如何将tensorflow1.x代码改写为pytorch代码（以图注意力网络(GAT)为例）

之前讲解了图注意力网络的官方tensorflow版的实现，由于自己更了解pytorch，所以打算将其改写为pytorch版本的。

对于图注意力网络还不了解的可以先去看看tensorflow版本的代码，之前讲解的地址：

非稀疏矩阵版：https://www.cnblogs.com/xiximayou/p/13622283.html

稀疏矩阵版：https://www.cnblogs.com/xiximayou/p/13623989.html

以下改写后的代码我已经上传到gihub上，地址为：

https://github.com/taishan1994/pytorch_gat

图注意力网络的官方代码使用的是tensorflow1.x版本的，地址为：

https://github.com/Diego999/pyGAT

下面开始进入正题了。

1、tensorflow1.x的一般建模过程：

• 定义好训练的数据
• 定义计算图（包含占位）
• 定义训练主函数、损失函数计算、优化器
• 定义Session，参数初始化以及实际的前向传播和反向传播计算都是在Session中

2、将tensorflow转换为pytorch代码

其他数据处理的代码都是一致的，主要是一些需要改变的地方：

2.1 数据的读取

在tensorflow中，标签是要经过onehot编码的，而在pytorch中确是不用的，在load_data中：

def load_data(dataset_str): # {'pubmed', 'citeseer', 'cora'}
    """Load data."""
    names = ['x', 'y', 'tx', 'ty', 'allx', 'ally', 'graph']
    objects = []
    for i in range(len(names)):
        with open("data/ind.{}.{}".format(dataset_str, names[i]), 'rb') as f:
            if sys.version_info > (3, 0):
                objects.append(pkl.load(f, encoding='latin1'))
            else:
                objects.append(pkl.load(f))

    x, y, tx, ty, allx, ally, graph = tuple(objects)
    test_idx_reorder = parse_index_file("data/ind.{}.test.index".format(dataset_str))
    test_idx_range = np.sort(test_idx_reorder)

    if dataset_str == 'citeseer':
        # Fix citeseer dataset (there are some isolated nodes in the graph)
        # Find isolated nodes, add them as zero-vecs into the right position
        test_idx_range_full = range(min(test_idx_reorder), max(test_idx_reorder)+1)
        tx_extended = sp.lil_matrix((len(test_idx_range_full), x.shape[1]))
        tx_extended[test_idx_range-min(test_idx_range), :] = tx
        tx = tx_extended
        ty_extended = np.zeros((len(test_idx_range_full), y.shape[1]))
        ty_extended[test_idx_range-min(test_idx_range), :] = ty
        ty = ty_extended

    features = sp.vstack((allx, tx)).tolil()
    features[test_idx_reorder, :] = features[test_idx_range, :]
    adj = nx.adjacency_matrix(nx.from_dict_of_lists(graph))

    labels = np.vstack((ally, ty))
    labels[test_idx_reorder, :] = labels[test_idx_range, :]

    #pytorch的标签不需要进行one-hot编码
    my_labels = np.where(labels==1)[1]
    idx_test = test_idx_range.tolist()
    idx_train = range(len(y))
    idx_val = range(len(y), len(y)+500)

    train_my_labels_mask = sample_mask(idx_train, my_labels.shape[0])
    val_my_labels_mask = sample_mask(idx_val, my_labels.shape[0])
    test_my_labels_mask = sample_mask(idx_test, my_labels.shape[0])
    train_my_labels = my_labels[train_my_labels_mask]
    val_my_labels = my_labels[val_my_labels_mask]
    test_my_labels = my_labels[test_my_labels_mask]

    train_mask = sample_mask(idx_train, labels.shape[0])
    val_mask = sample_mask(idx_val, labels.shape[0])
    test_mask = sample_mask(idx_test, labels.shape[0])

    y_train = np.zeros(labels.shape)
    y_val = np.zeros(labels.shape)
    y_test = np.zeros(labels.shape)
    y_train[train_mask, :] = labels[train_mask, :]
    y_val[val_mask, :] = labels[val_mask, :]
    y_test[test_mask, :] = labels[test_mask, :]

    print(adj.shape)
    print(features.shape)
    data_dict = {
      'adj': adj,
      'features': features,
      'y_train': y_train,
      'y_val': y_val,
      'y_test': y_test,
      'train_mask': train_mask,
      'val_mask': val_mask,
      'test_mask': test_mask,
      'train_my_labels': train_my_labels,
      'val_my_labels': val_my_labels,
      'test_my_labels': test_my_labels,
      'my_labels': my_labels
    }
    return data_dict

