[Feature] Add switch readonly state interface (#389)

* fix rgcn tutorial

* small fix

* add switch readonly state interface

* remove trailing ws

* fix

* fix

* change signature

* change signature

* remove trailing ws

* upd

* upd interface

* upd

* rm trailing ws

* reformat

* trailing space

* upd

python/dgl/graph.py

@@ -3043,6 +3043,38 @@ class DGLGraph(DGLBaseGraph):
             edges = F.tensor(edges)
             return F.boolean_mask(edges, e_mask)
 
+    def readonly(self, readonly_state=True):
+        """Set this graph's readonly state in-place.
+
+        Parameters
+        ----------
+        readonly_state : bool, optional
+            New readonly state of the graph, defaults to True.
+
+        Examples
+        --------
+        >>> G = dgl.DGLGraph()
+        >>> G.add_nodes(3)
+        >>> G.add_edge(0, 1)
+        >>> G.readonly()
+        >>> try:
+        >>>     G.add_nodes(5)
+        >>>     fail = False
+        >>> except:
+        >>>     fail = True
+        >>>
+        >>> fail
+        True
+        >>> G.readonly(False)
+        >>> G.add_nodes(5)
+        >>> G.number_of_nodes()
+        8
+        """
+        if readonly_state == self._graph.is_readonly():
+            return self
+        self._graph.readonly(readonly_state)
+        return self
+
     def __repr__(self):
         ret = ('DGLGraph(num_nodes={node}, num_edges={edge},\n'
                '         ndata_schemes={ndata}\n'

python/dgl/graph_index.py

@@ -54,7 +54,6 @@ class GraphIndex(object):
             self._init(src, dst, utils.toindex(F.arange(0, len(src))), n_nodes)
         else:
             self._handle = _CAPI_DGLGraphCreateMutable(multigraph)
-
             self.clear()
             self.add_nodes(n_nodes)
             self.add_edges(src, dst)
@@ -139,6 +138,19 @@ class GraphIndex(object):
             self._readonly = bool(_CAPI_DGLGraphIsReadonly(self._handle))
         return self._readonly
 
+    def readonly(self, readonly_state=True):
+        """Set the readonly state of graph index in-place.
+
+        Parameters
+        ----------
+        readonly_state : bool
+            New readonly state of current graph index.
+        """
+        n_nodes, multigraph, _, src, dst = self.__getstate__()
+        self.clear_cache()
+        state = (n_nodes, multigraph, readonly_state, src, dst)
+        self.__setstate__(state)
+
     def number_of_nodes(self):
         """Return the number of nodes.
 

tests/compute/test_graph.py

@@ -5,6 +5,7 @@ import scipy.sparse as sp
 import networkx as nx
 import dgl
 import backend as F
+from dgl import DGLError
 
 def test_graph_creation():
     g = dgl.DGLGraph()
@@ -126,9 +127,67 @@ def test_incmat_cache():
     inc4 = g.incidence_matrix("in")
     assert id(inc4) != id(inc35)
 
+def test_readonly():
+    g = dgl.DGLGraph()
+    g.add_nodes(5)
+    g.add_edges([0, 1, 2, 3], [1, 2, 3, 4])
+    g.ndata['x'] = F.zeros((5, 3))
+    g.edata['x'] = F.zeros((4, 4))
+
+    g.readonly(False)
+    assert g._graph.is_readonly() == False
+    assert g.number_of_nodes() == 5
+    assert g.number_of_edges() == 4
+
+    g.readonly()
+    assert g._graph.is_readonly() == True 
+    assert g.number_of_nodes() == 5
+    assert g.number_of_edges() == 4
+
+    try:
+        g.add_nodes(5)
+        fail = False
+    except DGLError:
+        fail = True
+    finally:
+        assert fail
+
+    g.readonly()
+    assert g._graph.is_readonly() == True 
+    assert g.number_of_nodes() == 5
+    assert g.number_of_edges() == 4
+
+    try:
+        g.add_nodes(5)
+        fail = False
+    except DGLError:
+        fail = True
+    finally:
+        assert fail
+
+    g.readonly(False)
+    assert g._graph.is_readonly() == False
+    assert g.number_of_nodes() == 5
+    assert g.number_of_edges() == 4
+
+    try:
+        g.add_nodes(10)
+        g.add_edges([4, 5, 6, 7, 8, 9, 10, 11, 12, 13],
+                    [5, 6, 7, 8, 9, 10, 11, 12, 13, 14])
+        fail = False
+    except DGLError:
+        fail = True
+    finally:
+        assert not fail
+        assert g.number_of_nodes() == 15
+        assert F.shape(g.ndata['x']) == (15, 3)
+        assert g.number_of_edges() == 14
+        assert F.shape(g.edata['x']) == (14, 4)
+
 if __name__ == '__main__':
     test_graph_creation()
     test_create_from_elist()
     test_adjmat_cache()
     test_incmat()
     test_incmat_cache()
+    test_readonly()