Information Technology Reference
In-Depth Information
are ready-made and easily available to integrate in the evolving models (68%
success rate as opposed to 10%).
How can we explain these results? First of all, we already know that the
creation of small integer constants can be easily achieved by performing
simple arithmetic operations and, therefore, the GEP algorithm has no prob-
lems in creating them. And second, by including numerical constants in the
terminal set, we are increasing, perhaps unnecessarily, the complexity of the
problem, and this might be responsible for the observed decrease in perform-
ance in the GEP-NC approach.
The comparison of the structures of the sub-ETs created with the simpler
approach (that is, without the explicit use of numerical constants) with the
structures of the sub-ETs created by using integer constants in the terminal
set can give us some pointers as to why the latter structures are more compli-
cated (or perhaps less flexible) and, consequently, trickier to handle by the
algorithm. Below are listed the first 10 perfect solutions discovered in the
experiment summarized in the first column of Table 5.1 and all the perfect
solutions (10 in total) obtained in the second experiment (the numbers in
square brackets indicate, respectively, the run number and the generation by
which they were discovered and the numbers in parentheses correspond to
the total number of nodes in the sub-ETs):
GEP without NCs:
012345678901234012345678901234012345678901234
/+aa-a+aaaaaaaa/*+*a+-aaaaaaaa+a+/+-aaaaaaaaa-[00,44] = 1000 (33)
-aaa---aaaaaaaa/+++*//aaaaaaaa+aa-/--aaaaaaaa-[01,39] = 1000 (21)
*/+a+*+aaaaaaaaa/a++*/aaaaaaaaaa/+*/+aaaaaaaa-[02,41] = 1000 (15)
-a**-*aaaaaaaaa+/a*aaaaaaaaaaa/*/aa+aaaaaaaaa-[04,10] = 1000 (27)
*a/a+//aaaaaaaa/-+a-/-aaaaaaaa-+*-+-*aaaaaaaa-[05,16] = 1000 (39)
+aa/aa+aaaaaaaaa/a-a/+aaaaaaaa*+/*-a+aaaaaaaa-[06,27] = 1000 (17)
+-+a/-+aaaaaaaa+a*//**aaaaaaaa-*a/*a+aaaaaaaa-[07,31] = 1000 (37)
+aa/--+aaaaaaaaaaaaaa/aaaaaaaa*/a*+aaaaaaaaaa-[10,23] = 1000 (13)
aaa**/+aaaaaaaa**//a*+aaaaaaaa+aa+/a*aaaaaaaa-[11,35] = 1000 (17)
*//a+*/aaaaaaaa*+a//**aaaaaaaa*//a///aaaaaaaa-[12,18] = 1000 (39)
GEP with NCs:
012345678901234012345678901234012345678901234
+0a223a0233aa12-33-2+-033aa312*a+1/+2a23111aa-[10,24] = 1000 (15)
+a0//a1a0aa0200*+a+2/0a2221011-3*31/003a000a3-[19,06] = 1000 (17)
-00++aaa001a03a*a+/*a221233302a+2021/3312a03a-[31,13] = 1000 (13)
/+/*a2a2311aa0001*a1-/13321a13*10a0003013a201-[37,12] = 1000 (13)
/*-/--3a2032010/*23a-3320a11a0*1*a/a223130a30-[59,22] = 1000 (25)
+-+a211322111aa*a++/2-a21112a2013-a/21a113022-[63,10] = 1000 (19)
Search WWH ::




Custom Search