我们要使用np.where()函数，将每一个ont-hot编码中值为1的索引（也就是标签）取出来，然后在对其进行划分训练标签、验证标签和测试标签。

顺便提一下，当我们要返回的值很多的时候，可以用一个字典包装起来，最后返回该字典就行了，这符合python的编码规范。

2.2 注意力层的搭建

在tensorflow中：

conv1d = tf.layers.conv1d

def attn_head(seq, out_sz, bias_mat, activation, in_drop=0.0, coef_drop=0.0, residual=False):
    with tf.name_scope('my_attn'):
        if in_drop != 0.0:
            seq = tf.nn.dropout(seq, 1.0 - in_drop)

        seq_fts = tf.layers.conv1d(seq, out_sz, 1, use_bias=False)

        # simplest self-attention possible
        f_1 = tf.layers.conv1d(seq_fts, 1, 1)
        f_2 = tf.layers.conv1d(seq_fts, 1, 1)
        logits = f_1 + tf.transpose(f_2, [0, 2, 1])
        coefs = tf.nn.softmax(tf.nn.leaky_relu(logits) + bias_mat)

        if coef_drop != 0.0:
            coefs = tf.nn.dropout(coefs, 1.0 - coef_drop)
        if in_drop != 0.0:
            seq_fts = tf.nn.dropout(seq_fts, 1.0 - in_drop)

        vals = tf.matmul(coefs, seq_fts)
        ret = tf.contrib.layers.bias_add(vals)

        # residual connection
        if residual:
            if seq.shape[-1] != ret.shape[-1]:
                ret = ret + conv1d(seq, ret.shape[-1], 1) # activation
            else:
                ret = ret + seq

        return activation(ret)  # activation

直接就可以使用相关api进行计算，但是在pytorch中，无论是定义自己的层还是模型，都需要先建立，然后再使用（一般是这样）。改写后的代码如下：

import torch
import torch.nn as nn

class Attn_head(nn.Module):
  def __init__(self,
        in_channel,
        out_sz,
        bias_mat,
        in_drop=0.0,
        coef_drop=0.0,
        activation=None,
        residual=False):
    super(Attn_head, self).__init__()
    self.in_channel = in_channel
    self.out_sz = out_sz
    self.bias_mat = bias_mat
    self.in_drop = in_drop
    self.coef_drop = coef_drop
    self.activation = activation
    self.residual = residual

    self.conv1 = nn.Conv1d(self.in_channel, self.out_sz, 1)
    self.conv2_1 = nn.Conv1d(self.out_sz, 1, 1)
    self.conv2_2 = nn.Conv1d(self.out_sz, 1, 1)
    self.leakyrelu = nn.LeakyReLU()
    self.softmax = nn.Softmax(dim=1)
    #pytorch中dropout的参数p表示每个神经元一定概率失活
    self.in_dropout = nn.Dropout()
    self.coef_dropout = nn.Dropout()
    self.res_conv = nn.Conv1d(self.in_channel, self.out_sz, 1)

  def forward(self,x):
    seq = x
    if self.in_drop != 0.0:
      seq = self.in_dropout(x)
    seq_fts = self.conv1(seq)
    f_1 = self.conv2_1(seq_fts)
    f_2 = self.conv2_2(seq_fts)
    logits = f_1 + torch.transpose(f_2, 2, 1)
    logits = self.leakyrelu(logits)
    coefs = self.softmax(logits + self.bias_mat)
    if self.coef_drop !=0.0:
      coefs = self.coef_dropout(coefs)
    if self.in_dropout !=0.0:
      seq_fts = self.in_dropout(seq_fts)
    ret = torch.matmul(coefs, torch.transpose(seq_fts, 2, 1))
    ret = torch.transpose(ret, 2, 1)
    if self.residual:
      if seq.shape[1] != ret.shape[1]:
        ret = ret + self.res_conv(seq)
      else:
        ret = ret + seq
    return self.activation(ret)

