def smooth_parcellation_matrix(parcellation_matrix, smoothing_kernel):
    """
    Perform CSS to smooth a brain atlas parcellation (in the form of a p x v matrix) to a new soft parcellation..

    Args:

        parcellation_matrix: The p x v sparse matrix representation of the atlas.

        smoothing_kernel: The v x v CSS high-resolution smoothing kernel.

    Returns:

        smoothed_parcellation_matrix: The p x v matrix representation of the smoothed soft parcellation.
    """
    return parcellation_matrix.dot(smoothing_kernel)