Add gen on manager option to forces tutorial

Author: shuds13

docs/tutorials/executor_forces_tutorial.rst

@@ -334,6 +334,42 @@ These may require additional browsing of the documentation to complete.
 
         ...
 
+Running the generator on the manager
+------------------------------------
+
+As of version 1.3.0, the generator can be run on a thread on the manager,
+using the :ref:`libE_specs<datastruct-libe-specs>` option **gen_on_manager**.
+
+Change the libE_specs as follows.
+
+   .. code-block:: python
+    :linenos:
+    :lineno-start: 28
+
+    nsim_workers = ensemble.nworkers
+
+    # Persistent gen does not need resources
+    ensemble.libE_specs = LibeSpecs(
+        gen_on_manager=True, sim_dirs_make=True, ensemble_dir_path="./test_executor_forces_tutorial"
+    )
+
+When running set ``nworkers`` to the number of workers desired for running simulations.
+E.g., Instead of:
+
+.. code-block:: bash
+
+    python run_libe_forces.py --comms local --nworkers 5
+
+use:
+
+.. code-block:: bash
+
+    python run_libe_forces.py --comms local --nworkers 4
+
+Note that as the generator random number seed will be zero instead of one, the checksum will change.
+
+For more information see :ref:`Running generator on the manager<gen-on-manager>`.
+
 .. _examples/tutorials/forces_with_executor: https://github.com/Libensemble/libensemble/tree/develop/examples/tutorials/forces_with_executor
 .. _forces_app: https://github.com/Libensemble/libensemble/tree/main/libensemble/tests/scaling_tests/forces/forces_app
 .. _forces_simple: https://github.com/Libensemble/libensemble/tree/main/libensemble/tests/scaling_tests/forces/forces_simple