# Computer Chess Club Archives

## Messages

### Subject: Re: Null-Move: Difference between R = 2 and R = 3 in action

Author: Robert Hyatt

Date: 19:23:53 07/20/02

Go up one level in this thread

```On July 20, 2002 at 09:20:41, Uri Blass wrote:

>On July 20, 2002 at 08:38:52, Sune Fischer wrote:
>
>>On July 20, 2002 at 08:13:44, Gian-Carlo Pascutto wrote:
>>
>>>On July 20, 2002 at 08:04:01, Sune Fischer wrote:
>>>
>>>>I think it matters "a factor of 2".
>>>>
>>>>1) it helps you to prune
>>>>2) you get better evaluation in the upper plies when you can return a score
>>>>based on a deeper search.
>>>>
>>>>number one will show itself directly because you iterate deeper, the second one
>>>>you don't "see", but it does improve depth along some branches in the same way.
>>>
>>>1) I get +- 10% hash hits (and less prunes) in typical middlegame. Not enough to
>>>matter a factor of two (but I didnt check this so not 100% sure).
>>>
>>>2) Uh?
>>
>>You have 1 ply to go, you probe and get a hit based on a 10 ply search.
>>
>>Or, what is perhaps more likely, a 6 ply result when you only had 4 plies to go,
>>that is still 2 more plies of accuracy and you also prune/transpose at the same
>>time.
>
>
>You may remember a draw score and use it
>when practically it is not a draw because
>the draw score is based on previous positions and when
>you get the same position again the previous positions
>are not the same.
>
>Uri

Simple test, again.  Use fine 70.  No hashing will take you 26 plies to
find the winning move Kb1, with the score showing you win a pawn. With a
decent hash table, you will solve this somewhat shallower.  Crafty finds
this at depth=18 for example.  It gets a 26 ply result from a 18 ply search
due to the effect Sune mentioned...

```