LeNet 分类 FashionMNIST

import mxnet as mx
from mxnet import autograd, gluon, init, nd
from mxnet.gluon import loss as gloss, nn
from mxnet.gluon import data as gdata
import time
import sys

net = nn.Sequential()
net.add(nn.Conv2D(channels=6, kernel_size=5, activation='sigmoid'),
        nn.MaxPool2D(pool_size=2, strides=2),
        nn.Conv2D(channels=16, kernel_size=5, activation='sigmoid'),
        nn.MaxPool2D(pool_size=2, strides=2),
        # Dense 会默认将（批量大小，通道，高，宽）形状的输入转换成
        # （批量大小，通道 * 高 * 宽）形状的输入。
        nn.Dense(120, activation='sigmoid'),
        nn.Dense(84, activation='sigmoid'),
        nn.Dense(10))

X = nd.random.uniform(shape=(1, 1, 28, 28))
net.initialize()
for layer in net:
    X = layer(X)
    print(layer.name, 'output shape:\t', X.shape)

# batch_size = 256
# train_iter, test_iter = gb.load_data_fashion_mnist(batch_size=batch_size)
mnist_train = gdata.vision.FashionMNIST(train=True)
mnist_test = gdata.vision.FashionMNIST(train=False)

batch_size = 256
transformer = gdata.vision.transforms.ToTensor()
if sys.platform.startswith('win'):
    num_workers = 0
else:
    num_workers = 4

# 小批量数据迭代器(在cpu上)
train_iter = gdata.DataLoader(mnist_train.transform_first(transformer), batch_size=batch_size, shuffle=True,
                              num_workers=num_workers)
test_iter = gdata.DataLoader(mnist_test.transform_first(transformer), batch_size=batch_size, shuffle=False,
                             num_workers=num_workers)

def try_gpu4():
    try:
        ctx = mx.gpu()
        _ = nd.zeros((1,), ctx=ctx)
    except mx.base.MXNetError:
        ctx = mx.cpu()
    return ctx

ctx = try_gpu4()

def accuracy(y_hat,y):
    return (y_hat.argmax(axis=1) == y.astype('float32')).mean().asscalar()

def evaluate_accuracy(data_iter, net, ctx):
    acc = nd.array([0], ctx=ctx)
    for X, y in data_iter:
        # 如果 ctx 是 GPU，将数据复制到 GPU 上。
        X, y = X.as_in_context(ctx), y.as_in_context(ctx)
        acc += accuracy(net(X), y)
    return acc.asscalar() / len(data_iter)

def train(net, train_iter, test_iter, batch_size, trainer, ctx,
              num_epochs):
    print('training on', ctx)
    loss = gloss.SoftmaxCrossEntropyLoss()
    for epoch in range(num_epochs):
        train_l_sum, train_acc_sum, start = 0, 0, time.time()
        for X, y in train_iter:
            X, y = X.as_in_context(ctx), y.as_in_context(ctx)
            with autograd.record():
                y_hat = net(X)
                l = loss(y_hat, y)
            l.backward()
            trainer.step(batch_size)
            train_l_sum += l.mean().asscalar()
            train_acc_sum += accuracy(y_hat, y)
        test_acc = evaluate_accuracy(test_iter, net, ctx)
        print('epoch %d, loss %.4f, train acc %.3f, test acc %.3f, '
              'time %.1f sec' % (epoch + 1, train_l_sum / len(train_iter),
                                 train_acc_sum / len(train_iter),
                                 test_acc, time.time() - start))

lr, num_epochs = 0.9, 200
net.initialize(force_reinit=True, ctx=ctx, init=init.Xavier())

trainer = gluon.Trainer(net.collect_params(), 'sgd', {'learning_rate': lr})
train(net, train_iter, test_iter, batch_size, trainer, ctx, num_epochs)