Author: Uri Blass
Date: 01:09:58 03/14/04
Go up one level in this thread
On March 14, 2004 at 04:03:44, Uri Blass wrote:
>On March 14, 2004 at 03:15:18, Uri Blass wrote:
>
>>On March 13, 2004 at 23:28:56, Dan Honeycutt wrote:
>>
>>>On March 13, 2004 at 20:43:01, Uri Blass wrote:
>>>
>>>>On March 13, 2004 at 20:29:34, Dan Honeycutt wrote:
>>>>
>>>>>On March 13, 2004 at 17:47:06, Uri Blass wrote:
>>>>>
>>>>>>On March 13, 2004 at 17:40:06, Russell Reagan wrote:
>>>>>>
>>>>>>>On March 13, 2004 at 17:32:49, Uri Blass wrote:
>>>>>>>
>>>>>>>>I think that you do not understand my idea
>>>>>>>>
>>>>>>>>I suggest to do exactly the same things in the same order but to check for
>>>>>>>>repetition or hash cut off before calling search and not after calling search.
>>>>>>>
>>>>>>>Is this what you are wanting to do? Let's say the search normally looks like
>>>>>>>this:
>>>>>>>
>>>>>>>int AlphaBeta(int depth, int alpha, int beta)
>>>>>>>{
>>>>>>> if (depth == 0)
>>>>>>> return Evaluate();
>>>>>>>
>>>>>>> TryRepetition(); // <--------
>>>>>>> TryHashTable(); // <--------
>>>>>>> TryNullMove(); // <--------
>>>>>>>
>>>>>>> GenerateLegalMoves();
>>>>>>> while (MovesLeft()) {
>>>>>>> MakeNextMove();
>>>>>>> val = -AlphaBeta(depth - 1, -beta, -alpha);
>>>>>>> UnmakeMove();
>>>>>>> if (val >= beta)
>>>>>>> return beta;
>>>>>>> if (val > alpha)
>>>>>>> alpha = val;
>>>>>>> }
>>>>>>> return alpha;
>>>>>>>}
>>>>>>>
>>>>>>>You are wanting to do this?
>>>>>>>
>>>>>>>int AlphaBeta(int depth, int alpha, int beta)
>>>>>>>{
>>>>>>> if (depth == 0)
>>>>>>> return Evaluate();
>>>>>>>
>>>>>>> GenerateLegalMoves();
>>>>>>> while (MovesLeft()) {
>>>>>>> MakeNextMove();
>>>>>>>
>>>>>>> TryRepetition(); // <--------
>>>>>>> TryHashTable(); // <--------
>>>>>>> TryNullMove(); // <--------
>>>>>>>
>>>>>>> val = -AlphaBeta(depth - 1, -beta, -alpha);
>>>>>>> UnmakeMove();
>>>>>>> if (val >= beta)
>>>>>>> return beta;
>>>>>>> if (val > alpha)
>>>>>>> alpha = val;
>>>>>>> }
>>>>>>> return alpha;
>>>>>>>}
>>>>>>>
>>>>>>>Basically to avoid the extra function call?
>>>>>>
>>>>>>Yes
>>>>>>Except that I thought to trynullmove in the beginning of the search.
>>>>>>
>>>>>>It may be better to try null move also not in the beginning of the search
>>>>>>because it is possible that null move does not have search call and only call
>>>>>>qsearch.
>>>>>>
>>>>>>Uri
>>>>>
>>>>>I don't think you want TryNullMove() where shown in the second example. After
>>>>>MakeNextMove() you have a new position which could be a repetition or be in the
>>>>>hash table. but TryNullMove() should come before GenerateLegalMoves().
>>>>>
>>>>>Dan H.
>>>>
>>>>I do not understand.
>>>>The order is the same order in both examples.
>>>
>>>In the first example TryNullMove() comes before GenerateLegalMoves(). In the
>>>second example TryNullMove() comes after GenerateLegalMoves().
>>
>>I look again in the examples I will fix them and try to explain why they should
>>be the same in the next post.
>>I also need to add pseudo code for iterate function to be clear.
>>
>>I think that the place of evaluate is wrong in the example that was given
>>because I do not want to return evaluate before checking for repetition.
>>checking for repetition is cheap and should be done first.
>>
>>Uri
>
>
>
>First example:
>
>int AlphaBeta(int depth, int alpha, int beta)
>{
> TryRepetition(); // <--------
> TryHashTable(); // <--------
> TryNullMove(); // <--------
> if (depth == 0)
> return Evaluate();
> GenerateLegalMoves();
> while (MovesLeft()) {
> MakeNextMove();
> Newdepth=depth+extensions();
> val = -AlphaBeta(Newdepth - PLY, -beta, -alpha);
> UnmakeMove();
> if (val >= beta)
> return beta;
> if (val > alpha)
> alpha = val;
> }
> return alpha;
>}
>
>I suggest to replace it with the following code
>
>int AlphaBeta(int depth, int alpha, int beta)
>{
> if (depth == 0)
> return Evaluate();
> GenerateLegalMoves();
> while (MovesLeft()) {
> MakeNextMove();
> Newdepth=depth+extensions();
> TryRepetition(); // <--------
> TryHashTable(); // <--------
> TryNullMove(); // <--------
> val = -AlphaBeta(Newdepth - PLY, -beta, -alpha);
> UnmakeMove();
> if (val >= beta)
> return beta;
> if (val > alpha)
> alpha = val;
> }
> return alpha;
>}
>
>
>Let see what happens after make move that leads to alphabeta.
>
>After MakeNextMove(); I do in both cases:
>
>1)Newdepth=depth+extensions();
>2)TryRepetition();
>3)TryHashTable();
>4)TryNullMove();
>5)if (depth == 0)
> return Evaluate();
>
>
>Usually calls for alphabeta happen after MakeNextMove();
>In cases that it does not happen then in the second case I need to care to do
>the relevant steps in another function but these cases are rare so I do not care
>about them.
>
>I need also to change my iterate function to take care about it.
>Crafty also does it and has searchroot function that I will look at it.
>
>Uri
Note only that I need if (depth<=0) return qsearch(alpha,beta,depth); and not
if (depth==0) return evaluate() and
I forgot to change it in the original code
I only talked about things that are general for many good programs(having
partial extensions so they do not reduce the depth by 1 and having extensions
and qsearch)
Practically my alphabeta and qsearch get more parameters.
Uri
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.