Author: Larry Griffiths
Date: 10:28:09 02/09/99
Go up one level in this thread
On February 09, 1999 at 02:49:17, Dann Corbit wrote:
>On February 09, 1999 at 02:43:52, Larry Griffiths wrote:
>
>>I have been using Floating point (double) for my evaluation (scoring)
>>function. I set some variables to 0.0 when starting the Alpha-Beta search.
>>I add values to these variables when a move is made and then subtract them
>>back out when restoreing the piece. I have found that the result is not
>>always returned back to 0.0. I get something like 3.56234567343534-18.
>>
>>Should I be using integers for scoring instead?
>print out the answers with something along the lines of:
>printf("%.2f", ce);
>which will show 0.00 for the example you gave. Subtraction is the most
>catastrophic operation with floating point. Using integers is not always
>faster, and sometimes can cause other unsuspected problems (e.g. 1.999 = 1).
Dan,
Printing out the score is not my problem. I am concerned because I have been
using incremental bonuses and penaltys at each ply that the leaf evaluation
node uses for its score. I saw a score of more than 80 returned one time
and my Queens are worth 9. I know that more than 9 queens of material
could not have been captured in the position. I compared floating point
verses integer at one time and it seemed that the floating point was
slightly faster (on a Pentium 350). I put the comparision for zero at
the root ply to verify that incremental scores that were being added were
also being backed out. I can see that trivial values could (the catastrophic
operation you mentioned) could grow larger when searching 10 to 12 nodes deep.
Is there documentation somewhere that describes this effect of
subtraction with floating point?
Thanks for your reply! :-}
Larry
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.