def accuracy(p2p, gt_p2p, D1_geod, return_all=False, sqrt_area=None):
    """
    Computes the geodesic accuracy of a vertex to vertex map. The map goes from
    the target shape to the source shape.
    Borrowed from Robin.
    Parameters
    ----------------------
    p2p        : (n2,) - vertex to vertex map giving the index of the matched vertex on the source shape
                 for each vertex on the target shape (from a functional map point of view)
    gt_p2p     : (n2,) - ground truth mapping between the pairs
    D1_geod    : (n1,n1) - geodesic distance between pairs of vertices on the source mesh
    return_all : bool - whether to return all the distances or only the average geodesic distance

    Output
    -----------------------
    acc   : float - average accuracy of the vertex to vertex map
    dists : (n2,) - if return_all is True, returns all the pairwise distances
    """

    dists = D1_geod[(p2p, gt_p2p)]
    if sqrt_area is not None:
        dists /= sqrt_area
    if return_all:
        return dists.mean(), dists
    return dists.mean()