VGG-16卷积神经网络实现

VGG简介

• ILSVRC2014比赛分类项目第2名（第1名是GoogLeNet）和定位项目第1名。
• 拓展性很强：迁移到其他图片数据上的泛化性非常好。
• 结构简洁：整个网络都使用了同样大小的卷积核尺寸（3X3)和最大池化尺寸（2X2)，到目前为止VGGNet依然经常被用来提取图像特征。

网络结构图

VGGNet训练时使用了4块Geforce GTX Titan GPU并行计算，速度比单块GPU快了3.75倍。每个网络耗时2~3周才可以训练完。（数据库ImageNet）

完整代码

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

def conv_op(input_op,name,kh,kw,n_out,dh,dw,p): 
    # 卷积核 （kh,kw,n_out）-高、宽、通道数
    # 步长 （dh，dw)
    # p 参数列表
    n_in = input_op.get_shape()[-1].value #获取输入的通道数
    
    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

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],
                                dtype=tf.float32,
                                initializer=tf.contrib.layers.xavier_initializer())
        biases = tf.Variable(tf.constant(0.1,shape=[n_out],dtype=tf.float32),name='b')
        activation = tf.nn.relu_layer(input_op,kernel,biases,name=scope)
        p += [kernel,biases]
        return activation

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)

def inference_op(input_op,keep_prob):
    p=[]
    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='con1_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,dh=2,dw=2)
    
    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='con2_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)

    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='con3_2',kh=3,kw=3,n_out=256,dh=1,dw=1,p=p)
    conv3_2 = conv_op(conv3_1,name='con3_2',kh=3,kw=3,n_out=256,dh=1,dw=1,p=p)       
    pool3 = mpool_op(conv3_2,name='pool3',kh=2,kw=2,dh=2,dw=2)

    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='con4_2',kh=3,kw=3,n_out=512,dh=1,dw=1,p=p)
    conv4_2 = conv_op(conv4_1,name='con4_2',kh=3,kw=3,n_out=512,dh=1,dw=1,p=p)       
    pool4 = mpool_op(conv4_2,name='pool4',kh=2,kw=2,dh=2,dw=2)

    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='con5_2',kh=3,kw=3,n_out=512,dh=1,dw=1,p=p)
    conv5_2 = conv_op(conv5_1,name='con5_2',kh=3,kw=3,n_out=512,dh=1,dw=1,p=p)       
    pool5 = mpool_op(conv5_2,name='pool5',kh=2,kw=2,dh=2,dw=2)

    shp = pool5.get_shape()
    # shp.shape ---  [batch_size,h,w,d] 0:batch_size 1:高 2：宽 3：通道
    flattened_shape = shp[1].value * shp[2].value * shp[3].value
    reshl = tf.reshape(pool5,[-1,flattened_shape],name='reshl')
    # 隐含节点数4096
    fc6 = fc_op(reshl,name='fc6',n_out=4096,p=p)
    fc6_drop = tf.nn.dropout(fc6,keep_prob,name='fc6_drop')
    #fc7
    fc7 = fc_op(fc6_drop,name='fc7',n_out=4096,p=p)
    fc7_drop = tf.nn.dropout(fc7,keep_prob,name='fc_drop')
    # fc8
    fc8 = fc_op(fc7_drop,name='fc8',n_out=1000,p=p)
    # softmax
    softmax = tf.nn.softmax(fc8)
    predictions = tf.argmax(softmax,1)
    return predictions,softmax,fc8,p

def time_tensorflow_run(session,target,feed,info_string):    
    # 预热
    num_step_burn_in = 10
    total_duration = 0.0
    total_duration_squared = 0.0
    for i in range(num_step_burn_in + num_batches):
        start_time = time.time()
        _ = session.run(target,feed_dict=feed)
        duration = time.time() - start_time
        if i >= num_step_burn_in:
            if not i % 10:
                print('%s: step : %d, duration = %.3f'
                     % (datetime.now(),i-num_step_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))

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()
        sess = tf.Session()
        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},'Backward')

batch_size = 32
num_batches = 100
run_benchmark()

运行结果

GPU：Quadro p2000 5GB