The error has been fixed.

http://psotoolbox.sourceforge.net/

2004-05-25

An error in PSO Toolbox

by Konstantinos E. Parsopoulos

I wanted to inform the PSO Community

regarding an error in the PSO Toolbox developed by Jagatpreet Singh.

The specific toolbox is also mentioned in the PSO Central website. I

contacted the developer a few months ago but I never got a reply, and,

since many of our collaborators use it and wonder why PSO is so bad,

I thought it would be a good idea to inform them through PSO Central.

The error is the following:

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In the PSO.M file (i'm talking about the 2nd version of the toolbox),

at line 165, where the update of the best particle's index is performed,

the developer wrote:

[fGBest, g] = min(fSwarm);

Although, it should be:

[fGBest, g] = min(fPBest);

since the index g corresponds to the best particle EVER attained

by the swarm (i.e. the best position ever visited in the search space)

and NOT the best particle of the current swarm. This is a common

mistake in many implementations. He used the same update

also in the beginning of the program (before the loop), but it

is harmless since at that stage the best positions' matrix is

the same as the initial population.

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Konstantinos E. Parsopoulos,

Dipl.-Math., MSc, PhD candidate

Department of Mathematics,

University of Patras,

GR-26110 Patras, Greece

Tel: +30 2610 997348

Fax: +30 2610 992965

email: kostasp@math.upatras.gr

URL: http://www.math.upatras.gr/~kostasp

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