========================================================================
PISA  (www.tik.ee.ethz.ch/pisa/)
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Computer Engineering (TIK)
ETH Zurich	 
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HypE - Hypervolume Estimation Algorithm for Multiobjective Optimization

Implementation in C for the selector side.

Documentation
  
author: Johannes Bader, johannes.bader@tik.ee.ethz.ch
last change: 22.10.2008
========================================================================



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

HypE is an hypervolume-based multiobjective evolutionary algorithm and has been
proposed by Johannes Bader and Eckart Zitzler at the ETH Zurich. Here, we present a
PISA-implementation of the algorithm based on the cited paper

@TECHREPORT{bz2008a,
  author = {J. Bader and E. Zitzler},
  title = {{HypE: Fast Hypervolume-Based Multiobjective Search Using Monte Carlo
	Sampling}},
  institution = {{Institut f\"ur Technische Informatik und Kommunikationsnetze, ETH
	Z\"urich}},
  year = {2006},
  type = {TIK Report},
  number = {286},
  month = oct
}


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

HypE 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)


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

seed         (seed for the random number generator)
tournament   (tournament size for mating selection)
mating       (if set to 1, HypE performes mating selection based on the proposed 
              fitness scheme. If set to 0, uniform mating selection is used instead)
bound        (upper bound defining the reference point as r = (bound, ..., bound) )
nrOfSamples  (number of samples to be used to estimate the fitness values. If set to -1,
              the exakt calculation is used instead of sampling.)

Recommended choices are
	tournament = 5
	mating = 1
	bound = (as tight as possible)
	nrOfSamples = 10000  if dim > 3, 
	                 -1  otherwise

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

The source code for HYPE is divided into four files:

'hype.h' is the header file.
'hype.c' contains the main function and implements the control flow.
'hype_io.c' implements the file i/o functions.
'hype_functions.c' implements all other functions including the selection.

Additionally a Makefile, a PISA_configuration file with common
parameters and a PISA_parameter file with local parameters are
contained in the tar file.

Depending on whether you compile on Windows or on Unix (any OS having
<unistd.h>) uncomment the according '#define' in the 'hype.h' file.


Usage
=====

Start HypE with the following arguments:

HypE paramfile filenamebase poll

paramfile: specifies the name of the file containing the local
parameters (e.g. HypE_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 (PISA_
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 HypE
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
===========

None limitations are known so far.



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

The behaviour in state 5 and 9 is not determined by the interface but
by each variator module specifically. HypE 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).