Fixes #281: Topology does not attempt to proxies for non-local nodes.

testsuite/mpitests/issue-281.sli

@@ -0,0 +1,62 @@
+/*
+ *  issue-281.sli
+ *
+ *  This file is part of NEST.
+ *
+ *  Copyright (C) 2004 The NEST Initiative
+ *
+ *  NEST is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  NEST is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with NEST.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+/* BeginDocumentation
+
+Name: testsuite::issue-281 - Check that ConnectLayers works MPI-parallel for fixed fan-out
+
+Synopsis: (issue-281) run -> NEST exits if test fails
+
+Description:
+ This test connects a layer with itself with fixed fan-out. 
+ The test should pass with any number of MPI processes.
+
+Author: Hans Ekkehard Plesser, 2016-03-18
+ */
+
+(unittest) run
+/unittest using
+
+[1 2 4]
+{
+  << 
+    /rows 3 
+    /columns 3
+    /elements /iaf_neuron
+  >>
+  CreateLayer
+  dup
+
+  << 
+     /connection_type /divergent
+     /number_of_connections 10
+
+     % weights are randomized to check that global RNGs stay in sync
+     /weights << /uniform << /min 1. /max 2. >> >>
+  >>
+  ConnectLayers
+
+  % Simulate call required to provoke global-rng-sync-check.
+  10 Simulate
+}
+distributed_pass_or_die
+

topology/connection_creator_impl.h

@@ -741,9 +741,19 @@ ConnectionCreator::divergent_connect_( Layer< D >& source, Layer< D >& target )
       }
       Position< D > target_displ = displacements[ random_id ];
       index target_id = targets[ random_id ];
-      Node* target_ptr = kernel().node_manager.get_node( target_id );
+
       double w, d;
       get_parameters_( target_displ, get_global_rng(), w, d );
+
+      // We bail out for non-local neurons only now after all possible
+      // random numbers haven been drawn. Bailing out any earlier may lead
+      // to desynchronized global rngs.
+      if ( not kernel().node_manager.is_local_gid( target_id ) )
+      {
+        continue;
+      }
+
+      Node* target_ptr = kernel().node_manager.get_node( target_id );
       kernel().connection_builder_manager.connect(
         source_id, target_ptr, target_ptr->get_thread(), synapse_model_, d, w );
       is_selected[ random_id ] = true;