from datetime import datetime
import math
import time
import tensorflow as tf

# 定义卷积层
def conv_op(input_op, name, kh, kw, n_out, dh, dw, p):
    # input_op是输入的tensor
    # name是这一层的名字
    # kh即kernel height 卷积核的高
    # kw即kernel width 卷积核的宽
    # n_out是卷积核数量即输出通道
    # dh是步长的高
    # dw是步长的宽
    # p是参数列表
    n_in = input_op.get_shape()[-1].value  # 获取input_op的通道数

    with tf.name_scope(name) as scope:
        kernel = tf.get_variable(scope+"w",
                                 shape=[kh, kw, n_in, n_out],
                                 dtype=tf.float32, 
                                 initializer=tf.contrib.layers.xavier_initializer_conv2d())
        conv = tf.nn.conv2d(input_op, kernel, (1, dh, dw, 1), padding=‘SAME‘)
        bias_init_val = tf.constant(0.0, shape=[n_out], dtype=tf.float32)
        biases = tf.Variable(bias_init_val, trainable=True, name=‘b‘)
        z = tf.nn.bias_add(conv, biases)
        activation = tf.nn.relu(z, name=scope)
        p += [kernel, biases]
        return activation

# 定义全连接层
def fc_op(input_op, name, n_out, p):
    n_in = input_op.get_shape()[-1].value

    with tf.name_scope(name) as scope:
        kernel = tf.get_variable(scope+"w",
                                 shape=[n_in, n_out],   # [输入的通道数，输出的通道数]
                                 dtype=tf.float32, 
                                 initializer=tf.contrib.layers.xavier_initializer())
        biases = tf.Variable(tf.constant(0.1, shape=[n_out], dtype=tf.float32), name=‘b‘) # 赋予0.1而不是0避免dead neuron
        activation = tf.nn.relu_layer(input_op, kernel, biases, name=scope)
        p += [kernel, biases]
        return activation

# 定义最大池化层
def mpool_op(input_op, name, kh, kw, dh, dw):
    return tf.nn.max_pool(input_op,
                          ksize=[1, kh, kw, 1],
                          strides=[1, dh, dw, 1],
                          padding=‘SAME‘,
                          name=name)



# 定义VGGNet-16网络结构
def inference_op(input_op, keep_prob):
    p = []
    # assume input_op shape is 224x224x3

    # block 1 -- outputs 112x112x64
    conv1_1 = conv_op(input_op, name="conv1_1", kh=3, kw=3, n_out=64, dh=1, dw=1, p=p)
    conv1_2 = conv_op(conv1_1,  name="conv1_2", kh=3, kw=3, n_out=64, dh=1, dw=1, p=p)
    pool1 = mpool_op(conv1_2,   name="pool1",   kh=2, kw=2, dw=2, dh=2)

    # block 2 -- outputs 56x56x128
    conv2_1 = conv_op(pool1,    name="conv2_1", kh=3, kw=3, n_out=128, dh=1, dw=1, p=p)
    conv2_2 = conv_op(conv2_1,  name="conv2_2", kh=3, kw=3, n_out=128, dh=1, dw=1, p=p)
    pool2 = mpool_op(conv2_2,   name="pool2",   kh=2, kw=2, dh=2, dw=2)

    # block 3 -- outputs 28x28x256
    conv3_1 = conv_op(pool2,    name="conv3_1", kh=3, kw=3, n_out=256, dh=1, dw=1, p=p)
    conv3_2 = conv_op(conv3_1,  name="conv3_2", kh=3, kw=3, n_out=256, dh=1, dw=1, p=p)
    conv3_3 = conv_op(conv3_2,  name="conv3_3", kh=3, kw=3, n_out=256, dh=1, dw=1, p=p)    
    pool3 = mpool_op(conv3_3,   name="pool3",   kh=2, kw=2, dh=2, dw=2)

