Move writing of `node_id_param.json`

Just sparing one test on rank.

Overlap/eddy_graph.f90

@@ -112,6 +112,10 @@ program eddy_graph
           "eddy_graph: n_proc should be <= n_dates / (max_delta + 1)")
      e_overestim = maxval([(hshp(i)%ishape_last(hshp(i)%d0) + 1, &
           ediff1d(hshp(i)%ishape_last), i = 1, n_shpc)])
+     open(unit, file = "node_id_param.json", status = "replace", &
+          action = "write")
+     write(unit, fmt = *) '{"e_overestim": ', e_overestim, '}'
+     close(unit)
      corner = corner_deg * deg_to_rad
      step = step_deg * deg_to_rad
   end if
@@ -127,13 +131,6 @@ program eddy_graph
   call ezmpi_bcast(n_dates, root = 0)
   call ezmpi_bcast(e_overestim, root = 0)
 
-  if (rank == 0) then
-     open(unit, file = "node_id_param.json", status = "replace", &
-          action = "write")
-     write(unit, fmt = *) '{"e_overestim": ', e_overestim, '}'
-     close(unit)
-  end if
-
   ! Open output files:
   
   call new_unit(unit_isolated)