========================================================================
PISA  (www.tik.ee.ethz.ch/pisa/)
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Computer Engineering (TIK)
ETH Zurich	 
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SEMO2 - Fair Evolutionary Multiobjective Optimizer

Implementation in C for the selector side using PISALib

Documentation
  
file: semo2_documentation.txt
author: Stefan Bleuler, bleuler@tik.ee.ethz.ch
last change: $date$
========================================================================

The Optimizer
=============

SEMO2 is the full version of SEMO.

SEMO2 is a simple evoluationary multiobjective optimizer used as
demonstration program for PISA. SEMO2 maintains an archive of all
non-dominated solutions. A parent individual is chosen uniformly from
this archive. A newly variated individual is only added to the archive
if it is not dominated by any other individual in the archive and if
it is not equal in all objective values to any other individual in the
archive.



@inproceedings{LTZWD2002b,
    author = {M. Laumanns and L. Thiele and E. Zitzler and
                  E. Welzl and K. Deb}, 
    booktitle = {Parallel Problem Solving From Nature --- PPSN VII},
    title = {Running time analysis of multi-objective evolutionary
                  algorithms on a simple discrete optimization problem},
    year = {2002}
}



The Parameters
==============

SEMO2 uses the following values for the common parameters.
These parameters are specified in 'PISA_cfg'.

alpha    (population size)
mu       (number of parent individuals)
lambda   (number of offspring individuals)
dim      (number of objectives)


SEMO2 takes one local parameter which is given in a parameter file.
The name of this parameter file is passed to SEMO2 as command line
argument.  (See 'semo2_param.txt' for an example.)

seed         (seed for the random number generator)



Source Files
============

The source code for SEMO2 is divided into six files.

Four generic files are taken from PISALib:

'selector.{h,c}' is a taken from PISALib. It contains the main
function and all functions implementing the control flow.

'selector_internal.{h,c}' is taken from PISALib. It contains functions
that are called by the functions in the 'selector' part and do the
work in the background (file access etc.). 
  
'selector_user.{h,c}' defines and implements the SEMO2 specific
operations.

Additionally a Makefile, a 'PISA_cfg' file with common parameters and a
'semo2_param.txt' file with local parameters are contained in the tar
file.

For compiling on Windows change the according '#define' in the
'selector_user.h' file.



Usage
=====

Start SEMO2 with the following arguments:

semo2 paramfile filenamebase poll

paramfile: specifies the name of the file containing the local
parameters (e.g. semo2_param.txt)

filenamebase: specifies the name (and optionally the directory) of the
communication files. The filenames of the communication files and the
configuration file are built by appending 'sta', 'var', 'sel','ini',
'arc' and 'cfg' to the filenamebase. This gives the following names for
the 'PISA_' filenamebase:

PISA_cfg - configuration file
PISA_ini - initial population
PISA_sel - individuals selected for variation (parents)
PISA_var - variated individuals (offspring)
PISA_arc - individuals in the archive

Caution: the filenamebase must be consistent with the name of
the configuration file and the filenamebase specified for the variator
module.

poll: gives the value for the polling time in seconds (e.g. 0.5). This
      polling time must be larger than 0.01 seconds.



Limitations
===========

No limitations are known so far.



Stopping and Resetting
======================

The behaviour in state 5 and 9 is not determined by the interface but
by each selector module specifically. SEMO2 behaves as follows:

state 5 (= variator terminated): set state to 6 (terminate as well).
state 9 (= variator resetted): set state to 10 (reset as well).