fixed pointer id overflow on MPI (e.g. for gap junctions)

CHANGES.md

@@ -6,6 +6,8 @@
 
 - Better handling of exceptions in `importCellParams()` (incl. issue 782)
 
+- Fixed pointer id overflow on MPI (e.g. for gap junctions)
+
 # Version 1.0.6
 
 **New features**

netpyne/cell/compartCell.py

@@ -1089,12 +1089,11 @@ def __parsePointerParams(self, params):
 
     def __generatePointerIds(self, pointerParams, params):
         from .. import sim
-
         # see comments in `__parsePointerParams()` for more details
-        if hasattr(sim, 'rank'):
-            preToPostId = 1e9 * sim.rank + sim.net.lastPointerId  # global index for presyn gap junc
-        else:
-            preToPostId = sim.net.lastPointerId
+
+        if sim.net.lastPointerId > sim.net.maxPointerIdPerNode:
+            print(f"WARNING: potential overflow of pointer connection id!")
+        preToPostId = sim.net.lastPointerId
         sim.net.lastPointerId += 1  # keep track of num of gap juncs in this node
 
         if pointerParams['bidirectional']:

netpyne/network/network.py

@@ -26,6 +26,8 @@ class Network(object):
     # initialize variables
     # -----------------------------------------------------------------------------
     def __init__(self, params=None):
+        from .. import sim
+
         self.params = params
 
         # params that can be expressed using string-based functions in connections
@@ -62,7 +64,11 @@ def __init__(self, params=None):
             {}
         )  # Empty dict for storing GID -> local index (key = gid; value = local id) -- ~x6 faster than .index()
         self.lastGid = 0  # keep track of last cell gid
-        self.lastPointerId = 0  # keep track of last gap junction gid
+
+        # keep track of last gap junction gid
+        intMax = 2**(32-1) # pointer connection id in NEURON is signed 32-bit int
+        self.maxPointerIdPerNode = int(intMax / sim.nhosts)
+        self.lastPointerId = sim.rank * self.maxPointerIdPerNode # to avoid overlap of gids from different nodes 
 
     # -----------------------------------------------------------------------------
     # Set network params