def build_pyramid(M, subsampling_factor=3):
    """Iterate over a given number of times on matrix M
    so as to compute smaller and smaller matrices with bin_dense.
    """

    subs = int(subsampling_factor)
    if subs < 1:
        raise ValueError(
            "Subsampling factor needs to be an integer greater than 1.")
    N = [M]
    while min(N[-1].shape) > 1:
        N.append(bin_matrix(N[-1], subsampling_factor=subs))
    return N
def build_pyramid ( M , subsampling_factor = 3 ) : subs = int ( subsampling_factor ) if subs < 1 : raise ValueError ( "Subsampling factor needs to be an integer greater than 1." ) N = [ M ] while min ( N [ - 1 ] . shape ) > 1 : N . append ( bin_matrix ( N [ - 1 ] , subsampling_factor = subs ) ) return N
Iterate over a given number of times on matrix M
    so as to compute smaller and smaller matrices with bin_dense.