wehub-resource-sync
328 lines
9.0 KiB
Python
328 lines
9.0 KiB
Python
"""MXNet modules for graph global pooling."""
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# pylint: disable= no-member, arguments-differ, invalid-name, W0235
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from mxnet import gluon, nd
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from mxnet.gluon import nn
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from ...readout import (
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broadcast_nodes,
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max_nodes,
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mean_nodes,
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softmax_nodes,
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sum_nodes,
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topk_nodes,
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)
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__all__ = [
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"SumPooling",
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"AvgPooling",
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"MaxPooling",
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"SortPooling",
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"GlobalAttentionPooling",
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"Set2Set",
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]
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class SumPooling(nn.Block):
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r"""Apply sum pooling over the nodes in the graph.
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.. math::
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r^{(i)} = \sum_{k=1}^{N_i} x^{(i)}_k
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"""
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def __init__(self):
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super(SumPooling, self).__init__()
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def forward(self, graph, feat):
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r"""Compute sum pooling.
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Parameters
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----------
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graph : DGLGraph
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The graph.
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feat : mxnet.NDArray
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The input feature with shape :math:`(N, *)` where
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:math:`N` is the number of nodes in the graph.
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Returns
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-------
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mxnet.NDArray
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The output feature with shape :math:`(B, *)`, where
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:math:`B` refers to the batch size.
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"""
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with graph.local_scope():
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graph.ndata["h"] = feat
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readout = sum_nodes(graph, "h")
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graph.ndata.pop("h")
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return readout
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def __repr__(self):
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return "SumPooling()"
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class AvgPooling(nn.Block):
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r"""Apply average pooling over the nodes in the graph.
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.. math::
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r^{(i)} = \frac{1}{N_i}\sum_{k=1}^{N_i} x^{(i)}_k
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"""
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def __init__(self):
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super(AvgPooling, self).__init__()
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def forward(self, graph, feat):
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r"""Compute average pooling.
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Parameters
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----------
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graph : DGLGraph
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The graph.
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feat : mxnet.NDArray
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The input feature with shape :math:`(N, *)` where
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:math:`N` is the number of nodes in the graph.
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Returns
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-------
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mxnet.NDArray
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The output feature with shape :math:`(B, *)`, where
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:math:`B` refers to the batch size.
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"""
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with graph.local_scope():
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graph.ndata["h"] = feat
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readout = mean_nodes(graph, "h")
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graph.ndata.pop("h")
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return readout
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def __repr__(self):
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return "AvgPooling()"
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class MaxPooling(nn.Block):
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r"""Apply max pooling over the nodes in the graph.
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.. math::
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r^{(i)} = \max_{k=1}^{N_i} \left( x^{(i)}_k \right)
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"""
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def __init__(self):
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super(MaxPooling, self).__init__()
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def forward(self, graph, feat):
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r"""Compute max pooling.
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Parameters
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----------
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graph : DGLGraph
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The graph.
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feat : mxnet.NDArray
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The input feature with shape :math:`(N, *)` where
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:math:`N` is the number of nodes in the graph.
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Returns
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-------
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mxnet.NDArray
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The output feature with shape :math:`(B, *)`, where
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:math:`B` refers to the batch size.
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"""
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with graph.local_scope():
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graph.ndata["h"] = feat
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readout = max_nodes(graph, "h")
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graph.ndata.pop("h")
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return readout
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def __repr__(self):
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return "MaxPooling()"
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class SortPooling(nn.Block):
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r"""Pooling layer from `An End-to-End Deep Learning Architecture for Graph Classification
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<https://www.cse.wustl.edu/~ychen/public/DGCNN.pdf>`__
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Parameters
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----------
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k : int
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The number of nodes to hold for each graph.
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"""
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def __init__(self, k):
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super(SortPooling, self).__init__()
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self.k = k
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def forward(self, graph, feat):
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r"""Compute sort pooling.
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Parameters
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----------
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graph : DGLGraph
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The graph.
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feat : mxnet.NDArray
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The input node feature with shape :math:`(N, D)` where
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:math:`N` is the number of nodes in the graph.
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Returns
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-------
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mxnet.NDArray
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The output feature with shape :math:`(B, k * D)`, where
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:math:`B` refers to the batch size.
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"""
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# Sort the feature of each node in ascending order.
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with graph.local_scope():
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feat = feat.sort(axis=-1)
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graph.ndata["h"] = feat
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# Sort nodes according to their last features.
