DGL學習(七): GAT官方教程代碼實現

 

DGL采用attention的方式為節點加權。

 

import torch
import torch.nn as nn
import torch.nn.functional as F
from dgl import DGLGraph
from dgl.data import citation_graph as citegrh
import networkx as nx
import numpy as np
from sklearn.manifold import TSNE
import matplotlib.pyplot as plt
from dgl.nn.pytorch import edge_softmax, GATConv


class GATLayer(nn.Module):
    def __init__(self, g, in_dim , out_dim):
        super(GATLayer, self).__init__()
        self.g = g
        self.fc = nn.Linear(in_dim, out_dim, bias=False)
        self.attn_fc = nn.Linear(2*out_dim, 1, bias=False)
        self.reset_parameters()

    def reset_parameters(self):
        gain = nn.init.calculate_gain('relu')
        nn.init.xavier_normal_(self.fc.weight, gain=gain)
        nn.init.xavier_normal_(self.attn_fc.weight, gain=gain)

    def edge_attention(self, edges):
        z2 = torch.cat([edges.src['z'], edges.dst['z']], dim=1)
        a = self.attn_fc(z2)
        return {'e': F.leaky_relu(a)}

    def message_func(self,edges):
        return {'z': edges.src['z'], 'e': edges.data['e']}

    def reduce_func(self, nodes):
        alpha = F.softmax(nodes.mailbox['e'], dim=1) # 歸一化每一條入邊的注意力系數
        h = torch.sum(alpha * nodes.mailbox['z'], dim=1)
        return {'h':h}

    def forward(self, h):
        z = self.fc(h)
        self.g.ndata['z'] = z # 每個節點的特征
        self.g.apply_edges(self.edge_attention) # 為每一條邊獲得其注意力系數
        self.g.update_all(self.message_func, self.reduce_func)
        return self.g.ndata.pop('h')

class MultiHeadGATLayer(nn.Module):
    def __init__(self, g, in_dim , out_dim , num_heads=1, merge='cat'):
        super(MultiHeadGATLayer, self).__init__()
        self.heads = nn.ModuleList()
        for i in range(num_heads):
            self.heads.append(GATLayer(g, in_dim, out_dim))
        self.merge = merge


    def forward(self, h):
        head_out = [attn_head(h) for attn_head in self.heads]
        if self.merge=='cat':
            return torch.cat(head_out, dim=1)
        else:
            return torch.mean(torch.stack(head_out))

class GAT(nn.Module):
    def __init__(self, g, in_dim, hidden_dim , out_dim, num_heads):
        super(GAT, self).__init__()
        self.layer1 = MultiHeadGATLayer(g , in_dim, hidden_dim, num_heads)
        self.layer2 = MultiHeadGATLayer(g, hidden_dim*num_heads, out_dim, 1)

    def forward(self, h):
        h = self.layer1(h)
        h = F.elu(h)
        h = self.layer2(h)
        return h


def load_cora_data():
    data = citegrh.load_cora()
    print(data.graph)

    features = torch.FloatTensor(data.features)
    labels = torch.LongTensor(data.labels)
    mask = torch.BoolTensor(data.train_mask)
    g = DGLGraph(data.graph)

    return  g,features, labels, mask

g, features, labels, mask =  load_cora_data()

net = GAT(g,features.size()[1], hidden_dim=16, out_dim=7, num_heads=2)

optimizer = torch.optim.Adam(net.parameters(), lr = 1e-3)

dur = []

print(net)
for epoch in range(400):
    logits = net(features)
    logp = F.log_softmax(logits, 1)
    loss = F.nll_loss(logp[mask], labels[mask])

    optimizer.zero_grad()
    loss.backward()
    optimizer.step()

    print("Epoch {:05d} | Loss {:.4f}".format(epoch, loss.item()))


embedding_weights = net(features).detach().numpy()  ## 得到所有節點的embedding。

print(embedding_weights[0])



def plot_embeddings(embeddings, X, Y):
    print(Y)
    emb_list = []
    for k in X:
        emb_list.append(embeddings[k])
    emb_list = np.array(emb_list)

    model = TSNE(n_components=2) ### 降維
    node_pos = model.fit_transform(emb_list)

    color_idx = {}
    for i in range(len(X)):
        color_idx.setdefault(Y[i], [])
        color_idx[Y[i]].append(i)

    for c, idx in color_idx.items():
        plt.scatter(node_pos[idx, 0], node_pos[idx, 1], label=c)
    plt.legend()
    plt.show()
plot_embeddings(embedding_weights, np.arange(features.size()[0]), labels.numpy()