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【PaddlePaddle系列】CIFAR-10图像分类

时间:2018-08-29 10:48:19      阅读:686      评论:0      收藏:0      [点我收藏+]

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前言

本文与前文对手写数字识别分类基本类似的,同样图像作为输入,类别作为输出。这里不同的是,不仅仅是使用简单的卷积神经网络加上全连接层的模型。卷积神经网络大火以来,发展出来许多经典的卷积神经网络模型,包括VGG、ResNet、AlexNet等等。下面将针对CIFAR-10数据集,对图像进行分类。

 

1、CIFAR-10数据集、Reader创建

CIFAR-10数据集分为5个batch的训练集和1个batch的测试集,每个batch包含10,000张图片。每张图像尺寸为32*32的RGB图像,且包含有标签。一共有10个标签:airplane、automobile、bird、cat、deer、dog、frog、horse、ship、truck十个类别。

技术分享图片

我在CIFAR-10网站中下载的是[CIFAR-10 python version](http://www.cs.toronto.edu/~kriz/cifar-10-python.tar.gz)。数据集完成后,解压得到上述六个文件。上述六个文件都是字典文件,使用cPickle模块即可读入。字典中‘data’需要重新定义维度为1000*32*32*3,维度分别代表[N H W C],即10,000张32*32尺寸的三通道(RGB)图像,再经过转换成为paddlepaddle读取的[N C H W ]维度形式;而字典‘labels’为10000个标签。如此一来,可以建立读取CIFAR-10的reader(与官方例程不同),如下:

技术分享图片
def reader_creator(ROOT,istrain=True,cycle=False):
    def load_CIFAR_batch(filename):
        """ load single batch of cifar """
        with open(filename,rb) as f:
            datadict = Pickle.load(f)
            X = datadict[data]
            Y = datadict[labels]
            """ (N C H W) transpose to (N H W C) """
            X = X.reshape(10000,3,32,32).transpose(0,2,3,1).astype(float)
            Y = np.array(Y)
            return X,Y
    def reader():
        while True:
            if istrain:
                for b in range(1,6):
                    f   = os.path.join(ROOT,data_batch_%d%(b))
                    X,Y = load_CIFAR_batch(f)
                    length = X.shape[0]
                    for i in range(length):
                        yield X[i],Y[i]
                if not cycle:
                    break
            else:
                f = os.path.join(ROOT,test_batch)
                X,Y = load_CIFAR_batch(f)
                length = X.shape[0]
                for i in range(length):
                    yield X[i],Y[i]
                if not cycle:
                    break
    return reader
View Code

 

2、VGG网络

VGG网络采用“减小卷积核大小,增加卷积核数量”的思想改造而成,这里直接采用paddlepaddle例程中的VGG网络了,值得提醒的是paddlepaddle中直接有函数img_conv_group提供卷积、池化、dropout一组操作,所以根据VGG的模型,前面卷积层可以划分为5组,然后再经过3层的全连接层得到结果。

技术分享图片

PaddlePaddle例程中根据上图D网络,加入dorpout:

def vgg_bn_drop(input):
    def conv_block(ipt, num_filter, groups, dropouts):
        return fluid.nets.img_conv_group(
            input=ipt,
            #一组的卷积层的卷积核总数,组成list[num_filter num_filter ...]
            conv_num_filter=[num_filter] * groups, 
            conv_filter_size=3,
            conv_act=relu,
            conv_with_batchnorm=True,
            #每组卷积层各层的droput概率
            conv_batchnorm_drop_rate=dropouts, 
            pool_size=2,
            pool_stride=2,
            pool_type=max)

    conv1 = conv_block(input, 64, 2, [0.3, 0]) #[0.3 0]即为第一组两层的dorpout概率,下同
    conv2 = conv_block(conv1, 128, 2, [0.4, 0])
    conv3 = conv_block(conv2, 256, 3, [0.4, 0.4, 0])
    conv4 = conv_block(conv3, 512, 3, [0.4, 0.4, 0])
    conv5 = conv_block(conv4, 512, 3, [0.4, 0.4, 0])

    drop = fluid.layers.dropout(x=conv5, dropout_prob=0.5)
    fc1 = fluid.layers.fc(input=drop, size=512, act=None)

    bn = fluid.layers.batch_norm(input=fc1, act=relu)

    drop2 = fluid.layers.dropout(x=bn, dropout_prob=0.5)
    fc2 = fluid.layers.fc(input=drop2, size=512, act=None)

    predict = fluid.layers.fc(input=fc2, size=10, act=softmax)
    return predict

 

