Fitness function

For the fitness function I tested both an L₁ and an L₂ norm of the sample-wise difference between the two traces as the criterion to measure the fit. That is, I used  

$$f_j=\sum_{i=0}^N \vert x_i-y_{j,i}\vert$$ (3)

and  

$$f_j=\sqrt{\sum_{i=0}^N (x_i-y_{j,i})^2}$$ (4)

where x and y are the sample amplitudes of the reference and the trial trace respectively, j represents the jth individual and N is the number of time samples. These fitness functions consider each sample in the sub-sampled well log as being completely independent of any other. Notice that I am using ``fitness'' here to actually mean the opposite of its usual meaning. That is, an individual will be considered to be highly fit if its fitness value, as defined above, is very low, i.e., it is a good match to the original trace.