要继承nn.Module类，然后在__init__中初始化相关参数以及对应的层，在forward中进行前向传播计算。

2.3 搭建模型

有了注意力层之后，就可以搭建模型了，tensorflow的代码：

 def inference(inputs, nb_classes, nb_nodes, training, attn_drop, ffd_drop,
            bias_mat, hid_units, n_heads, activation=tf.nn.elu, residual=False):
        attns = []
        for _ in range(n_heads[0]):
            attns.append(layers.attn_head(inputs, bias_mat=bias_mat,
                out_sz=hid_units[0], activation=activation,
                in_drop=ffd_drop, coef_drop=attn_drop, residual=False))
        h_1 = tf.concat(attns, axis=-1)
        for i in range(1, len(hid_units)):
            h_old = h_1
            attns = []
            for _ in range(n_heads[i]):
                attns.append(layers.attn_head(h_1, bias_mat=bias_mat,
                    out_sz=hid_units[i], activation=activation,
                    in_drop=ffd_drop, coef_drop=attn_drop, residual=residual))
            h_1 = tf.concat(attns, axis=-1)
        out = []
        for i in range(n_heads[-1]):
            out.append(layers.attn_head(h_1, bias_mat=bias_mat,
                out_sz=nb_classes, activation=lambda x: x,
                in_drop=ffd_drop, coef_drop=attn_drop, residual=False))
        logits = tf.add_n(out) / n_heads[-1]

        return logits

改写之后的pytorch代码：

import numpy as np
import torch.nn as nn
import torch
from layer import *

class GAT(nn.Module):
  def __init__(self,
      nb_classes,
      nb_nodes,
      attn_drop,
      ffd_drop,
      bias_mat,
      hid_units,
      n_heads,
      residual=False):
    super(GAT, self).__init__()
    self.nb_classes = nb_classes
    self.nb_nodes = nb_nodes
    self.attn_drop = attn_drop
    self.ffd_drop = ffd_drop
    self.bias_mat = bias_mat
    self.hid_units = hid_units
    self.n_heads = n_heads
    self.residual = residual

    self.attn1 = Attn_head(in_channel=1433, out_sz=self.hid_units[0],
                bias_mat=self.bias_mat, in_drop=self.ffd_drop,
                coef_drop=self.attn_drop, activation=nn.ELU(),
                residual=self.residual)
    self.attn2 = Attn_head(in_channel=64, out_sz=self.nb_classes,
                bias_mat=self.bias_mat, in_drop=self.ffd_drop,
                coef_drop=self.attn_drop, activation=nn.ELU(),
                residual=self.residual)
    self.softmax = nn.Softmax(dim=1)

  def forward(self, x):
    attns = []
    for _ in range(self.n_heads[0]):
      attns.append(self.attn1(x))
    h_1 = torch.cat(attns, dim=1)
    out = self.attn2(h_1)
    logits = torch.transpose(out.view(self.nb_classes,-1), 1, 0)
    logits = self.softmax(logits)
    return logits

和tensorflow代码不同的是，这里我们仅仅定义了两层注意力。还需要注意的是，我们在__init__中定义相关层的时候，对于输入和输出的维度我们是要预先知道的，并填充进去，如果在forward中实际的值与预先定义的维度不同，那么就会报错。

2.4 进行训练、验证和测试

首先还是来看一下tensorflow是怎么定义的：

with tf.Graph().as_default():
    with tf.name_scope('input'):
        ftr_in = tf.placeholder(dtype=tf.float32, shape=(batch_size, nb_nodes, ft_size))
        bias_in = tf.placeholder(dtype=tf.float32, shape=(batch_size, nb_nodes, nb_nodes))
        lbl_in = tf.placeholder(dtype=tf.int32, shape=(batch_size, nb_nodes, nb_classes))
        msk_in = tf.placeholder(dtype=tf.int32, shape=(batch_size, nb_nodes))
        attn_drop = tf.placeholder(dtype=tf.float32, shape=())
        ffd_drop = tf.placeholder(dtype=tf.float32, shape=())
        is_train = tf.placeholder(dtype=tf.bool, shape=())

