维度不匹配问题

有哪位大佬知道这个问题怎么解决 
dice += (pred[:,i] * target[:,il)sum(din=l)sum(din=l)sun(din=l) / ((pred[:,i] * target[:,i)sum(din=l)sum(din=l).sumn(din=l)+
RuntimeError: The size of tensor a (1024) must match the size of tensor b (512) at non-sinaleton dimension 3  