Summit Power9 CPUs documentation (#1162)

* Power9 CPU docs

* Update Tools/BatchScripts/batch_summit_power9.sh

Co-authored-by: Axel Huebl <axel.huebl@plasma.ninja>

* Subsection convention

Co-authored-by: Axel Huebl <axel.huebl@plasma.ninja>

Docs/source/running_cpp/platforms.rst

@@ -43,9 +43,14 @@ regime), the following set of parameters provided good performance:
 Running on Summit at OLCF
 -------------------------
 
+.. _running-cpp-summit-V100-GPUs:
+
+V100 GPUs
+^^^^^^^^^
+
 The batch script below can be used to run a WarpX simulation on 2 nodes on
 the supercomputer Summit at OLCF. Replace descriptions between chevrons ``<>``
-by relevalt values, for instance ``<input file>`` could be
+by relevant values, for instance ``<input file>`` could be
 ``plasma_mirror_inputs``. Note that the only option so far is to run with one
 MPI rank per GPU.
 
@@ -74,3 +79,33 @@ regime), the following set of parameters provided good performance:
 
 A batch script with more options regarding profiling on Summit can be found at
 :download:`Summit batch script<../../../Tools/BatchScripts/script_profiling_summit.sh>`
+
+.. _running-cpp-summit-Power9-CPUs:
+
+Power9 CPUs
+^^^^^^^^^^^
+
+Similar to above, the batch script below can be used to run a WarpX simulation on
+1 node on the supercomputer Summit at OLCF, on Power9 CPUs (i.e., the GPUs are
+ignored).
+
+.. literalinclude:: ../../../Tools/BatchScripts/batch_summit_power9.sh
+   :language: bash
+
+For a 3D simulation with a few (1-4) particles per cell using FDTD Maxwell
+solver on Summit for a well load-balanced problem, the following set of
+parameters provided good performance:
+
+* ``amr.max_grid_size=64`` and ``amr.blocking_factor=64``
+
+* **Two MPI ranks per node** (i.e. 2 resource sets per node; equivalently, 1
+  resource set per socket)
+
+* **21 physical CPU cores per MPI rank**
+
+* **21 OpenMP threads per MPI rank** (i.e. 1 OpenMP thread per physical core)
+
+* **SMT 1 (Simultaneous Multithreading level 1)**
+
+* **Sixteen `64x64x64` grids per MPI rank** (with default tiling in WarpX, this
+  results in ~49 tiles per OpenMP thread)

Tools/BatchScripts/batch_summit_power9.sh

@@ -0,0 +1,22 @@
+#!/bin/bash
+
+# Copyright 2019-2020 Maxence Thevenet, Axel Huebl, Michael Rowan
+#
+# This file is part of WarpX.
+#
+# License: BSD-3-Clause-LBNL
+#
+# Refs.:
+#   https://jsrunvisualizer.olcf.ornl.gov/?s1f0o121n2c21g0r11d1b1l0=
+
+#BSUB -P <allocation ID>
+#BSUB -W 00:10
+#BSUB -nnodes 1
+#BSUB -alloc_flags "smt1"
+#BSUB -J WarpX
+#BSUB -o WarpXo.%J
+#BSUB -e WarpXe.%J
+
+
+export OMP_NUM_THREADS=21
+jsrun -n 2 -a 1 -c 21 -r 2 -l CPU-CPU -d packed -b rs <path/to/executable> <input file> > output.txt