    logits = model.inference(ftr_in, nb_classes, nb_nodes, is_train,
                                attn_drop, ffd_drop,
                                bias_mat=bias_in,
                                hid_units=hid_units, n_heads=n_heads,
                                residual=residual, activation=nonlinearity)
    log_resh = tf.reshape(logits, [-1, nb_classes])
    lab_resh = tf.reshape(lbl_in, [-1, nb_classes])
    msk_resh = tf.reshape(msk_in, [-1])
    loss = model.masked_softmax_cross_entropy(log_resh, lab_resh, msk_resh)
    accuracy = model.masked_accuracy(log_resh, lab_resh, msk_resh)

    train_op = model.training(loss, lr, l2_coef)

    saver = tf.train.Saver()

    init_op = tf.group(tf.global_variables_initializer(), tf.local_variables_initializer())

    vlss_mn = np.inf
    vacc_mx = 0.0
    curr_step = 0

    with tf.Session() as sess:
        sess.run(init_op)

        train_loss_avg = 0
        train_acc_avg = 0
        val_loss_avg = 0
        val_acc_avg = 0

        for epoch in range(nb_epochs):
            print("epoch: ",epoch)
            tr_step = 0
            tr_size = features.shape[0]

            while tr_step * batch_size < tr_size:
                _, loss_value_tr, acc_tr = sess.run([train_op, loss, accuracy],
                    feed_dict={
                        ftr_in: features[tr_step*batch_size:(tr_step+1)*batch_size],
                        bias_in: biases[tr_step*batch_size:(tr_step+1)*batch_size],
                        lbl_in: y_train[tr_step*batch_size:(tr_step+1)*batch_size],
                        msk_in: train_mask[tr_step*batch_size:(tr_step+1)*batch_size],
                        is_train: True,
                        attn_drop: 0.6, ffd_drop: 0.6})
                train_loss_avg += loss_value_tr
                train_acc_avg += acc_tr
                tr_step += 1

            vl_step = 0
            vl_size = features.shape[0]

            while vl_step * batch_size < vl_size:
                loss_value_vl, acc_vl = sess.run([loss, accuracy],
                    feed_dict={
                        ftr_in: features[vl_step*batch_size:(vl_step+1)*batch_size],
                        bias_in: biases[vl_step*batch_size:(vl_step+1)*batch_size],
                        lbl_in: y_val[vl_step*batch_size:(vl_step+1)*batch_size],
                        msk_in: val_mask[vl_step*batch_size:(vl_step+1)*batch_size],
                        is_train: False,
                        attn_drop: 0.0, ffd_drop: 0.0})
                val_loss_avg += loss_value_vl
                val_acc_avg += acc_vl
                vl_step += 1

            print('Training: loss = %.5f, acc = %.5f | Val: loss = %.5f, acc = %.5f' %
                    (train_loss_avg/tr_step, train_acc_avg/tr_step,
                    val_loss_avg/vl_step, val_acc_avg/vl_step))

            if val_acc_avg/vl_step >= vacc_mx or val_loss_avg/vl_step <= vlss_mn:
                if val_acc_avg/vl_step >= vacc_mx and val_loss_avg/vl_step <= vlss_mn:
                    vacc_early_model = val_acc_avg/vl_step
                    vlss_early_model = val_loss_avg/vl_step
                    saver.save(sess, checkpt_file)
                vacc_mx = np.max((val_acc_avg/vl_step, vacc_mx))
                vlss_mn = np.min((val_loss_avg/vl_step, vlss_mn))
                curr_step = 0
            else:
                curr_step += 1
                if curr_step == patience:
                    print('Early stop! Min loss: ', vlss_mn, ', Max accuracy: ', vacc_mx)
                    print('Early stop model validation loss: ', vlss_early_model, ', accuracy: ', vacc_early_model)
                    break

            train_loss_avg = 0
            train_acc_avg = 0
            val_loss_avg = 0
            val_acc_avg = 0

        saver.restore(sess, checkpt_file)

        ts_size = features.shape[0]
        ts_step = 0
        ts_loss = 0.0
        ts_acc = 0.0

        while ts_step * batch_size < ts_size:
            loss_value_ts, acc_ts = sess.run([loss, accuracy],
                feed_dict={
                    ftr_in: features[ts_step*batch_size:(ts_step+1)*batch_size],
                    bias_in: biases[ts_step*batch_size:(ts_step+1)*batch_size],
                    lbl_in: y_test[ts_step*batch_size:(ts_step+1)*batch_size],
                    msk_in: test_mask[ts_step*batch_size:(ts_step+1)*batch_size],
                    is_train: False,
                    attn_drop: 0.0, ffd_drop: 0.0})
            ts_loss += loss_value_ts
            ts_acc += acc_ts
            ts_step += 1

        print('Test loss:', ts_loss/ts_step, '; Test accuracy:', ts_acc/ts_step)

        sess.close()

