At Uncommon Descent, W. Dembski presents us with a new weasel: Someone with the name Oxfordensis programmed years ago two Pascal versions.
The interesting aspect: In contrast to the usual weasels - as discussed in the earlier posts - not every letter is changed with a certain probability in this program, but exactly one letter is changed in each child. Here, the word change is used loosely, as with a probability of 1/27, no letter is changed at all.
Mathematically, this is easier to handle: the transition matrix of the corresponding Markov process gets sparser...
And you have only one parameter which can be changed: the size of the generation.
If I had any reader he may ask himself: Does this algorithm latch? Well, the pic provides the answer: it depends :-)
And here are some values for the probability that the program will show a change to the worse during a run of the program, depending on the size of the population:
- 99.999 %
- 98.485 %
- 83.879 %
- 55.944 %
- 30.008 %
- 14.071 %
- 6.168 %
- 2.649 %
- 1.137 %
- 0.491 %
- 0.214 %
- 0.094 %
So, even with a generation size of one hundred children, one in two hundred runs will show that this algorithm doesn't latch - it's not what W. Dembski and R. Marks describe as a partitioned search.