Get the smallest edge length.

def get_min_edge_size(coor, conns):
    """
    Get the smallest edge length.
    """
    mes = 1e16
    for conn in conns:
        n_ep = conn.shape[1]
        for ir in range( n_ep ):
            x1 = coor[conn[:,ir]]
            for ic in range( ir + 1, n_ep ):
                x2 = coor[conn[:,ic]]
                aux = nm.sqrt( nm.sum( (x2 - x1)**2.0, axis = 1 ).min() )
                mes = min( mes, aux )

    return mes