就是建立图、然后在Session中执行。

这里需要注意的是，features的维度是(2708,1433)，无论是tensorflow还是pytorch，都需要对其扩充一个维度：(1,2708,1433)，其余数据也同样。在计算损失的时候，网络输出的值的维度注意是：(2708,7)，就没有了之前的那个维度了。在pytorch中，输入的形状和tensorflow也不大一样，它的输入是：(1,1433,2708)，第二位是特征的维度，第三位才是节点的数目，这是和tensorflow主要的区别之一。

接下来看下pytorch中是怎么做的：

import torch
import torch.nn as nn
import torch.optim as optim
import numpy as np
from utils import *
from model import *

np.random.seed(1)
torch.manual_seed(1)
torch.cuda.manual_seed_all(1)

torch.backends.cudnn.deterministic = True
torch.backends.cudnn.benchmark = True

device = torch.device("cuda" if torch.cuda.is_available() else "cpu")

data = load_data("cora")
adj = data['adj']
features = data['features']
y_train = data['y_train']
y_val = data['y_val']
y_test = data['y_test']
train_mask = data['train_mask']
val_mask = data['val_mask']
test_mask = data['test_mask']
train_my_labels = data['train_my_labels']
val_my_labels = data['val_my_labels']
test_my_labels = data['test_my_labels']
my_labels = data['my_labels']

features, spars = preprocess_features(features)

#节点数目
nb_nodes = features.shape[0]
#特征维度
ft_sizes = features.shape[1]
#类别数目
nb_classes = my_labels.shape[0]

#将邻接矩阵的稀疏形式转换为原始矩阵
adj = adj.todense()

#新增加一个维度
adj = adj[np.newaxis]
features = features[np.newaxis]
y_train = y_train[np.newaxis]
y_val = y_val[np.newaxis]
y_test = y_test[np.newaxis]
#train_mask = train_mask[np.newaxis]
#val_mask = val_mask[np.newaxis]
#test_mask = test_mask[np.newaxis]

biases = torch.from_numpy(adj_to_bias(adj, [nb_nodes], nhood=1)).float().to(device)

features = torch.from_numpy(features)
#pytorch输入的特征:[batch, features，nodes]，第二位是特征维度
#而tensorflow的输入是：[batch, nodes, features]
features = torch.transpose(features,2,1).to(device)

#定义相关变量
hid_units=[8]
n_heads=[8, 1]
epochs = 5000
lr = 0.01

#定义模型
gat = GAT(nb_classes=nb_classes,
      nb_nodes=nb_nodes,
      attn_drop=0.0,
      ffd_drop=0.0,
      bias_mat=biases,
      hid_units=hid_units,
      n_heads=n_heads,
      residual=False).to(device)

criterion = nn.CrossEntropyLoss()
optimizer = optim.Adam(params=gat.parameters(),lr=lr,betas=(0.9, 0.99))

#y_train = torch.from_numpy(np.where(y_train==1)[2])
#y_val = torch.from_numpy(np.where(y_val==1)[2])
#y_test = torch.from_numpy(np.where(y_test==1)[2])
train_my_labels = torch.from_numpy(train_my_labels).long().to(device)
val_my_labels = torch.from_numpy(val_my_labels).long().to(device)
test_my_labels = torch.from_numpy(test_my_labels).long().to(device)

train_mask = np.where(train_mask == 1)[0]
val_mask = np.where(val_mask == 1)[0]
test_mask = np.where(test_mask == 1)[0]
train_mask = torch.from_numpy(train_mask).to(device)
val_mask = torch.from_numpy(val_mask).to(device)
test_mask = torch.from_numpy(test_mask).to(device)

print("训练节点个数：", len(train_my_labels))
print("验证节点个数：", len(val_my_labels))
print("测试节点个数：", len(test_my_labels))

