.. index::
    single: FAQ; bgq

.. highlight:: bash

How to run OmpSs on Blue Gene/Q?
================================

Installation
------------

.. note::
   If you want IBM compilers support, make sure that the full-name drivers
   (e.g. powerpc64-bgq-linux-xlc) are in the PATH. You can usually do so by
   setting the PATH variable before the configuration step::

      $ export PATH=/bgsys/drivers/ppcfloor/gnu-linux/powerpc64-bgq-linux/bin/:$PATH

   You don't need to keep this change after the configuration step.

Follow the instructions described here: :ref:`nanos-installation` and
:ref:`mercurium-installation`, and add these options for each configuration:

* For Nanos++::

   $ ./configure --host=powerpc64-bgq-linux ...

* For Mercurium::

   $ ./configure --target=powerpc64-bgq-linux ...

Finally compile and install as usual.

Compiling your application
--------------------------

Mercurium will install the drivers using the target keyword as the prefix,
so to build your application::

   $ powerpc64-bgq-linux-mcc --ompss test.c -o test

For MPI applications, you can use the MPI wrapper as long as the MPI
implementation allows to set the native compiler. For example, if using MPICH::

   $ export MPICH_CC="powerpc64-bgq-linux-xlmcc --ompss"
   $ mpicc test.c -o test.c

Instrumenting
-------------

For non-MPI applications, you can follow the same instructions described
here: :ref:`instrumentation-plugins-extrae`

For MPI applications, you should follow the same steps but preloading the
Extrae MPI library so that it can intercept the MPI calls. Blue Gene/Q does
not allow this method so you will have to link your application with
Extrae. You will find an example of how to do it in the Extrae
installation directory for BG/Q '$EXTRAE_HOME/share/example/MPI/'.