[Feature] Split data for distributed training (#1505)

* fix tests in graph partition book.

* implement node_split and edge_split.

* fix a bug.

* add tests.

* remove unnecessary code.

* avoid storing graph structure in partition book.

* add partition book in DistGraph.

* Revert "avoid storing graph structure in partition book."

This reverts commit 55b11fbf9293efcae5f8c97e93f1e121399dadae.

* small fixes.

* add a test for boolean mask vector.

* fix test.

* fix bugs.

* make it work for all different cases.

* fix tests.

* fix boolean mask

* fix for TF

* fix for tensorflow.

* fix test for TF

* only support boolean mask for now.

* fix tests.

* make the code more readable.

* fix test.
Co-authored-by: Chao Ma <mctt90@gmail.com>
Co-authored-by: Jinjing Zhou <VoVAllen@users.noreply.github.com>

python/dgl/backend/pytorch/tensor.py

@@ -239,6 +239,8 @@ def unsorted_1d_segment_mean(input, seg_id, n_segs, dim):
     return y
 
 def boolean_mask(input, mask):
+    if 'bool' not in str(mask.dtype):
+        mask = th.tensor(mask, dtype=th.bool)
     return input[mask]
 
 def equal(x, y):

python/dgl/distributed/__init__.py

 """DGL distributed."""
 
-from .dist_graph import DistGraphServer, DistGraph
+from .dist_graph import DistGraphServer, DistGraph, node_split, edge_split
 from .partition import partition_graph, load_partition
 from .graph_partition_book import GraphPartitionBook

python/dgl/distributed/dist_graph.py

@@ -12,7 +12,9 @@ from ..graph_index import from_shared_mem_graph_index
 from .._ffi.ndarray import empty_shared_mem
 from ..frame import infer_scheme
 from .partition import load_partition
+from .graph_partition_book import GraphPartitionBook
 from .. import ndarray as nd
+from .. import utils
 
 def _get_ndata_path(graph_name, ndata_name):
     return "/" + graph_name + "_node_" + ndata_name
@@ -52,6 +54,7 @@ def _copy_graph_to_shared_mem(g, graph_name):
     return new_g
 
 FIELD_DICT = {'local_node': F.int64,
+              'local_edge': F.int64,
               NID: F.int64,
               EID: F.int64}
 
@@ -116,22 +119,49 @@ def _get_graph_from_shared_mem(graph_name):
 
     g = DGLGraph(gidx)
     g.ndata['local_node'] = _get_shared_mem_ndata(g, graph_name, 'local_node')
+    g.edata['local_edge'] = _get_shared_mem_edata(g, graph_name, 'local_edge')
     g.ndata[NID] = _get_shared_mem_ndata(g, graph_name, NID)
     g.edata[EID] = _get_shared_mem_edata(g, graph_name, EID)
     return g
 
+def _move_metadata_to_shared_mam(graph_name, num_nodes, num_edges, part_id,
+                                 num_partitions, node_map, edge_map):
+    ''' Move all metadata to the shared memory.
+
+    We need these metadata to construct graph partition book.
+    '''
+    meta = _move_data_to_shared_mem_array(F.tensor([num_nodes, num_edges,
+                                                    num_partitions, part_id]),
+                                          _get_ndata_path(graph_name, 'meta'))
+    node_map = _move_data_to_shared_mem_array(node_map, _get_ndata_path(graph_name, 'node_map'))
+    edge_map = _move_data_to_shared_mem_array(edge_map, _get_edata_path(graph_name, 'edge_map'))
+    return meta, node_map, edge_map
+
 def _get_shared_mem_metadata(graph_name):
     ''' Get the metadata of the graph through shared memory.
 
     The metadata includes the number of nodes and the number of edges. In the future,
     we can add more information, especially for heterograph.
     '''
-    shape = (2,)
+    shape = (4,)
     dtype = F.int64
     dtype = DTYPE_DICT[dtype]
     data = empty_shared_mem(_get_ndata_path(graph_name, 'meta'), False, shape, dtype)
     dlpack = data.to_dlpack()
-    return F.zerocopy_from_dlpack(dlpack)
+    meta = F.asnumpy(F.zerocopy_from_dlpack(dlpack))
+    num_nodes, num_edges, num_partitions, part_id = meta[0], meta[1], meta[2], meta[3]
+
+    # Load node map
+    data = empty_shared_mem(_get_ndata_path(graph_name, 'node_map'), False, (num_nodes,), dtype)
+    dlpack = data.to_dlpack()
+    node_map = F.zerocopy_from_dlpack(dlpack)
+
+    # Load edge_map
+    data = empty_shared_mem(_get_edata_path(graph_name, 'edge_map'), False, (num_edges,), dtype)
+    dlpack = data.to_dlpack()
+    edge_map = F.zerocopy_from_dlpack(dlpack)
+
+    return num_nodes, num_edges, part_id, num_partitions, node_map, edge_map
 
