pytorch之 RNN classifier

   ###仅为自己练习，没有其他用途

 1 import torch
 from torch import nn
 import torchvision.datasets as dsets
 import torchvision.transforms as transforms
 import matplotlib.pyplot as plt

 # torch.manual_seed(1)    # reproducible

 # Hyper Parameters
 EPOCH = 1               # train the training data n times, to save time, we just train 1 epoch
 BATCH_SIZE = 64
 TIME_STEP = 28          # rnn time step / image height
 INPUT_SIZE = 28         # rnn input size / image width
 LR = 0.01               # learning rate
 DOWNLOAD_MNIST = True   # set to True if haven't download the data

 # Mnist digital dataset
 train_data = dsets.MNIST(
     root='./mnist/',
     train=True,                         # this is training data
     transform=transforms.ToTensor(),    # Converts a PIL.Image or numpy.ndarray to
                                         # torch.FloatTensor of shape (C x H x W) and normalize in the range [0.0, 1.0]
     download=DOWNLOAD_MNIST,            # download it if you don't have it
 )

 # # plot one example
 # print(train_data.train_data.size())     # (60000, 28, 28)
 # print(train_data.train_labels.size())   # (60000)
 # plt.imshow(train_data.train_data[0].numpy(), cmap='gray')
 # plt.title('%i' % train_data.train_labels[0])
 # plt.show()

 # Data Loader for easy mini-batch return in training
 train_loader = torch.utils.data.DataLoader(dataset=train_data, batch_size=BATCH_SIZE, shuffle=True)

 # convert test data into Variable, pick 2000 samples to speed up testing
 test_data = dsets.MNIST(root='./mnist/', train=False, transform=transforms.ToTensor())
 test_x = test_data.test_data.type(torch.FloatTensor)[:2000]/255.   # shape (2000, 28, 28) value in range(0,1)
 test_y = test_data.test_labels.numpy()[:2000]    # covert to numpy array

 class RNN(nn.Module):
     def __init__(self):
         super(RNN, self).__init__()

         self.rnn = nn.LSTM(         # if use nn.RNN(), it hardly learns
             input_size=INPUT_SIZE,
             hidden_size=64,         # rnn hidden unit
             num_layers=1,           # number of rnn layer
             batch_first=True,       # input & output will has batch size as 1s dimension. e.g. (batch, time_step, input_size)
         )

         self.out = nn.Linear(64, 10)

     def forward(self, x):
         # x shape (batch, time_step, input_size)
         # r_out shape (batch, time_step, output_size)
         # h_n shape (n_layers, batch, hidden_size)
         # h_c shape (n_layers, batch, hidden_size)
         r_out, (h_n, h_c) = self.rnn(x, None)   # None represents zero initial hidden state

         # choose r_out at the last time step
         out = self.out(r_out[:, -1, :])
         return out

 rnn = RNN()
 print(rnn)

 optimizer = torch.optim.Adam(rnn.parameters(), lr=LR)   # optimize all cnn parameters
 loss_func = nn.CrossEntropyLoss()                       # the target label is not one-hotted

 # training and testing
 for epoch in range(EPOCH):
     for step, (b_x, b_y) in enumerate(train_loader):        # gives batch data
         b_x = b_x.view(-1, 28, 28)              # reshape x to (batch, time_step, input_size)

         output = rnn(b_x)                               # rnn output
         loss = loss_func(output, b_y)                   # cross entropy loss
         optimizer.zero_grad()                           # clear gradients for this training step
         loss.backward()                                 # backpropagation, compute gradients
         optimizer.step()                                # apply gradients

         if step % 50 == 0:
             test_output = rnn(test_x)                   # (samples, time_step, input_size)
             pred_y = torch.max(test_output, 1)[1].data.numpy()
             accuracy = float((pred_y == test_y).astype(int).sum()) / float(test_y.size)
             print('Epoch: ', epoch, '| train loss: %.4f' % loss.data.numpy(), '| test accuracy: %.2f' % accuracy)

 # print 10 predictions from test data
 test_output = rnn(test_x[:10].view(-1, 28, 28))
 pred_y = torch.max(test_output, 1)[1].data.numpy()
 print(pred_y, 'prediction number')
 print(test_y[:10], 'real number')