# Computer Chess Club Archives

## Messages

### Subject: Re: Nodes per second........

Author: Jim Phillips

Date: 14:54:48 10/01/98

Go up one level in this thread

```On October 01, 1998 at 08:25:15, Roberto Waldteufel wrote:

>
>On September 28, 1998 at 11:28:42, Peter Fendrich wrote:
>
(snip)
>
>>Sure, winning games is better than losing them... :)
>>Search does in fact have some good effects by itself...
>>There was an intresesting article in ICCA Journal a few years ago. I don't
>>remember any details about the authors and such but here is what I remember from
>>the article.
>>They played two programs against each other with completely random evaluation.
>>One program searched the tree, gave the leafs a random evaluation and and backed
>>up the values in an alfa/beta manner. The other program just gave each move from
>>the root a random evaluation. The first thoughts about a match like this is that
>>the result will be as random as the evaluation code, but it wasn't!
>>The results showed that the tree version was better because of a tendency to get
>>more space just because of the tree search itself. Well, my memory is fading
>>here...
>>
>>//Peter
>
>Maybe the tree version would find shallow mates, and the root version would not?
>I think this might well account for the difference.
>
>Best wishes,
>Roberto

I'd like to throw in my 2 cents....  If you choose a move at random from
the "leaf" nodes, you are going to tend to return to a root move that
generates a "bushier branch".  Let's say you have three possible root
moves, and you search two plies deep and choose a move at random.  If
there are 10 "leaves" corresponding to the 1st root move, 20 leaves
corresponding to the 2nd root move, and 70 leaves for the 3rd root move,
there is a 70% chance that your random function will choose the 3rd root,
which is the one that will also lead you to a more open position with a
lot of possible moves to make.  The program that simply chooses a move at
the root at random has only a 33 1/3 % chance of picking the 3rd root....
Does this seem reasonable, or am I off around Jupiter?
-Jim Phillips

```