How to learn weight balance between two FC from two branches of a network?

I have a network has two branches: the first one provides the fully connected vector fc1, and the second one provides the fc2. The final fc is

fc = alpha_1 * fc_1 + alpha_2 * fc_2

where alpha_i is a learned parameter. It will be learned during training. For a batch size of 1, I used alpha = Parameter(torch.ones(1)) as the code

class fc_combined(nn.Module):
    def __init__(self):
        super(parameter_learning, self).__init__()        
        self.alpha_list = nn.ParameterList([])
        for i in range(2):           
            alpha = Parameter(torch.ones(1))
    def forward(self, prob):           
        fc = self.alpha_list[0]*fc_1+self.alpha_list[1]*fc_2 
        return fc

My question is that how to change the line alpha = Parameter(torch.ones(1)) to work on the batch size bigger than 1. Because each vector in fc_i will be weighted by alpha, if we have the batch of fc_i, as batch_sizex32, then I think alpha also has size of batch_sizex1 . I have tried

alpha = Parameter(torch.ones(batch_size, 1))

But it does not work on validation because the batch size of validation is 1, while we learned alpha size of batch_sizex1 in training. Any suggestion are welcome