def train():
  gat.train()
  correct = 0
  optimizer.zero_grad()
  outputs = gat(features)
  train_mask_outputs = torch.index_select(outputs, 0, train_mask)
  #print("train_mask_outputs.shape:",train_mask_outputs.shape)
  #print("train_my_labels.shape[0]:",train_my_labels.shape[0])
  _, preds =torch.max(train_mask_outputs.data, 1)
  loss = criterion(train_mask_outputs, train_my_labels)
  loss.backward()
  optimizer.step()
  correct += torch.sum(preds == train_my_labels).to(torch.float32)
  acc = correct / train_my_labels.shape[0]
  return loss,acc

def val():
  gat.eval()
  with torch.no_grad():
    correct = 0
    outputs = gat(features)
    val_mask_outputs = torch.index_select(outputs, 0, val_mask)
    #print("val_mask_outputs.shape:",val_mask_outputs.shape)
    #print("val_my_labels.shape[0]:",val_my_labels.shape[0])
    _, preds =torch.max(val_mask_outputs.data, 1)
    loss = criterion(val_mask_outputs, val_my_labels)
    correct += torch.sum(preds == val_my_labels).to(torch.float32)
    acc = correct / val_my_labels.shape[0]
  return loss,acc

def test():
  gat.eval()
  with torch.no_grad():
    correct = 0
    outputs = gat(features)
    test_mask_outputs = torch.index_select(outputs, 0, test_mask)
    #print("test_mask_outputs.shape:",test_mask_outputs.shape)
    #print("val_my_labels.shape[0]:",val_my_labels.shape[0])
    _, preds =torch.max(test_mask_outputs.data, 1)
    loss = criterion(test_mask_outputs, test_my_labels)
    correct += torch.sum(preds == test_my_labels).to(torch.float32)
    acc = correct / test_my_labels.shape[0]
    print("TestLoss:{:.4f},TestAcc:{:.4f}".format(loss,acc))
  return loss,acc,test_mask_outputs.cpu().numpy(),test_my_labels.cpu().numpy()

from sklearn.manifold import TSNE
import matplotlib.pyplot as plt

def main():
  train_loss_history = []
  val_loss_history = []
  train_acc_history = []
  val_acc_history = []
  for epoch in range(1,epochs+1):
    train_loss,train_acc = train()
    val_loss,val_acc = val()
    print("epoch:{:03d},TrainLoss:{:.4f},TrainAcc:{:.4f},ValLoss:{:.4f},ValAcc:{:.4f}"
        .format(epoch,train_loss,train_acc,val_loss,val_acc))
    train_loss_history.append(train_loss)
    train_acc_history.append(train_acc)
    val_loss_history.append(val_loss)
    val_acc_history.append(val_acc)
  num_epochs = range(1, epochs + 1)
  plt.plot(num_epochs, train_loss_history, 'b--')
  plt.plot(num_epochs, val_loss_history, 'r-')
  plt.title('Training and validation Loss ')
  plt.xlabel("Epochs")
  plt.ylabel("Loss")
  plt.legend(["train_loss", 'val_loss'])
  plt.savefig("loss.png")
  plt.close()

  plt.plot(num_epochs, train_acc_history, 'b--')
  plt.plot(num_epochs, val_acc_history, 'r-')
  plt.title('Training and validation Acc ')
  plt.xlabel("Epochs")
  plt.ylabel("Acc")
  plt.legend(['train_acc','val_acc'])
  plt.savefig("acc.png")
  plt.close()

  _, _, test_data, test_labels = test()
  tsne = TSNE(perplexity=30, n_components=2, init='pca', n_iter=5000) # TSNE降维，降到2
  low_dim_embs = tsne.fit_transform(test_data)
  plt.title('tsne result')
  plt.scatter(low_dim_embs[:,0], low_dim_embs[:,1], marker='o', c=test_labels)
  plt.savefig("tsne.png")
  plt.close()

main()

大体上还是很简单明了的，这里还是的注意一个问题。在pytorch中，我们首使用网络对整个图进行计算，但是我们只更新根据mask所得的节点的参数，如果直接是使用outputs[train_mask]，这样是不行的，pytroch的张量是不支持根据布尔值来进行分割的，如果我们将里面的True和False转换为1和0，虽然不会报错，但是就根本没有作用，因此在一开始，我们就要找到哪些节点是需要被训练的，取得其索引值，然后使用torch.index_select()进行切割。

