fix node/element indexing to work with latest esmpy

esmf_regrid/experimental/unstructured_regrid.py

@@ -75,19 +75,17 @@ def __init__(
         if location == "face":
             field_kwargs = {"meshloc": esmpy.MeshLoc.ELEMENT}
             shape = (len(face_node_connectivity),)
-            index_offset = self.esi
         elif location == "node":
             field_kwargs = {"meshloc": esmpy.MeshLoc.NODE}
             shape = (len(node_coords),)
-            index_offset = self.nsi
         else:
             raise ValueError(
                 f"The mesh location '{location}' is not supported, only "
                 f"'face' and 'node' are supported."
             )
         super().__init__(
             shape=shape,
-            index_offset=index_offset,
+            index_offset=1,
             field_kwargs=field_kwargs,
             mask=mask,
         )
@@ -97,10 +95,10 @@ def _as_esmf_info(self):
         # the data must be translated into a form ESMF understands
         num_node = self.node_coords.shape[0]
         num_elem = self.fnc.shape[0]
-        nodeId = np.array(range(self.nsi, self.nsi + num_node))
+        nodeId = np.arange(1, num_node + 1)
         nodeCoord = self.node_coords.flatten()
         nodeOwner = np.zeros([num_node])  # regridding currently serial
-        elemId = np.array(range(self.esi, self.esi + num_elem))
+        elemId = np.arange(1, num_elem + 1)
         elemType = self.fnc.count(axis=1)
         # Experiments seem to indicate that ESMF is using 0 indexing here
         elemConn = self.fnc.compressed() - self.nsi