How to calculate the FID for MNIST? about catch-up-distillation HOT 1 CLOSED

@main.command()
@click.option('--images', 'image_path', help='Path to the images', metavar='PATH|ZIP',              type=str, required=True)
@click.option('--ref', 'ref_path',      help='Dataset reference statistics ', metavar='NPZ|URL',    type=str, required=True)
@click.option('--num', 'num_expected',  help='Number of images to use', metavar='INT',              type=click.IntRange(min=2), default=50000, show_default=True)
@click.option('--seed',                 help='Random seed for selecting the images', metavar='INT', type=int, default=0, show_default=True)
@click.option('--batch',                help='Maximum batch size', metavar='INT',                   type=click.IntRange(min=1), default=64, show_default=True)

def calc(image_path, ref_path, num_expected, seed, batch):
    """Calculate FID for a given set of images."""
    torch.multiprocessing.set_start_method('spawn')
    os.environ['MASTER_PORT'] = f"{29500+ int(os.environ['CUDA_VISIBLE_DEVICES'])+1}"
    print(os.environ['MASTER_PORT'])
    dist.init()
    dist.print0(f'Loading dataset reference statistics from "{ref_path}"...')
    ref = None
    if dist.get_rank() == 0:
        with dnnlib.util.open_url(ref_path) as f:
            ref = dict(np.load(f))

    mu, sigma = calculate_inception_stats(image_path=image_path, num_expected=num_expected, seed=seed, max_batch_size=batch)
    dist.print0('Calculating FID...')
    if dist.get_rank() == 0:
        fid = calculate_fid_from_inception_stats(mu, sigma, ref['mu'], ref['sigma'])
        print(f'{fid:g}')
        # Save to image_path as a txt file
        with open(os.path.join(image_path, 'fid.txt'), 'w') as f:
            f.write(str(fid))
    torch.distributed.barrier()

    r_mu, r_sigma = calculate_inception_stats(image_path=ref, num_expected=num_expected, seed=seed, max_batch_size=batch)
 fid = calculate_fid_from_inception_stats(mu, sigma,r_mu, r_sigma)

@click.option('--ref', 'ref_path',      help='Dataset reference statistics', metavar='PATH|ZIP',  type=str, required=True)