Update default number of processes to 1 (#172)

Co-authored-by: Marcos Pedro Ferreira Leal Silva <[email protected]>

examples/reaction_prediction/rexgen_direct/candidate_ranking_train.py

@@ -167,7 +167,7 @@ def main(args, path_to_candidate_bonds):
     parser.add_argument('-rcb', '--reaction-center-batch-size', type=int, default=200,
                         help='Batch size to use for preparing candidate bonds from a trained '
                              'model on reaction center prediction')
-    parser.add_argument('-np', '--num-processes', type=int, default=8,
+    parser.add_argument('-np', '--num-processes', type=int, default=1,
                         help='Number of processes to use for data pre-processing')
     parser.add_argument('-nw', '--num-workers', type=int, default=100,
                         help='Number of workers to use for data loading in PyTorch data loader')