remove outdated documentation (#159)

Author: atmyers

Docs/source/GPU_Tutorial.rst

@@ -9,59 +9,10 @@
 GPU
 ==========================
 
-The tutorials in ``amrex-tutorials/ExampleCodes/GPU`` demonstrate the implementation
-of AMReX's GPU toolkit as well as provide GPU ported versions of CPU
-tutorials to help applications convert to GPUs.
-
-**Your first AMReX GPU application**
-------------------------------------
-
-This is a step-by-step guide to preparing, compiling and running your first
-AMReX GPU program.  This guide will use ``Tutorials/GPU/Launch``,
-and instructions will focus on ORNL's systems:
-
-1. Before compiling, the ``pgi`` and ``cuda`` software must be available.
-   On ORNL systems, the modules can be loaded directly by typing:
-
-.. highlight:: console
-
-::
-
-   module load pgi cuda
-
-2. Go to ``Tutorials/GPU/Launch`` to compile the executable.  Compile with
-   ``make USE_CUDA=TRUE COMP=pgi USE_MPI=TRUE USE_OMP=FALSE``, or edit the
-   ``GNUmakefile`` to match this configuration and run ``make``. This
-   should result in an executable: ``main3d.pgi.MPI.CUDA.ex``.
-
-3. On Summit systems, this executable can be submitted by using one of the run
-   scripts found in ``Tutorials/GPU``.  ``run.script`` can be used to run on
-   Summitdev, and ``run.summit`` can be used for Summit.  To change the number
-   of ranks and GPUs used in the simulation, change the number of resource sets,
-   ``n`` in the ``jsrun`` line.  For the first ``Launch`` tutorial, use ``n=1``
-   and set ``INPUTS=""`` because no input file is used in this example.
-
-When ready, submit the job script (on Summit: ``bsub run.script``).
-Congratulations! You've accelerated AMReX using GPUs!
-
-**Launch**
-----------
-
-Launch shows multiple examples of how GPU work can be offloaded using the tools
-available in AMReX. It includes examples of multiple AMReX macro launch methods,
-launching a Fortran function using CUDA and launching work using OpenACC and
-OpenMP offloading. This tutorial will be regularly updated with AMReX's
-preferred GPU launch methodologies.
+The tutorial in ``amrex-tutorials/ExampleCodes/GPU`` demonstrates how to implement a
+performance-portable application using AMReX's GPU offloading capabilities.
 
 **CNS**
 -------
 
-CNS is a direct GPU port of the ``ExampleCodes/EB/CNS`` example.
-
-**AmrCore**
------------
-
-AmrCore is a direct GPU port of the ``ExampleCodes/Amr/Advection_AmrCore`` tutorial
-that advects a single scalar field with a velocity field specified on faces, using
-strategies similar to HeatEquation and CNS.
-
+CNS solves the compressible Navier-Stokes equations on GPUs.