Fix loop-carried dependency.

tests/simple_model.c

@@ -222,8 +222,12 @@ modelRun(struct model_config setup, MPI_Comm comm)
                   xmpi(MPI_Gather(&chunk, 1, MPI_INT, chunks, 1, MPI_INT, 0, comm));
                   if (rank == 0)
                     {
-                      displs[0] = 0;
-                      for (size_t i = 1; i < (size_t) comm_size; ++i) displs[i] = displs[i - 1] + chunks[i - 1];
+                      int accum = 0;
+                      for (size_t i = 0; i < (size_t) comm_size; ++i)
+                        {
+                          displs[i] = accum;
+                          accum += chunks[i];
+                        }
                     }
                   xmpi(MPI_Gatherv(varslice, chunk, MPI_DOUBLE, var, chunks, displs, MPI_DOUBLE, 0, comm));
 #else