 class DistTensor:
     ''' Distributed tensor.
@@ -312,16 +342,14 @@ class DistGraphServer(KVServer):
         print('Server {}: host name: {}, ip: {}'.format(server_id, host_name, host_ip))
 
         self.client_g, node_feats, edge_feats, self.meta = load_partition(conf_file, server_id)
-        num_nodes, num_edges, node_map, edge_map = self.meta
+        num_nodes, num_edges, node_map, edge_map, num_partitions = self.meta
         self.client_g = _copy_graph_to_shared_mem(self.client_g, graph_name)
-        self.meta = _move_data_to_shared_mem_array(F.tensor([num_nodes, num_edges]),
-                                                   _get_ndata_path(graph_name, 'meta'))
 
         # Create node global2local map.
         node_g2l = F.zeros((num_nodes), dtype=F.int64, ctx=F.cpu()) - 1
         # The nodes that belong to this partition.
         local_nids = F.nonzero_1d(self.client_g.ndata['local_node'])
-        nids = self.client_g.ndata[NID][local_nids]
+        nids = F.asnumpy(F.gather_row(self.client_g.ndata[NID], local_nids))
         assert np.all(node_map[nids] == server_id), 'Load a wrong partition'
         F.scatter_row_inplace(node_g2l, nids, F.arange(0, len(nids)))
 
@@ -329,7 +357,7 @@ class DistGraphServer(KVServer):
         if len(edge_feats) > 0:
             edge_g2l = F.zeros((num_edges), dtype=F.int64, ctx=F.cpu()) - 1
             local_eids = F.nonzero_1d(self.client_g.edata['local_edge'])
-            eids = self.client_g.edata[EID][local_eids]
+            eids = F.asnumpy(F.gather_row(self.client_g.edata[EID], local_eids))
             assert np.all(edge_map[eids] == server_id), 'Load a wrong partition'
             F.scatter_row_inplace(edge_g2l, eids, F.arange(0, len(eids)))
 
@@ -354,6 +382,14 @@ class DistGraphServer(KVServer):
                 self.init_data(name=_get_edata_name(name))
                 self.set_partition_book(name=_get_edata_name(name), partition_book=edge_map)
 
+        # TODO(zhengda) this is temporary solution. We don't need this in the future.
+        self.meta, self.node_map, self.edge_map = _move_metadata_to_shared_mam(graph_name,
+                                                                               num_nodes,
+                                                                               num_edges,
+                                                                               server_id,
+                                                                               num_partitions,
+                                                                               node_map, edge_map)
+
 class DistGraph:
     ''' The DistGraph client.
 
@@ -383,19 +419,12 @@ class DistGraph:
         self._client = KVClient(server_namebook=server_namebook)
         self._client.connect()
 
-        self.g = _get_graph_from_shared_mem(graph_name)
-        self.graph_name = graph_name
-        self.meta = F.asnumpy(_get_shared_mem_metadata(graph_name))
+        self._g = _get_graph_from_shared_mem(graph_name)
+        self._tot_num_nodes, self._tot_num_edges, self._part_id, num_parts, node_map, \
+                edge_map = _get_shared_mem_metadata(graph_name)
+        self._gpb = GraphPartitionBook(self._part_id, num_parts, node_map, edge_map, self._g)
 
         self._client.barrier()
-
-        if self.g is not None:
-            self._local_nids = F.nonzero_1d(self.g.ndata['local_node'])
-            self._local_gnid = self.g.ndata[NID][self._local_nids]
-        else:
-            self._local_nids = None
-            self._local_gnid = None
-
         self._ndata = NodeDataView(self)
         self._edata = EdgeDataView(self)
 
@@ -496,11 +525,11 @@ class DistGraph:
 
     def number_of_nodes(self):
         """Return the number of nodes"""
-        return self.meta[0]
+        return self._tot_num_nodes
 
     def number_of_edges(self):
         """Return the number of edges"""
-        return self.meta[1]
+        return self._tot_num_edges
 
     def node_attr_schemes(self):
         """Return the node feature and embedding schemes."""
@@ -524,7 +553,20 @@ class DistGraph:
         int
             The rank of the current graph store.
         '''
-        return self._client.get_id()
+        # Here the rank of the client should be the same as the partition Id to ensure
+        # that we always get the local partition.
+        # TODO(zhengda) we need to change this if we support two-level partitioning.
+        return self._part_id
+
+    def get_partition_book(self):
+        """Get the partition information.
+
+        Returns
+        -------
+        GraphPartitionBook
+            Object that stores all kinds of partition information.
+        """
+        return self._gpb
 
