def read_fake_mapping(fake_genome_mapping_filename):
    """
    :param fake_genome_mapping_filename: fake genome mapping file
    :return: dict of fake position -> (chr, ref position)
    """
    fake_map = {}
    with open(fake_genome_mapping_filename) as (f):
        for line in f:
            fake_pos, ref_chr, ref_pos = line.strip().split(',')
            fake_map[int(fake_pos)] = (ref_chr, int(ref_pos))

    return fake_map