.. index:: Scalasca, Profiling; Scalasca
.. _Scalasca:

Scalasca
========

Description
-----------

Scalasca is a software tool that supports the performance optimization of parallel programs by measuring and analyzing their runtime behavior. The analysis identifies potential performance bottlenecks---in particular those concerning communication and synchronization---and offers guidance in exploring their causes.

Scalasca supports the performance optimization of simulation codes on a wide range of current HPC platforms. Its powerful analysis and intuitive result presentation guides the developer through the tuning process.

User instructions
-----------------

Scalasca is available for both the GNU and Intel compiler families.  It can analyse OpenMP code as well as MPI programs.  To use it, first load the relevant module:

.. code-block:: bash

    $ module load scalasca/2.3.1

Programs must be recompiled and run in a specific fashion in order for scalasca to analyse the program's performance.  This amounts to prefacing the compilation and execution commands with a Scalasca command.

Running

.. code-block:: bash

    $ scalasca -h

gives a short overview.  Further documentation is available in $SCALASCA_ROOT/share/doc.

Source
------

http://www.scalasca.org

License
-------

New BSD license.

Admin notes
-----------

Scalasca requires QT4 libraries for its GUI interface.  This was slightly excessive to install on the NFS server, so I compiled it using the builder account on a workstation.

.. code-block:: bash

    mkdir build-gcc63ompi21; cd build-gcc63ompi21
    ml purge; ml gcc openmpi
    ../scalasca-2.3.1/configure --prefix=/common/debian/9.1/MPI/gcc/6.3/openmpi/2.1/scalasca/scalasca-2.3.1
    make
    make install

and for the Intel compilers:

.. code-block:: bash

    mkdir build-intel2017ompi21; cd build-intel2017ompi21
    ml intel openmpi
    ../scalasca-2.3.1/configure --prefix=/common/debian/9.1/MPI/intel/2017.4/openmpi/2.1/scalasca/scalasca-2.3.1 CC=icc CXX=icpc FC=ifort F77=ifort
    make
    # Make fails with an error - so the intel version was not installed.

with the appropriate compiler, :ref:`Open MPI`, :ref:`Cube` and :ref:`Score-P` modules loaded.