     def shut_down(self):
         """Shut down all KVServer nodes.
@@ -557,3 +599,98 @@ class DistGraph:
                 # Remove the prefix "edge:"
                 edata_names.append(name[5:])
         return edata_names
+
+def _get_overlap(mask_arr, ids):
+    """ Select the Ids given a boolean mask array.
+
+    The boolean mask array indicates all of the Ids to be selected. We want to
+    find the overlap between the Ids selected by the boolean mask array and
+    the Id array.
+
+    Parameters
+    ----------
+    mask_arr : 1D tensor
+        A boolean mask array.
+    ids : 1D tensor
+        A vector with Ids.
+
+    Returns
+    -------
+    1D tensor
+        The selected Ids.
+    """
+    if isinstance(mask_arr, DistTensor):
+        masks = mask_arr[ids]
+        return F.boolean_mask(ids, masks)
+    else:
+        mask_arr = utils.toindex(mask_arr)
+        masks = F.gather_row(mask_arr.tousertensor(), ids)
+        return F.boolean_mask(ids, masks)
+
+def node_split(nodes, partition_book, rank):
+    ''' Split nodes and return a subset for the local rank.
+
+    This function splits the input nodes based on the partition book and
+    returns a subset of nodes for the local rank. This method is used for
+    dividing workloads for distributed training.
+
+    The input nodes can be stored as a vector of masks. The length of the vector is
+    the same as the number of nodes in a graph; 1 indicates that the vertex in
+    the corresponding location exists.
+
+    Parameters
+    ----------
+    nodes : 1D tensor or DistTensor
+        A boolean mask vector that indicates input nodes.
+    partition_book : GraphPartitionBook
+        The graph partition book
+    rank : int
+        The rank of the current process
+
+    Returns
+    -------
+    1D-tensor
+        The vector of node Ids that belong to the rank.
+    '''
+    num_nodes = 0
+    for part in partition_book.metadata():
+        num_nodes += part['num_nodes']
+    assert len(nodes) == num_nodes, \
+            'The length of boolean mask vector should be the number of nodes in the graph.'
+    # Get all nodes that belong to the rank.
+    local_nids = partition_book.partid2nids(rank)
+    return _get_overlap(nodes, local_nids)
+
+def edge_split(edges, partition_book, rank):
+    ''' Split edges and return a subset for the local rank.
+
+    This function splits the input edges based on the partition book and
+    returns a subset of edges for the local rank. This method is used for
+    dividing workloads for distributed training.
+
+    The input edges can be stored as a vector of masks. The length of the vector is
+    the same as the number of edges in a graph; 1 indicates that the edge in
+    the corresponding location exists.
+
+    Parameters
+    ----------
+    edges : 1D tensor or DistTensor
+        A boolean mask vector that indicates input nodes.
+    partition_book : GraphPartitionBook
+        The graph partition book
+    rank : int
+        The rank of the current process
+
+    Returns
+    -------
+    1D-tensor
+        The vector of edge Ids that belong to the rank.
+    '''
+    num_edges = 0
+    for part in partition_book.metadata():
+        num_edges += part['num_edges']
+    assert len(edges) == num_edges, \
+            'The length of boolean mask vector should be the number of edges in the graph.'
+    # Get all edges that belong to the rank.
+    local_eids = partition_book.partid2eids(rank)
+    return _get_overlap(edges, local_eids)

python/dgl/distributed/graph_partition_book.py

@@ -4,6 +4,7 @@ import numpy as np
 
 from .. import backend as F
 from ..base import NID, EID
+from .. import utils
 
 class GraphPartitionBook:
     """GraphPartitionBook is used to store parition information.
@@ -14,9 +15,9 @@ class GraphPartitionBook:
         partition id of current GraphPartitionBook
     num_parts : int
         number of total partitions
-    node_map : numpy array
+    node_map : tensor
         global node id mapping to partition id
-    edge_map : numpy array
+    edge_map : tensor
         global edge id mapping to partition id
     part_graph : DGLGraph
         The graph partition structure.
@@ -26,8 +27,10 @@ class GraphPartitionBook:
         assert num_parts > 0, 'num_parts must be greater than zero.'
         self._part_id = part_id
         self._num_partitions = num_parts
-        self._nid2partid = F.zerocopy_from_numpy(node_map)
-        self._eid2partid = F.zerocopy_from_numpy(edge_map)
+        node_map = utils.toindex(node_map)
+        self._nid2partid = node_map.tousertensor()
+        edge_map = utils.toindex(edge_map)
+        self._eid2partid = edge_map.tousertensor()
         self._graph = part_graph
         # Get meta data of GraphPartitionBook
         self._partition_meta_data = []

tests/distributed/test_dist_graph_store.py

@@ -11,7 +11,7 @@ import multiprocessing as mp
 from dgl.graph_index import create_graph_index
 from dgl.data.utils import load_graphs, save_graphs
 from dgl.distributed import DistGraphServer, DistGraph
-from dgl.distributed import partition_graph
+from dgl.distributed import partition_graph, load_partition, GraphPartitionBook, node_split, edge_split
 import backend as F
 import unittest
 import pickle
@@ -76,10 +76,20 @@ def run_client(graph_name, barrier, num_nodes, num_edges):
     assert g.node_attr_schemes()['test1'].dtype == F.int32
     assert g.node_attr_schemes()['features'].shape == (1,)
 