最后绘制了损失函数和准确率随epoch的变化情况以及降维之后测试数据的分布情况。

3、结果

官方实现：

Dataset: cora
----- Opt. hyperparams -----
lr: 0.005
l2_coef: 0.0005
----- Archi. hyperparams -----
nb. layers: 1
nb. units per layer: [8]
nb. attention heads: [8, 1]
residual: False
nonlinearity: <function elu at 0x7f1b7507af28>
model: <class 'models.gat.GAT'>
(2708, 2708)
(2708, 1433)

epoch:  1
Training: loss = 1.94574, acc = 0.14286 | Val: loss = 1.93655, acc = 0.13600
epoch:  2
Training: loss = 1.94598, acc = 0.15714 | Val: loss = 1.93377, acc = 0.14800
epoch:  3
Training: loss = 1.94945, acc = 0.14286 | Val: loss = 1.93257, acc = 0.19600
epoch:  4
Training: loss = 1.93438, acc = 0.24286 | Val: loss = 1.93172, acc = 0.22800
epoch:  5
Training: loss = 1.93199, acc = 0.17143 | Val: loss = 1.93013, acc = 0.36400
。。。。。。
epoch:  674
Training: loss = 1.23833, acc = 0.49286 | Val: loss = 1.01357, acc = 0.81200
Early stop! Min loss:  1.010906457901001 , Max accuracy:  0.8219999074935913
Early stop model validation loss:  1.3742048740386963 , accuracy:  0.8219999074935913
Test loss: 1.3630210161209106 ; Test accuracy: 0.8219999074935913

自己的pytorch实现：

(2708, 2708)
(2708, 1433)
训练节点个数： 140
验证节点个数： 500
测试节点个数： 1000
epoch:001,TrainLoss:7.9040,TrainAcc:0.0000,ValLoss:7.9040,ValAcc:0.0000
epoch:002,TrainLoss:7.9040,TrainAcc:0.0000,ValLoss:7.9039,ValAcc:0.1920
epoch:003,TrainLoss:7.9039,TrainAcc:0.0714,ValLoss:7.9039,ValAcc:0.1600
epoch:004,TrainLoss:7.9038,TrainAcc:0.1000,ValLoss:7.9039,ValAcc:0.1020
。。。。。。
epoch:2396,TrainLoss:7.0191,TrainAcc:0.8929,ValLoss:7.4967,ValAcc:0.7440
epoch:2397,TrainLoss:7.0400,TrainAcc:0.8786,ValLoss:7.4969,ValAcc:0.7580
epoch:2398,TrainLoss:7.0188,TrainAcc:0.8929,ValLoss:7.4974,ValAcc:0.7580
epoch:2399,TrainLoss:7.0045,TrainAcc:0.9071,ValLoss:7.4983,ValAcc:0.7620
epoch:2400,TrainLoss:7.0402,TrainAcc:0.8714,ValLoss:7.4994,ValAcc:0.7620
TestLoss:7.4805,TestAcc:0.7700

可能实现的和原始tensorflow版本的还有一些差别，自己实现的只有0.77。还有点奇怪的地方是loss比官方的大好多。。。

4、总结

关于tensorflow代码转pytorch需要注意的一些地方：

（1）输入的数据不同，比如特征，tensorflow是(1,2708,1433)，pytorch的是(1,1433,2708)。

（2）标签的编码方式不同，tensorflow是onehot编码，比如[[0,0,1],[1,0,0],[0,1,0]]，pytorch就是原始的类[2,0,1]。

（3）构建模型的方式不同，tensorflow直接使用，pytorch要继承nn.Module，然后在__init__建立层，在forward中进行计算。

（4）训练验证测试的不同，tensorflow要先构建计算图，然后在Session中执行计算，也就是静态图，pytorch是动态图，没有显示的定义计算图。

（5）相关的接口也不同，这是自然而然的，毕竟都有着自己的设计理念，比如tf.concat()对应torch.cat()，即使名字相同的两个类，使用的方法也可能是不同的。

总而言之，动手是最重要的。

如果哪里有问题，还请指出。