3、训练

训练程序与上一节例程一样,同样是选取交叉熵作为损失函数,不多累赘讲述。

技术分享图片
def train_network():
    predict = inference_network()
    label = fluid.layers.data(name=label,shape=[1],dtype=int64)
    cost  = fluid.layers.cross_entropy(input=predict,label=label)
    avg_cost = fluid.layers.mean(cost)
    accuracy = fluid.layers.accuracy(input=predict,label=label)
    return [avg_cost,accuracy]

def optimizer_program():
    return fluid.optimizer.Adam(learning_rate=0.001)

def train(data_path,save_path):
    BATCH_SIZE = 128
    EPOCH_NUM  = 2
    train_reader = paddle.batch(
        paddle.reader.shuffle(reader_creator(data_path),buf_size=50000),
        batch_size = BATCH_SIZE)
    test_reader  = paddle.batch(
        reader_creator(data_path,False),
        batch_size=BATCH_SIZE)
    def event_handler(event):
        if isinstance(event, fluid.EndStepEvent):
            if event.step % 100 == 0:
                print("\nPass %d, Epoch %d, Cost %f, Acc %f" %
                      (event.step, event.epoch, event.metrics[0],
                       event.metrics[1]))
            else:
                sys.stdout.write(.)
                sys.stdout.flush()
        if isinstance(event, fluid.EndEpochEvent):
            avg_cost, accuracy = trainer.test(
                reader=test_reader, feed_order=[image, label])
            print(\nTest with Pass {0}, Loss {1:2.2}, Acc {2:2.2}.format(
                event.epoch, avg_cost, accuracy))
            if save_path is not None:
                trainer.save_params(save_path)
    place = fluid.CUDAPlace(0) 
    trainer = fluid.Trainer(
        train_func=train_network, optimizer_func=optimizer_program, place=place)
    trainer.train(
        reader=train_reader,
        num_epochs=EPOCH_NUM,
        event_handler=event_handler,
        feed_order=[image, label])
View Code

4、测试接口

测试接口也类似,需要特别注意的是图像维度要改为[N C H W]的顺序!

技术分享图片
def infer(params_dir):
    place = fluid.CUDAPlace(0)
    inferencer = fluid.Inferencer(
        infer_func=inference_network, param_path=params_dir, place=place)
     # Prepare testing data. 
    from PIL import Image
    import numpy as np
    import os

    def load_image(file):
        im = Image.open(file)
        im = im.resize((32, 32), Image.ANTIALIAS)
        im = np.array(im).astype(np.float32)
        """transpose [H W C] to [C H W]"""
        im = im.transpose((2, 0, 1)) 
        im = im / 255.0

        # Add one dimension, [N C H W] N=1
        im = np.expand_dims(im, axis=0)
        return im
    cur_dir = os.path.dirname(os.path.realpath(__file__))
    img = load_image(cur_dir + /dog.png)
    # inference
    results = inferencer.infer({image: img})
    print(results)
    lab = np.argsort(results)  # probs and lab are the results of one batch data
    print("infer results: ", cifar_classes[lab[0][0][-1]])
View Code

5、运行结果

由于笔者没有GPU服务器,所以只迭代了50次,已经用了8个多小时,但是准确率只有15.6%,测试集方面准确率有17%,效果不理想,用于验证的结果也是错的!

Pass 300, Epoch 49, Cost 2.261115, Acc 0.156250
.........................................................................................
Test with Pass 49, Loss 2.2, Acc 0.17

Classify the cifar10 images...
[array([[0.05997971, 0.13485196, 0.096842 , 0.09973737, 0.11053724,
0.08180068, 0.13847008, 0.08627985, 0.06851784, 0.12298328]],
dtype=float32)]
infer results: frog

 

结语

网络比较深,且数据集比较大,训练时间比较长,普通笔记本上面的GT840M聊以胜无吧。

 

本文代码:02_cifar

参考:book/03.image_classification/

 

【PaddlePaddle系列】CIFAR-10图像分类

标签:dimens   line   git   ace   下载   join   Dimension   end   alt   

原文地址:https://www.cnblogs.com/dzqiu/p/9544746.html

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