I get the following error
IndexError: Dimension out of range (expected to be in range of [-1, 0], but got 1)

from this line:  x = torch.cat([a, b], 1)
in the snippet code below:
class Critic(nn.Module):
    def __init__(self, input_size, hidden_size, output_size):
        super(Critic, self).__init__()
        self.linear1 = nn.Linear(input_size, hidden_size)
        self.linear2 = nn.Linear(hidden_size, hidden_size)
        self.linear3 = nn.Linear(hidden_size, output_size)

    def forward(self, a, b):

        x = torch.cat([a, b], 1)
        x = F.relu(self.linear1(x))
        x = F.relu(self.linear2(x))
        x = self.linear3(x)

        return x


Any help on this appreciated.