[Bugfix] Fix the default value of `num_bases` in RelGraphConv module (#4321)

* Fix doc and default settings for RelGraphConv

* Add unit test

* Split msg in two lines to pass CI-lint

python/dgl/nn/pytorch/conv/relgraphconv.py

@@ -49,16 +49,20 @@ class RelGraphConv(nn.Module):
     out_feat : int
         Output feature size; i.e., the number of dimensions of :math:`h_i^{(l+1)}`.
     num_rels : int
-        Number of relations. .
+        Number of relations.
     regularizer : str, optional
-        Which weight regularizer to use "basis" or "bdd":
+        Which weight regularizer to use ("basis", "bdd" or ``None``):
 
-         - "basis" is short for basis-decomposition.
-         - "bdd" is short for block-diagonal-decomposition.
+         - "basis" is for basis-decomposition.
+         - "bdd" is for block-diagonal-decomposition.
+         - ``None`` applies no regularization.
 
-        Default applies no regularization.
+        Default: ``None``.
     num_bases : int, optional
-        Number of bases. Needed when ``regularizer`` is specified. Default: ``None``.
+        Number of bases. It comes into effect when a regularizer is applied.
+        If ``None``, it uses number of relations (``num_rels``). Default: ``None``.
+        Note that ``in_feat`` and ``out_feat`` must be divisible by ``num_bases``
+        when applying "bdd" regularizer.
     bias : bool, optional
         True if bias is added. Default: ``True``.
     activation : callable, optional
@@ -67,8 +71,8 @@ class RelGraphConv(nn.Module):
         True to include self loop message. Default: ``True``.
     dropout : float, optional
         Dropout rate. Default: ``0.0``
-    layer_norm: float, optional
-        Add layer norm. Default: ``False``
+    layer_norm: bool, optional
+        True to add layer norm. Default: ``False``
 
     Examples
     --------
@@ -102,6 +106,8 @@ class RelGraphConv(nn.Module):
                  dropout=0.0,
                  layer_norm=False):
         super().__init__()
+        if regularizer is not None and num_bases is None:
+            num_bases = num_rels
         self.linear_r = TypedLinear(in_feat, out_feat, num_rels, regularizer, num_bases)
         self.bias = bias
         self.activation = activation

tests/pytorch/test_nn.py

@@ -412,6 +412,60 @@ def test_rgcn(idtype, O):
         h_new = rgc_bdd(g, h, r, norm)
         assert h_new.shape == (100, O)
 
+@parametrize_idtype
+@pytest.mark.parametrize('O', [1, 10, 40])
+def test_rgcn_default_nbasis(idtype, O):
+    ctx = F.ctx()
+    etype = []
+    g = dgl.from_scipy(sp.sparse.random(100, 100, density=0.1))
+    g = g.astype(idtype).to(F.ctx())
+    # 5 etypes
+    R = 5
+    for i in range(g.number_of_edges()):
+        etype.append(i % 5)
+    I = 10
+
+    h = th.randn((100, I)).to(ctx)
+    r = th.tensor(etype).to(ctx)
+    norm = th.rand((g.number_of_edges(), 1)).to(ctx)
+    sorted_r, idx = th.sort(r)
+    sorted_g = dgl.reorder_graph(g, edge_permute_algo='custom', permute_config={'edges_perm' : idx.to(idtype)})
+    sorted_norm = norm[idx]
+
+    rgc = nn.RelGraphConv(I, O, R).to(ctx)
+    th.save(rgc, tmp_buffer)  # test pickle
+    rgc_basis = nn.RelGraphConv(I, O, R, "basis").to(ctx)
+    th.save(rgc_basis, tmp_buffer)  # test pickle
+    if O % R == 0:
+        rgc_bdd = nn.RelGraphConv(I, O, R, "bdd").to(ctx)
+        th.save(rgc_bdd, tmp_buffer)  # test pickle
+
+    # basic usage
+    h_new = rgc(g, h, r)
+    assert h_new.shape == (100, O)
+    h_new_basis = rgc_basis(g, h, r)
+    assert h_new_basis.shape == (100, O)
+    if O % R == 0:
+        h_new_bdd = rgc_bdd(g, h, r)
+        assert h_new_bdd.shape == (100, O)
+
+    # sorted input
+    h_new_sorted = rgc(sorted_g, h, sorted_r, presorted=True)
+    assert th.allclose(h_new, h_new_sorted, atol=1e-4, rtol=1e-4)
+    h_new_basis_sorted = rgc_basis(sorted_g, h, sorted_r, presorted=True)
+    assert th.allclose(h_new_basis, h_new_basis_sorted, atol=1e-4, rtol=1e-4)
+    if O % R == 0:
+        h_new_bdd_sorted = rgc_bdd(sorted_g, h, sorted_r, presorted=True)
+        assert th.allclose(h_new_bdd, h_new_bdd_sorted, atol=1e-4, rtol=1e-4)
+
+    # norm input
+    h_new = rgc(g, h, r, norm)
+    assert h_new.shape == (100, O)
+    h_new = rgc_basis(g, h, r, norm)
+    assert h_new.shape == (100, O)
+    if O % R == 0:
+        h_new = rgc_bdd(g, h, r, norm)
+        assert h_new.shape == (100, O)
 
 @parametrize_idtype
 @pytest.mark.parametrize('g', get_cases(['homo', 'block-bipartite'], exclude=['zero-degree']))