+    selected_nodes = np.random.randint(0, 100, size=g.number_of_nodes()) > 30
+    # Test node split
+    nodes = node_split(selected_nodes, g.get_partition_book(), g.rank())
+    nodes = F.asnumpy(nodes)
+    # We only have one partition, so the local nodes are basically all nodes in the graph.
+    local_nids = np.arange(g.number_of_nodes())
+    for n in nodes:
+        assert n in local_nids
+
     g.shut_down()
     print('end')
 
-def run_server_client():
+@unittest.skipIf(dgl.backend.backend_name == "tensorflow", reason="TF doesn't support some of operations in DistGraph")
+def test_server_client():
     g = create_random_graph(10000)
 
     # Partition the graph
@@ -110,5 +120,42 @@ def run_server_client():
         p.join()
     print('clients have terminated')
 
+def test_split():
+    g = create_random_graph(10000)
+    num_parts = 4
+    num_hops = 2
+    partition_graph(g, 'test', num_parts, '/tmp', num_hops=num_hops, part_method='metis')
+
+    node_mask = np.random.randint(0, 100, size=g.number_of_nodes()) > 30
+    edge_mask = np.random.randint(0, 100, size=g.number_of_edges()) > 30
+    selected_nodes = np.nonzero(node_mask)[0]
+    selected_edges = np.nonzero(edge_mask)[0]
+    for i in range(num_parts):
+        part_g, node_feats, edge_feats, meta = load_partition('/tmp/test.json', i)
+        num_nodes, num_edges, node_map, edge_map, num_partitions = meta
+        gpb = GraphPartitionBook(part_id=i,
+                                 num_parts=num_partitions,
+                                 node_map=node_map,
+                                 edge_map=edge_map,
+                                 part_graph=part_g)
+        local_nids = F.nonzero_1d(part_g.ndata['local_node'])
+        local_nids = F.gather_row(part_g.ndata[dgl.NID], local_nids)
+        nodes1 = np.intersect1d(selected_nodes, F.asnumpy(local_nids))
+        nodes2 = node_split(node_mask, gpb, i)
+        assert np.all(np.sort(nodes1) == np.sort(F.asnumpy(nodes2)))
+        local_nids = F.asnumpy(local_nids)
+        for n in nodes1:
+            assert n in local_nids
+
+        local_eids = F.nonzero_1d(part_g.edata['local_edge'])
+        local_eids = F.gather_row(part_g.edata[dgl.EID], local_eids)
+        edges1 = np.intersect1d(selected_edges, F.asnumpy(local_eids))
+        edges2 = edge_split(edge_mask, gpb, i)
+        assert np.all(np.sort(edges1) == np.sort(F.asnumpy(edges2)))
+        local_eids = F.asnumpy(local_eids)
+        for e in edges1:
+            assert e in local_eids
+
 if __name__ == '__main__':
-    run_server_client()
+    test_split()
+    test_server_client()

tests/distributed/test_graph_partition_book.py

@@ -9,14 +9,6 @@ import backend as F
 import unittest
 import pickle
 
-def create_ip_config():
-    ip_config = open("ip_config.txt", "w")
-    ip_config.write('192.168.9.12 30050 0\n')
-    ip_config.write('192.168.9.13 30050 1\n')
-    ip_config.write('192.168.9.14 30050 2\n')
-    ip_config.write('192.168.9.15 30050 3\n')
-    ip_config.close()
-
 def create_random_graph(n):
     arr = (spsp.random(n, n, density=0.001, format='coo') != 0).astype(np.int64)
     ig = create_graph_index(arr, readonly=True)
@@ -30,7 +22,6 @@ def test_graph_partition_book():
     num_parts = 4
     num_hops = 2
 
-    create_ip_config()
     partition_graph(g, 'test', num_parts, '/tmp', num_hops=num_hops, part_method='metis')
 
     for i in range(num_parts):
@@ -55,4 +46,4 @@ def test_graph_partition_book():
 
 
 if __name__ == '__main__':
-    test_graph_partition_book()
\ No newline at end of file
+    test_graph_partition_book()