Example #1
0
def parse_sparse6(string):
    """Read an undirected graph in sparse6 format from string.

    Parameters
    ----------
    string : string
       Data in sparse6 format

    Returns
    -------
    G : Graph

    Raises
    ------
    NetworkXError
        If the string is unable to be parsed in sparse6 format

    Examples
    --------
    >>> G = nx.parse_sparse6(':A_')
    >>> sorted(G.edges())
    [(0, 1), (0, 1), (0, 1)]

    See Also
    --------
    generate_sparse6, read_sparse6, write_sparse6

    References
    ----------
    Sparse6 specification: http://cs.anu.edu.au/~bdm/data/formats.txt
    """
    if string.startswith('>>sparse6<<'):
        string = string[11:]
    if not string.startswith(':'):
        raise NetworkXError('Expected leading colon in sparse6')
    n, data = data_to_n(graph6_to_data(string[1:]))
    k = 1
    while 1 << k < n:
        k += 1

    def parseData():
        """Return stream of pairs b[i], x[i] for sparse6 format."""
        chunks = iter(data)
        d = None  # partial data word
        dLen = 0  # how many unparsed bits are left in d

        while 1:
            if dLen < 1:
                d = next(chunks)
                dLen = 6
            dLen -= 1
            b = (d >> dLen) & 1  # grab top remaining bit

            x = d & ((1 << dLen) - 1)  # partially built up value of x
            xLen = dLen  # how many bits included so far in x
            while xLen < k:  # now grab full chunks until we have enough
                d = next(chunks)
                dLen = 6
                x = (x << 6) + d
                xLen += 6
            x = (x >> (xLen - k))  # shift back the extra bits
            dLen = xLen - k
            yield b, x

    v = 0

    G = nx.MultiGraph()
    G.add_nodes_from(range(n))

    multigraph = False
    for b, x in parseData():
        if b == 1:
            v += 1
        # padding with ones can cause overlarge number here
        if x >= n or v >= n:
            break
        elif x > v:
            v = x
        else:
            if G.has_edge(x, v):
                multigraph = True
            G.add_edge(x, v)
    if not multigraph:
        G = nx.Graph(G)
    return G
Example #2
0
def parse_sparse6(string):
    """Read an undirected graph in sparse6 format from string.

    Parameters
    ----------
    string : string
       Data in sparse6 format

    Returns
    -------
    G : Graph

    Raises
    ------
    NetworkXError
        If the string is unable to be parsed in sparse6 format

    Examples
    --------
    >>> G = nx.parse_sparse6(':A_')
    >>> sorted(G.edges())
    [(0, 1), (0, 1), (0, 1)]

    See Also
    --------
    generate_sparse6, read_sparse6, write_sparse6

    References
    ----------
    Sparse6 specification: http://cs.anu.edu.au/~bdm/data/formats.txt
    """
    if string.startswith('>>sparse6<<'):
        string = string[11:]
    if not string.startswith(':'):
        raise NetworkXError('Expected leading colon in sparse6')
    n, data = data_to_n(graph6_to_data(string[1:]))
    k = 1
    while 1<<k < n:
        k += 1

    def parseData():
        """Return stream of pairs b[i], x[i] for sparse6 format."""
        chunks = iter(data)
        d = None # partial data word
        dLen = 0 # how many unparsed bits are left in d

        while 1:
            if dLen < 1:
                d = next(chunks)
                dLen = 6
            dLen -= 1
            b = (d>>dLen) & 1 # grab top remaining bit

            x = d & ((1<<dLen)-1) # partially built up value of x
            xLen = dLen		# how many bits included so far in x
            while xLen < k:	# now grab full chunks until we have enough
                d = next(chunks)
                dLen = 6
                x = (x<<6) + d
                xLen += 6
            x = (x >> (xLen - k)) # shift back the extra bits
            dLen = xLen - k
            yield b,x

    v = 0

    G = nx.MultiGraph()
    G.add_nodes_from(range(n))

    multigraph = False
    for b,x in parseData():
        if b == 1:
            v += 1
        # padding with ones can cause overlarge number here
        if x >= n or v >= n:
            break
        elif x > v:
            v = x
        else:
            if G.has_edge(x,v):
                multigraph = True
            G.add_edge(x,v)
    if not multigraph:
        G = nx.Graph(G)
    return G
Example #3
0
 def test_data_sparse6_data_conversion(self):
     for data in [[], [0], [63], [63, 63], [0] * 42,
                  [0, 1, 62, 42, 3, 11, 0, 11]]:
         assert_equal(g6.graph6_to_data(g6.data_to_graph6(data)), data)
         assert_equal(len(g6.data_to_graph6(data)), len(data))
Example #4
0
 def test_data_sparse6_data_conversion(self):
     for data in [[], [0], [63], [63, 63], [0]*42,
                  [0, 1, 62, 42, 3, 11, 0, 11]]:
         assert_equal(g6.graph6_to_data(g6.data_to_graph6(data)), data)
         assert_equal(len(g6.data_to_graph6(data)), len(data))