[Fix] Enable mini-batch rgcn for CPU (dmlc#2345)

Author: mszarma

examples/pytorch/rgcn/entity_classify_mp.py

@@ -185,7 +185,7 @@ def evaluate(model, embed_layer, eval_loader, node_feats):
 
 @thread_wrapped_func
 def run(proc_id, n_gpus, args, devices, dataset, split, queue=None):
-    dev_id = devices[proc_id]
+    dev_id = devices[proc_id] if devices[proc_id] != 'cpu' else -1
     g, node_feats, num_of_ntype, num_classes, num_rels, target_idx, \
         train_idx, val_idx, test_idx, labels = dataset
     if split is not None:

examples/pytorch/rgcn/model.py

@@ -78,7 +78,7 @@ def __init__(self,
                  sparse_emb=False,
                  embed_name='embed'):
         super(RelGraphEmbedLayer, self).__init__()
-        self.dev_id = dev_id
+        self.dev_id = th.device(dev_id if dev_id >= 0 else 'cpu')
         self.embed_size = embed_size
         self.embed_name = embed_name
         self.num_nodes = num_nodes