.. highlight:: rst

Gluing Stand-Alone Applications
===============================

This section follows closely the approach of Langtangen: Python Scripting for
Computational Science and Engineering, chapter 2.3.


Scripting
---------

Suppose you have a stand-alone code for solving the ODE:


:math:`m\frac{d^2 u}{dt^2} + b \frac{du}{dt} + cf(u) = A \cos \omega t`


and you wish to have simulation results for varoius choices of the 
parameters. 
For instance, the provided 


oscillator.f
inp
run

(gfortran -O3 -o oscillator oscillator.f)


reads the following parameters from the standard input, in the listed order:
 :math:`m,b,c`, name of f(y) function, A, 
 :math:`\omega, y_0, t_{{stop}}, \Delta t`  

The values of the parameters may be placed in a file inp: and the program can
be run as

   oscillator < inp


The output consists of data points :math:`t_i u(t_i)`, a suitable format to
plot, e.g. with gnuplot.


Under the `link
<http://www.sam.math.ethz.ch/~gradinar/Teaching/SciPyTools/oscillator.tar.gz>`_
you'll find fortran, C and python versions of this stand-alon code.

.. highlight:: python
   :linenothreshold: 5



Our first goal is to simplify the user's interaction with the program; with
the script simviz1.py it is possible to adjust the parameters through
command-line options::
  
    python simviz1.py -m 3.3 -b 0.9 -dt 0.05

The result should be png-files and an otional plot on the screen. The files
for each such experiment should go in a subdirectory.


.. literalinclude:: SAMtut01/oscillator/F77/simviz1.py
   :language: python


One can easily generate an automatic LaTeX-report or HTML-report 
containing the values of the parameters and the corresponding pictures.


Conducting Numerical Experiments
--------------------------------

Suppose we want to keep most of the parameters fixed and vary one parameter
between a minimum and a maximum value; the results should be collected in a
HTML-report::
   
   python loop4simviz1.py m_min m_max m_increment [ simviz1.py options ]
   

.. literalinclude:: SAMtut01/oscillator/F77/loop4simviz1.py
   :language: python

or let vary any parameter::

    loop4simviz2.py parameter min max increment [ simviz2.py options ]

.. literalinclude:: SAMtut01/oscillator/F77/loop4simviz2.py
   :language: python