As the warning says, nn.DataParallel will chunk the data in dim0 (batch dimension) and send each chunk to the corresponding device.
E.g. if you are dealing with an input of [16, 3, 100] and two GPUs, each GPU will receive an input of [8, 3, 100].
b_input_ids doesn’t seem to have the right shape, so could you check, what type and shape you are using at the moment?