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ret = topk_nodes(graph, "h", self.k, sortby=-1)[0].reshape(
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-1, self.k * feat.shape[-1]
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)
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return ret
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def __repr__(self):
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return "SortPooling(k={})".format(self.k)
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class GlobalAttentionPooling(nn.Block):
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r"""Global Attention Pooling layer from `Gated Graph Sequence Neural Networks
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<https://arxiv.org/abs/1511.05493.pdf>`__
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.. math::
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r^{(i)} = \sum_{k=1}^{N_i}\mathrm{softmax}\left(f_{gate}
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\left(x^{(i)}_k\right)\right) f_{feat}\left(x^{(i)}_k\right)
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Parameters
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----------
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gate_nn : gluon.nn.Block
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A neural network that computes attention scores for each feature.
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feat_nn : gluon.nn.Block, optional
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A neural network applied to each feature before combining them
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with attention scores.
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"""
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def __init__(self, gate_nn, feat_nn=None):
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super(GlobalAttentionPooling, self).__init__()
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with self.name_scope():
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self.gate_nn = gate_nn
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self.feat_nn = feat_nn
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def forward(self, graph, feat):
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r"""Compute global attention pooling.
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Parameters
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----------
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graph : DGLGraph
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The graph.
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feat : mxnet.NDArray
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The input node feature with shape :math:`(N, D)` where
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:math:`N` is the number of nodes in the graph.
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Returns
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-------
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mxnet.NDArray
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The output feature with shape :math:`(B, D)`, where
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:math:`B` refers to the batch size.
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"""
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with graph.local_scope():
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gate = self.gate_nn(feat)
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assert (
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gate.shape[-1] == 1
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), "The output of gate_nn should have size 1 at the last axis."
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feat = self.feat_nn(feat) if self.feat_nn else feat
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graph.ndata["gate"] = gate
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gate = softmax_nodes(graph, "gate")
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graph.ndata["r"] = feat * gate
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readout = sum_nodes(graph, "r")
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return readout
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class Set2Set(nn.Block):
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r"""Set2Set operator from `Order Matters: Sequence to sequence for sets
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<https://arxiv.org/pdf/1511.06391.pdf>`__
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For each individual graph in the batch, set2set computes
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.. math::
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q_t &= \mathrm{LSTM} (q^*_{t-1})
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\alpha_{i,t} &= \mathrm{softmax}(x_i \cdot q_t)
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r_t &= \sum_{i=1}^N \alpha_{i,t} x_i
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q^*_t &= q_t \Vert r_t
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for this graph.
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Parameters
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----------
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input_dim : int
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Size of each input sample
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n_iters : int
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Number of iterations.
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n_layers : int
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Number of recurrent layers.
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"""
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def __init__(self, input_dim, n_iters, n_layers):
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super(Set2Set, self).__init__()
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self.input_dim = input_dim
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self.output_dim = 2 * input_dim
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self.n_iters = n_iters
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self.n_layers = n_layers
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with self.name_scope():
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self.lstm = gluon.rnn.LSTM(
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self.input_dim, num_layers=n_layers, input_size=self.output_dim
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)
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def forward(self, graph, feat):
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r"""Compute set2set pooling.
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Parameters
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----------
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graph : DGLGraph
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The graph.
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feat : mxnet.NDArray
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The input node feature with shape :math:`(N, D)` where
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:math:`N` is the number of nodes in the graph.
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Returns
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-------
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mxnet.NDArray
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The output feature with shape :math:`(B, D)`, where
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:math:`B` refers to the batch size.
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"""
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with graph.local_scope():
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batch_size = graph.batch_size
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h = (
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nd.zeros(
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(self.n_layers, batch_size, self.input_dim),
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ctx=feat.context,
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),
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nd.zeros(
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(self.n_layers, batch_size, self.input_dim),
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ctx=feat.context,
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),
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)
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q_star = nd.zeros((batch_size, self.output_dim), ctx=feat.context)
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for _ in range(self.n_iters):
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q, h = self.lstm(q_star.expand_dims(axis=0), h)
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q = q.reshape((batch_size, self.input_dim))
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e = (feat * broadcast_nodes(graph, q)).sum(
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axis=-1, keepdims=True
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)
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graph.ndata["e"] = e
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alpha = softmax_nodes(graph, "e")
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graph.ndata["r"] = feat * alpha
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readout = sum_nodes(graph, "r")
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q_star = nd.concat(q, readout, dim=-1)
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return q_star
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def __repr__(self):
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summary = "Set2Set("
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summary += "in={}, out={}, " "n_iters={}, n_layers={}".format(
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self.input_dim, self.output_dim, self.n_iters, self.n_layers
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)
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summary += ")"
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return summary
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