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Analyzing the inflience of number of particles.
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cmenguy committed Nov 5, 2013
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Expand Up @@ -113,4 +113,24 @@ The De Jong 2 function is just another name for the [Rosenbrock](#rosenbrock) fu

### Ackley Path

![minima](/data/ackley.png)
![minima](/data/ackley.png)

## Analysis

There are 3 important parameters to analyze to see how the particle swarm performs

- number of particles : how does performance behave as we increase the number of particles?
- initial speed variation coefficient : this parameter is tied to the inner workings of the particles behavior, and changing this will greatly affect how the algorithm behave.
- mobility of the particles : if particles are more mobile, we will see different properties of the algorithm.

### Influence of the number of particles

The following diagram takes the [Michalewicz](#michalewicz) function as an example and shows 1 curve for different number of particles used in the algorithm. Here is some observations we can make:

- with 10 particles, parts of the solution space won't be examined, and so we are bound to converge towards a local minima where the particles will be trapped.
- with 25 particles, the solution space is examined more widely, but we are still not converging towards the global minima.
- with 50 particles, it takes more time to converge, but the value towards which we converge is closer to the global minima.

![analysis](/data/particles.png)

These observations make sense with the intuition, so it's important to use a reasonably high number of particles if we want to get closer to the global minima.
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