            or isinstance(module, torch.nn.ModuleList)
        ) and not hasattr(module, "_restricted")

    @staticmethod
    def _flatten_model(module):
        modules = []
        child = False
        for (name, c) in module.named_children():
            child = True
            flattened_c = FlattableModel._flatten_model(c)
            modules += flattened_c
        if not child and FlattableModel._selection_method(module):
            modules = [module]
        return modules

    def get_layer_io(self, layer, nb_samples, data_loader):
        ios = []
        hook = layer.register_forward_hook(
            lambda m, i, o: ios.append((i[0].data.cpu(), o.data.cpu()))
        )

        nbatch = 1
        for batch_idx, (xs, ys) in enumerate(data_loader):
            # -1 takes all of them
            if nb_samples != -1 and nbatch > nb_samples:
                break
            _ = self.model(xs.cuda())
            nbatch += 1

        hook.remove()
        return ios

    def get_attributes_name(self):
        def _real_get_attributes_name(module):
            modules = []
            child = False
            for (name, c) in module.named_children():
                child = True
                flattened_c = _real_get_attributes_name(c)
                modules += map(lambda e: [name] + e, flattened_c)
            if not child and FlattableModel._selection_method(module):
                modules = [[]]
            return modules

        return _real_get_attributes_name(self.model)

    def update_model(self, flat_model):
        """
        Take a list representing the flatten model and rebuild its internals.
        :type flat_model: List[nn.Module]
        """

        def _apply_changes_on_layer(block, idxs, layer):
            assert len(idxs) > 0
            if len(idxs) == 1:
                setattr(block, idxs[0], layer)
            else:
                _apply_changes_on_layer(getattr(block, idxs[0]), idxs[1:], layer)

        def _apply_changes_model(model_list):
            for i in range(len(model_list)):
                _apply_changes_on_layer(self.model, self._attr_names[i], model_list[i])

        _apply_changes_model(flat_model)
        self._attr_names = self.get_attributes_name()
        self._flat_model = None

    def cuda(self):
        self.model = self.model.cuda()
        return self

    def cpu(self):
        self.model = self.model.cpu()
        return self


def bn_fuse(model):
    model = model.cpu()
    flattable = FlattableModel(model)
    fmodel = flattable.flatten_model()

    for index, item in enumerate(fmodel):
        if (
            isinstance(item, torch.nn.Conv2d)
            and index + 1 < len(fmodel)
            and isinstance(fmodel[index + 1], torch.nn.BatchNorm2d)
        ):
            alpha, beta = _calculate_alpha_beta(fmodel[index + 1])
            if item.weight.shape[0] != alpha.shape[0]:
                # this case happens if there was actually something else
                # between the conv and the
                # bn layer which is not picked up in flat model logic. (see densenet)
                continue
            item.weight.data = item.weight.data * alpha.view(-1, 1, 1, 1)
            item.bias = torch.nn.Parameter(beta)
            fmodel[index + 1] = _IdentityLayer()
    flattable.update_model(fmodel)
    return flattable.model


def _calculate_alpha_beta(batchnorm_layer):
    alpha = batchnorm_layer.weight.data / (
        torch.sqrt(batchnorm_layer.running_var + batchnorm_layer.eps)
    )
    beta = (
        -(batchnorm_layer.weight.data * batchnorm_layer.running_mean)
        / (torch.sqrt(batchnorm_layer.running_var + batchnorm_layer.eps))
        + batchnorm_layer.bias.data
    )
    alpha = alpha.cpu()
    beta = beta.cpu()
    return alpha, beta


class _IdentityLayer(torch.nn.Module):
    def forward(self, input):
        return input