Source code for dgl.dataloading.shadow

"""ShaDow-GNN subgraph samplers."""
from .. import transforms
from ..base import NID
from ..sampling.utils import EidExcluder
from .base import Sampler, set_edge_lazy_features, set_node_lazy_features

[docs]class ShaDowKHopSampler(Sampler): """K-hop subgraph sampler from `Deep Graph Neural Networks with Shallow Subgraph Samplers <>`__. It performs node-wise neighbor sampling and returns the subgraph induced by all the sampled nodes. The seed nodes from which the neighbors are sampled will appear the first in the induced nodes of the subgraph. Parameters ---------- fanouts : list[int] or list[dict[etype, int]] List of neighbors to sample per edge type for each GNN layer, with the i-th element being the fanout for the i-th GNN layer. If only a single integer is provided, DGL assumes that every edge type will have the same fanout. If -1 is provided for one edge type on one layer, then all inbound edges of that edge type will be included. replace : bool, default True Whether to sample with replacement prob : str, optional If given, the probability of each neighbor being sampled is proportional to the edge feature value with the given name in ``g.edata``. The feature must be a scalar on each edge. Examples -------- **Node classification** To train a 3-layer GNN for node classification on a set of nodes ``train_nid`` on a homogeneous graph where each node takes messages from 5, 10, 15 neighbors for the first, second, and third layer respectively (assuming the backend is PyTorch): >>> g =[0] >>> sampler = dgl.dataloading.ShaDowKHopSampler([5, 10, 15]) >>> dataloader = dgl.dataloading.DataLoader( ... g, torch.arange(g.num_nodes()), sampler, ... batch_size=5, shuffle=True, drop_last=False, num_workers=4) >>> for input_nodes, output_nodes, subgraph in dataloader: ... print(subgraph) ... assert torch.equal(input_nodes, subgraph.ndata[dgl.NID]) ... assert torch.equal(input_nodes[:output_nodes.shape[0]], output_nodes) ... break Graph(num_nodes=529, num_edges=3796, ndata_schemes={'label': Scheme(shape=(), dtype=torch.int64), 'feat': Scheme(shape=(8710,), dtype=torch.float32), '_ID': Scheme(shape=(), dtype=torch.int64)} edata_schemes={'_ID': Scheme(shape=(), dtype=torch.int64)}) If training on a heterogeneous graph and you want different number of neighbors for each edge type, one should instead provide a list of dicts. Each dict would specify the number of neighbors to pick per edge type. >>> sampler = dgl.dataloading.ShaDowKHopSampler([ ... {('user', 'follows', 'user'): 5, ... ('user', 'plays', 'game'): 4, ... ('game', 'played-by', 'user'): 3}] * 3) If you would like non-uniform neighbor sampling: >>> g.edata['p'] = torch.rand(g.num_edges()) # any non-negative 1D vector works >>> sampler = dgl.dataloading.ShaDowKHopSampler([5, 10, 15], prob='p') """ def __init__( self, fanouts, replace=False, prob=None, prefetch_node_feats=None, prefetch_edge_feats=None, output_device=None, ): super().__init__() self.fanouts = fanouts self.replace = replace self.prob = prob self.prefetch_node_feats = prefetch_node_feats self.prefetch_edge_feats = prefetch_edge_feats self.output_device = output_device def sample( self, g, seed_nodes, exclude_eids=None ): # pylint: disable=arguments-differ """Sampling function. Parameters ---------- g : DGLGraph The graph to sample nodes from. seed_nodes : Tensor or dict[str, Tensor] The nodes sampled in the current minibatch. exclude_eids : Tensor or dict[etype, Tensor], optional The edges to exclude from neighborhood expansion. Returns ------- input_nodes, output_nodes, subg A triplet containing (1) the node IDs inducing the subgraph, (2) the node IDs that are sampled in this minibatch, and (3) the subgraph itself. """ output_nodes = seed_nodes for fanout in reversed(self.fanouts): frontier = g.sample_neighbors( seed_nodes, fanout, output_device=self.output_device, replace=self.replace, prob=self.prob, exclude_edges=exclude_eids, ) block = transforms.to_block(frontier, seed_nodes) seed_nodes = block.srcdata[NID] subg = g.subgraph( seed_nodes, relabel_nodes=True, output_device=self.output_device ) if exclude_eids is not None: subg = EidExcluder(exclude_eids)(subg) set_node_lazy_features(subg, self.prefetch_node_feats) set_edge_lazy_features(subg, self.prefetch_edge_feats) return seed_nodes, output_nodes, subg