import torch
import shutil
def save_ckp(state, is_best, checkpoint_dir, best_model_dir):
    f_path = checkpoint_dir / 'checkpoint.pt'
    torch.save(state, f_path)
    if is_best:
        best_fpath = best_model_dir / 'best_model.pt'
        shutil.copyfile(f_path, best_fpath)