import torch

def _prepare_device(n_gpu_use):
    n_gpu = torch.cuda.device_count()
    if n_gpu_use > 0 and n_gpu == 0:
        print("Warning: There\'s no GPU available on this machine," "training will be performed on CPU.")
        n_gpu_use = 0
    if n_gpu_use > n_gpu:
        print("Warning: The number of GPU\'s configured to use is {}, but only {} are available " "on this machine.".
                format(n_gpu_use, n_gpu))
        n_gpu_use = n_gpu
    device = torch.device('cuda:0' if n_gpu_use > 0 else 'cpu')
    list_ids = list(range(n_gpu_use))
    return device, list_ids