    # block 4 -- outputs 14x14x512
    conv4_1 = conv_op(pool3,    name="conv4_1", kh=3, kw=3, n_out=512, dh=1, dw=1, p=p)
    conv4_2 = conv_op(conv4_1,  name="conv4_2", kh=3, kw=3, n_out=512, dh=1, dw=1, p=p)
    conv4_3 = conv_op(conv4_2,  name="conv4_3", kh=3, kw=3, n_out=512, dh=1, dw=1, p=p)
    pool4 = mpool_op(conv4_3,   name="pool4",   kh=2, kw=2, dh=2, dw=2)
    # 到这里，VGGNet-16的每一段网络都会将图像的边长缩小一半，但是将卷积输出通道数翻倍的规律

    # block 5 -- outputs 7x7x512
    conv5_1 = conv_op(pool4,    name="conv5_1", kh=3, kw=3, n_out=512, dh=1, dw=1, p=p)
    conv5_2 = conv_op(conv5_1,  name="conv5_2", kh=3, kw=3, n_out=512, dh=1, dw=1, p=p)
    conv5_3 = conv_op(conv5_2,  name="conv5_3", kh=3, kw=3, n_out=512, dh=1, dw=1, p=p)
    pool5 = mpool_op(conv5_3,   name="pool5",   kh=2, kw=2, dw=2, dh=2)

    # flatten
    # 将第五段卷积网络的输出结果进行扁平化，转化成7*7*512=25088的一维向量
    shp = pool5.get_shape()
    flattened_shape = shp[1].value * shp[2].value * shp[3].value
    resh1 = tf.reshape(pool5, [-1, flattened_shape], name="resh1")

    # fully connected
    fc6 = fc_op(resh1, name="fc6", n_out=4096, p=p)
    fc6_drop = tf.nn.dropout(fc6, keep_prob, name="fc6_drop")

    fc7 = fc_op(fc6_drop, name="fc7", n_out=4096, p=p)
    fc7_drop = tf.nn.dropout(fc7, keep_prob, name="fc7_drop")

    fc8 = fc_op(fc7_drop, name="fc8", n_out=1000, p=p)
    softmax = tf.nn.softmax(fc8)
    predictions = tf.argmax(softmax, 1)
    return predictions, softmax, fc8, p
    
    
# 定义评测函数
def time_tensorflow_run(session, target, feed, info_string):
    num_steps_burn_in = 10
    total_duration = 0.0
    total_duration_squared = 0.0
    for i in range(num_batches + num_steps_burn_in):
        start_time = time.time()
        _ = session.run(target, feed_dict=feed)
        duration = time.time() - start_time
        if i >= num_steps_burn_in:
            if not i % 10:
                print (‘%s: step %d, duration = %.3f‘ %
                       (datetime.now(), i - num_steps_burn_in, duration))
            total_duration += duration
            total_duration_squared += duration * duration
    mn = total_duration / num_batches
    vr = total_duration_squared / num_batches - mn * mn
    sd = math.sqrt(vr)
    print (‘%s: %s across %d steps, %.3f +/- %.3f sec / batch‘ %
           (datetime.now(), info_string, num_batches, mn, sd))


# 定义评测主函数
# 输入数据依然是随机生成的
def run_benchmark():
    with tf.Graph().as_default():
        image_size = 224
        images = tf.Variable(tf.random_normal([batch_size,
                                               image_size,
                                               image_size, 3],
                                               dtype=tf.float32,
                                               stddev=1e-1))

        keep_prob = tf.placeholder(tf.float32)
        predictions, softmax, fc8, p = inference_op(images, keep_prob)

        init = tf.global_variables_initializer()

        config = tf.ConfigProto()
        config.gpu_options.allocator_type = ‘BFC‘
        sess = tf.Session(config=config)
        sess.run(init)

        time_tensorflow_run(sess, predictions, {keep_prob:1.0}, "Forward")

        objective = tf.nn.l2_loss(fc8)
        grad = tf.gradients(objective, p)
        time_tensorflow_run(sess, grad, {keep_prob:0.5}, "Forward-backward")

batch_size=32
num_batches=100
run_benchmark()