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In-Depth Information
Fig. 5.
Trackers matching trends T1 to T7 with memory feedback
This experiment was repeated to examine the impact of removing the short-
ening mutation function from the TEA. Considering presentation of A1 the
tracker population levels reached a slightly higher peak of 218 compared to 191
with no shortening, however the impact on the quality of the memory pool was
significant. Whilst the TEA's detection rate for trends T1 and T2 varied insignif-
icantly, without shortening the detection rate for T3 fell from 100% to 10%, T3
was undetected in 9 of the 10 execution runs. Of more concern was the fact that
the resulting memory pool contained 33 redundant price values compared to the
100% memory eciency found through using mutation by shortening. It is clear
that the shortening mutation is vital for the proper performance of the TEA.
6.3
Experiment 3. Antigen Scalability
To assess scalability antigen A was presented to the TEA from generations 1
to 20. Scanning A we see a new trend T8 becomes apparent when we combine
subsets A1 and A2. Detection of this trend would not be possible in any of the
previous experiments because its occurrence in A1 and A2 does not satisfy the
definition of a trend in those individual sub sets. This highlights an issue with
the approach as the point of split in the antigen has an impact on the potential
number of trends to be detected in the sub parts of that antigen, this issue is
addressed later.
The tracker population reaches a maximum of 2,244 trackers compared to the
maximum population in experiment 2 of 323. The memory pool created is able
to successfully map to 77 of the 80 possible trends across the 10 runs (96.3%
coverage). The TEA failed to find T7 twice and T5 once. Memory ineciency
dropped to 2% as 4 excess price values were noted in the memory pool.
6.4
Experiment 4. Comparison with Random Search
From experiments 2 and 3 approximately 1,000 and 4,000 trackers respectively
were generated by the TEA in order to generate the memory pool of solutions.
