"""Torch Module for Gated Graph Convolution layer"""
# pylint: disable= no-member, arguments-differ, invalid-name, cell-var-from-loop
import torch as th
from torch import nn
from torch.nn import init
from .... import function as fn
[docs]class GatedGraphConv(nn.Module):
r"""
Description
-----------
Gated Graph Convolution layer from paper `Gated Graph Sequence
Neural Networks <https://arxiv.org/pdf/1511.05493.pdf>`__.
.. math::
h_{i}^{0} &= [ x_i \| \mathbf{0} ]
a_{i}^{t} &= \sum_{j\in\mathcal{N}(i)} W_{e_{ij}} h_{j}^{t}
h_{i}^{t+1} &= \mathrm{GRU}(a_{i}^{t}, h_{i}^{t})
Parameters
----------
in_feats : int
Input feature size; i.e, the number of dimensions of :math:`x_i`.
out_feats : int
Output feature size; i.e., the number of dimensions of :math:`h_i^{(t+1)}`.
n_steps : int
Number of recurrent steps; i.e, the :math:`t` in the above formula.
n_etypes : int
Number of edge types.
bias : bool
If True, adds a learnable bias to the output. Default: ``True``.
Example
-------
>>> import dgl
>>> import numpy as np
>>> import torch as th
>>> from dgl.nn import GatedGraphConv
>>>
>>> g = dgl.graph(([0,1,2,3,2,5], [1,2,3,4,0,3]))
>>> feat = th.ones(6, 10)
>>> conv = GatedGraphConv(10, 10, 2, 3)
>>> etype = th.tensor([0,1,2,0,1,2])
>>> res = conv(g, feat, etype)
>>> res
tensor([[ 0.4652, 0.4458, 0.5169, 0.4126, 0.4847, 0.2303, 0.2757, 0.7721,
0.0523, 0.0857],
[ 0.0832, 0.1388, -0.5643, 0.7053, -0.2524, -0.3847, 0.7587, 0.8245,
0.9315, 0.4063],
[ 0.6340, 0.4096, 0.7692, 0.2125, 0.2106, 0.4542, -0.0580, 0.3364,
-0.1376, 0.4948],
[ 0.5551, 0.7946, 0.6220, 0.8058, 0.5711, 0.3063, -0.5454, 0.2272,
-0.6931, -0.1607],
[ 0.2644, 0.2469, -0.6143, 0.6008, -0.1516, -0.3781, 0.5878, 0.7993,
0.9241, 0.1835],
[ 0.6393, 0.3447, 0.3893, 0.4279, 0.3342, 0.3809, 0.0406, 0.5030,
0.1342, 0.0425]], grad_fn=<AddBackward0>)
"""
def __init__(self,
in_feats,
out_feats,
n_steps,
n_etypes,
bias=True):
super(GatedGraphConv, self).__init__()
self._in_feats = in_feats
self._out_feats = out_feats
self._n_steps = n_steps
self._n_etypes = n_etypes
self.linears = nn.ModuleList(
[nn.Linear(out_feats, out_feats) for _ in range(n_etypes)]
)
self.gru = nn.GRUCell(out_feats, out_feats, bias=bias)
self.reset_parameters()
def reset_parameters(self):
r"""
Description
-----------
Reinitialize learnable parameters.
Note
----
The model parameters are initialized using Glorot uniform initialization
and the bias is initialized to be zero.
"""
gain = init.calculate_gain('relu')
self.gru.reset_parameters()
for linear in self.linears:
init.xavier_normal_(linear.weight, gain=gain)
init.zeros_(linear.bias)
def set_allow_zero_in_degree(self, set_value):
r"""
Description
-----------
Set allow_zero_in_degree flag.
Parameters
----------
set_value : bool
The value to be set to the flag.
"""
self._allow_zero_in_degree = set_value
[docs] def forward(self, graph, feat, etypes=None):
"""
Description
-----------
Compute Gated Graph Convolution layer.
Parameters
----------
graph : DGLGraph
The graph.
feat : torch.Tensor
The input feature of shape :math:`(N, D_{in})` where :math:`N`
is the number of nodes of the graph and :math:`D_{in}` is the
input feature size.
etypes : torch.LongTensor, or None
The edge type tensor of shape :math:`(E,)` where :math:`E` is
the number of edges of the graph. When there's only one edge type,
this argument can be skipped
Returns
-------
torch.Tensor
The output feature of shape :math:`(N, D_{out})` where :math:`D_{out}`
is the output feature size.
"""
with graph.local_scope():
assert graph.is_homogeneous, \
"not a homogeneous graph; convert it with to_homogeneous " \
"and pass in the edge type as argument"
if self._n_etypes != 1:
assert etypes.min() >= 0 and etypes.max() < self._n_etypes, \
"edge type indices out of range [0, {})".format(
self._n_etypes)
zero_pad = feat.new_zeros(
(feat.shape[0], self._out_feats - feat.shape[1]))
feat = th.cat([feat, zero_pad], -1)
for _ in range(self._n_steps):
if self._n_etypes == 1 and etypes is None:
# Fast path when graph has only one edge type
graph.ndata['h'] = self.linears[0](feat)
graph.update_all(fn.copy_u('h', 'm'), fn.sum('m', 'a'))
a = graph.ndata.pop('a') # (N, D)
else:
graph.ndata['h'] = feat
for i in range(self._n_etypes):
eids = th.nonzero(
etypes == i, as_tuple=False).view(-1).type(graph.idtype)
if len(eids) > 0:
graph.apply_edges(
lambda edges: {
'W_e*h': self.linears[i](edges.src['h'])},
eids
)
graph.update_all(fn.copy_e('W_e*h', 'm'), fn.sum('m', 'a'))
a = graph.ndata.pop('a') # (N, D)
feat = self.gru(a, feat)
return feat