def determine_chunkshape(size1, size2):
    """
    returns optimum size for chuncks for a dataset of file size1, size2
    and update cachesize for accomodating dataset
    """
    c1 = int(size1 / 64.0 + 1)
    c2 = int(size2 / 64.0 + 1)
    return c1, c2
