Graph Convolutional Network work badly: my accuracy doesn't grow

Hello everyone,
I’m trying to classify some drugs like very active, active, non active (label: 0, 1, 2) against the cancer. To do that I built a Graph Convolutional Network using PyTorch Geometric, this is the code:

n_features = 14
# definenet
class Net(torch.nn.Module):
  def __init__(self):
    super(Net, self).__init__()
    self.conv1 = GCNConv(n_features, 50, cached=False) 
    self.bn1 = BatchNorm1d(50)
    self.conv2 = GCNConv(50, 25, cached=False)
    self.bn2 = BatchNorm1d(25)
    self.fc1 = Linear(25, 25)
    self.bn3 = BatchNorm1d(25)
    self.fc2 = Linear(25, 25)
    self.fc3 = Linear(25, 3)
  def forward(self, x, edge_index, batch):
    x = F.relu(self.conv1(x, edge_index))
    x = self.bn1(x)
    x = F.relu(self.conv2(x, edge_index))
    x = self.bn2(x)
    x = global_add_pool(x, batch)
    x = F.relu(self.fc1(x))
    x = self.bn3(x)
    x = F.relu(self.fc2(x))
    x = F.dropout(x, p=0.2,
    x = self.fc3(x)
    x = F.softmax(x, dim=1)
    return x       

My dataset contain 2476 samples where:

  • 0, 1184 samples;
  • 1, 826 samples;
  • 2, 466 samples.

Every nodes of a graph contain a nodes features matrix with 14 features. When I train the net the loss seems to go down well, but the accuracy grows slowly and very badly. Below I show you the charts of the loss (train and val), of the accuracy (train and val) and the training loop that I use. What could I do to improve my model’s performance? Thank you all!

model = Net()
optimizer = torch.optim.Adam(model.parameters(), lr=0.001,
criterion = torch.nn.CrossEntropyLoss()

def train():
    loss_all = 0
    for data in train_loader:
        output = model(data.x, data.edge_index, data.batch)
        loss = criterion(output, data.y)
        loss_all += loss.item() * data.num_graphs
    return loss_all / len(train_loader.dataset)

def test_loss(loader):
    total_loss_val = 0

    with torch.no_grad():
         for data in loader:
           output = model(data.x, data.edge_index, data.batch)
           batch_loss = criterion(output, data.y)
           total_loss_val += batch_loss.item() * data.num_graphs
    return total_loss_val / len(loader.dataset)

def test(loader):
    correct = 0
    for data in loader:
        output = model(data.x, data.edge_index, data.batch)
        pred = output.max(dim=1)[1]
        correct += pred.eq(data.y).sum().item()
    return correct / len(loader.dataset)

hist = {"train_loss":[], "val_loss":[], "acc":[], "test_acc":[]}
for epoch in range(1, 301):
    train_loss = train()
    val_loss = test_loss(val_loader)
    train_acc = test(train_loader)
    test_acc = test(val_loader)
    print(f'Epoch: {epoch}, Train loss: {train_loss:.3}, Val loss: {val_loss:.3}, Train_acc: {train_acc:.3}, Test_acc: {test_acc:.3}')