Function to_simple

python/dgl/transforms/functional.py:2371–2549

r"""Convert a graph to a simple graph without parallel edges and return. For a heterogeneous graph with multiple edge types, DGL treats edges with the same edge type and endpoints as parallel edges and removes them. Optionally, one can get the the number of parallel edges by specifying

(
    g,
    return_counts="count",
    writeback_mapping=False,
    copy_ndata=True,
    copy_edata=False,
    aggregator="arbitrary",
)

def to_simple(
    g,
    return_counts="count",
    writeback_mapping=False,
    copy_ndata=True,
    copy_edata=False,
    aggregator="arbitrary",
):
    r"""Convert a graph to a simple graph without parallel edges and return.

    For a heterogeneous graph with multiple edge types, DGL treats edges with the same
    edge type and endpoints as parallel edges and removes them.
    Optionally, one can get the the number of parallel edges by specifying the
    :attr:`return_counts` argument. To get the a mapping from the edge IDs in the
    input graph to the edge IDs in the resulting graph, set :attr:`writeback_mapping`
    to true.

    Parameters
    ----------
    g : DGLGraph
        The input graph.  Must be on CPU.
    return_counts : str, optional
        If given, the count of each edge in the original graph
        will be stored as edge features under the name
        ``return_counts``.  The old features with the same name will be replaced.

        (Default: "count")
    writeback_mapping: bool, optional
        If True, return an extra write-back mapping for each edge
        type. The write-back mapping is a tensor recording
        the mapping from the edge IDs in the input graph to
        the edge IDs in the result graph. If the graph is
        heterogeneous, DGL returns a dictionary of edge types and such
        tensors.

        If False, only the simple graph is returned.

        (Default: False)
    copy_ndata: bool, optional
        If True, the node features of the simple graph are copied
        from the original graph.

        If False, the simple graph will not have any node features.

        (Default: True)
    copy_edata: bool, optional
        If True, the edge features of the simple graph are copied
        from the original graph. If there exists duplicate edges between
        two nodes (u, v), the feature of the edge is the aggregation
        of edge feature of duplicate edges.

        If False, the simple graph will not have any edge features.

        (Default: False)
    aggregator: str, optional
        Indicate how to coalesce edge feature of duplicate edges.
        If ``arbitrary``, select one of the duplicate edges' feature.
        If ``sum``, compute the summation of duplicate edges' feature.