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#   http://www.apache.org/licenses/LICENSE-2.0
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# =============================================================================
"""The resnet model is adapted from http://torch.ch/blog/2016/02/04/resnets.html
The best validation accuracy we achieved is about 83% without data augmentation.
The performance could be improved by tuning some hyper-parameters, including
learning rate, weight decay, max_epoch, parameter initialization, etc.
"""
from __future__ import print_function
from builtins import zip

from singa import layer
from singa import initializer
from singa import metric
from singa import loss
from singa import net as ffnet


def Block(net, name, nb_filters, stride):
    split = net.add(layer.Split(name + "-split", 2))
    if stride > 1:
        net.add(layer.Conv2D(name + "-br2-conv", nb_filters, 1, stride, pad=0), split)
        br2bn = net.add(layer.BatchNormalization(name + "-br2-bn"))
    net.add(layer.Conv2D(name + "-br1-conv1", nb_filters, 3, stride, pad=1), split)
    net.add(layer.BatchNormalization(name + "-br1-bn1"))
    net.add(layer.Activation(name + "-br1-relu"))
    net.add(layer.Conv2D(name + "-br1-conv2", nb_filters, 3, 1, pad=1))
    br1bn2 = net.add(layer.BatchNormalization(name + "-br1-bn2"))
    if stride > 1:
        net.add(layer.Merge(name + "-merge"), [br1bn2, br2bn])
    else:
        net.add(layer.Merge(name + "-merge"), [br1bn2, split])


def create_net(use_cpu=False):
    if use_cpu:
        layer.engine = 'singacpp'

    net = ffnet.FeedForwardNet(loss.SoftmaxCrossEntropy(), metric.Accuracy())
    net.add(layer.Conv2D("conv1", 16, 3, 1, pad=1, input_sample_shape=(3, 32, 32)))
    net.add(layer.BatchNormalization("bn1"))
    net.add(layer.Activation("relu1"))

    Block(net, "2a", 16, 1)
    Block(net, "2b", 16, 1)
    Block(net, "2c", 16, 1)

    Block(net, "3a", 32, 2)
    Block(net, "3b", 32, 1)
    Block(net, "3c", 32, 1)

    Block(net, "4a", 64, 2)
    Block(net, "4b", 64, 1)
    Block(net, "4c", 64, 1)

    net.add(layer.AvgPooling2D("pool4", 8, 8, border_mode='valid'))
    net.add(layer.Flatten('flat'))
    net.add(layer.Dense('ip5', 10))
    print('Start intialization............')
    for (p, name) in zip(net.param_values(), net.param_names()):
        # print name, p.shape
        if 'mean' in name or 'beta' in name:
            p.set_value(0.0)
        elif 'var' in name:
            p.set_value(1.0)
        elif 'gamma' in name:
            initializer.uniform(p, 0, 1)
        elif len(p.shape) > 1:
            if 'conv' in name:
                # initializer.gaussian(p, 0, math.sqrt(2.0/p.shape[1]))
                initializer.gaussian(p, 0, 9.0 * p.shape[0])
            else:
                initializer.uniform(p, p.shape[0], p.shape[1])
        else:
            p.set_value(0)
        # print name, p.l1()

    return net