"""Tensorflow Module for Graph Isomorphism Network layer"""
# pylint: disable= no-member, arguments-differ, invalid-name
import tensorflow as tf
from tensorflow.keras import layers
from .... import function as fn
from ....utils import expand_as_pair
[docs]class GINConv(layers.Layer):
r"""Graph Isomorphism Network layer from `How Powerful are Graph
Neural Networks? <https://arxiv.org/pdf/1810.00826.pdf>`__
.. math::
h_i^{(l+1)} = f_\Theta \left((1 + \epsilon) h_i^{l} +
\mathrm{aggregate}\left(\left\{h_j^{l}, j\in\mathcal{N}(i)
\right\}\right)\right)
Parameters
----------
apply_func : callable activation function/layer or None
If not None, apply this function to the updated node feature,
the :math:`f_\Theta` in the formula.
aggregator_type : str
Aggregator type to use (``sum``, ``max`` or ``mean``).
init_eps : float, optional
Initial :math:`\epsilon` value, default: ``0``.
learn_eps : bool, optional
If True, :math:`\epsilon` will be a learnable parameter. Default: ``False``.
Example
-------
>>> import dgl
>>> import numpy as np
>>> import tensorflow as tf
>>> from dgl.nn import GINConv
>>>
>>> with tf.device("CPU:0"):
>>> g = dgl.graph(([0,1,2,3,2,5], [1,2,3,4,0,3]))
>>> feat = tf.ones((6, 10))
>>> lin = tf.keras.layers.Dense(10)
>>> conv = GINConv(lin, 'max')
>>> res = conv(g, feat)
>>> res
<tf.Tensor: shape=(6, 10), dtype=float32, numpy=
array([[-0.1090256 , 1.9050574 , -0.30704725, -1.995831 , -0.36399186,
1.10414 , 2.4885745 , -0.35387516, 1.3568261 , 1.7267858 ],
[-0.1090256 , 1.9050574 , -0.30704725, -1.995831 , -0.36399186,
1.10414 , 2.4885745 , -0.35387516, 1.3568261 , 1.7267858 ],
[-0.1090256 , 1.9050574 , -0.30704725, -1.995831 , -0.36399186,
1.10414 , 2.4885745 , -0.35387516, 1.3568261 , 1.7267858 ],
[-0.1090256 , 1.9050574 , -0.30704725, -1.995831 , -0.36399186,
1.10414 , 2.4885745 , -0.35387516, 1.3568261 , 1.7267858 ],
[-0.1090256 , 1.9050574 , -0.30704725, -1.995831 , -0.36399186,
1.10414 , 2.4885745 , -0.35387516, 1.3568261 , 1.7267858 ],
[-0.0545128 , 0.9525287 , -0.15352362, -0.9979155 , -0.18199593,
0.55207 , 1.2442873 , -0.17693758, 0.67841303, 0.8633929 ]],
dtype=float32)>
"""
def __init__(self,
apply_func,
aggregator_type,
init_eps=0,
learn_eps=False):
super(GINConv, self).__init__()
self.apply_func = apply_func
if aggregator_type == 'sum':
self._reducer = fn.sum
elif aggregator_type == 'max':
self._reducer = fn.max
elif aggregator_type == 'mean':
self._reducer = fn.mean
else:
raise KeyError('Aggregator type {} not recognized.'.format(aggregator_type))
# to specify whether eps is trainable or not.
self.eps = tf.Variable(initial_value=[init_eps], dtype=tf.float32, trainable=learn_eps)
def call(self, graph, feat):
r"""Compute Graph Isomorphism Network layer.
Parameters
----------
graph : DGLGraph
The graph.
feat : tf.Tensor or pair of tf.Tensor
If a tf.Tensor is given, the input feature of shape :math:`(N, D_{in})` where
:math:`D_{in}` is size of input feature, :math:`N` is the number of nodes.
If a pair of tf.Tensor is given, the pair must contain two tensors of shape
:math:`(N_{in}, D_{in})` and :math:`(N_{out}, D_{in})`.
If ``apply_func`` is not None, :math:`D_{in}` should
fit the input dimensionality requirement of ``apply_func``.
Returns
-------
tf.Tensor
The output feature of shape :math:`(N, D_{out})` where
:math:`D_{out}` is the output dimensionality of ``apply_func``.
If ``apply_func`` is None, :math:`D_{out}` should be the same
as input dimensionality.
"""
with graph.local_scope():
feat_src, feat_dst = expand_as_pair(feat, graph)
graph.srcdata['h'] = feat_src
graph.update_all(fn.copy_u('h', 'm'), self._reducer('m', 'neigh'))
rst = (1 + self.eps) * feat_dst + graph.dstdata['neigh']
if self.apply_func is not None:
rst = self.apply_func(rst)
return rst